阅读说明：本技术 乳剂稳定性的表征 (Characterization of emulsion stability ) 是由 B·T·伯雷森 M·坦德 K·彼得森 于 2017-03-01 设计创作，主要内容包括：一种评估生产化学品对水和油乳剂的稳定性的影响的方法,乳剂包括生产化学品。方法包括：在检测部位处横跨乳剂施加电势差；测量由于施加的电势差而流经乳剂的电流；以及使用该测得的电流来评估生产化学品的影响。使用该测得的电流来评估生产化学品的影响的步骤可以包括,基于测得的电流确定是否已经达到或超过乳剂的临界电势。乳剂可以是原油乳剂。其可以是油包水乳剂。生产化学品可以是破乳剂。还提供了一种用于评估生产化学品对水和油乳剂的影响的设备。(methods of evaluating the effect of a production chemical on the stability of a water and oil emulsion, the emulsion including the production chemical, the method comprising applying a potential difference across the emulsion at a detection site, measuring a current flowing through the emulsion as a result of the applied potential difference, and using the measured current to evaluate the effect of the production chemical the step of using the measured current to evaluate the effect of the production chemical may comprise determining whether a critical potential of the emulsion has been reached or exceeded based on the measured current.)

A method of evaluating the effect of a production chemical on the stability of a water and oil emulsion, the emulsion comprising the production chemical, wherein the method comprises:

applying a potential difference across the emulsion at a detection site;

measuring the current flowing through the emulsion as a result of the applied potential difference; and

this measured current is used to provide an indication of the stability of the emulsion to assess the effect of the production chemical.

2. The method of claim 1, wherein the step of using the measured current to provide an indication of the stability of the emulsion comprises: determining whether a critical potential of the emulsion has been reached or exceeded based on the measured current.

3. The method of claim 2, wherein the measured current is compared to a reference current corresponding to the critical potential and if the measured current is greater than or equal to the reference current, it is determined that the critical potential of the emulsion has been reached or exceeded; determining that the critical potential has not been reached if the measured current is less than the reference current.

4. The method of claim 2, wherein after the step of measuring the current flowing through the emulsion, the method further comprises the step of :

increasing the potential difference across the emulsion;

measuring the current flowing through the emulsion as a result of the increased potential difference;

determining a rate of change of the current with respect to the potential difference;

comparing the determined rate of change to a reference rate of change value;

and determining that the critical potential of the emulsion has been reached or exceeded if the measured rate of change is greater than or equal to the reference rate of change value; determining that the critical potential has not been reached if the measured rate of change is less than the reference rate of change value.

5. The method of any of claims 2-4, wherein if it has been determined that the critical potential of the emulsion has not been reached, the method further steps include increasing the potential difference across the emulsion at the detection site, and repeating these steps:

measuring the current flowing through the emulsion as a result of the applied potential difference; and

using the measured current to provide an indication of the stability of the emulsion by determining whether a critical potential of the emulsion has been reached or exceeded based on the measured current.

6. The method of claim 5, wherein the method is repeated until the critical potential has been reached or exceeded.

7. The method of claim 5, wherein the method is repeated with a predetermined range of applied potential difference values; preferably in increments between 1 and 100V.

8. The method of any of the claims, wherein if it has been determined that the critical potential of the emulsion has been reached or exceeded, the method further comprises:

determining the critical potential based on the potential difference applied when it is determined that the critical potential has been reached or exceeded; and

comparing the critical potential of the emulsion to a reference critical potential to provide an indication of the stability of the emulsion to provide an effect of the production chemical.

9. The method of claim 8, wherein

Determining that the stability of the emulsion is at a desired level such that the production chemical is providing the correct effect if the critical potential corresponds to the reference critical potential or falls within a reference window around the reference critical potential;

determining that the stability of the emulsion is too high and the production chemical is not effective enough to break the emulsion if the critical potential is above the reference critical potential or above a reference window around the reference critical potential;

if the critical potential is below the reference critical potential or below a reference window around the reference critical potential, it is determined that the stability of the emulsion is too low and the production chemical is too effective in breaking the emulsion.

10. The method of any of the , further steps include adjusting a dosage of production chemicals to be added to the emulsion or to a process stream forming the emulsion based on the determined effect of the production chemicals;

or adjusting the type of production chemical to be added to the emulsion or to a process stream forming the emulsion based on the determined effect of the production chemical.

11. The method of claim 10 when dependent on claim 9, wherein if the critical potential exceeds the reference critical potential or is above a reference window around the reference critical potential, the dose of production chemical to be added to the emulsion or the process stream is reduced; and increasing the dosage of production chemicals to be added to the emulsion or the process stream if the critical potential is less than the reference critical potential or below a reference window around the reference critical potential.

