阅读说明：本技术 一种天然气水合物形成和分解流程的核磁共振系统 (Nuclear magnetic resonance system for natural gas hydrate forming and decomposing process ) 是由 邢东辉 秦绪文 陆程 沙志斌 耿澜涛 齐荣荣 李贤� 孟凡乐 余路 于 2020-12-24 设计创作，主要内容包括：本发明公开了一种天然气水合物形成和分解流程的核磁共振系统,包括用于存放岩心或填砂样品的岩心夹持器,所述岩心夹持器的左侧端口分别接入用于输入水源的水输入机构以及输入气源的气输入机构,所述岩心夹持器的外侧设有用于向所述岩心夹持器内部输入低场核磁共振的核磁共振生成器,所述岩心夹持器的内部连通有用于维持低温高压的低温高压机构,所述岩心夹持器的右侧端口连通有用于计量输出物质的计量机构,天然气水合物无核磁信号,因此天然气水合物生成过程中核磁信号逐渐降低,分解过程中核磁信号逐渐增加,核磁共振技术是定量评价天然气水合物生成分解过程的一种重要方法。(The invention discloses a nuclear magnetic resonance system for natural gas hydrate forming and decomposing process, which comprises a rock core holder for storing rock core or sand filling samples, the left port of the core holder is respectively connected with a water input mechanism for inputting a water source and an air input mechanism for inputting an air source, a nuclear magnetic resonance generator for inputting low-field nuclear magnetic resonance into the core holder is arranged on the outer side of the core holder, the inner part of the core holder is communicated with a low-temperature high-pressure mechanism for maintaining low temperature and high pressure, the right port of the core holder is communicated with a metering mechanism for metering output substances, the natural gas hydrate is free of nuclear magnetic signals, therefore, the nuclear magnetic signal is gradually reduced in the natural gas hydrate generation process, and the nuclear magnetic signal is gradually increased in the decomposition process, and the nuclear magnetic resonance technology is an important method for quantitatively evaluating the natural gas hydrate generation and decomposition process.)

1. A nuclear magnetic resonance system for natural gas hydrate forming and decomposing process comprises a core holder (1) for storing a core or a sand-filled sample, and is characterized in that: the utility model discloses a water input mechanism (2) and the gas input mechanism (3) of input air supply that are used for the input water source are inserted respectively to the left side port of core holder (1), the outside of core holder (1) is equipped with be used for to the inside nuclear magnetic resonance generator (4) of low-field nuclear magnetic resonance that inputs of core holder (1), the inside intercommunication of core holder (1) has low temperature high pressure mechanism (5) that are used for maintaining low temperature high pressure, the right side port intercommunication of core holder (1) has metering mechanism (6) that are used for the measurement output material, detection mechanism (7) that are used for detecting hydrate relevant parameter are installed to the left side access port and the right side discharge port of core holder (1).

2. The system of claim 1, wherein the system comprises: the core holder (1) comprises a core mixing chamber (11) for storing a core or a sand filling sample and accessing the water input mechanism (2) and the gas input mechanism (3), input materials of the water input mechanism (2) and the gas input mechanism (3) flow along the positive direction of the inside of the core mixing chamber (11), and a holder (12) forming a closed space with the core mixing chamber (11) is sleeved on the outer side of the core mixing chamber (11).

3. The system of claim 2, wherein the system further comprises: the water input mechanism (2) comprises a water source device (21) for generating hydrate, the output end of the water source device (21) is communicated with a constant-pressure constant-flow pump (22) for adjusting the pressure and the flow rate of a water source, the output end of the constant-pressure constant-flow pump (22) is communicated with a pressure-bearing container (23) for protection, and the output end of the pressure-bearing container (23) is communicated with the input end of the rock core mixing cavity (11).

4. The system of claim 2, wherein the system further comprises: the gas input mechanism (3) comprises a gas source device (31) used for generating hydrate materials, the output end of the gas source device (31) is communicated with a gas booster pump (32) used for enhancing gas pressure, the output end of the gas booster pump (32) is communicated with a pressure regulating valve (33) used for regulating gas conveying pressure, the output end of the pressure regulating valve (33) is communicated with a flow controller (34) used for controlling gas flow, and the output end of the flow controller (34) is communicated with the input end of the core mixing cavity (11).

