阅读说明：本技术 用于脱盐装置的计算机化控制系统 (Computerized control system for desalination plant ) 是由 J·H·克劳奇 于 2019-06-06 设计创作，主要内容包括：一种控制系统,其被配置成控制反渗透(RO)阵列、纳滤(NF)阵列和/或混合系统的操作,所述控制系统包括控制面板(CP)、调节控制器(RC)和监控控制器(SC),其中SC与CP且与RC信号通信,其中SC被配置成：从CP接收用户输入并从RC接收关于来自传感器的数据的输入,其中RC与所述多个传感器信号通信,其中RC被配置成：从传感器接收数据,向SC提供输出并从SC接收许可,并且响应从SC接收到的许可来指示设备,并且其中SC被配置成：监测关于从RC接收的数据的输入的趋势和/或从所述数据预测结果并基于所监测的趋势和/或来自CP的用户输入来确定RC的许可。(A control system configured to control operation of a Reverse Osmosis (RO) array, a Nanofiltration (NF) array and/or a hybrid system, the control system comprising a Control Panel (CP), a conditioning controller (RC) and a Supervisory Controller (SC), wherein the SC is in signal communication with the CP and with the RC, wherein the SC is configured to: receiving user input from the CP and input from the RC regarding data from the sensors, wherein the RC is in signal communication with the plurality of sensors, wherein the RC is configured to: receiving data from the sensor, providing an output to the SC and receiving permission from the SC, and instructing the device in response to the permission received from the SC, and wherein the SC is configured to: trends of input regarding data received from the RC are monitored and/or results are predicted from the data and permissions of the RC are determined based on the monitored trends and/or user input from the CP.)

1. A control system configured to control operation of one or more Reverse Osmosis (RO) arrays, one or more Nanofiltration (NF) arrays, mixing systems, or combinations thereof within a desalination plant, wherein the control system comprises:

a Control Panel (CP);

a plurality of Regulation Controllers (RC); and

a Supervisory Controller (SC), wherein the SC is in signal communication with the CP and with each of the plurality of RCs, wherein the SC is configured to: receiving user input from the CP and input from the plurality of RCs regarding data from a plurality of sensors within the desalter,

wherein each of the plurality of RCs is in signal communication with the plurality of sensors, wherein the plurality of RCs are configured to: receive data from one or more of the plurality of sensors, provide an output to the SC and receive permission from the SC, and indicate one or more of a plurality of devices of the desalination apparatus in response to the received permission from the SC, and

wherein the SC is configured to: monitoring trends in input regarding data received from the plurality of RCs and/or predicting results from data received from the plurality of RCs, and determining the permissions of each of the RCs based on the monitored trends, user input from the CP, or a combination thereof.

2. The control system of claim 1, wherein the plurality of sensors are selected from the group consisting of:

an ion concentration sensor configured to measure at least one of conductivity, salinity, total concentration of dissolved ions, and/or concentration of individual ions (Ci) in various flow lines of the desalination device; temperature sensors configured to measure temperatures in various flow lines within the desalination device; a pressure sensor configured to measure pressure in various flow lines within the desalination device; a flow rate sensor configured to measure flow rates of various flow lines within the desalination device; or a combination thereof.

3. The control system of claim 2, wherein the various flow lines comprise one or more selected from the group consisting of: an RO array feed line, an NF array feed line, an RO permeate line, an NF permeate line, an RO concentrate line, an NF concentrate line, a combined RO/NF permeate line, a mixed low salinity water stream line, an RO array permeate dump line, an NF array permeate dump line, a combined RO/NF permeate dump line, an ion concentrate feed line, a feed water bypass line, a Produced Water (PW) mixing line, or a combination thereof.

4. The control system of claim 3, wherein the sensor is configured to provide data to the RC, wherein the RC provides its output to the SC, and/or wherein the SC monitors trends in one or more operating parameters selected from: a degree of fouling of the RO membranes of the one or more RO arrays, the NF membranes of the one or more NF arrays, or both; feed pressure to one or more RO arrays, one or more NF arrays, or both; a rate of change in feed pressure to one or more RO arrays, one or more NF arrays, or both; a feed flow rate to one or more RO arrays, one or more NF arrays, or both; pressure of concentrate from one or more RO arrays, one or more NF arrays, or both; pressure of permeate from one or more RO arrays, one or more NF arrays, or both; a pressure differential across one or more RO arrays, one or more NF arrays, or both; conductivity of permeate from one or more RO arrays, one or more NF arrays, or both; total dissolved solids, TDS, of permeate from one or more RO arrays, one or more NF arrays, or both; the temperature of the permeate from one or more RO arrays, one or more NF arrays, or both; permeate flow rates from one or more RO arrays, one or more NF arrays, or both; a concentrate flow rate from one or more RO arrays, one or more NF arrays, or both; recovery from one or more RO arrays, one or more NF arrays, or both; a flow rate, salinity, conductivity, and/or TDS of a feed water bypass stream, a flow rate, salinity, conductivity, and/or TDS of a Produced Water (PW) mixed stream, a flow rate, salinity, conductivity, and/or TDS of the mixed low salinity water stream; or a combination thereof.

5. The control system of claim 1, wherein the plurality of devices comprises a plurality of valves and pumps, wherein the plurality of valves and pumps comprise one or more of: one or more valves and/or pumps on the feed lines to the RO array, the NF array, or a combination thereof; one or more valves and/or pumps on the permeate line from the RO array, the NF array, or a combination thereof; one or more valves and/or pumps on a permeate feed line from the RO array, the NF array, or both to the mixing system; one or more valves and/or pumps on the concentrate line from the RO array, the NF array, or a combination thereof; one or more valves and/or pumps on the combined RO/NF permeate line; one or more valves and/or pumps on the mixed low salinity water flow line from the mixing system; one or more valves and/or pumps on an ion concentrate line that introduces ion concentrate from an ion concentrate tank to the mixing system; one or more valves and/or pumps on permeate dump lines from the RO array, the NF array, or both; one or more valves and/or pumps on a feedwater bypass line from a feedwater source to the mixing system; one or more valves and/or pumps on the PW mixing line to the mixing system; or a combination thereof.

6. A desalination apparatus comprising:

a water inlet line;

one or more Reverse Osmosis (RO) arrays in fluid communication with the water inlet line, wherein each of the one or more RO arrays is configured to receive RO feedwater and generate an RO permeate and an RO concentrate;

a Nanofiltration (NF) array in fluid communication with the water inlet line, the one or more RO arrays, or both, wherein the NF array is configured to generate a NF permeate and a NF concentrate;

a mixing system, wherein the mixing system comprises:

the RO permeate feed line is connected to the RO permeate,

the NF permeate feed line is connected to the permeate,

a mixing point configured to mix RO permeate from the RO permeate feed line and NF permeate from the NF permeate feed line to form a mixed low salinity injection water, and

a discharge line configured to deliver the mixed low salinity injection water to an injection system;

a plurality of valves and pumps configured to regulate the flow rate or pressure of various streams within the desalination device;

a plurality of sensors configured to measure flow rate, pressure, temperature, composition, or a combination thereof, of various streams within the desalination device;

a control system, wherein the control system is configured to: controlling operation of the one or more RO arrays, the NF array, and the mixing system to be within operating parameters and to maintain composition of the mixed low salinity injection water within an operating envelope,

wherein the control system comprises a Supervisory Controller (SC), a control panel, and a plurality of Regulatory Controllers (RCs), wherein the SC is in electronic communication with the CP and with each of a plurality of RCs, the SC receiving user input from the CP and input from the RCs regarding data from the sensors, wherein each of the plurality of RCs receives data from one or more of the plurality of sensors, provides output to the SC and receives permissions from the SC, and indicates one or more of the plurality of valves and pumps in response to permissions received from the SC, and wherein the SC monitors trends of the input received from the plurality of RCs and determines permissions for each of the RCs based on the monitored trends, user input from the control panel, or a combination thereof.

7. The desalination apparatus of claim 6, wherein the valves comprise one or more valves configured to selectively combine at least a portion of the RO permeate with at least a portion of the NF permeate to generate injection water having a composition within the operational envelope.

8. The desalination apparatus of claim 6, further comprising:

a bypass line coupled to the water inlet line and the mixing system, a PW mixing inlet line fluidly connected to the mixing system, or both, wherein the valves further comprise one or more valves configured to selectively combine at least a portion of the feedwater from the water inlet line, at least a portion of the PW in the PW mixing line, or both, with RO permeate from the RO permeate feed line and NF permeate from the NF permeate feed line to generate the injection water having a composition within the operating envelope.

9. The desalination apparatus of claim 8, wherein the feed water comprises a greater concentration of divalent cations than the RO permeate.

10. The desalination apparatus of claim 6, wherein the sensor is selected from a temperature sensor, a pressure sensor, a flow rate sensor, an ion concentration sensor, or a combination thereof configured to measure at least one of conductivity, salinity, total concentration of dissolved ions, or concentration of individual ions (Ci).

11. The desalination apparatus of claim 6, wherein the sensor comprises one or more flow rate sensors, one or more pressure sensors, or a combination thereof.

12. The desalination apparatus of claim 11, wherein the one or more flow rate sensors, the one or more pressure sensors, or a combination thereof comprise sensors configured to measure a flow rate, a pressure, or both of at least one of: the RO permeate, the NF permeate, the mixed low salinity injection water, a feedwater by-pass stream, a Produced Water (PW) mixed stream, an ion concentrate stream, or a combination thereof.

13. The desalination apparatus of claim 6, further comprising a vessel containing an ion concentrate, wherein the valves comprise one or more valves configured to mix the ion concentrate with at least one of the reverse osmosis permeate, the nanofiltration permeate, the feed water, or the mixed low salinity injection water to generate the components within the operating envelope.

14. The desalination apparatus of claim 6, further comprising at least one of: an RO permeate dump line configured to pass a non-used portion of the RO permeate out of the desalination unit; a NF permeate dump line configured to pass a non-used portion of the NF permeate out of the desalter; or a feedwater bypass line dump line configured such that a non-used portion of the feedwater bypass flow passes out of the desalination device.

15. A method of generating injection water, the method comprising:

generating a reverse osmosis permeate stream;

generating a nanofiltration permeate stream;

mixing at least a portion of the reverse osmosis permeate stream with at least a portion of the nanofiltration permeate stream, the high salinity stream, or a combination thereof to provide a mixed low salinity water stream; and

controlling the generation of the RO permeate stream, the NF permeate stream and the mixture within operating parameters and maintaining the composition of the mixed low salinity water stream within an operating envelope via a control system comprising a Supervisory Controller (SC), a control panel and a plurality of Regulatory Controllers (RCs), wherein the SC is in signal communication with the CP and with each of the plurality of RCs, the SC receiving user input from the CP and input from the RCs regarding data from a plurality of sensors, wherein each of the plurality of RCs receives data from one or more of the plurality of sensors, provides output to the SC and receives permission from the SC, and indicates one or more of the plurality of valves and pumps in response to permission received from the SC, and wherein the SC monitors trends regarding input of the data received from the plurality of RCs, and determining permissions for each of the RCs based on the monitored trends, user input from the control panel, or a combination thereof.

16. The method of claim 15, further comprising:

controlling the dumping of a portion of the RO permeate stream from the desalination unit using the control system; dumping of a portion of the NF permeate stream from the desalination device, or a combination thereof, to provide the mixed low salinity water stream having a composition within the operating envelope.

17. The method of claim 15, wherein the RO permeate stream and the NF permeate stream are generated from a feed water, and wherein the high salinity stream comprises at least a portion of the feed water, a Produced Water (PW) stream, or a combination thereof.

18. The method of claim 17, wherein the composition comprises a sulfate anion concentration below a sulfate concentration threshold.

19. The method of claim 15, wherein the mixing further comprises mixing at least a portion of an ion concentrate with the at least a portion of the RO permeate stream, the at least a portion of the nanofiltration permeate stream, the high salinity stream, or a combination thereof to provide the mixed low salinity water stream.

20. A method of controlling a composition of an injection fluid, the method comprising:

receiving, by a Supervisory Controller (SC) of a control system, one or more compositional parameter targets of an injection fluid; and

automatically adjusting a state of one or more valves within a desalination unit to generate an injection fluid that satisfies the one or more constituent parameters via communication from the supervisory controller to one or more Regulatory Controllers (RCs) of the control system that are in communication with the one or more valves.

21. The method of claim 20, wherein the one or more composition parameters comprise a total dissolved solids content of the injection fluid.

22. The method of claim 20, wherein

Automatically adjusting the state of the one or more valves includes adjusting one or more valves to change a flow rate of an RO permeate, an NF permeate, a PW flow, a feedwater bypass flow, an ion concentrate flow, or a combination thereof, mixed to provide the injection fluid.

Technical Field

The present disclosure relates to a process for providing low salinity injection water to an oil reservoir having a desired composition, and a desalination system for producing such injection water; more particularly, the present disclosure relates to a process and system for producing water having controlled low salinity, controlled sulfate anion concentration, and/or controlled multivalent cation concentration; in particular, the present disclosure relates to a process and system for producing water having controlled low salinity, controlled sulfate anion concentration, and/or controlled multivalent cation concentration via a computerized control system.

Background

As described in international patent application WO 2008/029124, which is incorporated herein by reference for the purpose of not violating the present disclosure, low salinity water can be injected into the oil-bearing layer of a reservoir to enhance the oil recovery from the reservoir.

A problem associated with low salinity water flooding is that desalination techniques can produce water at less than optimal salinity for continuous injection into oil bearing reservoirs during Enhanced Oil Recovery (EOR). In fact, desalinated water can damage the petroliferous rock formations of a reservoir and may inhibit oil production, for example, by causing the clay to swell or mobilize, thereby causing the clay to plug the formation. Thus, there is an optimum salinity of the injected water which both enhances oil recovery and reduces the risk of formation damage, and the optimum salinity varies from formation to formation and within a single reservoir as the rock composition varies spatially (in the vertical and/or lateral directions) throughout the reservoir. Typically, where an oil-bearing formation comprises rock containing high levels of swelling clay, when the total dissolved solids content (TDS) of the injected water is in the range 200 to 10000 ppm, for example 500 to 5000 ppm or 1000 to 5000 ppm, layer damage is avoided while still releasing oil from the formation.

Another problem associated with low salinity water flooding is that for reservoirs that are prone to acidizing or scaling, the sulfate level of the low salinity injection water should typically be controlled. It is well known that injection of water containing high levels of sulfate anions can stimulate the growth of sulfate-reducing bacteria, which produce hydrogen sulfide as a metabolite, leading to reservoir acidification. The scale formation is due to the deposition of mineral scale from the injection water containing sulfate mixed with connate water containing precipitation precursor cations (e.g., barium ions). If it is desired to reduce the risk of mineral scale formation, the level of sulphate anions in the miscellaneous water supply should be below 40 ppm. If it is desired to reduce the risk of acidification in the reservoir, the level of sulfate anions in the mixed water supply should be as low as possible, for example less than 7.5 ppm or less than 5 ppm.

Thus, due to the high sulfate anion content and/or the high multivalent cation content of high salinity water, it may not be desirable to mix desalinated water having a low multivalent cation content with high salinity water (e.g., seawater). The high sulfate anion content of such mixed water streams may lead to reservoir acidizing and/or precipitation of unacceptable levels of insoluble mineral salts (scale formation) when the injected water contacts precipitation precursor cations (such as barium, strontium, and calcium cations) that are typically present in the connate water of the formation. Furthermore, commingling desalinated water with high salinity water (e.g., seawater) can result in an unacceptably high level of multivalent cations, particularly calcium and magnesium cations, in the commingled water stream. In an embodiment, to achieve incremental oil recovery using a low salinity waterflood, the ratio of the multivalent cation concentration in the low salinity waterflood to the multivalent cation concentration in the connate water of the reservoir should be less than 1, and sometimes may even be lower, such as less than 0.9, less than 0.8, less than 0.6, or less than 0.5.