12. The method of claim 10 when dependent on claim 9 or claim 11, further comprising the step of adding an adjusted dose of the production chemical to the emulsion or the process stream from which the emulsion is formed.

13. The method of claim 1, wherein the step of using the measured current to provide an indication of the stability of the emulsion comprises: the measured current is compared to a reference current value.

14. The method of claim 13, wherein the stability of the emulsion is determined to be acceptably low or too low if the measured current is greater than the reference current value or a window around the reference current value; preferably wherein the dosage of production chemicals to be added to the emulsion or to a process stream forming the emulsion is reduced if it is determined that the stability is too low.

15. The method of claim 13, wherein the stability of the emulsion is determined to be too high if the measured current is less than the reference current value or a window around the reference current value; preferably wherein the dosage of production chemicals to be added to the emulsion or to the process stream forming the emulsion is increased.

16. The method of any of the preceding claims , wherein the emulsion is a crude oil emulsion and/or wherein the emulsion is a water-in-oil emulsion.

17. The method of any of claims 10-12 or 14-16, wherein the production chemical to be added to the emulsion or the process stream is added upstream and/or downstream of the detection site.

18. The method of any of the , wherein the emulsion flows in a tube.

19. The method of claim 18, wherein the th of the pairs of electrodes is mounted on a wall of the tube.

20. The method of claim 19, wherein a second electrode of the pairs of electrodes is:

mounted on the wall of said tube and radially offset from said th electrode, and/or

Mounted on the wall of said tube and axially offset from said th electrode, and/or

Disposed within the emulsion.

21. The method of any of the , further steps include regulating the flow of the emulsion upstream of the detection site, preferably using a valve or a flow regulating device or a flow shifting device.

22. The method of any preceding claim , wherein the emulsion is diverted from a main emulsion flow path and the detection site is on the diverted flow path.

A method of for optimizing the stability of water and oil emulsions comprising the method of any of of claims 10-12 or 14-16.

24, apparatus configured to carry out the method of any of the preceding claims .

25, an apparatus for evaluating the effect of a production chemical on a water and oil emulsion comprising the production chemical, the apparatus comprising:

a counter electrode, the counter electrode configured to be disposed across the emulsion at a detection site;

a power supply connected across the counter electrode and configured to apply a potential difference across the counter electrode, and

a processing unit;

wherein the processing unit is configured to:

measuring the current flowing through the emulsion as a result of the applied potential difference, and

using the measured current to provide an indication of the stability of the emulsion to provide an effect of the production chemical.

26. The apparatus of claim 25, wherein the apparatus is configured to be disposed across a pipe carrying the emulsion.

27. The apparatus of claim 25 wherein the th of the pairs of electrodes is configured to be mounted on a wall of the tube.

28. The apparatus of claim 27, wherein a second electrode of the pairs of electrodes is configured to:

mounted on the wall of said tube and radially offset from said th electrode, and/or

Mounted on the wall of said tube and axially offset from said th electrode, and/or

Disposed within the emulsion.

29. The device of any of claims 25-28, further step includes an additional or more pairs of electrodes configured to be disposed across the emulsion at the detection site.

30. The method or apparatus of any preceding claim , wherein the production chemical is a demulsifier, a corrosion inhibitor, a bactericide or a scale inhibitor.

a tube for transporting an emulsion comprising the apparatus according to any of claims 25 to 29.

32. The tube of claim 31, wherein the detection site is located at a bypass section of the tube.

33. A tube according to claim 31 or 32, wherein a valve or flow altering or flow changing means is provided upstream of the detection site.

Technical Field

The present invention relates to the characterization of emulsion stability. In particular, it relates to a method and apparatus for assessing the effect of production chemicals, such as demulsifiers, on the emulsion stability of water or oil emulsions, preferably crude oil emulsions.

Background

Water-in-oil or oil-in-water emulsions can form in all stages from oil reservoirs and wellheads to the production and processing of separated and stored crude oil. These emulsions must be dissolved (i.e., the water and oil must be separated) to provide the end product with the desired quality.

Water-in-oil emulsions are stabilized by an interfacial film formed around water droplets at the oil/water interface. The components in these films enhance the stability of the emulsion by increasing the interfacial viscosity. The separation of emulsions into oil and water requires destabilization of these emulsion membranes. Demulsifiers (demulsifiers) may be added to assist in the destabilization of these membranes and ultimately enhance the separation of the emulsion.

Other production chemicals may be added to the process stream comprising a water-in-oil emulsion including a corrosion inhibitor and a biocide. These production chemicals may affect the stability of the emulsion if they are surface active and act directly on the water/oil mixture, or may interact with and reduce or increase the efficiency of the emulsion breaker that has been added to the emulsion.