5. The system of claim 2, wherein the system further comprises: the low-temperature high-pressure mechanism (5) comprises a cooling device (51) and a ring pressure tracking pump (52) which are respectively communicated with two ends of the holder (12) and are communicated with a closed space formed by the holder (12) and the core mixing cavity (11), the output end of the ring pressure tracking pump (52) is communicated with the input end of the cooling device (51), and fluorinated liquid flow in the closed space formed by the holder (12) and the core mixing cavity (11) forms reverse low-temperature circulating flow through the ring pressure tracking pump (52) and the cooling device (51).

6. The system of claim 1, wherein the system comprises: the metering mechanism (6) comprises a back pressure valve (61) which is installed at the right outlet end of the core mixing cavity (11) and used for limiting discharge pressure, and the discharge end of the back pressure valve (61) is respectively communicated with a balance (62) with a gas-liquid separator and a wet flowmeter (63).

7. The system of claim 2, wherein the system further comprises: the detection mechanism (7) comprises a computer terminal (71) used for receiving signals and controlling, a temperature sensor (72) used for detecting hydrate temperature and two pressure sensors (73) used for detecting hydrate pressure are communicated with the computer terminal (71), the two pressure sensors (73) are respectively communicated with ports on the left side and the right side of the rock core mixing cavity (11), and the temperature sensor (72) is communicated with a right side output port of the pressure sensor (73) at a right side discharge port of the rock core mixing cavity (11).

8. A nmr system according to any of claims 1-7, wherein the nmr system comprises:

step 100, measuring nuclear magnetism T2 spectrum signals of the dry rock core, and removing nuclear magnetism base signals during inversion;

step 200, saturating a sample, obtaining the porosity of the sample, and measuring the water content in the rock core;

step 300, loading a saturated water sample into a holder, starting a holder confining pressure liquid circulating cooling function, setting the temperature to be 2 ℃, keeping the pressure difference between confining pressure and pore pressure to be 2MPa by using a confining pressure tracking system, setting a high-pressure pump, increasing the pore pressure to be 5MPa by injecting water, and measuring the T2 distribution and nuclear magnetic resonance imaging of a saturated water core at the moment;

step 400, reducing the pore pressure of the rock core to atmospheric pressure, injecting methane gas into the rock core by using a gas booster pump, and monitoring the moisture change in the injection process;

500, after the temperature and the pressure meet the experimental requirements and are stabilized, performing a T2 spectrum test to obtain the water signal quantity of the rock core as initial experimental data and collecting nuclear magnetic resonance imaging data;

step 600, collecting a T2 spectrum in the experiment process, and acquiring nuclear magnetic image data when hydrate synthesis is obvious;

step 700, when the water signal quantity of the rock core is not reduced any more, considering that the hydrate synthesis reaches the maximum saturation, and acquiring the T2 spectrum and nuclear magnetic imaging data at the moment;

step 800, changing the pressure value of an outlet end back pressure valve to gradually reduce the pore pressure of the rock core to atmospheric pressure, observing the nuclear magnetic water signal quantity of the rock core, and when the signal quantity begins to increase, indicating that the hydrate in the rock core begins to decompose;

and 900, collecting a T2 spectrum in the hydrate decomposition process until the water signal quantity of the core does not change obviously, and obtaining the T2 spectrum and nuclear magnetic imaging data when the hydrate is considered to be completely decomposed.

9. The system of claim 8, wherein the system further comprises: in step 400, the specific steps of monitoring the moisture change are:

step 401, if the moisture change is small, and meanwhile, the gas can pass through the rock core to reach the outlet end, the experiment can be continued, and the gas is continuously and slowly pressurized until the pore pressure 5Mpa required by the experiment is reached;

step 402, if the water content changes greatly under gas displacement and a large amount of water is lost, sample loading needs to be carried out again, or a water pump is used for injecting water to saturate a sample;

and 403, if the gas can not pass through the rock core while keeping the moisture, connecting the inlet and the outlet of the holder by using the gas path, and injecting the gas from the inlet and the outlet simultaneously to slowly dissolve the gas into the rock core.

10. The nmr system of claim 8, wherein the experimental requirements for the temperature and pressure to be achieved in step 500 are as follows:

the experiment requires that the temperature to be reached is 2 ℃, and the core pore pressure to be reached is 5 Mpa.

Technical Field

The invention relates to the technical field of natural gas hydrate research, in particular to a nuclear magnetic resonance system for a natural gas hydrate forming and decomposing process.