As described in international patent application WO 2007/138327, which is incorporated herein by reference for the purpose of not violating the present disclosure, is a method of increasing the salinity of an ultra-low salinity water supply by mixing with high salinity water. According to WO 2007/138327, this can be achieved by: substantially desalinating the first feedwater supply to provide a first treated water supply having low salinity; treating the second feedwater supply to provide a second treated water supply having a reduced divalent ion concentration and a higher salinity than the first treated water supply as compared to the second feedwater supply; and blending the first treated water supply and the second treated water supply to provide a blended water supply having a desired salinity suitable for injection into the oil-bearing reservoir.

In the embodiment of invention WO 2007/138327, the first feed water supply is substantially desalinated by a reverse osmosis process, while in the embodiment the step of treating the second feed water supply is performed by nanofiltration. Nanofiltration is commonly used in the petroleum industry to remove sulfate ions from source water. The treated water can then be injected into the formation without the risk of forming unacceptable levels of insoluble mineral salts when the injected water contacts the precipitated precursor cations present in the connate water of the formation. The invention WO 2007/138327 thus allows for the supply of hybrid water having a desired salinity suitable for injection into an oil-bearing reservoir and having a reduced level of sulphate anions to reduce the risk of acidification and precipitation of mineral structures in the formation or production well.

Disclosure of Invention

Disclosed herein is a control system configured to control operation of one or more Reverse Osmosis (RO) arrays, one or more Nanofiltration (NF) arrays, mixing systems, or combinations thereof, within a desalination unit, wherein the control system comprises: a Control Panel (CP); a plurality of Regulation Controllers (RC); and a Supervisory Controller (SC), wherein the SC is in signal communication with the CP and with each of the plurality of RCs, wherein the SC is configured to: receiving user input from a CP and input from a plurality of RCs regarding data from a plurality of sensors within a desalination device, wherein each of the plurality of RCs is in signal communication with the plurality of sensors, wherein the plurality of RCs are configured to: receive data from one or more of the plurality of sensors, provide an output to the SC and receive a permission from the SC, and instruct one or more of the plurality of devices of the desalination apparatus in response to the permission received from the SC, and wherein the SC is configured to: trends of input regarding data received from the plurality of RCs are monitored and/or results are predicted from the data, and permissions of each RC are determined based on the monitored trends, user input from the CP, or a combination thereof.

Also disclosed herein is a desalination apparatus comprising: a water inlet line; one or more Reverse Osmosis (RO) arrays in fluid communication with the water inlet line, wherein each of the one or more RO arrays is configured to receive RO feedwater and generate an RO permeate and an RO concentrate; a Nanofiltration (NF) array in fluid communication with the water inlet line, the one or more RO arrays, or both, wherein the NF array is configured to generate a NF permeate and a NF concentrate; a mixing system, wherein the mixing system comprises: an RO permeate feed line, an NF permeate feed line, a mixing point configured to mix RO permeate from the RO permeate feed line and NF permeate from the NF permeate feed line to form a mixed low salinity injection water, and a discharge line configured to deliver the mixed low salinity injection water to the injection system; a plurality of valves and pumps configured to regulate the flow rate or pressure of various streams within the desalination device; a plurality of sensors configured to measure flow rate, pressure, temperature, composition, or a combination thereof, of various streams within the desalination device; a control system, wherein the control system is configured to: controlling operation of the one or more RO arrays, NF arrays, and mixing system to be within operating parameters and maintaining composition of the mixed low salinity injection water within an operating envelope, wherein the control system comprises a plurality of Regulating Controllers (RC), a monitoring controller (SC) and a control panel, wherein a SC is in electronic communication with each of a plurality of RCs and with a CP, the SC receiving user input from the CP and input from the RCs regarding data of a sensor, wherein each of the plurality of RCs receives data from one or more of the plurality of sensors, provides output to the SC and receives permission from the SC, and indicating one or more of the plurality of valves and pumps in response to the permission received from the SC, and wherein the SC monitors trends in inputs received from the plurality of RCs and determines permissions for each RC based on the monitored trends, user inputs from the control panel, or a combination thereof.

Further disclosed herein is a method of generating injection water, the method comprising: generating a reverse osmosis permeate stream; generating a nanofiltration permeate stream; mixing at least a portion of the reverse osmosis permeate stream with at least a portion of the nanofiltration permeate stream, the high salinity stream, or a combination thereof to provide a mixed low salinity water stream; and, controlling the generation of the RO permeate stream, the NF permeate stream and the mixture within the operating parameters and maintaining the composition of the mixed low salinity water stream within the operating envelope via a control system, wherein the control system comprises a Supervisory Controller (SC), a control panel and a plurality of Regulatory Controllers (RCs), wherein SC is in signal communication with the CP and with each of the plurality of RCs, the SC receiving user input from the CP and input from the RCs regarding data from a plurality of sensors. Wherein each of the plurality of RCs receives data from one or more of the plurality of sensors, provides an output to the SC and receives permission from the SC, and indicates one or more of the plurality of valves and pumps in response to the permission received from the SC, and wherein the SC monitors trends in input regarding the data received from the plurality of RCs and determines the permission for each RC based on the monitored trends, user input from a control panel, or a combination thereof.

Also disclosed herein is a method of controlling the composition of an injection fluid, the method comprising: receiving, by a Supervisory Controller (SC) of a control system, one or more compositional parameter targets of an injection fluid; and automatically adjusting the state of one or more valves to generate an injection fluid meeting the one or more constituent parameters via communication from the supervisory controller to one or more Regulatory Controllers (RCs) of the control system in communication with the one or more valves within the desalination unit.

While various embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description. As will be apparent, certain embodiments disclosed herein can be modified in various respects, all without departing from the spirit and scope of the claims set forth herein. The following detailed description is, therefore, to be regarded as illustrative in nature and not as restrictive.

Drawings

The following figures illustrate embodiments of the subject matter disclosed herein. The claimed subject matter can be understood by reference to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a desalination system operable via a computerized control system according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a desalination system operable via a computerized control system, according to an embodiment of the present disclosure;

FIG. 3 is a schematic diagram of an ultrafiltration section of a desalination system operable via a computerized control system, according to an embodiment of the present disclosure; and

fig. 4 is a schematic diagram of a control system according to an embodiment of the present disclosure.

Detailed Description

Throughout the following description, the following terms are referred to:

as used herein, the term "membrane" refers to an element used for Microfiltration (MF), Ultrafiltration (UF), Reverse Osmosis (RO), or Nanofiltration (NF). Technically, MF/UF elements can be classified as filters, but for simplicity they are referred to herein as membranes.

"Low salinity water" is water resulting from the removal of at least a portion of salts (e.g., NaCl) or other Total Dissolved Solids (TDS) from high salinity feed water or Produced Water (PW). As used herein, the low salinity water can be water having a salinity or TDS content of less than 10,000, 7,500, or 5,000, or in the range of from 200 to 10,000, from 500 to 5,000, or from 1,000 to 5,000 ppm.

The "high salinity feed water" is the feed water for the desalination unit and is typically Seawater (SW), estuary water, aquifer water, or mixtures thereof.

"softened water" is water resulting from the removal of at least some amount of hardness ions (e.g., multivalent cations including magnesium and calcium) from a high salinity feed water or PW.

An "Ultrafiltration (UF) filtration unit" includes a pressure vessel containing one or more UF elements, such as between 1 and 8 membrane elements, between 1 and 4, or between 4 and 8 UF membrane elements.

A "Reverse Osmosis (RO) filtration unit" comprises a pressure vessel, alternatively referred to as a housing, and containing one or more RO membrane elements, for example between 1 and 8 RO membrane elements, or between 4 and 8 RO membrane elements.

A "Nanofiltration (NF) filtration unit" comprises a pressure vessel containing one or more NF elements, for example between 1 and 8 membrane elements or between 4 and 8 NF membrane elements.

A Reverse Osmosis (RO) "stage" or "array" of a desalination plant is a group of RO filtration units connected together in parallel. Similarly, a Nanofiltration (NF) "stage" or "array" of a desalination plant is a group of NF filtration units connected together in parallel.

"membrane blocks" include RO and NF filtration stages connected together to provide concentrate fractionation and typically share common valves and piping. One membrane block or two or more membrane blocks may be mounted on a membrane stack (skin).

"connate water" is water that is present in the pore space of the oil-bearing formation of a reservoir.

A "water-driving fluid" is an aqueous fluid that may be injected into an injection well after injection of a low Pore Volume (PV) slug of mixed low salinity injection water.

"reservoir" is a term well known to those skilled in the art and refers to a portion of a reservoir rock formation that has increased oil saturation due to the application of an enhanced oil recovery process for immobile oil.

"swept Pore Volume (PVR)" refers to the pore volume of a layer of reservoir rock where the injection fluids (low salinity injection water and any water driving fluids) are swept between the injection well and the production well, averaged over all flow paths between the injection well and the production well. Where an injection well has two or more associated production wells, the term "swept pore volume" means the pore volume of a layer of reservoir rock swept by an injection fluid between the injection well and its associated production well.

A "slug" is a low pore volume of fluid injected into the oil-bearing formation of a reservoir. The values of pore volume given for the slug of low salinity injection water are based on the swept Pore Volume (PVR) of the reservoir rock strata.

"TDS content" is the total dissolved solids content of the water stream and is typically in units of mg/L.

The unit "pmv" is parts per million on a volume basis and is equivalent to the unit "mg/L". Unless otherwise specified, "ppm" when used herein means "ppmv".

The present disclosure relates to a computerized control system having a plurality of controllers for providing a mixed or "mixed" water flow of controlled composition (e.g., salinity, sulfate anion content, etc.) suitable as an injection water for a low salinity waterflood while mitigating risk of formation damage and/or controlling acidizing in the reservoir. The desired composition of the mixed injection water can vary during operation of the desalination apparatus, for example, during commissioning of a well. The computerized control systems and methods described herein may be used to control the operating conditions of such desalination processes or devices.

The computerized control system and method of the present disclosure can be used to control the operation of a desalination plant having a distributed control scheme. Fig. 1 is a schematic diagram of a desalination system I operable via a computerized control system according to an embodiment of the present disclosure. Although reference is made to low salinity EOR injection water, the computerized control system disclosed herein may also be used to control the generation of softened water, in embodiments wherein the "desalination" system or apparatus comprises a water softening system or apparatus.

The desalination apparatus comprises: RO/NF membrane block 1 of a desalination plant for treating feed water 2 (typically seawater); a mixing system comprised of various flow lines for forming a mixed low salinity injection water stream having a variable composition; one or more control units or systems 52 for controlling the operation of the desalination unit and for controlling the mixing of the low salinity injection water stream in the mixing system; an optional concentrate tank 50 and pump 25 for clay stabilization concentrate; and an injection system for injecting well 20. Although referred to as a RO/NF membrane block 1, in embodiments, only RO or only NF may be contained within the RO/NF membrane block 1. That is, in an embodiment, RO/NF can mean RO only, NF only, or a combination of RO and NF.

The membrane block 1 of the desalination system I of the embodiment of fig. 1 comprises a feed pump 3, an RO array 4 and an NF array 5. Each array may be a single or multi-stage array. The RO array 4 comprises a plurality of RO units. The NF array 5 includes a plurality of NF units. Typically, the number of units of the RO and NF arrays is selected to match the required production capacity of the RO and NF permeates 9, 13 for injection into the water stream 18 during the main stage of the low salinity waterflood. The desalination unit may also be provided with a bypass line 17 for feed water 2, a line 17a for a mixture of Produced Water (PW) and RO/NF water, or both. Both the RO array and the NF array may have the same feed water (e.g., SW or Ultrafiltration (UF) water), as shown in fig. 1. However, it is also contemplated that the RO concentrate (also referred to in the art as "retentate") from a first RO stage or array may be split to form a feed stream for a second RO stage or array and for the NF array, as shown in the embodiment of fig. 2, described further below.

In the configuration of fig. 1, the feed pump 3 pumps feed water 2 to the RO array 4 where the feed water is separated into RO permeate (which flows through RO permeate line 9) and RO concentrate (which flows through RO concentrate line 8), and pumps feed water 2 to the NF array 5 via feed line 12 where the feed water is separated into NF permeate (which flows through NF permeate feed line 13) and NF concentrate (which flows through NF concentrate line 7). Because NF units typically operate at a lower pressure than RO units, the pressure of the feed water to the RO and NF arrays may be adjusted (e.g. using a booster pump for the RO feed or a pressure reducing valve (e.g. valve V7) for the NF feed) to match the operating pressures of the RO units of RO array 4 and the NF units of NF array 5. Optionally, the feed pump 3 pumps a portion of the feed water (e.g., SW) through the bypass line 17 to the mixing system.

Valves V1 and V2 may be at least partially opened to provide for the discharge of RO concentrate line 8 and NF concentrate line 7, respectively, from the desalter. Typically, the RO concentrate and NF concentrate blowdown streams are discharged to a body of water (e.g., sea) via lines 8 and 7 and valves V1 and V2, respectively. The NF permeate may be injected into the RO permeate line 9 in a mixing system to form a combined RO/NF permeate stream that flows through the RO/NF permeate stream line 16. Optionally, the combined RO/NF permeate stream also comprises SW, PW and/or clay stabilising concentrate (which is added via feed lines 17, 17a and/or 26 respectively).

Fluid produced from the production wells is transported to a production facility, which may optionally be connected to a main production line. The produced fluid is separated in the production facility into an oil stream, a gaseous stream and a Produced Water (PW) stream. Part or all of the PW stream may be mixed with a low RO/NF stream (e.g., in PW mixing line 17 a) to provide a mixed low salinity injection water in line 18.

The control unit 52, described in detail below, may monitor the pressure sensor 23 for any pressure increase in the injection well 20 near an oil-bearing formation section in a region 22 of the reservoir. Alternatively or additionally, control unit 52 may monitor a flow sensor Q9 located downstream of infusion pump 24 for any decrease in flow rate. Both an increase in pressure in the injection well and a decrease in flow rate downstream of injection pump 24 may indicate an unacceptable decline in injectivity due to formation damage. The values of the maximum allowable increase in pressure in the injection well 20 and/or the maximum allowable decrease in flow rate in the injection line 58 may be input into the control unit 52 (e.g., into its supervisory controller 55), where they are correlated to an acceptable reduction in injectability. If the pressure in the injection well 20 adjacent the oil-bearing interval increases to a value near or at which the maximum allowable increase in pressure is reached or the flow rate downstream of the injection pump in injection line 58 decreases to a value near or at which the maximum allowable decrease in flow rate is reached, the control unit 52 may select a preferred operating envelope for mixing the components of the low salinity injection water stream that is predicted to reduce the risk of formation damage in the oil-bearing zone of the reservoir or in the zone of the interval 22. For example, a preferred operating envelope for mixing the components of the low salinity injection water may be defined by one or more of: larger boundary values for TDS; larger border values for divalent cation content (in particular calcium cation content); alternatively, a larger boundary value for the one or more clay stabilizer additives. The control unit 52 may then control (as described in detail below) the operation of the desalter to adjust the composition of the combined RO/NF permeate stream line 16 so that the mixed low salinity injection water has a composition that falls within the preferred operating envelope of the zone of the oil-bearing layer of the reservoir. This may be accomplished, for example, by the control unit 52 sending instructions to: increasing the amount of RO permeate poured through RO permeate pouring line 11 by increasing the degree of opening of throttle valve V4; increasing the amount of SW mixed with the combined RO/NF permeate stream by increasing the degree of opening of throttle valve V5, whereby the mixing increases the divalent cation content of the low salinity injection water stream; increasing the amount of PW mixed with the combined RO/NF permeate stream by increasing the degree of opening of throttle valve V6, whereby the mixing increases the divalent cation content of the low salinity injection water stream; and/or increasing the amount of clay stabilizing concentrate in the mixed low salinity water stream 18 by increasing the degree of opening of the throttling valve V10. The control unit 52 may monitor the effect of operational changes to the desalination apparatus on the flow rate or composition of the low salinity injection water stream 18 (by using flow rate sensors Q9 and/or Q10 and sensor S7, respectively) in order to determine whether adjustments to the operation of the apparatus result in the flow rate and composition of the mixed low salinity injection water falling within the preferred operating envelope for the region of the reservoir, and if necessary, further adjustments to the operation of the apparatus may be made in order to achieve the composition within a more preferred operating envelope that further ensures resistance to the risk of formation damage. Thus, the computerized control system of the present disclosure utilizes a control unit 52 with a feedback loop that enables the system to generate a mixed low salinity injection water stream having a composition that avoids or mitigates the risk of formation damage in the region of the oil-bearing layer of the reservoir.