Various methods are known for determining the stability of emulsions to which demulsifiers have been added, including:

1. the bottle test method, in which a demulsifier is added to the emulsion, the mixture is shaken to disperse the demulsifier, and the time to separation phase is recorded.

A technique for measuring coalescence of water droplets to determine emulsion stability based on light scattering in crude oil emulsions.

3. The dielectric constant of an emulsion is measured as measures of its stability the change in dielectric constant over time or the amount of demulsifier can be used as a measure of the stability of the emulsion.

The first two of these techniques are not suitable for real-time characterization of emulsions during crude oil processing, while the third technique requires advanced equipment for analyzing the frequency response.

Disclosure of Invention

Viewed from an aspect, the invention provides methods of assessing the effect of a production chemical on the stability of a water and oil emulsion, the emulsion comprising the production chemical, wherein the method comprises applying a potential difference across the emulsion at a detection site, measuring the current flowing through the emulsion as a result of the applied potential difference, and using the measured current to provide an indication of the stability of the emulsion to assess the sum of the effects of the production chemical.

Thus, the emulsion is an emulsion of water and oil. The water and oil emulsion may be a crude oil emulsion. May be a water-in-oil emulsion. Preferably, it is a water-in-oil crude oil emulsion.

In the "development of colloid and interface science recent techniques studied for measuring emulsion stability of oil/water emulsions are discussed in Advances in Colloid and interface Science, 100-_{Critical point of}) Therefore, it can be an index of the stability of the emulsion. E_{Critical point of}A larger value of (c) reflects a more stable dispersion because a larger electric field is required to align the water droplets to achieve electrical conduction.

An electric field strength ofThe potential difference is divided by the distance between the electrodes. Thus, with a constant separation distance of the electrodes, the electric field is proportional to the potential difference across the electrodes. As such, the potential difference at which the conductivity of the emulsion increases, i.e. corresponds to E_{Critical point of}Critical potential V of_{Critical point of}And can be used as an index of the stability of the emulsion.

The present inventors have realised that this technique can be developed for the assessment of the impact of production chemicals in water and oil emulsions, as described in aspect of the above-identified text invention, with significant advantages over the prior art methods discussed previously, particularly in terms of crude oil processing.

First, because there is no need to physically sample the process stream, the method is well suited for remote operation and process control.

Moreover, the method enables real-time measurement of the properties of the emulsion to be taken, which is highly advantageous in terms of process control. Because the effects of the production chemicals can be readily evaluated in real time, it can be determined in real time whether a change is required, such as a change in the dosage or type of production chemicals. Thus, the present invention is advantageous for short response times to correct for actions such as adjusting the dosage of production chemicals added to the emulsion.

This efficient control of emulsion stability facilitates careful control of the dosage of production chemicals being added to the emulsion and thus avoids waste of chemicals.

The production chemicals may be any type of production chemical used that affects the stability of the emulsion, such as demulsifiers, corrosion inhibitors, bactericides, or scale inhibitors, such production chemicals may directly affect the stability of the emulsion by having surface activity and acting directly on the water/oil mixture, or indirectly affect the emulsion properties by interacting with or reducing the efficiency of another production chemical present.

The concept of the present invention is independent of the type of emulsion or production chemical used. It can therefore be used to optimize the amount of production chemicals (e.g., demulsifiers) for a given crude oil or water composition.

It will be understood that "detection site" refers to the location at which the emulsion is to be examined, for example if the emulsion is flowing in a pipeline, the detection site may be a specific location on the pipeline.

Preferably, the step of using the measured current to provide an indication of the stability of the emulsion comprises determining whether a critical potential of the emulsion has been reached or exceeded based on the measured current. Thus, the critical potential can be used for online real-time monitoring of the effect of production chemicals, which in turn can be used for process control. Process changes that increase the stability of the emulsion will cause the critical potential to shift to higher values, while destabilization will lead to the opposite effect.

In embodiments, the measured current is correlated with the critical potential V_{Critical point of}It may thus be seen that in a second aspect the invention provides a method of assessing the effect of a production chemical on the stability of a water and oil emulsion, the emulsion comprising the production chemical, wherein the method comprises applying a potential difference across the emulsion at a detection site, measuring the current flowing through the emulsion as a result of the applied potential difference, and based on the measured current, determining that the critical potential of the emulsion has been reached or exceeded when the measured current is greater than a reference current corresponding to the critical potential, thereby assessing the effect of the production chemical on the stability of the emulsion.