Background

The natural gas hydrate is a clathrate crystal structure compound composed of natural gas and water under the conditions of low temperature and high pressure, is widely distributed in land permafrost regions and seabed deep gravel at the edges of continents, has the characteristics of wide distribution, large resource quantity, large energy density and the like, and is the key point of future exploration.

At present, some researches consider that natural gas hydrate mainly takes pore filling as main part and preferentially generates in coarse-grained sediment, and some researchers also consider that natural gas hydrate mainly takes particle cementing as main part and preferentially generates in fine-grained sediment, so that the generation and decomposition process of natural gas hydrate is not clear, and related petrophysical experiments and analysis are required to be carried out.

Because the natural gas hydrate needs to have a demand for the temperature and pressure of the environment during generation or decomposition, the prior art mainly prepares the natural gas hydrate in a small amount in a laboratory, and considering that the application of the natural gas hydrate and the future energy market are generally regarded well, a device for generating or decomposing the natural gas hydrate and detecting the generation and decomposition process of the natural gas hydrate is urgently needed to implement research.

Disclosure of Invention

The invention aims to provide a nuclear magnetic resonance system for a natural gas hydrate forming and decomposing process, which aims to solve the problems that the natural gas hydrate in the prior art needs to have requirements on the temperature and the pressure of the environment during the generation or decomposition and simultaneously detects and researches the generation and decomposition processes.

In order to solve the technical problems, the invention specifically provides the following technical scheme:

the utility model provides a nuclear magnetic resonance system of natural gas hydrate formation and decomposition flow, is including the rock core holder that is used for depositing rock core or sand pack sample, the left side port of rock core holder inserts the gas input mechanism that is used for inputing the water input mechanism at water source and input air supply respectively, the outside of rock core holder be equipped with be used for to the inside nuclear magnetic resonance generator of inputing low-field nuclear magnetic resonance of rock core holder, the inside intercommunication of rock core holder has the low temperature high pressure mechanism that is used for maintaining low temperature high pressure, the right side port intercommunication of rock core holder has the metering mechanism who is used for measuring output material, left side access port and right side discharge port install the detection mechanism who is used for detecting hydrate relevant parameter.

As a preferable scheme of the invention, the core holder comprises a core mixing chamber for storing a core or a sand-filled sample and connecting the water input mechanism and the gas input mechanism, the input materials of the water input mechanism and the gas input mechanism positively flow along the inside of the core mixing chamber, and the holder forming a closed space with the core mixing chamber is sleeved on the outer side of the core mixing chamber.

As a preferable scheme of the invention, the water input mechanism comprises a water source device for generating hydrate, an output end of the water source device is communicated with a constant-pressure constant-flow pump for adjusting the pressure and the flow rate of the water source, an output end of the constant-pressure constant-flow pump is communicated with a pressure-bearing container for protection, and an output end of the pressure-bearing container is communicated with an input end of the core mixing cavity.

As a preferable scheme of the present invention, the gas input mechanism includes a gas source device for generating a hydrate material, an output end of the gas source device is communicated with a gas booster pump for boosting gas pressure, an output end of the gas booster pump is communicated with a pressure regulating valve for regulating gas delivery pressure, an output end of the pressure regulating valve is communicated with a flow controller for controlling gas flow, and an output end of the flow controller is communicated with an input end of the core mixing chamber.

As a preferable scheme of the invention, the low-temperature high-pressure mechanism comprises a cooling device and a ring pressure tracking pump which are respectively communicated with two ends of the holder and communicated with a closed space formed by the holder and the core mixing cavity, an output end of the ring pressure tracking pump is communicated with an input end of the cooling device, and a fluorinated liquid flow in the closed space formed by the holder and the core mixing cavity forms reverse low-temperature circulation flow through the ring pressure tracking pump and the cooling device.

In a preferred embodiment of the present invention, the metering mechanism includes a back-pressure valve installed at the right outlet end for limiting a discharge pressure, and discharge ends of the back-pressure valve are respectively communicated with a balance with a gas-liquid separator and a wet flowmeter.

As a preferred scheme of the present invention, the detection mechanism includes a computer terminal for receiving and controlling signals, the computer terminal is communicated with a temperature sensor for detecting hydrate temperature and two pressure sensors for detecting hydrate pressure, the two pressure sensors are respectively communicated with left and right side ports of the core mixing chamber, and the temperature sensor is communicated with a right side output port of the pressure sensor located at a right side discharge port of the core mixing chamber.