After the low pore volume slug of mixed low salinity injection water has been injected into the injection well 20, a water-driving fluid, for example, Produced Water (PW) or a mixture of SW and PW, may be injected into the injection well 20 via injection line 58 for driving the low pore volume slug and thus the released reservoir toward the production well. Thus, the RO permeate and NF permeate streams are no longer required for the injection wells 20 and may be diverted to generate a mixed low salinity injection water for at least one injection well that penetrates another region of the reservoir.

The mixing ratio of the NF permeate stream to the RO permeate stream can be adjusted by varying the composition of the injection water pumped into the injection well 20 via one or more injection pumps 24 by varying the degree of opening of the throttle valve on either the RO permeate dump line 11 (valve V4) or the NF permeate dump line 10 (valve V3).

Figure 2 shows a more complex desalination system II for providing a mixed or mixed water stream with controlled composition for use as injection water for a low salinity waterflood, while mitigating the risk of formation damage and controlling acidizing in the reservoir. The system II includes RO/NF membrane blocks 1 of a desalination unit for treating feed water 2. In the embodiment of fig. 2, the membrane block 1 comprises a feed pump 3, an RO section comprising a first RO array or stage 4A and a second RO array or stage 4B, and an NF array or stage comprising a single NF stage 5. Each RO array or stage 4A/4B comprises a plurality of RO units. The NF array or stage 5 comprises a plurality of NF units. In order to maintain improved or optimal operation of the membrane separation process, the second RO array or stage 4B typically comprises fewer RO units than the first RO array or stage 4A.

The membrane block 1 of the embodiment of fig. 1 and 2 includes various valves V1-V10 and various conduits configured to provide the flow paths described herein. In an embodiment, valves V1-V6 and V10 can be throttle valves, which can be set to various intermediate positions, while valve V7 can be a pressure relief valve. The flow and pressure through the membrane block 1 may be controlled by the feed pump 3, valves V1 to V9, or a combination thereof. In an embodiment, various flow rate sensors Q1-Q16 are provided to determine the flow rates in the various lines in the desalination systems I and I of fig. 1 and 2. The flow rate data is sent to its control system 52 (e.g., to its regulator controller 56 (RC 56), as described further below) via an electrical signal line (dashed line in fig. 1 and 2). Sensors S1-S11 are also provided to determine the composition (e.g., total concentration of TDS, concentration of individual ions, such as determined by measuring conductivity), temperature, pressure, or a combination thereof within the respective flow lines. The sensed data can be sent to the control system 52 (e.g., the RC56 of the control system 52, as described below) via an electrical signal line or wirelessly.

In the configuration of fig. 2, the feed pump 3 pumps the feed water 2 to the first RO stage or array 4A where the feed water 2 is separated into a first stage RO permeate 9 and a first stage or array RO concentrate 8 a. Optionally, the feed pump 3 pumps a portion of the feed water (SW) through the SW bypass line 17. The first stage or array RO concentrate 8a is split at a branch point into a feed 2B forming a second RO stage or array 4B and a feed line 12 for the NF stage or array 5. As described below, the flow and pressure through the membrane block 1 may be adjusted (via the computerized control system and control unit 52 disclosed herein) so that the pressure of the feed 2B to the second RO array or stage 4B matches the operating pressure of the second RO stage or array 4B. The pressure of the feed in the feed line 12 to the NF stage or array 5 may be adjusted (e.g., by using a pressure relief valve V7) to match the operating pressure of the NF stage or array 5. The pressure of the feed 8B to the second RO array or stage 4B may be increased above the minimum operating pressure of the second RO array or stage 4B by using a booster pump, if necessary. Alternatively, a back pressure valve or restrictive orifice may be located on the conduit of the first stage or array RO permeate 9 in order to increase the pressure of the first array or stage RO concentrate 8a above the minimum operating pressure of the second RO stage or array 4B.

The second RO stage or array 4B separates feed 2B into a second stage or array RO permeate line 27 and a second stage or array RO concentrate 8B that is discharged from the membrane block 1. Thus, in an embodiment, valve V8 can be at least partially opened to provide for the bleed of the second RO array or stage RO concentrate 8 b. The second stage or array RO permeate in the second stage or array RO permeate line 27 is then combined with the first stage or array RO permeate 9 to form the combined RO permeate stream 14.

The NF stage or array 5 separates the feed in feed line 12 into NF permeate 13 and NF concentrate 7 discharged from the membrane block 1. Thus, in an embodiment, the valve V2 can be at least partially opened to provide a bleed of the NF concentrate 7. The NF permeate 13 is then injected into the combined RO permeate 14 to form the RO/NF permeate stream line 16.

The mixing ratio of the NF permeate stream to the RO permeate stream can be adjusted, for example via the computerized system disclosed herein, by varying the degree of opening of a throttle valve (valve V4) on the RO permeate dump line 11 or a throttle valve (V3) on the NF permeate dump line 10 to vary the composition of the injection water pumped into the injection well 20 via one or more injection pumps 24.

As discussed herein, a planned concentration profile of the reduction in TDS concentration (or a planned concentration profile for changing the concentration of one or more ions in the injection water) can be input to the control system 52 (e.g., via the control panel 53, which is described below). The control system 52 monitors the pressure near the hydrocarbon containing interval 22 of the injection well 20 by using the pressure sensor 23 or, for a decrease in flow rate, a flow sensor Q9 located downstream of the injection pump 24 of the injection system (both of which indicate a decrease in injectivity due to formation damage). The control system 52 then changes the composition of the injection water 18 in response to an unacceptable reduction in injectability, such as by increasing the TDS concentration of the injection water 18, increasing the divalent cation content (specifically the calcium cation content) of the injection water 18 by mixing an increased amount of SW and/or PW via the feed water bypass line 17 and/or PW mixing line 17a, and/or by adding an increased amount of clay stabilization concentrate from the concentrate tank 50 to the RO/NF permeate stream line 16 via the pump 25. In an embodiment, the composition of the injection water 18 is determined by using the sensor S7. In an embodiment, the change in composition is automatic such that the composition is controlled in real time along a planned concentration profile for achieving the target composition of the low salinity water during the main phase of the low salinity waterflood (which is input into the control unit 52 as described below) or along a planned concentration profile for addressing the abnormal condition (which is input into the control unit 52). The abnormal condition may include a decrease in injectivity as evidenced by a decrease in flow rate at sensor Q9/Q10 or an increase in pressure in the wellbore of the injection well 20 near the hydrocarbon containing region or interval 22 of the reservoir. An upper limit for the flow rate decrease or pressure increase can also be input into the control system 52 (e.g., via a Control Panel (CP) 53, which is described in more detail below). The control system 52 (e.g., its supervisory controller 55, described in detail below) may send instructions (e.g., to one or more Regulating Controllers (RCs) 56) to change the mixing ratio of the RO permeate 9 and the NF permeate 13 by changing the degree of opening of the throttling valves V4 and/or V3 to achieve a planned concentration profile or to address an abnormal condition. The control unit or system 52 may also manipulate the concentration of individual ions in the injected water 18 as described in detail below by controlling the amount of feedwater that is optionally intermixed with the RO permeate 9 and NF permeate 13 mixed stream 14 and the amount of any optional clay stabilizing concentrate (including clay stabilizing ions) that is intermixed with this stream to form the injected water stream 18.

The feed water in line 2 of fig. 1 and 2 may be ultra-filtered (UF) water, such as ultra-filtered Seawater (SW). In such embodiments, the desalination system I, II controlled via the computerized control system disclosed herein may therefore further comprise an ultrafiltration section configured to subject the high salinity feedwater to ultrafiltration. For example, FIG. 3 shows a UF section III that includes 8 stacks of ultrafiltration membranes 40A-40H. Each UF membrane stack 40A-40H houses a plurality of UF containers or units, and each UF unit or container houses a plurality of UF elements or filters. The UF units and membranes may be any known to those of skill in the art. In an embodiment, the UF unit or membrane comprises a dead-end membrane (dead-end membrane), as shown in the application of international patent application No. PCT/EP2017/067443 and disclosed as WO/2018/015223, the disclosure of which is incorporated herein in its entirety for purposes not contrary to the present disclosure.

Within the UF membrane stack, particulates are removed from feedwater introduced via UF feedwater inlet line 34 to provide UF filtered water removed from the UF membrane stack via UF outlet line 41. For example, feedwater may be introduced into UF membrane stacks 40A, 40B, 40C, 40D, 40E, 40F, 40G, 40H via lines 34A, 34B, 34C, 34D, 34E, 34F, 34G, 34H, respectively, and ultrafiltration water removed from UF membrane stacks 40A, 40B, 40C, 40D, 40E, 40F, 40G, 40H via UF outlet lines 41A, 41B, 41C, 41D, 41E, 41G, 41H, respectively. The UF water in UF outlet lines 41A, 41B, 41C, 41D, 41E, 41F, 41G, 41H may be combined to provide UF water in UF line 42. The feedwater in the feedwater line 34 may include Seawater (SW), brackish water, aquifer water, PW, or combinations thereof, and may be introduced to the UF membrane stack via one or more high-pressure pumps (e.g., seawater lift pumps), heat exchangers, and the like. For example, as shown in the embodiment of fig. 3, a portion 30a of the feedwater from the feedwater feed pump and coarse filter in line 30 can be passed through a heat exchanger 32 before being introduced into the UF membrane stack via line 34. Line 30b may be used to bypass heat exchanger 32. UF water may be stored in buffer tank 45 before being introduced via line 2 to downstream RO/NF membrane block 1 (of fig. 1 and 2). UF section III may include a plurality of pumps, valves V and/or sensors S and Q. For example, UF section III can include one or more of sensors S12, S13, S14, and Q17, valves V11, V12, and V13, as described further below. UF section III can remove a majority of suspended solids (e.g., 99% of suspended solids having a diameter greater than 0.02 micron) to provide UF water in line 42/2.

The desalination system controlled via the computerized control system disclosed herein includes a plurality of valves (e.g., valves V1-V13 of fig. 1-3) and various flow lines (conduits) configured to provide flow paths as described below. The valves V1-V13 may be throttle valves, and the degree of opening of the throttle valves (e.g., fully open position, fully closed position, or various intermediate positions) may be controlled by the control unit 52 (e.g., via its RC56, as described below) and described further below. For example, as described above, the control unit 52 may control the flow and pressure through the membrane block 1 by controlling the feed pump 3, the valves V1 to V13, or a combination thereof. For the sake of simplicity, electrical connections between the control unit 52 and the various units it controls (such as, but not limited to, the feed pump 3 and the valves V1 to V13) are omitted from fig. 1-3. Further, as described below, in some embodiments, communication between the control unit 52 and the various units it controls may include wireless communication, such as Wi-Fi or Bluetooth. Desalination systems and methods according to the present disclosure may or may not include each valve shown in the figures, and may include additional valves not mentioned herein. As will be apparent to those skilled in the art.

The desalination system, which is controlled via the computerized control system disclosed herein, includes several sensors, which are shown as "S" and "Q" in the figures. For example, as described in more detail below with reference to the control system 52, the desalination system can include a plurality of flow rate sensors Q. In the embodiment of fig. 1-3, flow rate sensors Q1-Q17 are provided for determining flow rates in the various flow lines. The flow rate data may be sent from the flow rate sensors Q1-Q17 to the control unit 52 (e.g., to its RC56, as described further below) via electrical signal lines (dashed lines in fig. 1-3) or by wireless communication such as Wi-Fi or bluetooth communication. Desalination systems and methods according to the present disclosure may or may not include each flow rate sensor Q shown in the figures, and may include additional flow rate sensors not mentioned herein. As will be apparent to those skilled in the art. For example, the flow rate sensors Q1 and Q2 in the embodiment of fig. 1 on the RO concentrate line 8 and the NF concentrate line 7, respectively, may be omitted in embodiments.

As again described in more detail below with reference to the control system 52, the desalination system controlled via the computerized control systems and methods provided in the present disclosure can include a plurality of sensors S configured to measure other parameters within the desalination system, such as, but not limited to, temperature, pressure, flow rate, composition (e.g., concentration of Total Dissolved Solids (TDS), conductivity, concentration of individual ions, or ion type, such as multivalent cations or divalent cations, etc.) in various flow lines. For example, data can also be sent from the sensors S1-S14 of fig. 1-3 to the control unit 52 (e.g., to its RC56, as described below) via electrical signal lines (dashed lines shown in fig. 1-3) or by wireless communication such as Wi-Fi or bluetooth communication. Desalination systems and methods according to the present disclosure may or may not include each sensor S shown in the figures, and may include additional sensors not mentioned herein. As will be apparent to those skilled in the art. For example, sensors S4 and S5 on the NF concentrate line 7 and RO concentrate line 8, respectively, may be omitted. The sensor S6 on the optional clay stabilizer concentrate feed line 26 may also be omitted if the concentration of the additive in the concentrate tank has been measured before and remains stable over time (in which case the measured concentration of the additive in the concentrate may be input into the control unit 52). It is also contemplated that sensors S11, S2, and S3 on optional SW bypass line 17, RO permeate line 9, and NF permeate feed line 13, respectively, may be omitted when the composition of SW, RO permeate, and NF permeate is predicted to remain substantially constant over time.

According to an embodiment of the present disclosure, the control system 52 includes central control software. In an embodiment, there is a central computerized control system 52 for the desalination facility. As shown in fig. 4, which fig. 4 is an illustration of a control system 52, in an embodiment, the control system 52 includes a Control Panel (CP) 53, a supervisory controller (or high level controller) 55 that manages one or more regulatory controllers 56 (e.g., a first regulatory controller RC1 (56A), a second regulatory controller RC2 (56B), a third regulatory controller RC3 (56C) … …, an nth regulatory controller RCn (56 n)) in real time. The computerized control system 52 can include one or more supervisory controllers 55. For example, in an embodiment, another level of control is provided in which a plurality of supervisory controllers 55 communicate, for example, with a smaller number (e.g., a single) of master controllers. For example, the various controllers may control the operation of RO to generate a desired RO water, NF to generate a desired NF water, mixing to generate a desired mixed water (e.g., a desired RO/NF water optionally combined with SW, PW, and/or ion concentrate), and so forth. In an embodiment, the control system 52 can incorporate the capabilities of high-level control logic. For example, the control system 52 can include a digital model of the device from which the supervisory controller 55 can make predictions about the effects of actions and/or to normalize events in real time. In embodiments, the SC 55 references a process model that runs in real time, which allows the SC 55 to make changes to prevent parameter drift from occurring and/or to minimize the duration of drift by one or more controlled determinations.

The conditioning controller 56 is capable of controlling a single operation, such as opening and closing valves during operation of the various modules (UF, RO, and NF modules) and during cleaning cycles thereof. The regulator controller 56 is capable of maintaining various sensor readings at set point values or within predetermined ranges thereof. In addition to providing operational permissives to the regulatory controller 56, the supervisory controller 55 is also capable of providing data and set point values to the regulatory controller 56. For example, the supervisory controller 55 can instruct the regulator controller 56 when to open and close the valve and the rate at which the valve opens and closes. For example, if the supervisory controller 55 determines that the pressure in the line or the flow rate therein does not match a set limit, the supervisory controller 55 can intercede. This can be applied to a single regulator controller or a plurality of regulator controllers. For example, the supervisory controller 55 can intercede when the pressure in the upstream line is above or below a threshold or set point value and the upstream and/or downstream units are shut down (e.g., by not allowing operation of the regulator controller (s)). The central control system 52 is thus able to optimize the performance of the desalination unit I, II during online operation of the various modules. In an embodiment, the central control system 52 also controls the composition of the mixed RO permeate/NF permeate stream (within preset limits), and coordinates the Production Water (PW) mixing and/or the mixing of SW, clay stabilizer concentrate, or both, into the mixed RO permeate/NF permeate stream (within preset limits), as described herein.