In another embodiment, after the step of measuring the current flowing through the emulsion, the method further comprises increasing the potential difference across the emulsion, measuring the current flowing through the emulsion due to the increased potential difference, and determining a rate of change of the current with respect to the potential difference, wherein it is determined that the critical potential of the emulsion has been reached or exceeded when the rate of change of the current with respect to the potential difference is equal to or greater than a reference rate of change value.

Thus, in a third aspect, the invention may be said to provide methods of assessing the effect of a production chemical on the stability of a water and oil emulsion, the emulsion comprising the production chemical, wherein the method comprises applying a potential difference across the emulsion at a detection site, measuring the current flowing through the emulsion as a result of the applied potential difference, increasing the potential difference across the emulsion, measuring the current flowing through the emulsion as a result of the increased potential difference, and determining the rate of change of the current with respect to the potential difference, wherein it is determined that a critical potential of the emulsion has been reached or exceeded when the rate of change of the current with respect to the potential difference is equal to or greater than a reference rate of change value, thereby assessing the effect of the production chemical on the stability of the emulsion.

It is understood that reaching or exceeding means that the potential applied to the emulsion is equal to or above the critical potential of the emulsion.

If it has been determined that the critical potential of the emulsion has not been reached, the method described above may further comprise the step of increasing the potential difference across the emulsion at the detection site and repeating the steps of measuring the current flowing through the emulsion as a result of the applied potential difference and using the measured current to provide an indication of the stability of the emulsion by determining whether the critical potential of the emulsion has been reached or exceeded based on the measured current.

If it has been determined that the critical potential of the emulsion has been reached or exceeded, the method may further comprise the steps of determining the critical potential based on the potential difference applied when it is determined that the critical potential has been reached or exceeded, and comparing the critical potential of the emulsion to a reference critical potential to provide an indication of the stability of the emulsion to provide an effect of the production chemical.

In embodiments, if the critical potential corresponds to the reference critical potential or falls within a reference window around the reference critical potential, it is determined that the stability of the emulsion is at a desired level and the production chemical is providing the correct impact.

The effect of the production chemicals on the stability of the emulsion was thereby evaluated and understood. In case the production chemical is a demulsifier, the efficiency of the demulsifier can be understood from this. Embodiments of the method of the invention can thus be envisaged for carrying out different production chemicals, combinations of different production chemicals and different quantities of production chemicals to assess the effect of these different options on the stability of the emulsion and thus characterise the effect of the production chemicals.

By "reference window around the reference critical potential" is meant a range of values below and/or above the reference critical potential, which are considered to be close enough to the reference critical potential to represent the reference critical potential.

As discussed above, the critical potential is the potential difference applied when the water droplets align and the conductivity of the emulsion increases significantly. Therefore, the skilled person can easily define the reference current or the reference rate of change of the current corresponding to such critical potential, and the critical potential as appropriate for the particular application. The skilled person is also able to easily define a reference critical potential indicating a preferred stability of the emulsion, depending on the particular desired properties of the emulsion and the particular application.

Thus, while in a particular setting where the electrode spacing is constant, it is entirely convenient and somewhat simple to consider the applied potential difference and critical potential difference, it may alternatively be at the applied electric field and critical electric field E_{Critical point of}The invention is understood in the context of (1). In the case of electrode spacing changes, the applied electric field and the critical electric field should be used to ensure consistency viewed from a further aspect the invention therefore provides a method of assessing the effect of a production chemical on the stability of a water-in-oil emulsion comprising adding the production chemical to the emulsion, applying an electric field across the emulsion at a detection site, measuring the current flowing through the emulsion as a result of the applied electric field, and using this measured current to provide an indication of the stability of the emulsion to assess the effect of the production chemical.

Thus, the present method may adjust the dosage of the same production chemical, or the evaluation of the effect of the production chemical may adjust the dosage of another production chemical, a second production chemical, to be added to the emulsion or the emulsion-forming process stream.

Where it does not include adding the adjusted dosage to the emulsion or process stream, the method may further include adding the adjusted dosage of the production chemical to the emulsion or process stream.

In another embodiment, the type of production chemical may be adjusted based on the determined impact of the production chemical.

Thus, monitoring the effect of production chemicals by the present invention enables control of the stability of water and oil emulsions.

For example, if the critical potential exceeds the reference critical potential or is above a reference window around the reference critical potential, the dosage of production chemicals to be added to the emulsion or process stream may be reduced; alternatively, if the critical potential is less than the reference critical potential or below a reference window around the reference critical potential, the dosage of production chemicals to be added to the emulsion or process stream may be increased.