As a preferable scheme of the invention, the method further comprises the following steps:

step 100, measuring nuclear magnetism T2 spectrum signals of the dry rock core, and removing nuclear magnetism base signals during inversion;

step 200, saturating a sample, obtaining the porosity of the sample, and measuring the water content in the rock core;

and 300, loading the saturated water sample into a holder, starting a pressure liquid circulating cooling function of the holder at a confining pressure of 2 ℃, and keeping the pressure difference between the confining pressure and the pore pressure at 2MPa by using a confining pressure tracking system. Setting a high-pressure pump, increasing the pore pressure to 5MPa by injecting water, and measuring the T2 distribution and the nuclear magnetic resonance imaging of the saturated water core at the moment;

step 400, reducing the pore pressure of the rock core to atmospheric pressure, injecting methane gas into the rock core by using a gas booster pump, and monitoring the moisture change in the injection process;

500, after the temperature and the pressure meet the experimental requirements and are stabilized, performing a T2 spectrum test to obtain the water signal quantity of the rock core as initial experimental data and collecting nuclear magnetic resonance imaging data;

step 600, collecting a T2 spectrum in the experiment process, and acquiring nuclear magnetic image data when hydrate synthesis is obvious;

step 700, when the water signal quantity of the rock core is not reduced any more, considering that the hydrate synthesis reaches the maximum saturation, and acquiring the T2 spectrum and nuclear magnetic imaging data at the moment;

step 800, changing the pressure value of an outlet end back pressure valve to gradually reduce the pore pressure of the rock core to atmospheric pressure, observing the nuclear magnetic water signal quantity of the rock core, and when the signal quantity begins to increase, indicating that the hydrate in the rock core begins to decompose;

and 900, collecting a T2 spectrum in the hydrate decomposition process until the water signal quantity of the core does not change obviously, and obtaining the T2 spectrum and nuclear magnetic imaging data when the hydrate is considered to be completely decomposed.

As a preferred embodiment of the present invention, in step 400, the specific steps of monitoring the moisture change are:

step 401, if the moisture change is small, and meanwhile, the gas can pass through the rock core to reach the outlet end, the experiment can be continued, and the gas is continuously and slowly pressurized until the pore pressure 5Mpa required by the experiment is reached;

step 402, if the water content changes greatly under gas displacement and a large amount of water is lost, sample loading needs to be carried out again, or a water pump is used for injecting water to saturate a sample;

and 403, if the gas can not pass through the rock core while keeping the moisture, connecting the inlet and the outlet of the holder by using the gas path, and injecting the gas from the inlet and the outlet simultaneously to slowly dissolve the gas into the rock core.

As a preferred embodiment of the present invention, in step 500, the specific values of the temperature, the pressure and the pressure required to be achieved by the experiment are:

the experiment requires that the temperature to be reached is 2 ℃, and the core pore pressure to be reached is 5 MPa.

As a preferable scheme, compared with the prior art, the invention has the following beneficial effects:

(1) the natural gas hydrate has no nuclear magnetic signal, so the nuclear magnetic signal is gradually reduced in the generation process of the natural gas hydrate, and the nuclear magnetic signal is gradually increased in the decomposition process, and the nuclear magnetic resonance technology is an important method for quantitatively evaluating the generation and decomposition process of the natural gas hydrate;

(2) the natural gas hydrate is generated in macropores firstly, and phase balance is achieved in a rock core with large porosity and large pore diameter more easily;

(3) the signal quantity of a small-aperture interval can be changed in the process of generating and decomposing the natural gas hydrate, the signal quantity is increased along with the generation of the hydrate and is reduced along with the decomposition of the hydrate;

(4) the decomposition rates of natural gas hydrate in cores with different pore structures are not uniform, and the larger the porosity and the pore diameter of the core are, the larger the initial decomposition rate of the hydrate is.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.

Fig. 1 provides an overall schematic connection diagram for an embodiment of the present invention.

Fig. 2 provides a hydrate formation core nmr T2 spectrum for an embodiment of the invention.

FIG. 3 provides a hydrate decomposed core NMR T2 spectrum for an embodiment of the invention;

fig. 4 provides a nuclear magnetic imaging of hydrate formation and decomposed cores according to an embodiment of the present invention.