The computerized control system 52 can therefore include a plurality of adjustment controllers 56. A throttle controller 56 may be associated with each module, e.g., throttle controller 56 may be configured to control the operation of each RO array, each NF array, etc. For example, the regulation controller may control the operation of a pump such as the high-pressure feed pump 3. Such a regulation controller can, for example, receive upstream and downstream pressure readings (as well as other inputs, such as temperature, threshold inputs, etc.). The regulator 56 may then control the pressure valve and/or the speed of the pump to control the pressure change across the pump or the final pressure downstream of the pump. In an embodiment, each primary process (e.g., UF, RO, NF, mixing, injection) of the desalination system I, II has its own regulator or supervisory controller.

A given conditioning controller 56 can be associated with and control the operation of a particular cell of the desalination system I, II. Each throttle controller is capable of operating as an I/O device, receiving input and providing output. Each regulator controller thus receives input from one or more sensors (e.g., from sensors S1-S14 configured to provide temperature, pressure, and/or composition values of the various process streams, and/or from flow rate sensors Q1-Q17 configured to provide flow rate values of the various process streams) and from supervisory controller 55. In response to the received inputs, each throttle controller 56 is operable to provide an output in response to the inputs. For example, the RC56 may be operable to effect positioning of the valve to an open, closed, or partially open position, to indicate pump operation or to cease operation, or a combination thereof. Thus, each RC56 may be connected with an associated unit (e.g., pump and/or valve) via a direct electrical connection or a radio connection (e.g., Wi-Fi, bluetooth).

As mentioned above with reference to the embodiments of fig. 1-3, various sensors (e.g., analog sensors) may be located within the UF and RO/NF sections and communicate with one or more conditioning controllers 56, which conditioning controllers 56 in turn communicate with a supervisory controller 55. For example, the RO sensors may include, but are not limited to, one or more sensors configured to measure and/or enable calculation (e.g., by adjusting the controller 56) of a feed pressure to the RO array (e.g., to the RO array 4 or the first RO array 4A), a rate of change of a feed pressure to the RO array (e.g., to the RO array 4, the first RO array 4A, and/or the second RO array 4B), a feed flow rate to the RO array (e.g., to the RO array 4, the first RO array 4A, and/or the second RO array 4B), a pressure of a concentrate from the RO array (e.g., from the RO array 4, the first RO array 4A, and/or the second RO array 4B), (e.g., a permeate pressure of a RO array permeate from the array 4, the first RO array 4A, and/or the second RO array 4B), differential pressure across the RO arrays (e.g., across RO array 4, first RO array 4A, and/or second RO array 4B), permeate conductivity of the RO arrays (e.g., RO array 4, first RO array 4A, and/or second RO array 4B), TDS of permeate from the RO arrays (e.g., from RO array 4, first RO array 4A, and/or second RO array 4B), pressure of concentrate from the RO arrays (e.g., from RO array 4, first RO array 4A, and/or second RO array 4B), temperature of permeate from the RO arrays (e.g., from RO array 4, first RO array 4A, second RO array 4B, combined RO permeate, e.g., in line 14), recovery factor of the RO arrays (e.g., calculated as a fraction of the difference between feed flow rate to the RO arrays and concentrate flow rate from the RO arrays relative to feed flow rate to the RO arrays), or a combination thereof. For example, as shown in the embodiment of fig. 1, the one or more sensors S1 may be configured to measure and/or enable calculation (e.g., by RC 56) of a feed pressure to an RO array (e.g., RO array 4), a rate of change of the feed pressure to the RO array 4, or a combination thereof; the one or more sensors S2 may be configured to measure and/or enable calculation (e.g., by RC 56) of pressure of the permeate from RO array 4, conductivity of the permeate from RO array 4, TDS of the permeate from RO array 4, temperature of the permeate from RO array 4, or a combination thereof; the one or more sensors S5 may be configured to measure and/or enable calculation (e.g., by RC 56) of the pressure of the concentrate from RO array 4; one or more flow rate sensors Q14 may be configured to measure and/or enable calculation (e.g., by RC 56) of the feed flow rate to RO array 4; one or more flow rate sensors Q1 may be configured to measure and/or enable calculation (e.g., by RC 56) of the flow rate of concentrate from RO array 4; one or more flow rate sensors Q4 may be configured to measure and/or enable calculation (e.g., by RC 56) of the flow rate of RO permeate dumped via RO permeate dump line 11 and RO permeate dump valve V4; one or more flow rate sensors Q6 may be configured to measure and/or enable calculation (e.g., by RC 56) of the flow rate of RO permeate in RO permeate line 9; or a combination thereof.

In the embodiment of fig. 2, the one or more sensors S1 may be configured to measure and/or enable calculation (e.g., by RC 56) of the feed pressure to the first RO array 4A, the rate of change of the feed pressure to the first RO array 4A, or a combination thereof; the one or more sensors S5 may be configured to measure and/or enable calculation (e.g., by adjusting the controller 56) of the pressure of the concentrate from the first RO array 4A, the feed pressure to the second RO array 4B, the rate of change of the feed pressure to the second RO array 4B, or a combination thereof; the one or more sensors S2 may be configured to measure and/or enable calculation (e.g., by the adjustment controller 56) of a pressure of the permeate from the first RO array 4A, a conductivity of the permeate from the first RO array 4A, a TDS of the permeate from the first RO array 4A, a temperature of the permeate from the first RO array 4A, or a combination thereof; the one or more sensors S9 may be configured to measure and/or enable calculation (e.g., by the adjustment controller 56) of a pressure of the permeate from the second RO array 4B, a conductivity of the permeate from the second RO array 4B, a TDS of the permeate from the second RO array 4B, a temperature of the permeate from the second RO array 4B, or a combination thereof; one or more flow rate sensors Q14 may be configured to measure and/or calculate a feed flow rate to first RO array 4A; one or more flow rate sensors Q12 may be configured to measure and/or enable calculation (e.g., by the adjustment controller 56) of the flow rate of concentrate from the second RO array 4B; one or more flow rate sensors Q4 may be configured to measure and/or enable calculation (e.g., by adjusting the controller 56) of the flow rate of RO permeate being dumped via RO permeate dump line 11 and RO permeate dump valve V4; the one or more flow rate sensors Q6 may be configured to measure and/or enable calculation (e.g., by the adjustment controller 56) of the flow rate of the RO permeate in the combined RO permeate line 14; one or more flow rate sensors Q16 may be configured to measure and/or enable calculation (e.g., by the tuning controller 56) of the flow rate of the feed material to the second RO array 4B; or a combination thereof.

By way of non-limiting example, the NF sensors (which may provide input to the tuning controller 56) may include, but are not limited to, one or more sensors configured to measure and/or enable calculation (e.g., by the tuning controller 56) of: a feed pressure to the NF array, a permeate pressure from the NF array, a permeate conductivity from the NF array, a TDS of a permeate from the NF array, a pressure of a concentrate from the NF array, a flow rate of a concentrate from the NF array, a differential pressure across the NF array, a rate of change of the feed pressure to the NF array, a recovery factor of the NF array (e.g., calculated as a fraction of a difference between a feed flow rate to the NF array and a concentrate flow rate from the NF array relative to a feed flow rate to the NF array), or a combination thereof.

For example, as shown in the embodiments of fig. 1 and 2, the one or more sensors S3 may be configured to measure and/or calculate a pressure of the permeate from the NF array 5, a conductivity of the permeate from the NF array 5, a TDS of the permeate from the NF array 5, a temperature of the permeate from the NF array 5, or a combination thereof; the one or more sensors S4 may be configured to measure and/or enable calculation (e.g., by the RC 56) of the pressure of the concentrate from the NF array 5; the one or more sensors S10 may be configured to measure and/or enable calculation (e.g., by the RC 56) of a feed pressure to the NF array 5, a rate of change of the feed pressure to the NF array 5, or a combination thereof; one or more flow rate sensors Q15 may be configured to measure and/or enable calculation (e.g., by RC 56) of the feed flow rate to NF array 5; one or more flow rate sensors Q2 may be configured to measure and/or enable calculation (e.g., by RC 56) of the flow rate of the concentrate from NF array 5; one or more flow rate sensors Q3 may be configured to measure and/or enable calculation (e.g., by adjusting controller 56) of the flow rate of NF permeate dumped via NF permeate dump line 10 and NF permeate dump valve V3; one or more flow rate sensors Q7 may be configured to measure and/or enable calculation (e.g., by adjusting the controller 56) of the flow rate of the NF permeate in the NF permeate line 13; or a combination thereof.

As shown in fig. 1, the sensor S6 may be configured to provide and/or enable calculation (e.g., by the RC 56) of the composition, temperature, pressure, or a combination thereof of the concentrate stream in the concentrate line 26 from the concentrate tank 50, and the flow rate sensor Q8 may be configured to measure and/or enable calculation (e.g., by the RC 56) of the flow rate in the concentrate line 26 from the concentrate pump 25. One or more sensors S7 may be configured to measure and/or enable calculation (e.g., by RC 56) of the temperature, pressure, and/or composition of the low salinity injection water stream from the low salinity EOR water line 18, and the flow rate sensor Q10 may be configured to measure and/or enable calculation (e.g., by RC 56) of the flow rate therein. When desalination system I, II provides low salinity mixed EOR water that includes RO/NF (e.g., RO and/or NF water) water combined with Seawater (SW) and/or Produced Water (PW), one or more sensors S11 may be configured to measure and/or enable calculation (e.g., by RC 56) of the temperature, pressure, and/or composition of the seawater in SW bypass line 17, flow rate sensor Q5 may be configured to measure and/or enable calculation (e.g., by RC 56) of the flow rate of the seawater from SW bypass line 17, one or more sensors S8 may be configured to measure and/or enable calculation (e.g., by RC 56) of the temperature, pressure, and/or composition of the produced water in PW line 17a, sensor Q11 may be configured to measure and/or enable calculation (e.g., through RC 56) the flow rate of produced water in PW line 17a, or a combination thereof.

By way of example, UF sensors (which provide input to RC 56) may include, but are not limited to, one or more sensors configured to measure and/or enable calculation (e.g., by RC 56) of: a feed pressure to UF, a feed flow to UF, a header backwash pressure to UF, a filtrate pressure from UF, a UF differential pressure, a rate of change of the UF transmembrane pressure, or a combination thereof. For example, as shown in the embodiment of fig. 3, one or more sensors S12 may be configured to measure and/or enable calculation (e.g., by RC 56) of the temperature in UF feed line 34; one or more sensors S13 may be configured to measure and/or enable calculation (e.g., by RC 56) of the pressure in UF feed line 34; one or more sensors S14 may be configured to measure and/or enable calculation (e.g., by RC 56) of the pressure in UF filtrate line 41; one or more flow rate sensors Q17 may be configured to measure and/or enable calculation (e.g., by RC 56) of the flow rate in UF feed line 34; or a combination thereof.

In response to input from sensors (S, Q) and/or SC 55, RC56 may be operable to position one or more valves to an open, closed, or partially open position. For example, one or more RO/NF or mixing valves may be configured to control the flow rate of the RO feed, RO permeate, NF permeate, RO concentrate, NF concentrate, PW mixed into the low salinity EOR water, SW mixed into the low salinity EOR water, concentrate mixed into the low salinity EOR water, poured RO permeate water, poured NF permeate water, or a combination thereof. For example, as shown in the embodiments of fig. 1 and 2, one or more valves V9 may control the flow rate of the high pressure high salinity water in line 2; one or more valves V1 may control the flow of RO concentrate in RO concentrate line 8/8 a; one or more valves V2 may control the flow of NF concentrate in the NF concentrate line 7; one or more valves V3 may control the flow of NF permeate in the NF permeate dump line 10; one or more valves V4 may control the flow of RO permeate in the RO permeate dump line 11; one or more valves V5 may control the flow of SW in SW bypass line 17; one or more valves V6 may control the flow of PW in PW mixing line 17 a; one or more valves V7 may control the flow and/or pressure of the feedwater to NF 5; one or more valves V8 may control the flow of RO concentrate from the second RO array 4B; one or more valves V10 may control the flow of PW in PW mixing line 17 a; or a combination thereof.

For example, one or more UF valves may be configured to control the flow rate of the UF feed, the flow rate around heat exchanger 32, UF backwash, or a combination thereof. For example, in the embodiment of fig. 3, one or more valves V11 may be configured to control a bypass around heat exchanger 32; one or more valves V12 may be configured to control flow into each UF membrane stack 40A/40B/40C/40D/40E/40F/40G/40H; one or more valves V13 may be configured to control the flow of Backwash (BW) into each UF membrane stack; or a combination thereof.

RC56 may also provide an output to SC 55 indicating the "state" or "mode" of the associated cell. For example, a UF mode can include options such as UF maintenance, UF off, UF standby, UF operation, UF backwash, UF chlorine-enhanced backwash (CEB), UF cleaning (e.g., field chemical cleaning or CIP), UF emptying (e.g., emptying a stack of UF membranes), UF filling (e.g., filling a stack of UF membranes with water), UF integrity testing (e.g., testing the condition of the membrane fibers), UF preservation/antifreeze (e.g., adding preservative chemicals), preserved UF (e.g., membranes at preservation conditions), UF leave preservation (e.g., flushing preservative chemicals), and so forth. Similarly, RO/NF states or modes may include RO/NF maintenance, RO/NF off, RO/NF standby, RO/NF operation, RO/NF online sterilization, RO/NF flushing, RO/NF array cleaning using CIP (e.g., first RO array CIP, second RO array CIP, NF array CIP, etc.), RO/NF preservation/freeze protection (e.g., first RO array preservation/freeze protection, second RO array preservation/freeze protection, and/or NF array preservation/freeze protection), preserved RO/NF (e.g., first RO array preserved/freeze protection, second RO array preserved/freeze protection, NF array preserved/freeze protection, etc.), RO/NF leave-preservation (e.g., first RO array leave-freeze protection, second RO array leave-preservation/freeze protection, etc.), RO/NF leave-freeze protection (e.g., first RO array leave-freeze protection, second RO array leave-freeze protection/freeze protection, etc.), RO/NF leave-freeze protection, NF array away preservation/freeze protection), etc. The mode may indicate to the SC 55 whether the associated cell is healthy.

Generally, the low salinity generating system loses pressure. For example, for RO and NF membrane stacks producing mixed low salinity RO/NF injection water, typically about 50 percent of the permeate fluid is recovered, with the remainder being the retentate; as the temperature of the system decreases, the pressure requirements increase and recovery (i.e., the amount of permeate) decreases. Via the computerized control systems and methods of the present disclosure, the control unit 52 can control the desalination system to within the vessel pressure limits,whilst in the embodiments it is attempted to obtain and maintain the necessary flow rate of the low salinity water within the required concentration envelope. As a non-limiting example, in an embodiment, SC 55 operates via RC to: maintaining the pressure of the feed to the first RO array 4A in the range from about 0 to about 80 barg, maintaining the differential pressure across the first RO array 4A in the range from about 0 to about 5 barg, maintaining the pressure in the first RO permeate in the range from about 0 to about 16 barg, maintaining the rate of change of the feed pressure to the first RO array 4A in the range from about 0 to about 5 barg/s, maintaining the first RO array concentrate pressure in the range from about 0 to about 80 barg, maintaining the first RO array permeate conductivity in the range from about 50 to about 500 μ s/cm, maintaining the pressure of the feed to the second RO array 4B in the range from about 0 to about 80 barg, maintaining the differential pressure across the second RO array 4B in the range from about 0 to about 5 barg, maintaining a pressure in the second RO permeate in the range of from about 0 to about 16 barg, maintaining a rate of change of feed pressure to the second RO array 4B in the range of from about 0 to about 5 barg/s, maintaining a second RO array permeate conductivity in the range of from about 50 to about 500 μ s/cm, maintaining a RO permeate TDS content in the range of from about 50 to about 4,000 ppm, maintaining a pressure of feed to the NF array 5 in the range of from about 0 to about 50 barg, maintaining a differential pressure across the NF array 5 in the range of from about 0 to about 5 barg, maintaining a pressure in the NF permeate in the range of from about 0 to about 16 barg, maintaining a rate of change of feed pressure to the NF array in the range of from about 0 to about 5 barg/s, maintaining a NF concentrate pressure in the range of from about 0 to about 50 barg, the NF permeate conductivity is maintained in the range of from about 50,000 to about 120,000 μ s/cm, the NF permeate TDS content is maintained in the range of from about 20,000 to about 60,000 ppm, and the feed flow rate to the first RO array 4A is maintained in the range of from about 0 to about 800 m³In the range of/h, the feed flow rate to the second RO array 4B is maintained from about 0 to about 600 m³In the range of/h, a concentrate (or retentate) stream from the second RO array 4BThe rate is maintained from about 0 to about 600 m³In the range of/h, the feed flow rate to the NF array 5 is maintained from about 0 to about 100 m³In the range of/h, the concentrate (or retentate) flow rate from the NF array 5 is maintained from about 0 to about 50 m³In the range of/h, the RO and/or NF array permeate temperature is maintained in the range of from about 0 to about 40 degrees celsius, the first RO array, the second RO array, and/or NF array recovery factor is maintained in the range of from 10 to 35% by volume, or a combination thereof. In an embodiment, the RO membrane unit is operated with a pressure differential across the membrane, which provides an RO permeate recovery factor in the range of 35 to 75% by volume, 35 to 65% by volume, 35 to 60% by volume, 45 to 55% by volume, or 50 to 55% by volume, depending on the volume of RO feed water.