Thus, a fourth aspect of the present invention can be seen as providing methods of assessing the effect of a production chemical on the stability of a water and oil emulsion, the emulsion comprising the production chemical, wherein the method comprises applying a potential difference across the emulsion at a detection site, measuring the current flowing through the emulsion as a result of the applied potential difference, and comparing the measured current to a reference current value to assess the effect of the production chemical.

If the measured current is greater than the reference current value or a window around the reference current value, it can be determined that the stability of the emulsion is acceptably low. Alternatively, it may be determined that the stability is too low, then preferably the dosage of the production chemical to be added to the emulsion or to the process stream forming the emulsion is subsequently reduced. Alternatively, if the measured current is less than the reference current value or a window around the reference current value, it may be determined that the stability of the emulsion is too high. Preferably, the dosage of production chemicals to be added to the emulsion or to the processing stream forming the emulsion is subsequently increased.

In a very simple aspect, the embodiments of the invention can be thought of as follows.A power supply connected to the electrodes scans to a potential within a predetermined value.A water droplet will align at a given potential, producing a current.

Thus, viewed from a fifth aspect, the invention can be seen as providing methods of optimizing the stability of a water and oil emulsion, comprising adding a production chemical to an emulsion or an emulsion-forming process stream, applying a potential difference across the emulsion at a detection site, measuring a current flowing through the emulsion as a result of the applied potential difference, using the measured current to assess the effect of the production chemical, adjusting the dose of the production chemical to be added to the emulsion based on the determined effect of the production chemical, and adding the adjusted dose of the production chemical to the emulsion or the emulsion-forming process stream.

When production chemicals are added upstream, the effect of the production chemicals can be measured and further controlled based on the measured response.

Typically, the emulsion may flow in the tube. the st of the pair of electrodes may be mounted on the wall of the tube.A second of the pair of electrodes may be mounted on the wall of the tube and radially offset from the th electrode and/or mounted on the wall of the tube and axially offset from the th electrode and/or disposed within the emulsion.

In embodiments, the method can further include regulating the flow of emulsion upstream of the test site, preferably using a valve or a flow regulating device or a flow shifting device.

In particular embodiments, the emulsion is diverted from the main emulsion flow path and the detection site is on the diverted flow path.

Although embodiments of the present invention allow for optimization of emulsion stability through dosage adjustments of production chemicals, embodiments are also contemplated in which emulsion stability is not optimized through dosage adjustments. In such embodiments, the method of the invention can be used to simply characterize the response of different production chemicals by assessing their effect on the stability of the emulsion and the changes in the behaviour of the emulsion due to interference with other additives. The method can therefore be used to determine a reference critical potential for an emulsion to which production chemicals have been added.

The invention also extends to apparatus configured to carry out any of the above methods in particular, viewed from a sixth aspect, the invention provides apparatus for assessing the effect of a production chemical on the stability of a water and oil emulsion comprising the production chemical, the apparatus comprising a counter electrode configured to be arranged across the emulsion at a detection site, a power supply connected across the counter electrode and configured to apply a potential difference across the counter electrode, and a processing unit, wherein the processing unit is configured to measure the current flowing through the emulsion as a result of the applied potential difference and to use the measured current to provide an indication of the stability of the emulsion to provide the effect of the production chemical.

It will be appreciated that the critical potential of the emulsion depends on the spacing between the electrodes. Thus, the critical potential of the emulsion to which the production chemicals are added may differ depending on the setting of the electrodes. The critical electric field strength is constant regardless of the electrode spacing. However, since the electrode spacing is known, this critical potential can be used as an indicator of emulsion stability.

The device is easy to implement and does not require complex equipment.

The apparatus may be disposed across a pipe carrying the emulsion. The apparatus can thus be retrofitted or installed on existing pipes.

The th electrode of the pair may be mounted on the wall of the tube, the second electrode of the pair may be mounted on the wall of the tube and radially offset from the th electrode, and/or mounted on the wall of the tube and axially offset from the th electrode, and/or disposed within the emulsion.

The device may further include an additional or more pairs of electrodes configured to be disposed across the emulsion at the detection site for example, the pair of electrodes may be disposed horizontally at the detection site while the second pair of electrodes may be disposed perpendicular to the pair of electrodes the or another power supply would preferably connect the additional pair of electrodes across to apply a potential difference across the additional pair of electrodes and the processing unit would preferably measure the current flowing due to the potential difference applied across all of the pair of electrodes in this way the stratification of the flow of emulsion can be explained.

pipes for transporting emulsions including the above apparatus are also provided, as well as crude oil processing systems including such pipes.

The detection site may be located in a bypass section of the pipe upstream of the detection site a valve or a flow altering or flow shifting device may be provided.