The supervisory controller 55 is in signal communication with each Regulator Controller (RC) 56 and can learn the effects of the changes via a digital model. In an embodiment, the SC 55 cross-checks various thresholds and parameters, and can reset the thresholds of the various RCs 56 or simply override their commands to achieve the goal of a larger overall process. In an embodiment, SC 55 may monitor a trend of values from RC56 and predict future operations (and provide permissions to RC 56) based on the monitored trend. In such embodiments, RC56 sends back readings (e.g., both inputs from the sensors as well as outputs, such as calculated values (e.g., rate of change of feed pressure, recovery factor, etc.)) to SC 55. In an embodiment, the SC 55 is licensed in that it sends back to each RC56 a license that allows its operation. In such embodiments, the RC56 is permitted to control the process or is instructed to shut down. Other control schemes are possible (e.g., simply changing the set point or threshold to achieve a target) and are within the scope of the present disclosure.

The supervisory controller 55 is operable to ensure that the operation of the desalination device I, II is changed in a safe manner while monitoring a series of changes. For example, as previously described, the supervisory controller 55 may monitor the rate of change of pressure or the rate of change of flow in the line. The supervisory controller 55 may also take into account the time delay from taking an action to the action taking effect (e.g., such delay is due to dead volume inherent in the design of the desalination device), and may, for example, instruct the regulatory controller 56 to open (or close) the outlet valve of the module slightly before opening (or closing) the inlet valve of the module. The supervisory controller 55 may be operable to ensure that changes in valve status, etc., do not compromise the safe operation of the desalination device I, II.

In an embodiment, the computerized control system further includes a Control Panel (CP) 53 that accepts inputs and commands from the user, displays various information, and sends inputs, thresholds, targets, etc. to SC 55. The SC 55 then determines the grant and sends it to each RC 56. The return path is similar in that each RC56 sends its readings (e.g., values from sensor S, Q and/or calculations made thereby) and/or "status" back to SC 55, which may then be displayed on CP 53.

The SC 55 is able to respond to changes in conditions. For example, the SC 55 can be controlled based on a logical table (e.g., a look-up table), an equation, a control scheme, or numerical modeling, or can be cycled through options that may require some user input via the control panel 53. Thus, in embodiments, SC 55 can be used to partially or fully automate desalination processes (e.g., generation of RO water, generation of NF water, RO permeate, NF permeate, SW, PW, mixing of ion concentrates, etc.). In an embodiment, the CP 53 has an interface that allows an operator or user to collectively control the sequence of actions in the process by controlling the SC 55 of the RC 56. In this case, licensing can simply control the sequence of actions by controlling the ability of various processes to operate when needed. For example, valves associated with cleaning cycles of RO or NF units can be closed by the SC 55 until such units require a cleaning cycle. At this point, a portion of the NF or RO units can be isolated and a cleaning cycle can be initiated in response to the SC 55 allowing the RC56 associated with the cleaning cycle to operate. Other process-specific controllers can be similarly operated by using a permission-based control scheme from the SC 55.

In an embodiment, control panel 53 includes soft buttons on a screen display (e.g., a touch screen or via a mouse or other input) and a display in which various aspects of low salinity injection system I, II can be displayed and/or controlled. For example, an authorized request may be input to the control panel 53 to change the operation of the desalination device, e.g., close a valve, operate a pump, or change a mixing ratio. The request is then passed to the monitoring controller 55.

The computerized control system disclosed herein can also be operable as a cleaning routine for RO and/or NF arrays. To clean RO or NF filters or membranes, RC56 may be used to monitor trend lines of various operating parameters, which can be used by SC 55, e.g., via a reference enhanced performance monitoring module, to determine which soils are present and to determine the appropriate cleaning routines and/or protocols, e.g., as shown in international patent application No. PCT/EP2017/067443 and published as WO/2018/015223, the disclosure of which is incorporated herein in its entirety for purposes not contrary to this disclosure.

In an embodiment, the SC 55 operates and acts on data from the RC56 and/or CP 53 by setting permissions of the RC56, while the RC56 has state-dependent operations that act on inputs they receive from sensors (e.g., one or more of the sensors S1-S14 and Q1-Q17, or others) only when permitted or "permitted" by the SC 55.

In an embodiment, SC 55 and RC56 can be implemented using similar hardware configurations. For example, the SC 55 and RC56 can be implemented using dedicated controller modules that can include computerized or dedicated controller modules. In other embodiments, SC 55 and/or RC56 can be implemented in software via controller software stored in memory and executed on a processor. A dedicated control module (e.g., which can be implemented as a software module stored in memory and executed on a processor) may be associated with each RC56 to configure the RC56 for the associated cell of the RC 56. For example, the pump control module may be associated with the RC56 associated with the feed pump 3, the valve control module may be associated with the RC56 associated with the SW bypass valve V5, and so on. Each control module can be mounted on otherwise similar RC hardware. During the generation of low salinity water via the mixing of RO permeate with NF permeate, SW and/or PW additives, the control module can adapt any setting of the RO/NF array or membrane stack for TDS management. For example, in an embodiment, the control module may be operable to isolate the NF section of the membrane stack or to operate the membrane stack, wherein the NF elements are replaced with RO elements.

In some embodiments, the controller (e.g., SC 55 and/or RC 56) can be implemented at or near the unit being controlled. In other embodiments, the controllers (both SC 55 and RC 56) can be installed in a host that is in signal communication with the units and the sensors associated with the various units. Each controller may be a separate blade (blade) in the server stack, or each controller may be a virtual controller with its own inputs and outputs (e.g., with multiple controllers operating on a single server blade). Alternatively, the conditioning controller 56 may be a separate computerized unit located in the vicinity of the unit with which it is associated. In either arrangement, the input to each RC56 and the output from each RC56 can be sent to the level of the SC 55.

The control system 52 of the present disclosure may include a CPU (central processing unit), a RAM (random access memory), a ROM (read only memory), an HDD (hard disk drive), an I/F (interface), computer executable code (e.g., software and/or firmware), and the like. The control unit 52 can store instructions in the memory, where the instructions can be executed on the processor to configure the processor to perform any function or action related to or attributable to the control system in accordance with the instructions stored in the memory. Although described as including a processor and memory, in some aspects, an Application Specific Integrated Circuit (ASIC) can be developed to perform the same functions.

In embodiments, the computerized control systems and methods disclosed herein can be used to generate: a first mixed low salinity injection water for injection into at least one injection well penetrating a first region of an oil-bearing reservoir; and a second mixed low salinity injection water for injection into at least one injection well penetrating a second region of the oil-bearing reservoir, wherein the reservoir rocks of the first and second regions have first and second rock compositions that respectively exhibit different risk of formation damage, and wherein the first and second mixed low salinity injection waters comprise variable amounts of nanofiltration permeate, reverse osmosis permeate, and optionally variable amounts of seawater and/or clay stabilizing additives, and wherein the compositions of the first and second mixed low salinity injection waters are maintained within first and second predetermined operating envelopes, respectively, thereby balancing enhanced oil recovery from the first and second regions of the reservoir while reducing or minimizing formation damage upon injection of the first and second mixed low salinity injection waters from the injection well into the first and second regions of the oil-bearing reservoir.

Thus, a system for injecting a single mixed low salinity injection water having a variable composition into at least one injection well penetrating an area of an oil-bearing reservoir may comprise a control unit, a desalination device, a mixing system and an injection system. The desalination apparatus can include an RO array for generating and delivering a RO permeate mixed stream to a mixing system and an NF array for generating and delivering a NF permeate mixed stream to the mixing system. The mixing system can include an RO permeate feed line (e.g., (first) RO permeate line 9, a second stage RO permeate line 27, a combined RO permeate line 14), an NF permeate feed line (e.g., NF permeate line 13), an RO permeate dump line (e.g., RO permeate dump line 11), an NF permeate dump line (e.g., NF permeate dump line 10), a mixing point for mixing the RO permeate and the NF permeate to form a mixed low salinity injection water, and a discharge line (e.g., mixed low salinity injection water line 18) for delivering the mixed low salinity injection water to the injection system. The injection system can include an injection line (e.g., injection line 58) having at least one injection pump (e.g., injection pump 24) for delivering mixed injection water to an injection well (e.g., injection well 20) that penetrates a region 22 of the oil-bearing reservoir. The control unit of the desalination apparatus may be a control unit 52 comprising SC 55 and RC56 operable to adjust the operation of the desalination apparatus in real time so as to adjust the amount of the RO permeate and/or NF permeate mixed stream to be mixed at the mixing point so as to maintain the composition of the mixed low salinity water stream within an operation envelope defined by the boundary values of the region, wherein the predetermined operation envelope balances increasing or maximizing oil recovery of the reservoir region while reducing or minimizing formation damage in the reservoir region, and wherein the predetermined operation window has been input into the control unit.

In an embodiment, a mixing system that generates a mixed low salinity water includes a tank (e.g., tank 50) for a concentrated aqueous solution of at least one clay stabilizing additive (hereinafter referred to as a "clay stabilizing concentrate") and a clay stabilizing concentrate feed line (e.g., ionic concentrate line 26) provided with an adjustable flow control valve (e.g., valve V10) capable of delivering varying amounts of the clay stabilizing concentrate to the mixed low salinity injection water. Alternatively, the tank may be provided with a metering pump for accurately dosing the clay stabilizing concentrate into the injection water. The metering pump may be linked to a flow rate meter, which may be used to adjust the concentration of the clay stabilizing additive to match the concentration profile of the clay stabilizing additive. The control unit 52 of the system can change the operation of the mixing system in real time in order to adjust the amount of clay stabilizing concentrate that is delivered to the following locations: the mixing point or injection line of the mixing system such that the composition of the resulting mixed low salinity water (e.g., in the injection water line 18) is maintained within an operating envelope further defined by the boundary values of the concentration of the clay stabilizing additive for the region of the reservoir. Thus, the predetermined operating envelope for a region of the reservoir includes upper and lower limits for one or more clay stabilizing additives.

It is contemplated that the computerized control system or method of the present disclosure may be located or used onshore for use in onshore reservoirs, or may be located or used offshore (e.g., on a platform or Floating Production Storage and Offloading (FPSO) unit) for use in offshore reservoirs. However, where the computerized control system is used in an offshore reservoir, it is also contemplated that the desalter may be located onshore and the RO and NF permeate streams may be delivered to a mixing system located offshore.

The boundary values for the composition of the mixed low salinity injection water for each zone of the oil reservoir may be input into the control system 52, for example, into the SC 55. The SC may then determine an operational envelope for the composition of the mixed low salinity injection water for each region of the reservoir, where the operational envelope is defined by the boundary values. However, it is also conceivable that the operation envelope may be determined by inputting the boundary values to a computer located at a remote location, outputting the operation envelope, and transmitting the output operation envelope to the control unit 52 of the system via a network. The operating envelope may be defined by boundary values (upper and lower limits) of parameters including one or more of the following parameters: TDS content (salinity), ionic strength, concentration of individual ions (such as sulfate anions, nitrate anions, calcium ions, or magnesium ions), concentration of individual ion types (such as monovalent cations, monovalent anions, polyvalent cations, or divalent cations), ratios of individual ion types, ratios of individual ions (such as sodium adsorption ratios), or combinations thereof. Sodium Adsorption Ratio (SAR) is used to evaluate the flocculation or dispersion state of clay in reservoir rock. Generally, sodium ions aid in the dispersion of the clay particles, while calcium and magnesium ions aid in their flocculation. The formula for calculating Sodium Adsorption Ratio (SAR) is:

wherein the sodium, calcium, and magnesium cation concentrations of the mixed low salinity injection water are expressed as milliequivalents per liter.

The constituents within the operational envelope of the zones of the reservoir are those predicted to enable Enhanced Oil Recovery (EOR) from each zone of the reservoir while avoiding, reducing, or minimizing the risk of formation damage in the reservoir zone.

In the event that the reservoir is at risk of acidizing or scaling, the constituents within the operational envelope of the regions of the reservoir (e.g., the first, second, and any other regions) are those that are also predicted to be capable of slowing reservoir acidizing or inhibiting scaling. Those skilled in the art will appreciate that not all reservoirs are at risk of acidizing or scaling. Thus, when the reservoir contains a local population of sulfate-reducing bacteria, these bacteria gain energy by oxidizing organic compounds while reducing sulfate to hydrogen sulfide, and acidification occurs. Scaling occurs when connate water containing high levels of precipitating precursor cations (e.g., barium and strontium cations) is mixed with injection water containing relatively high amounts of sulfate anions, resulting in precipitation of insoluble sulfate (mineral scale).

It is contemplated that each region of the reservoir may have a plurality of different operational envelopes defined by different boundary values for each parameter, wherein the different operational envelopes balance different levels of Enhanced Oil Recovery (EOR) and different levels of formation damage risk for each region of the reservoir. The multiple operational envelopes for each region of the reservoir may also account for risk of acidizing or scaling of the reservoir. The plurality of different operating envelopes for the composition of the mixed low salinity injection water for each zone (first, second or any other zone) of the reservoir may be input into the control unit 52.

In order to maintain the composition of the mixed low salinity water within a predetermined (predefined) operating window of the reservoir region, the amount of NF permeate, RO permeate, PW, SW, or combinations thereof, that is mixed to produce the mixed low salinity water stream, can be adjusted in real time via the computerized control system disclosed herein in response to a reduction in injection in one or more regions of the reservoir.

In the mixing system of the present disclosure, the amount of NF permeate stream (e.g., NF permeate in the NF permeate line 14) and/or RO permeate (e.g., RO permeate in the (first) RO array permeate line 9, RO permeate in the second RO array permeate line 27, or combined RO permeate in the combined RO permeate line 14) that can be mixed to form the mixed low salinity injection water stream can be rapidly (in real time) adjusted by: varying amounts of the NF or RO permeate stream from the desalination plant are discharged into, for example, a body of water (sea) via NF permeate or RO permeate "dump lines" (e.g., RO permeate dump line 11, NF permeate dump line 10) each provided with a "dump valve" (e.g., RO permeate dump valve V4, NF permeate dump valve V3), respectively. The dump valve is an adjustable valve (e.g., a throttle valve) that can be set to various positions (between fully closed and fully open positions) in order to adjust the amount of NF permeate or RO permeate discharged from the mixing system.

If the discharge of excess NF permeate or excess RO permeate continues for a long period of time, e.g., hours or days, the control unit 52 may adjust the desalination apparatus by taking one or more NF units of the array or one or more RO units of the RO array offline, thereby reducing the capacity of the NF permeate or RO permeate, respectively. If the discharge of excess NF permeate or RO permeate lasts weeks or months (optionally), the NF elements of one or more NF units of the desalination apparatus may be replaced with RO elements, or the RO elements of one or more RO units may be replaced with NF elements, to increase the amount of RO permeate or NF permeate produced by the desalination apparatus.