The detection site may be located upstream of the pump. In this way, the stability of the emulsion upstream of the pump can be determined in order to ensure a correct understanding of the behaviour of the fluid entering the pump. Alternatively, the detection site may be located downstream of the pump. The pump may have a tendency to produce an emulsion. The stability of the emulsion exiting the pump can thus be determined in order to understand the behavior of the fluid exiting the pump.

Drawings

So that those skilled in the art to which the subject invention pertains will readily understand how to make and use the devices and methods of the subject invention without undue experimentation, embodiments herein will be described in detail, by way of example only, with reference to the figures, wherein:

FIG. 1 shows an exemplary embodiment of an apparatus for evaluating the effect of production chemicals on water-in-oil emulsions;

FIG. 2A shows an alternative exemplary embodiment of an apparatus for evaluating the effect of production chemicals on water-in-oil emulsions;

FIG. 2B shows an alternative exemplary embodiment of an apparatus for evaluating the effect of production chemicals on water-in-oil emulsions;

FIG. 3 shows an alternative exemplary embodiment of an apparatus for evaluating the effect of production chemicals on water-in-oil emulsions; and

FIG. 4 is a graph of critical potential in volts (V) versus emulsion breaker concentration for exemplary embodiments reference will now be made to the drawings in which like reference numerals identify like structural features or aspects of the present disclosure for purposes of explanation and illustration, and not limitation, a schematic of embodiments of an apparatus for assessing the effect of production chemicals on emulsion stability of a water-in-oil crude emulsion is shown in FIG. 1 and designated generally by reference numeral 100. other embodiments are shown in FIGS. 2A-4. production chemicals are typically emulsion breakers, but can be any production chemicals that have an effect on emulsion stability.

Detailed Description

The apparatus 100 includes counter electrodes 120a, 120b disposed across the crude oil emulsion at the detection site 116. the -th 120a of the counter electrodes 120a, 120b is arranged such that it is substantially parallel to the second 120b of the counter electrodes the apparatus 100 is disposed on the tube 110. the -th electrode 120a is disposed on the wall of the tube 110. the second electrode 120b is disposed on the wall of the tube 110, radially offset from the -th electrode 120a and substantially opposite the -th electrode 120 a.

The emulsion may be stagnant or may be allowed to flow within the pipe 110 carrying the crude oil emulsion and the production chemicals. Where the emulsion is allowed to flow, the direction of flow 130 of the emulsion may be generally from the upstream side 112 of the detection site 116 to the downstream side 114 of the detection site 116. Production chemicals, such as emulsion breakers, are added to the emulsion upstream 112 and/or downstream 114 of the detection site 116.

The pair of electrodes 120a, 120b is connected to a power source 140. The power source 140 provides a voltage, which may be either an ac or dc voltage (potential difference), or a combination thereof. In a preferred embodiment, a direct potential difference is applied. The power supply 140 may provide a fixed potential difference or may provide a variable potential difference. The maximum potential difference applied across the pair of electrodes 120a, 120b may vary depending on the application, but may be limited to less than 10,000V, and typically less than 1000V, due to the risk of sparking at high voltages. The electrodes may be formed of any suitable material; for many systems, stainless steel may be suitable, but for more corrosive environments, precious metals, precious metal oxides, carbon, and/or lead may be considered.

A processing unit 150 is disposed across the pair of electrodes 120a, 120 b. The processing unit 150 is configured to control the power supply 140 and measure the current flowing between the pair of electrodes 120a, 120 b.

The processing unit 150 can store values of the potential difference or series of potential differences applied across the pair of electrodes 120a, 120b, and further step can store corresponding measured current values.

The processing unit 150 may store or more reference characteristics the reference characteristics may be potential or current values representing preferred emulsion stability the processing unit 150 may store reference emulsion stability characteristics for different types of emulsions and production chemicals and different combinations of different emulsions and production chemicals.

The processing unit 150 may be connected to a display (not shown) configured to display to the operator the various measured and calculated values, such as the critical potential of the emulsion being evaluated and the manner of comparison of the value with a reference value.

The processing unit 150 is configured to determine and control the amount of emulsion breaker to be added to the emulsion upstream 112 and/or downstream 114 of the detection site 116 based on the measured current values, as discussed later.

The detection site 116 may be located at any stage in the crude processing line. The apparatus 100 may be installed in a well, in a pipeline, or in a process device (e.g., at or in a separator).

A th method of using the apparatus 100 of FIG. 1 to evaluate the effect of the emulsion breaker will now be described, the method utilizes measured current values to determine if a critical potential has been reached, the emulsion breaker is added to the emulsion at a point upstream 112 of the detection site 116, the emulsion with the emulsion breaker added then flows through the tubing 110 to the detection site 116, the power supply 140 applies a potential difference across the th electrode 120a and the second electrode 120b, the processing unit 150 then measures and records the potential difference across the th electrode 120a and the second electrode 120b and the current flowing between the th electrode 120a and the second electrode 120b, the processing unit 150 calculates the difference between the recorded current and the reference current to provide a current change value.

If the recorded current is less than the reference current, i.e., the current change value is a negative number, then it is determined that the potential difference applied across the th electrode 120a and the second electrode 120b is below the critical potential of the emulsion.

If it has been determined that the potential difference applied across the th and second electrodes 120a, 120b is below the critical potential of the emulsion being characterized, then the potential difference applied to the th and second electrodes 120a, 120b is subsequently increased, and the above process is repeated until it is determined that the current change value is zero or positive the potential difference applied across the th and second electrodes 120a, 120b may be increased at intervals (i.e., in steps of 1-100V.) in other words, the series of potential differences is "swept" in a step-wise fashion to determine when the critical potential has been reached.

If it has been determined that the potential difference applied across the th electrode 120a and the second electrode 120b is at or above the critical potential of the emulsion, the potential difference applied across the th electrode 120a and the second electrode 120b is stored as the measured critical potential in the processing unit 150.

The measured critical potential is then compared with a reference critical potential. The processing unit 150 calculates the difference between the measured critical potential and the reference critical potential and stores this value as the critical potential error. This error is then used to adjust the dosage of emulsion breaker added to the emulsion upstream 112 or downstream 114 of the detection site 116.

For example, if the measured critical potential is greater than the reference critical potential, i.e. the critical potential error is positive, the stability of the emulsion is determined to be too high. The dosage of the emulsion breaker to be added to the emulsion is then increased.

In another aspect, if the measured critical potential is less than the reference critical potential, i.e., the critical potential error is negative, then the stability of the emulsion is determined to be too low and the dosage of the emulsion breaker to be added to the emulsion may be reduced in the manner described above.

If the measured critical potential is equal to the reference critical potential, i.e., the critical potential error is zero, or the measured critical potential is within of the reference critical potential, then it is determined that the stability of the emulsion is desired or within a desired range.

A second method of using the apparatus 100 of FIG. 1 to assess the effect of the emulsion breaker will now be described, which is similar to the method of described above, except that instead of using measured current values, it uses the measured rate of change of the flowing current to determine whether the critical potential has been reached.

The potential difference applied across the electrode 120a and the second electrode 120b can be increased at intervals (i.e., in steps of 1-100V) across the first electrode 120a and the second electrode 120 b. the processing unit 150 measures and records the potential difference applied across the electrode 120a and the second electrode 120b and the corresponding current flowing through the emulsion.

If this calculated current value is less than the reference rate of change value (the reference rate of change value being indicative of the applied critical potential), then it is determined that the applied second potential difference is not at the critical potential of the emulsion the potential difference applied to the electrode 120a and the second electrode 120b is then increased and the above process is repeated until the calculated value is greater than or equal to the reference rate of change value.

However, if the calculated current value is greater than or equal to the reference rate of change value, it is determined that the applied second potential difference is at or above the critical potential of the emulsion.

The critical potential of the emulsion may be set to the arithmetic mean of the th potential difference and the second potential difference and stored in the processing unit 150 as the measured critical potential alternatively, the measured critical potential may be set equal to the applied second potential difference.

The measured critical potential is then compared with a reference critical potential. The processing unit 150 calculates the difference between the measured critical potential and the reference critical potential and stores this value as the critical potential error. This error is then used to adjust the dosage of emulsion breaker added to the emulsion upstream 112 or downstream 114 of the detection site 116, as described above.

A third method of assessing the effect of the emulsion breaker using the apparatus 100 of figure 1 will now be described. In this method, V is not actually calculated_{Critical point of}The emulsion with the emulsion breaker added thereto flows through the tubing 110 to the detection site 116. the power supply 140 applies a fixed potential difference across the th electrode 120a and the second electrode 120 b.

If the measured current is equal to the reference current, the conductivity of the emulsion is determined to determine that the stability of the emulsion is at a desired level or within a desired range. The dosage of the demulsifier added to the emulsion may not need to be adjusted.

If the measured current is greater than the reference current, the conductivity of the emulsion is determined to be too high and thus the stability of the emulsion is determined to be too low. To increase the stability of the emulsion, the dosage of the emulsion breaker to be added to the emulsion may be reduced in the manner described above. Alternatively, it may be determined that low stability of the emulsion is appropriate, so that the dosage of the demulsifier is not adjusted. This may depend on the magnitude of the difference between the measured current and the reference current.