It is well known that divalent cations may contribute to the stabilization of clays. Optionally, the desalination plant may have a bypass line (e.g., bypass line 17) for high salinity water used as feed to the RO and NF arrays of the plant and/or an inlet line for PW (e.g., PW mixing line 17 a) because such high salinity feed water or PW, e.g., Seawater (SW), typically contains high levels of divalent cations. This bypass line or PW line can be used to deliver a high salinity water mixed stream (e.g., SW or PW mixed stream) to the mixing system. Thus, the mixing system optionally has a high salinity water (e.g., PW, SW) feed line.

The bypass line 17 and/or PW inlet line 17a of the high salinity feed water may be provided with an adjustable valve (e.g., throttle valve V5 or V6, respectively) which may be set at various positions between fully closed and fully open positions to provide variable amounts of high salinity feed water (e.g., SW) or PW and/or NF permeate mixed stream 13 (or combined RO/NF permeate mixed stream 14) mixed with RO permeate mixed stream 9 to form mixed low salinity injection water 18. However, any excess high salinity water may also be dumped overboard, if desired, via a high salinity water dump line provided with an adjustable valve (e.g., a choke valve). In an embodiment, the use of an adjustable valve on the optional SW bypass line (or SW dump line provided with an adjustable valve) and/or the optional PW mixing line also allows for rapid (real-time) adjustment of the TDS, the concentration of one or more individual ions, to the composition of the mixed low salinity injection water stream.

Thus, the control unit 52 may vary the amount of any high salinity water (e.g., NF permeate and/or SW and/or PW) included in the mixed low salinity injection water stream in response to injection variations in one or more regions of the reservoir, thereby moving the components of the mixed low salinity water stream within a preferred predetermined (preselected) operating envelope (or preferred coverage envelope) that presents a lesser risk of formation damage. Those skilled in the art will appreciate that SW contains high levels of sulfate anions. Therefore, when mixing the RO permeate mixed stream and the NF permeate mixed stream with the SW mixed stream, the risk of acidizing (and the risk of scaling) of the reservoir must be strictly managed. The risk of acidification or scaling of the reservoir may be managed by inputting into the control unit 52 (e.g. to its SC 55) an upper limit (boundary value) for the sulphate concentration of the mixed low salinity injection water, typically 40 mg/L; e.g. 25 mg/L or 10 mg/L.

As previously described, the mixing system may optionally include a tank 50 (for storing a concentrate of an aqueous solution or dispersion containing one or more clay stabilizing additives) and a concentrate feed line 26. The concentrate feed line may be provided with a throttle valve (e.g., valve V10) for delivering a variable amount of a concentrate mixed stream (which includes an aqueous solution or dispersion of one or more clay stabilizing additives) to the mixing point of the low salinity injection water stream. Accordingly, the adjustable valve may be set (e.g., via one or more RCs 56) to various positions between the fully closed and fully open positions to provide variable amounts of concentrate to the mixing point. The control unit 52 (e.g., its SC 55) may monitor the flow rate of the concentrate in the concentrate feed line 26 in real-time (e.g., via the flow rate sensor Q8 and one or more RCs 56), and may change the concentration of the one or more clay stabilizing additives in the mixed injection water stream by rapidly adjusting the flow rate of the concentrate using an adjustable valve.

The clay stabilizing additive may be an inorganic salt, such as a salt of a divalent cation or a potassium salt, or mixtures/combinations thereof. In an embodiment, the salt of the divalent cation may be a calcium salt, such as calcium chloride, calcium bromide, calcium nitrite, or calcium nitrate, e.g. calcium chloride or calcium nitrate. Calcium nitrate also has the advantage of providing acidification control because nitrate anions can promote the growth of nitrate-reducing bacteria (NR) and thus outweigh sulfate-reducing bacteria (SRB) in terms of nutrients and available organic carbon. In such embodiments, care should be taken to ensure that facultative NRSRB is not present prior to the addition of nitrate. In an embodiment, the potassium salt is selected from potassium chloride, potassium bromide, and potassium nitrate. Potassium nitrate has the advantage of also providing acidification control.

The control unit 52 (e.g. its SC 55) may automatically adjust the operation of the hybrid system (e.g. via RC56 and appropriate valve V) and thus the amount of RO permeate stream, NF permeate stream (and any optional high salinity water stream, such as SW or PW or optional clay stabilizer concentrate stream) included in the hybrid low salinity injection water stream in response to changes in the injection in one or more regions of the reservoir.

The flow rate and composition of the mixed low salinity injection water may be monitored in real time (e.g., via flow rate sensors Q9 and/or Q10 and/or sensor S7, and associated RC 56) in order to determine whether the changes made by control unit 52 to the operation of the mixing system to maintain the composition of the single mixed low salinity injection water within the operating envelope are effective. If not, the SC 55 of the control unit 52 may make further changes to the operation of the mixing system (via the RC56 and associated pumps and/or valves). Thus, the control unit has a feedback loop for controlling the mixing of the mixed low salinity water stream.

Controlling the amount of RO permeate and NF permeate available for mixing in real time by varying the amount of RO permeate or NF permeate discharged from the mixing system, e.g., into a body of water (e.g., an ocean), via an RO permeate or NF permeate dump line, provides robust control of TDS and/or one or more individual ion concentrations within the operating envelope of the mixed low salinity injection water stream. Thus, the response is faster (due to dead volume in the feed lines leading from the RO and NF arrays to the mixing point of the mixed low salinity injection water stream) than if one attempted to change the flow rate of the feed water to the RO and NF arrays of the desalination unit.

Further, where high salinity water (e.g., SW and/or PW) or clay stabilized concentrate may be used as the mixed stream, controlling the degree of opening of a variable (variable) valve (e.g., a throttle valve) on the high salinity water bypass line, PW inlet line, or on the clay stabilized concentrate line may adjust the composition of the individual mixed low salinity injection water to fall within a predetermined operating envelope in response to injection changes in the injection well penetrating the reservoir zone.

It can thus be seen that the SC 55 of the control unit 52 can change the operation of the desalination device in real time by way of one or more of the RC56, the degree of opening of the valve V4 on the RO permeate dump line 11, the degree of opening of the valve V3 on the NF permeate dump line 10, the degree of opening of the valve V5 on the optional high salinity water bypass line 17, the degree of opening of the valve V6 on the optional PW inlet line 17a, and/or the degree of opening of the valve V10 on the optional clay stabilization concentrate line 26.

As mentioned above, various probes (sensors S, Q) may be included in the system of the present invention, particularly in a hybrid system. These probes can be used to determine the TDS and/or ionic composition of the mixed low salinity injection water stream. For example, the TDS of the mixed low salinity injection water stream can be determined by its conductivity, while the concentration of individual ions or the type of individual ions can be determined by using a glass probe having a membrane that is permeable to the particular individual ion or individual ion type. Similarly, probes (sensors) may be present on the RO and NF permeate lines, any combined RO/NF permeate line (where the combined RO/NF permeate stream is optionally mixed with SW, PW, or clay stabilizing concentrate to form a mixed low salinity injection water), an optional high salinity water bypass line, and/or an optional PW inlet line, in order to obtain data relating to TDS and ionic composition in the RO permeate stream, the NF permeate stream, any combined RO/NF permeate stream, an optional high salinity water stream, an optional PW inlet mix stream, or combinations thereof. Flow rate sensors may also be provided on the flow line for determining the flow rates of various mixed streams (RO permeate stream, NF permeate stream, optional high salinity feed water stream, optional high salinity PW mixed stream, any combination of RO/NF permeate streams, and/or optional clay stabilization concentrate stream) and for determining the flow rates of the RO permeate in the RO permeate pour line and the NF permeate in the NF permeate pour line.

Thus, in an embodiment, the mixing system includes an ion concentration sensor S for measuring the salinity or total concentration (Ct) of dissolved solids, the concentration of individual ions (Ci) or the concentration of individual ion types in the RO permeate mixed stream, the NF permeate mixed stream, the RO/NF permeate mixed stream in any combination, the optional SW mixed stream, the optional PW mixed stream, the optional clay stable concentrate mixed stream, and the mixed low salinity injection water stream. In particular, the mixing system may have an ion concentration sensor for measuring at least one of a TDS concentration, a chloride anion concentration, a bromide anion concentration, a calcium cation concentration, a magnesium cation concentration, a potassium cation concentration, a nitrate anion concentration, and a sulfate anion concentration of the RO permeate mixed stream, the NF permeate mixed stream, the RO/NF permeate mixed stream in any combination, the selectable high salinity water mixed stream, and/or the high salinity PW mixed stream. The mixing system may alternatively or additionally comprise a flow rate sensor Q for measuring the flow rate of one or more of: an RO permeate mixed stream, an RO permeate dump stream, an NF permeate mixed stream, an NF permeate dump stream, any combination of RO/NF permeate mixed streams, an optional high salinity water bypass stream, an optional PW mixed stream, an optional clay stabilization concentrate stream, and a mixed low salinity injection water stream. As described above, each of the sensors S and Q provides input/data to one or more RCs 56.

Accordingly, the ion concentration sensor, flow rate sensor, and any other sensors described herein may communicate with the control unit 52 (e.g., RC56 thereof) via any suitable communication technique, such as a direct electrical or radio connection (e.g., Wi-Fi, bluetooth).

The maximum allowable increase in downhole pressure for an injection well penetrating the reservoir region may be input into the control unit 52 (e.g., via CP 53 into SC 55) due to the risk of formation damage during the low salinity water injection. In the case where dedicated injection lines are used to deliver injection water to an injection well penetrating a reservoir zone, a maximum allowable reduction in the flow rate of each incoming water stream downstream of the injection pump on each dedicated flowline may be input to the control unit (beyond which there may be an unacceptable reduction in injection). An increase in downhole pressure in an injection well penetrating a region of the reservoir and a decrease in flow rate downstream of an injection pump of a dedicated flowline may both indicate a loss of injection due to formation damage in a region of the reservoir.

The downhole pressure in the injection wells adjacent the oil-bearing layers in each region of the reservoir (or the flow rate of the mixed low salinity injection water downstream of the injection pumps of the dedicated injection lines of the injection system) may be monitored in real time (e.g., by SC 55). The pressure in the injection well may be monitored via downhole measurement equipment such as a pressure sensor 23 connected to the control unit, e.g. via a fibre optic telemetry line or any other suitable communication technique.

If the control unit 52 (e.g., its SC 55) determines that there is a reduction of injection in an injection well that penetrates one or more regions of the reservoir, the control unit 52 may select and/or be instructed to select a different operational envelope for the composition of the mixed injection water stream that is expected to have a lower risk of causing formation damage (while maintaining an acceptable level of EOR from the reservoir region) and may then adjust (e.g., via the RC56 and various associated valves and/or pumps) the mixing ratio of the various mixed streams so that the composition of the mixed low salinity injection water injected into the injection well that penetrates the reservoir region falls within the different operational envelope. The SC 55 of the control unit 52 continues to monitor in real time the downhole pressure in the injection well penetrating the injection well in which the reduced injection reservoir region already exists (or the flow rate downstream of the injection pump leading to the dedicated injection line penetrating the injection well in which the reduced injection reservoir region already exists) in order to determine whether the pressure (or flow rate) begins to stabilize in response to the injection of the mixed low salinity injection water having a composition within the predetermined operating window. If not, the control unit 52 (e.g., its SC 55) may begin or be instructed to begin further changes to the operation of the hybrid system in order to adjust the composition of the hybrid low salinity injection water stream to fall within yet another operating envelope that is predicted to have less risk of causing formation damage. This process is iterative and may be repeated multiple times. Alternatively, if the pressure continues to rise, the control unit 52 (e.g., its SC 55) may make a decision to reduce the flow rate of the low salinity injection water or to stop injecting the low salinity injection water into the injection well of one or more regions of the reservoir. The control unit 52 may then make a decision to inject a clay stabilizing component (e.g., an undiluted clay stabilizing concentrate) into the oil-bearing layer where the injection-reduced reservoir zone already exists for a period of several days before resuming the low salinity waterflood.

In an embodiment, the correlations between the mixing ratio of the various mixed streams and the composition of the mixed low salinity injection water stream (e.g., via CP 53 and/or SC 55) are input into the control unit 52 (e.g., correlations between the mixing ratio of the various mixed streams and the TDS, osmolarity, concentration of the individual ions, concentration of the individual ion types, ratio of the individual ions, and ratio of the individual ion types of the mixed low salinity injection water stream). These correlations may be based on the assumption that the composition of the NF permeate, RO permeate, and optionally the mixed stream of high salinity water (e.g., SW and/or PW) remains substantially constant (within predetermined tolerances) during operation of the desalter. The mixing ratio of each mixed stream depends on the flow rate of the various mixed streams supplied to the mixing point of the mixing system to form the mixed low salinity injection water stream.

The following correlations may also be input to the control unit 52 (e.g., via CP 53 and/or SC 55): correlation between the degree of opening of the NF permeate dump valve (e.g., valve V3), the degree of opening of the RO permeate dump valve (e.g., valve V4), the degree of opening of the adjustable valve (e.g., valve V9) on the optional primary high salinity water feed line, the degree of opening of the adjustable valve (e.g., valve V6) on the optional PW inlet line, and the degree of opening of the adjustable valve (e.g., valve V10) on the optional clay stable concentrate line, and the flow rates of the NF permeate, RO permeate, optional high salinity water, optional PW, and optional clay stable concentrate mixed streams (e.g., as measured by flow rate sensors Q7, Q6/Q6', Q5, Q11, and Q8, respectively). Thus, the control unit 52 may control the mixing ratio and hence the composition of the mixed low salinity injection water stream by varying the degree of opening of one or more of the adjustable valves described above (e.g., via the associated RC 56) to achieve that the composition of the mixed low salinity injection water is within a predetermined (preselected or predetermined) operating envelope of the reservoir region. Thus, the flow rates of the various mixed streams to be supplied to the mixing points may be adjusted in real time to ensure that the composition of the mixed low salinity injection water is within the operating envelope of the reservoir region.

Typically, the boundary value of the TDS of the mixed low salinity injection water stream (e.g., in line 18) can be in the range of 200 to 10,000 mg/L, such as from 500 to 10,000 mg/L. In general, lower TDS ranges provide greater EOR, while higher TDS ranges mitigate the risk of formation damage, particularly in reservoirs including rocks with high content of swellable and/or migratable clays. Alternatively, the boundary value of TDS may be, for example, in the range of 500 to 5,000 mg/L, 500 to 3,000 mg/L, 1,000 to 2,000 mg/L, 2000 to 5000 mg/L, or 3000 to 7000 mg/L (depending on the risk of formation damage). The control unit 52 may control the composition of the mixed low salinity injection water of the reservoir zone to be within a selected range of TDS boundary values.

In the event that there is a risk of acidification or a risk of scaling of the reservoir, the computerized control system of the present disclosure can be used to control the sulfate anion concentration of the low salinity injection water of the reservoir zone to a value of less than 50 mg/L, such as less than 40 mg/L or less than 10 mg/L.

The computerized control system described herein can further control the mixing to achieve a desired multivalent cation concentration in the mixed injection water. Such desired multivalent cation concentrations are described, for example, in the international patent application No. PCT/GB2007/003337 and published as WO/2008/029124, the disclosure of which is hereby incorporated by reference in its entirety for purposes not contrary to the present disclosure. For example, in an embodiment, the control unit 52 controls the total multivalent cation concentration of the mixed injection water (e.g., in line 18) of the reservoir zone to be in the range of 1 to 250 mg/L, such as 3 to 150 mg/L, or 50 to 150 mg/L, with the proviso that the ratio of the multivalent cation content of the mixed low salinity injection water to the multivalent cation content of the connate water contained in the reservoir rock pores of each zone of the reservoir is less than 1. In an embodiment, the control unit 52 controls the calcium cation concentration of the mixed injection water of the reservoir zone to be in the range of 1 to 200 mg/L, such as 5 to 150 mg/L or 50 to 150 mg/L, provided that the ratio of the calcium cation content of the mixed low salinity injection water to the calcium cation content of the connate water contained in the reservoir rock pores of each zone of the reservoir is less than 1.

In an embodiment, the control unit 52 controls the concentration of magnesium cations in (in) the mixed injection water of the reservoir zone to be in the range of 2 to 400 mg/L, for example from 10 to 300 mg/L or from 100 to 300 mg/L, provided that the ratio of the magnesium cation content of the mixed low salinity injection water to the magnesium cation content of the connate water contained in the pores of each zone of the reservoir is less than 1.

In an embodiment, the control unit 52 controls the potassium cation concentration of the mixed injection water of the reservoir zone to be in the range of 10 to 2000 mg/L, for example from 250 to 1000 mg/L, provided that the TDS of the mixed low salinity injection water is maintained within the boundary values of the predetermined operating envelope.

In an embodiment, the control unit 52 may control the composition of the mixed low salinity injection water to be within a selected range defined by the boundary values of TDS (and within a selected range defined by the boundary values of multivalent cation content, calcium cation content, magnesium cation content, and potassium cation content).

The boundary values of the TDS of the mixed low salinity injection water and the concentrations of the individual ions and the concentrations of any clay stabilizing additives may vary depending on the following factors: the low salinity EOR response of each region of the reservoir and the composition of the rock of the oil-bearing layer of each region of the reservoir, and in particular the content of swellable and migratable clays and minerals known to be associated with formation damage.

Boundary values have been determined by analyzing samples of reservoir rock taken from each region of the oil-bearing layer of the reservoir. The sample of reservoir rock may be a rock chip or a sidewall core. Alternatively, reservoir rock surrounding the injection wellbore may be analyzed by geophysical logging using a downhole logging device. Analyzing the rock of each region of the oil-bearing layer of the reservoir may include, but is not limited to, determining the total rock clay content of the reservoir rock surrounding the injection wellbore in the first, second, and any other regions of the reservoir. The total rock clay content of the reservoir rock of the first, second and any other region of the reservoir may be determined by geophysical logging, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), infrared scintillation point counting or sieve analysis. The total rock clay content of the reservoir rock may range from about 2 wt% to about 20 wt%. Analyzing the rock of each region of the oil-bearing layer of the reservoir may also include determining the mineral content of the clay portion of the rock, in particular clays of the montmorillonite type (e.g., montmorillonite), pyrophyllite, kaolinite, illite, chlorite and glauconite types, which may be determined by X-ray diffraction (XRD) or Scanning Electron Microscopy (SEM) analysis. The optimum salinity (and composition) of the mixed low salinity injection water for each region of the reservoir may be determined from the correlation of formation damage occurring at different salinity boundary values (and different concentrations of individual ions or types of individual ions) of the injection water for a series of rock samples having different clay contents and clay compositions and the selection of boundary values for the salinity (or composition) of the mixed low salinity injection water for the rock samples that most closely match (e.g., using historical data) the rock composition of each region of the reservoir that will be subjected to the low salinity waterflood. Alternatively, rock samples taken from the reservoir region where the injection well has been drilled using different boundary values for salinity and composition (concentration of individual ions or concentration of individual ion types) of the mixed low salinity injection water may be tested to determine the optimal envelope of salinity and composition of the injection water to be injected into each region of the reservoir during the low salinity waterflood.

Typically, the injection capacity of the mixed low salinity injection water is limited due to the limited capacity of the desalination device I, II. Thus, the low salinity waterfloods may be designed to inject low Pore Volume (PV) slugs of mixed low salinity injection water in an amount of at least 0.3 pore volume or at least 0.4 pore volume into injection wells that penetrate the oil-bearing layer of each region of the reservoir because slugs with such minimum pore volume tend to maintain their integrity in the formation. To limit the amount of water injected into each region of the reservoir from the injection well, the pore volume of the mixed low salinity injection water may be less than 1, e.g., less than or equal to 0.9 PV, less than or equal to 0.7 PV, less than or equal to 0.6 PV, less than or equal to 0.5 PV.

After injecting the low pore volume mixed low salinity injection water into the injection well that penetrates the region of the reservoir, drive water may be injected from the injection well into the region of the oil-bearing layer of the reservoir in order to ensure that a slug of the mixed low salinity injection water (and thus the released reservoir) is swept through the oil-bearing layer of the reservoir to the production well that penetrates the region of the oil-bearing layer of the reservoir. In addition, injection of drive water may be required to maintain pressure in the reservoir region. Typically, the drive water has a greater PV than the slug of aqueous displacement fluid.

In an embodiment, the drive water is produced water or a mixture of seawater and produced water, depending on the amount of produced water separated from the produced fluid at the production facility. The use of produced water as drive water is advantageous because there is a limit to the treatment of produced water into the ocean, which can limit the amount of produced water that can be treated into the ocean or simply prevent the treated or produced water from entering the ocean altogether. Thus, after injecting the low salinity injection water slug into the injection well penetrating the reservoir region, the injection well may be used as a produced water treatment well.

Typically, different components of the mixed low salinity injection water (TDS, concentration of one or more ions, concentration of each ion type, concentration ratio of each ion type, or concentration of one or more clay stabilizing additives) are associated with different mixing ratios of the combined RO/NF permeate stream. Different components are also associated with different components of the combined RO/NF permeate stream (including components of the combined RO/NF permeate stream that include SW, PW, and/or one or more clay stabilizing additives). These correlations may be input into the control unit 52 (e.g., into the SC 55 via CP 53) so that the control unit may control the operation of the desalination device (e.g., via RC 56) to vary the mixing ratio of the NF and RO permeate streams of the combined NF/RO permeate stream and the amount of optional SW, PW, and/or clay stabilizing concentrate mixed into the combined RO/NF permeate stream so as to provide a composition of mixed low salinity injection water that falls within the operating envelope of the reservoir zone.

In an embodiment, a computerized control system according to the present disclosure is used to generate a controlled salinity injection water as described in U.S. patent No. 9,492,790, the disclosure of which is incorporated herein in its entirety for purposes not contrary to the present disclosure. In such embodiments, a computerized control system as described in the present disclosure may be used in a process for controlling the production of an injected water stream having a controlled salinity and a controlled sulfate anion concentration, the injected water stream being suitable for injection into an oil-bearing formation of an oil reservoir, the process comprising the steps of: feeding source water having a total dissolved solids content in the range of 20,000 to 45,000 ppm and a sulfate anion concentration in the range of from 1,000 to 4,000 ppm or from 1,500 ppm to 4,000 ppm to a desalination apparatus, wherein the desalination apparatus comprises a plurality of Reverse Osmosis (RO) membrane units and a plurality of Nanofiltration (NF) membrane units, wherein the source water is pressurized to a pressure in the range of 350 to 1250 psi absolute; and splitting the source water to provide feed water for the RO membrane units (hereinafter referred to as "RO feed water") and feed water for the NF membrane units (hereinafter referred to as "NF feed water"); increasing the pressure of the RO feed water, if necessary, to a value in the range of 900 to 1250 psi absolute pressure prior to introduction of the RO feed water to the RO membrane units, and withdrawing the RO permeate and the RO retentate from the RO membrane units, wherein the RO membrane units are operated in a single pass single stage mode or a single pass dual stage mode, and wherein the recovery factor of the RO permeate is in the range of from 35 to 75% by volume or from 35 to 60% by volume based on the volume of the RO feed water fed to the RO membrane units, such that the RO permeate has a total dissolved solids content of less than 250 ppm and a sulfate anion concentration of less than 3 ppm; if necessary, reducing the pressure of the NF feed water to a value in the range of 350 to 450 psi absolute prior to introduction of the NF feed water into the NF membrane units, and withdrawing the NF permeate and the NF retentate from the NF membrane units, wherein the NF membrane units are operated in a single pass, single stage mode, and wherein the recovery factor of the NF membrane units being operated such that the NF permeate is in the range of 35 to 60% by volume based on the volume of the NF feed water fed to the NF membrane units, such that the NF permeate has a total dissolved solids content in the range of from 15,000 to 60,000 ppm or from 15,000 to 45,000 ppm and a sulfate anion concentration of less than 40 ppm or less than 30 ppm; and mixing at least a portion of the RO permeate and at least a portion of the NF permeate in a ratio ranging from 2:1 to 40:1, 4:1 to 27:1, or from 10:1 to 25:1, so as to provide the injection water having a total dissolved solids content ranging from 500 to 5,000 ppm or from 1,000 to 5,000 ppm and a sulfate anion concentration of less than 7.5 ppm, less than 5 ppm, or less than 3 ppm. The source water may be seawater, estuary water, produced water, aquifer water, or wastewater. In an embodiment, the total dissolved solids content (TDS) of the RO permeate is in a range from 50 to 225 ppm, from 100 to 225 ppm, from 125 to 200 ppm, or from 150 to 175 ppm. In embodiments, the RO permeate has a sulfate anion concentration in the range of from 0.5 to 2.5 ppm, or from 0.5 to 1.5 ppm. In an embodiment, the TDS of the NF permeate is no greater than 15,000 ppm or 10,000 ppm and less than the TDS of the source water. In embodiments, the NF permeate has a sulfate anion concentration in a range from 10 to 28 ppm, from 10 to 25 ppm, or from 15 to 20 ppm.

The sulphate anion concentration of the injected water will depend on the desired total dissolved solids content (TDS) of the stream and hence on the mixing ratio of the RO permeate and the NF permeate. Thus, the sulfate anion concentration of the injected water will increase with increasing amount of NF permeate in the mixed stream. Typically, the sulfate anion concentration of an injection water stream having a total dissolved solids content of 1000 ppm is in the range of 1 to 2 ppm, and the range values for sulfate anion concentration should be scaled for injection water of higher TDS.

In addition to providing the injection water with a sufficiently high TDS to mitigate the risk of formation damage and with a sufficiently low sulfate concentration to mitigate the risk of reservoir acidizing, the injection water may also have a sufficiently low multivalent cation concentration to be used as a low salinity injection water, depending on the source water selection, to achieve incremental oil recovery from the reservoir. Thus, in an embodiment, the computerized control system of the present disclosure is used to provide a mixed water stream with controlled salinity, controlled low sulfate anion concentration, and controlled multivalent cation concentration for use as injection water for low salinity waterfloods while mitigating the risk of formation damage and controlling acidizing in the reservoir. In such embodiments, the computerized control system of the present disclosure is used to produce an injection water stream having a controlled salinity, a controlled sulfate anion concentration, and a controlled multivalent cation concentration suitable for injection into an oil-bearing formation of an oil reservoir by: feeding source water having a total dissolved solids content in the range of 20,000 to 45,000 ppm, a sulfate concentration in the range of from 1,000 to 4,000 ppm or from 1,500 ppm to 4,000 ppm, and a multivalent cation concentration in the range of from 700 to 3,000 ppm, from 1,000 to 3,000 ppm or from 1,500 to 2,500 ppm to a desalination apparatus comprising a plurality of Reverse Osmosis (RO) membrane units and a plurality of Nanofiltration (NF) membrane units, wherein the source water is pressurized to a value in the range of 350 to 1250 psi absolute; and separating the source water to provide RO feed water and NF feed water; increasing the pressure of the RO feed water, if necessary, to a value in the range of 900 to 1250 psi absolute pressure prior to introduction of the RO feed water to the RO membrane units, and withdrawing the RO permeate and the RO retentate from the RO membrane units, wherein the RO membrane units are operated in a single pass single stage mode or a single pass dual stage mode, and wherein the recovery factor of the RO permeate is in the range of from 35 to 75% by volume or from 35 to 65% by volume based on the volume of the RO feed water fed to the RO membrane units, such that the RO permeate has a total dissolved solids content of less than 250 ppm, a sulfate anion concentration of less than 3 ppm, and a multivalent cation content of up to 10 ppm; if necessary, reducing the pressure of the NF feed water to a value in the range of 350 to 450 psi absolute prior to introducing the NF feed water into the NF membrane unit, and withdrawing the NF permeate and the NF retentate from the NF membrane unit, wherein the NF membrane unit is operated in a single pass, single stage mode wherein the recovery factor of the NF permeate ranges from 35 to 60% by volume based on the volume of the NF feed water fed to the NF membrane unit such that the NF permeate has a total dissolved solids content in the range of from 15,000 to 40,000 ppm or from 15,000 to 35,000 ppm, a sulfate anion concentration of less than 40 ppm or less than 30 ppm, and a multivalent cation content of up to 200 ppm, up to 150 ppm or up to 100 ppm; and mixing at least a portion of the RO permeate and at least a portion of the NF permeate in a ratio ranging from 2:1 to 40:1, from 4:1 to 27:1, or from 10:1 to 25:1, so as to provide an injected water having a total dissolved solids content ranging from 500 to 5,000 ppm or from 1,000 to 5,000 ppm, a sulfate anion concentration of less than 7.5 ppm, less than 5 ppm, or less than 3 ppm, and a multivalent cation content of up to 50 ppm. Likewise, the source water may be seawater, estuary water, produced water, aquifer water, or wastewater. The TDS of the source water, RO permeate, NF permeate and injection water may be as given above. In an embodiment, the source water has a calcium cation concentration in the range of from 200 to 600 ppm. In an embodiment, the source water has a magnesium cation concentration in the range from 500 to 2000 ppm. The sulfate anion concentration in the RO permeate, NF permeate and injection water can be given as above. In embodiments, the concentration of multivalent cations in the RO permeate is in the range of from 1 to 10 ppm, from 1 to 5 ppm, or from 1 to 3 ppm. In embodiments, the concentration of multivalent cations in the NF permeate is in the range of from 50 to 200 ppm or from 50 to 150 ppm. The multivalent cation concentration of the injected water will depend on the desired TDS of the stream and thus on the mixing ratio of the RO permeate and the NF permeate. Thus, the multivalent cation concentration of the injected water will increase with increasing amount of NF permeate in the mixed stream. Typically, the multivalent cation concentration of the injection water stream with a total dissolved solids content of 1000 ppm is in the range of 2 to 10 ppm, and the range values of multivalent cation concentration should be scaled for injection water of higher TDS. Alternatively or additionally, in an embodiment, the NF source water can be an intermediate stream from the RO membrane stack, such as the effluent/retentate from the first RO array, resulting in a proportional increase in TDS and ion concentration in the NF permeate.

As discussed above, where increased oil recovery is desired with a low salinity injection water, the ratio of the multivalent cation concentration of the low salinity injection water to the multivalent cation concentration of the connate water should be less than 1. The multivalent cation concentration of the connate water is typically several times the multivalent cation concentration of the injection water formed by mixing the RO permeate and the NF permeate according to the process of the present invention. Thus, the injection water has a desired low salinity and a desired low multivalent cation concentration in order to achieve increased oil recovery when injected into the hydrocarbon containing formation of the reservoir, while having a sufficient total dissolved solids content to prevent formation damage and a sufficiently low sulfate concentration to mitigate the risk of acidizing in the reservoir (and to mitigate the risk of precipitation of insoluble mineral salts in the formation and/or the production well).

Typically, the formation into which the injection water having controlled salinity (controlled TDS), controlled low sulfate anion concentration, and controlled low multivalent cation concentration is injected is an oil bearing sandstone formation containing high swelling clay (e.g., montmorillonite clay) content. A high swelling clay content means that the swelling clay content is 10% by weight or more, for example the swelling clay content is in the range of 10 to 30% by weight.

In embodiments, the RO permeate and the NF permeate are mixed in a volume ratio (volume of RO permeate to volume of NF permeate) of from 2:1 to 40:1, from 4:1 to 27:1, or from 10:1 to 25: 1. Those skilled in the art will appreciate that the specific mixing ratio depends on one or more of the following factors: (a) salinity of the source water; (b) sulfate concentration of source water; (c) a multivalent cation concentration of the source water; (d) the temperature at which the RO and NF membrane units are operated; (e) the volume percent recovery at which the RO and NF membrane units are operated; (f) the desired salinity of the injected water; (g) the desired sulfate anion concentration of the injected water; and (h) the desired multivalent cation concentration of the injected water. The factors (f), (g) and (h) in turn depend on the characteristics of the reservoir into which the treated water is to be injected, such as the amount of swelling clay, the content and characteristics of Sulfate Reducing Bacteria (SRB) and the multivalent cation concentration of the connate water. Thus, depending on the mixing ratio of RO permeate to NF permeate, the injection water stream will have a salinity sufficient to control formation damage, a sufficiently low sulfate concentration to control acidization in the oil reservoir, and a sufficiently low multivalent cation concentration, where the ratio of the multivalent cation concentration of the injection water to the multivalent cation concentration of the connate water of the formation is less than 1.