If the measured current is less than the reference current, it is determined that the conductivity is too low such that the stability of the emulsion is too high. The dosage of emulsion breaker to be added to the emulsion upstream 112 or downstream 114 of the detection site 116 may then be adjusted (i.e., increased) as described above to reduce the stability of the emulsion.

In this manner, the dosage of emulsion breaker to be added to the emulsion may be adjusted if necessary to ensure that the stability of the emulsion is at or below a desired level.

For each of the above methods, once the dose of production chemical (e.g., demulsifier) to be added to the emulsion has been adjusted, the adjusted dose of production chemical is then added to the emulsion.

Each of the above methods describes an adjustment of the dose of production chemicals, such as emulsion breakers, initially added to the emulsion however, in other embodiments, another production chemicals may be adjusted based on whether the stability of the emulsion is determined to be too high or too low, for example, if the stability of the emulsion is determined to be too high, another production chemicals, such as another emulsion breaker, may also be added to correct the stability of the emulsion (or the dose of this other emulsion breaker may be increased). likewise, if the stability of the emulsion is determined to be too low, the dose of different production chemicals, such as a different emulsion breaker, being added to the emulsion may be decreased.

Also, instead of adjusting the dosage of production chemicals ( added initially or different), the type of production chemicals may be changed in order to correct the stability of the emulsion.

The production chemicals may be added upstream or downstream of the detection site.

The steps of adjusting the dosage of the production chemical and adding the production chemical to the emulsion may be fully automated and controlled by the processing unit 150 alternatively, for a manually controlled device, the critical potential of the emulsion to be evaluated and/or its comparison to a reference value may be indicated to the operator by a display.

FIG. 2A shows an alternative apparatus 200 for evaluating the effect of production chemicals on emulsion stability of crude oil emulsions according to embodiments of the invention electrode 120a may be disposed on the wall of tube 110 and a second electrode 120b may be disposed adjacent to electrode 120a such that it is axially offset from electrode 120a in a direction generally aligned with the flow direction 130 of the emulsion.

FIG. 2B shows another alternative apparatus 300 for evaluating the effect of production chemicals on emulsion stability of crude oil emulsions according to embodiments of the present invention the th electrode 120a may be disposed on the wall of the tube 110 and the second electrode 120B may be disposed within the tube 110 such that it is within the emulsion.

Fig. 3 shows yet another alternative apparatus 400 for evaluating the effect of production chemicals on emulsion stability of crude oil emulsions, a bypass pipe section 210 may be provided across pipe 110, an emulsion stream 230 to be characterized may be diverted from pipe 110 and flowed into bypass pipe section 210, the apparatus 100, 200, 400 described above may be provided across bypass pipe section 210 (instead of across the pipe itself as in those previous embodiments), the emulsion may be returned to pipe 110 downstream 214 of detection site 216 through flow path 240.

Optionally, a valve or a flow regulating/shifting device (e.g., a vortex element) may be provided upstream of the detection sites 116, 216 in order to regulate the flow of the emulsion before it reaches the detection sites 116, 216.

It can be clearly understood that the apparatus described above is not only capable of assessing the effect of the production chemicals on the water-in-oil emulsion, but also of optimizing the emulsion stability through dosage adjustments of the production chemicals. Accordingly, the apparatus and method of embodiments of the present invention may be considered to provide an apparatus and method for optimizing emulsion stability of a water-in-oil emulsion.

However, embodiments are also contemplated that do not optimize emulsion stability. Specifically, only the effect of the production chemical is evaluated in order to characterize the response of the production chemical. Different additives can be added to the emulsion and any changes made by the effect of the production chemicals evaluated.

FIG. 4 is a graph of critical potential versus emulsion breaker concentration for exemplary embodiments of the present invention showing the concept that as the emulsion breaker concentration increases (and thus the stability of the emulsion decreases), the critical potential will reach the point (here, near 660V) when it suddenly decreases, thus at this point the stability of the emulsion has decreased to the point where water droplets are easily aligned by the applied potential and current can flow.

Although the above embodiments are described in terms of applying a potential difference, it will also be appreciated from the previous description of the present application that the electric field generated by the applied potential difference is important in altering the physical properties of the conductivity of the emulsion, in other words the destabilization of the emulsion is caused by the electric field_{Critical point of}Can alternatively be applied in the applied electric field and the critical electric field E_{Critical point of}In the case of a change in electrode spacing, it should be the electric field applied and the critical electric field that ensures consistency is used.

While the apparatus and methods of the present disclosure have been shown and described with reference to embodiments, it will be readily understood by those skilled in the art that changes or modifications may be made thereto without departing from the scope of the present disclosure.