Advantageously, via the control system 52, the mixing ratio of RO permeate and NF permeate is controlled in accordance with the measured variable provided to the RC56 from the sensor S, Q and monitored by the monitoring controller 55 and/or the trend of the measured or calculated value from the RC56 monitored by the monitoring controller 55 in coordination with the measured or calculated value from the regulating controller. Control may be automatic or semi-automatic (e.g., through user input via CP 53), utilizing a supervisory controller 55 as well as the above-described regulatory controller 56 and feedback control system. As mentioned above, the measured variable may be one or more properties of the injected water, for example, the measured variable may be related to the salinity (TDS content) of the injected water and may be the conductivity of the injected water. Conductivity is a measure of the TDS content of the injected water. Alternatively or additionally, the measured variable may be related to the multivalent anion concentration in the injected water or the NF permeate, or to the selected divalent anion (such as sulfate anion) concentration in the injected water or in the NF permeate. Alternatively or additionally, the measured variable may be related to the multivalent cation concentration in the injected water or the NF permeate, or to the concentration of selected multivalent cations (such as calcium cations and/or magnesium cations) in the injected water or in the NF permeate. As described above, the flow rate of the injected water flow (e.g., in lines 18 and/or 58) or the source water flow (e.g., in lines 30 and/or 2) may also be controlled based on a measured variable (e.g., via one or more variables measured by sensor S or flow rate sensor Q).

The "single pass, single stage" mode means that feed water is passed through a plurality of individual membrane units arranged in parallel. Thus, feed water is delivered to each of the membrane units and permeate and retentate streams are removed from each membrane unit. The permeate streams are then combined to form a combined permeate stream. When operating in the "single pass single stage" mode, the percent recovery of the membrane unit is: [ (volume of combined permeate stream/volume of feed water) x 100 ]. These volumes are determined over a set period of time, such as the volume of feedwater treated during a day and the volume of the combined permeate stream produced during a day.

By "single pass dual stage" mode is meant that the feed water is fed to the first of two membrane units arranged in series, with the retentate from the first membrane unit serving as feed water to the second membrane unit in series. Typically, there is a plurality of first membrane units arranged in parallel and a plurality of second membrane units arranged in parallel. In general, there are fewer second membrane units than first membrane units, because the second membrane units will handle a smaller volume of water than the first membrane units in a set period of time. Typically, the permeate streams from the first membrane units are mixed to obtain a first permeate stream, and the retentate streams from the first membrane units are mixed to form a first retentate stream. The first retentate stream is then used as feed water to the plurality of second membrane units arranged in parallel. The permeate streams from the second membrane units are then typically mixed to obtain a second permeate stream. The second permeate stream is then combined with the first permeate stream to produce a combined permeate stream. The retentate streams from the second membrane units are typically mixed to obtain a combined retentate stream that is discharged from the desalination unit. However, when operating multiple membrane units in a "single pass bipolar" mode, there are other ways of combining the various flows that are within the common general knowledge of those skilled in the art.

When operating in "single pass dual stage" mode, the percent recovery of the membrane unit is: [ (volume of first permeate stream from first membrane unit + volume of second permeate stream from second membrane unit)/volume of feed water to first membrane unit)) x 100 ]. These volumes are determined over a set period of time, such as a day.

In an embodiment, the NF membrane unit is operated in a "single pass single stage" mode. In an embodiment, the RO membrane unit is operated in a "single pass single stage" mode or a "single pass dual stage" mode, in particular in a "single pass single stage" mode.

In embodiments, the computerized control systems and methods of the present disclosure may be used to provide low salinity injection water within a desired composition envelope. Such computerized control systems and methods may be particularly applicable during commissioning of a well, and in embodiments the computerized control systems and methods of the present disclosure may be used to commission a well via controlling the composition of low salinity injection water used during commissioning of the well.

Additional disclosure

The particular embodiments disclosed above are illustrative only, as the disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and such variations are considered within the scope and spirit of the disclosure. Alternative embodiments resulting from combining, integrating, and/or omitting features of the embodiments also fall within the scope of the present disclosure. Although the compositions and methods are described in open-ended terms for various elements or steps, including, comprising, including and including, the compositions and methods may be described as "consisting essentially of or" consisting of various elements and steps. Use of the term "optionally" with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives falling within the scope of the claim.

The numbers and ranges disclosed above may vary by some amount. Once a numerical range having a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, each range of values (of the form "from about a to about b" or, equivalently, "from approximately a to b" or, equivalently, "from approximately a-b") disclosed herein is to be understood as setting forth each number and range encompassed within the broader range of values. Also, the terms in the claims have their ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Furthermore, as used in the claims, the indefinite article a or an is defined herein to mean one or more of the element that it introduces. To the extent that any conflict arises in the use of a term or phrase in this specification and one or more patents or other documents, the definitions shall apply, consistent with this specification.

Embodiments disclosed herein include:

a: a control system configured to control operation of one or more Reverse Osmosis (RO) arrays, one or more Nanofiltration (NF) arrays, mixing systems, or combinations thereof within a desalination plant, wherein the control system comprises: a Control Panel (CP); a plurality of Regulation Controllers (RC); and a Supervisory Controller (SC), wherein the SC is in signal communication with the CP and with each of the plurality of RCs, wherein the SC is configured to: receiving user input from a CP and input from a plurality of RCs regarding data from a plurality of sensors within a desalination device, wherein each of the plurality of RCs is in signal communication with the plurality of sensors, wherein the plurality of RCs are configured to: receive data from one or more of the plurality of sensors, provide an output to the SC and receive a permission from the SC, and instruct one or more of the plurality of devices of the desalination apparatus in response to the permission received from the SC, and wherein the SC is configured to: input trends with respect to data received from the plurality of RCs and/or predictions from data received from the plurality of RCs are monitored and permissions for each RC are determined based on the monitored trends, user input from the CP, or a combination thereof.

B: a desalination apparatus comprising: a water inlet line; one or more Reverse Osmosis (RO) arrays in fluid communication with the water inlet line, wherein each of the one or more RO arrays is configured to receive RO feedwater and generate an RO permeate and an RO concentrate; a Nanofiltration (NF) array in fluid communication with the water inlet line, the one or more RO arrays, or both, wherein the NF array is configured to generate a NF permeate and a NF concentrate; a mixing system, wherein the mixing system comprises: an RO permeate feed line, an NF permeate feed line, a mixing point configured to mix RO permeate from the RO permeate feed line and NF permeate from the NF permeate feed line to form a mixed low salinity injection water, and a discharge line configured to deliver the mixed low salinity injection water to the injection system; a plurality of valves and pumps configured to regulate the flow rate or pressure of various streams within the desalination device; a plurality of sensors configured to measure flow rate, pressure, temperature, composition, or a combination thereof, of various streams within the desalination device; a control system, wherein the control system is configured to: controlling operation of the one or more RO arrays, NF arrays and mixing system to be within operating parameters and maintaining composition of the mixed low salinity injection water within an operating envelope, wherein the control system comprises a plurality of Regulating Controllers (RC), a monitoring controller (SC) and a control panel, wherein a SC is in electronic communication with a CP and with each of a plurality of RCs, the SC receiving user input from the CP and input from the RCs regarding data of a sensor, wherein each of the plurality of RCs receives data from one or more of the plurality of sensors, provides output to the SC and receives permission from the SC, and indicating one or more of the plurality of valves and pumps in response to the permission received from the SC, and wherein the SC monitors trends in inputs received from the plurality of RCs and determines permissions for each RC based on the monitored trends, user inputs from the control panel, or a combination thereof.

A method of generating injection water, the method comprising: generating a reverse osmosis permeate stream; generating a nanofiltration permeate stream; mixing at least a portion of the reverse osmosis permeate stream with at least a portion of the nanofiltration permeate stream, the high salinity stream, or a combination thereof to provide a mixed low salinity water stream; and controlling the generation of the RO permeate stream, the NF permeate stream and the mixture within operating parameters and maintaining the composition of the mixed low salinity water stream within an operating envelope via a control system, wherein the control system comprises a plurality of conditioning controllers (RCs), a Supervisory Controller (SC) and a control panel, wherein the SC is in signal communication with the CP and with each of the plurality of RCs, the SC receiving user input from the CP and input from the RC regarding data from a plurality of sensors. Wherein each of the plurality of RCs receives data from one or more of the plurality of sensors, provides an output to the SC and receives permission from the SC, and indicates one or more of the plurality of valves and pumps in response to the permission received from the SC, and wherein the SC monitors trends in input regarding the data received from the plurality of RCs and determines the permission for each RC based on the monitored trends, user input from a control panel, or a combination thereof.

D: a method of controlling the composition of an injection fluid, the method comprising: receiving, by a Supervisory Controller (SC) of a control system, one or more compositional parameter targets of an injection fluid; and automatically adjusting the state of one or more valves to generate an injection fluid meeting the one or more constituent parameters via communication from the supervisory controller to one or more Regulatory Controllers (RCs) of the control system in communication with the one or more valves within the desalination unit.

Each of embodiments A, B, C and D may have one or more of the following additional elements:

element 1: wherein the plurality of sensors are selected from: an ion concentration sensor configured to measure at least one of conductivity, salinity, total concentration of dissolved ions, and/or concentration of individual ions (Ci) in various flow lines of the desalination device; temperature sensors configured to measure temperatures in various flow lines within the desalination device; a pressure sensor configured to measure pressure in various flow lines within the desalination device; a flow rate sensor configured to measure flow rates of various flow lines within the desalination device; or a combination thereof. Element 2: wherein the various flow lines include one or more selected from the following: an RO array feed line, an NF array feed line, an RO permeate line, an NF permeate line, an RO concentrate line, an NF concentrate line, a combined RO/NF permeate line, a mixed low salinity water stream line, an RO array permeate dump line, an NF array permeate dump line, a combined RO/NF permeate dump line, an ion concentrate feed line, a feed water bypass line, a Produced Water (PW) mixing line, or a combination thereof. Element 3: wherein the sensor is configured to provide data to the RC, wherein the RC provides its output to the SC, and/or wherein the SC monitors trends in one or more operating parameters selected from: a degree of fouling of the RO membranes of the one or more RO arrays, the NF membranes of the one or more NF arrays, or both; feed pressure to one or more RO arrays, one or more NF arrays, or both; a rate of change in feed pressure to one or more RO arrays, one or more NF arrays, or both; a feed flow rate to one or more RO arrays, one or more NF arrays, or both; pressure of concentrate from one or more RO arrays, one or more NF arrays, or both; pressure of permeate from one or more RO arrays, one or more NF arrays, or both; a pressure differential across one or more RO arrays, one or more NF arrays, or both; conductivity of permeate from one or more RO arrays, one or more NF arrays, or both; total Dissolved Solids (TDS) of permeate from one or more RO arrays, one or more NF arrays, or both; the temperature of the permeate from one or more RO arrays, one or more NF arrays, or both; permeate flow rates from one or more RO arrays, one or more NF arrays, or both; a concentrate flow rate from one or more RO arrays, one or more NF arrays, or both; recovery from one or more RO arrays, one or more NF arrays, or both; the flow rate, salinity, conductivity, and/or TDS of the feed water bypass stream, the flow rate, salinity, conductivity, and/or TDS of the Produced Water (PW) mixed stream, the flow rate, salinity, conductivity, and/or TDS of the mixed low salinity water stream, or a combination thereof. Element 4: wherein the plurality of devices comprise a plurality of valves and pumps, wherein the plurality of valves and pumps comprise one or more of: one or more valves and/or pumps on the feed lines to the RO array, the NF array, or a combination thereof; one or more valves and/or pumps on the permeate line from the RO array, the NF array, or a combination thereof; one or more valves and/or pumps on the permeate feed line from the RO array, the NF array, or both to the mixing system; one or more valves and/or pumps on the concentrate line from the RO array, the NF array, or a combination thereof; one or more valves and/or pumps on the combined RO/NF permeate line; one or more valves and/or pumps on the mixed low salinity water flow line from the mixing system; one or more valves and/or pumps in an ion concentrate line that introduces ion concentrate from the ion concentrate tank into the mixing system; (ii) a One or more valves and/or pumps on permeate dump lines from the RO array, the NF array, or both; one or more valves and/or pumps on a feedwater bypass line from the feedwater source to the mixing system; one or more valves and/or pumps on the PW mixing line to the mixing system; or a combination thereof. Element 5: wherein the valves comprise one or more valves configured to selectively combine at least a portion of the RO permeate with at least a portion of the NF permeate to generate the injection water having a composition within the operating envelope. Element 6: further comprising: a bypass line coupled to the water inlet line and the mixing system, a PW mixing inlet line fluidly connected to the mixing system, or both, wherein the valve further comprises one or more valves configured to selectively combine at least a portion of the feedwater from the water inlet line, at least a portion of the PW in the PW mixing line, or both, with the RO permeate from the RO permeate feed line and the NF permeate from the NF permeate feed line to generate the injection water having a composition within an operating envelope. Element 7: wherein the feed water comprises a greater concentration of divalent cations than the RO permeate. Element 8: wherein the sensor is selected from a temperature sensor, a pressure sensor, a flow rate sensor, an ion concentration sensor, or a combination thereof configured to measure at least one of conductivity, salinity, total concentration of dissolved ions, or concentration of individual ions (Ci). Element 9: wherein the sensors include one or more flow rate sensors, one or more pressure sensors, or a combination thereof. Element 10: wherein the one or more flow rate sensors, the one or more pressure sensors, or a combination thereof comprise sensors configured to measure a flow rate, a pressure, or both of at least one of: an RO permeate, an NF permeate, a mixed low salinity injection water, a feed water bypass stream, a Produced Water (PW) mixed stream, an ion concentrate stream, or a combination thereof. Element 11: further comprising a vessel containing an ion concentrate, wherein the valves comprise one or more valves configured to mix the ion concentrate with at least one of a reverse osmosis permeate, a nanofiltration permeate, a feedwater, or a mixed low salinity injection water to generate a composition within an operating envelope. Element 12: further comprising at least one of: an RO permeate dump line configured to pass a non-used portion of the RO permeate out of the desalination unit; a NF permeate dump line configured to pass a non-used portion of the NF permeate out of the desalination unit; or a feedwater bypass line dump line configured such that a non-used portion of the feedwater bypass flow passes out of the desalination device. Element 13: further comprising: controlling the dumping of a portion of the RO permeate stream from the desalination unit using a control system; dumping of a portion of the NF permeate stream from the desalination device, or a combination thereof, to provide a mixed low salinity water stream having a composition within the operating envelope. Element 14: wherein the RO permeate stream and the NF permeate stream are generated from a feed water, and wherein the high salinity stream comprises at least a portion of the feed water, a Produced Water (PW) stream, or a combination thereof. Element 15: wherein the composition comprises a sulfate anion concentration below a sulfate concentration threshold. Element 16: wherein the mixing further comprises mixing at least a portion of the ion concentrate with the at least a portion of the RO permeate stream, the at least a portion of the nanofiltration permeate stream, the high salinity stream, or a combination thereof to provide the mixed low salinity water stream. Element 17: wherein the one or more composition parameters include a total dissolved solids content of the injected fluid. Element 18: wherein automatically adjusting the state of the one or more valves comprises adjusting the one or more valves to change the flow rates of the RO permeate, the NF permeate, the PW flow, the feedwater bypass flow, the ion concentrate flow, or a combination thereof that are mixed to provide the injection fluid.

While certain embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the teachings of the disclosure.

Numerous other modifications, equivalents, and alternatives will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace such modifications, equivalents, and alternatives as may be appropriate. Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including equivalents of the subject matter of the claims.