The reference numerals in the drawings denote the following, respectively:

1-a core holder; 2-a water input mechanism; 3-gas input mechanism; 4-nuclear magnetic resonance generator; 5-a low temperature and high pressure mechanism; 6-a metering mechanism; 7-a detection mechanism;

11-core mixing chamber; 12-a gripper;

21-water source; 22-constant pressure constant flow pump; 23-a pressure-bearing container;

31-a gas source; 32-gas booster pump; 33-a pressure regulating valve; 34-a flow controller;

51-a cooling device; 52-ring pressure tracking pump;

61-a back pressure valve; 62-balance with gas-liquid separator; 63-a wet flow meter;

71-a computer terminal; 72-a pressure sensor; 73-temperature sensor.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1 to 3, the invention provides a nuclear magnetic resonance system for a natural gas hydrate formation and decomposition process, which includes a core holder 1 for storing a core or a sand-filled sample, a water input mechanism 2 for inputting a water source and an air input mechanism 3 for inputting an air source are respectively connected to a left port of the core holder 1, a nuclear magnetic resonance generator 4 for inputting low-field nuclear magnetic resonance into the core holder 1 is arranged on the outer side of the core holder 1, a low-temperature high-pressure mechanism 5 for maintaining low-temperature high-pressure is communicated with the interior of the core holder 1, a metering mechanism 6 for metering output substances is communicated with a right port of the core holder 1, and detection mechanisms 7 for detecting related parameters of hydrates are installed on a left access port and a right discharge port of the core holder 1.

The core holder 1 comprises a core mixing cavity 11 for storing a core or a sand filling sample and connecting a water input mechanism 2 and an air input mechanism 3, input materials of the water input mechanism 2 and the air input mechanism 3 positively flow along the inside of the core mixing cavity 11, and a holder 12 forming a closed space with the core mixing cavity 11 is sleeved on the outer side of the core mixing cavity 11.

The water input mechanism 2 comprises a water source device 21 for generating hydrate, the output end of the water source device 21 is communicated with a constant-pressure constant-flow pump 22 for adjusting the pressure and the flow rate of the water source, the output end of the constant-pressure constant-flow pump 22 is communicated with a pressure-bearing container 23 for protection, and the output end of the pressure-bearing container 23 is communicated with the input end of the rock core mixing cavity 11.

The gas input mechanism 3 comprises a gas source device 31 for generating hydrate materials, the output end of the gas source device 31 is communicated with a gas booster pump 32 for enhancing gas pressure, the output end of the gas booster pump 32 is communicated with a pressure regulating valve 33 for regulating gas conveying pressure, the output end of the pressure regulating valve 33 is communicated with a flow controller 34 for controlling gas flow, and the output end of the flow controller 34 is communicated with the input end of the core mixing cavity 11.

The low-temperature high-pressure mechanism 5 comprises a cooling device 51 and a ring pressure tracking pump 52 which are respectively communicated with two ends of the holder 12 and communicated with a closed space formed by the holder 12 and the core mixing cavity 11, the output end of the ring pressure tracking pump 52 is communicated with the input end of the cooling device 51, and the fluorinated liquid flow in the closed space formed by the holder 12 and the core mixing cavity 11 forms reverse low-temperature circulating flow through the ring pressure tracking pump 52 and the cooling device 51.

The metering mechanism 6 includes a back-pressure valve 61 installed at the right-side outlet end of the 11 and limiting the discharge pressure, and the discharge ends of the back-pressure valve 61 are communicated with a balance 62 with a gas-liquid separator and a wet flowmeter 63, respectively.

The detection mechanism 7 comprises a computer terminal 71 used for receiving signals and controlling, a temperature sensor 72 used for detecting hydrate temperature and two pressure sensors 73 used for detecting hydrate pressure are communicated with the computer terminal 71, the two pressure sensors 73 are respectively communicated with left and right side ports of the core mixing cavity 11, and the temperature sensor 72 is communicated with a right side output port of the pressure sensor 73 at a right side discharge port of the core mixing cavity 11.

The method comprises the following steps:

and step 100, measuring nuclear magnetism T2 spectrum signals of the dry rock core, and removing nuclear magnetism base signals during inversion.

And step 200, saturating the sample, obtaining the porosity of the sample, and measuring the water content in the rock core.

And 300, loading the saturated water sample into a holder, starting a pressure liquid circulating cooling function of the holder at a confining pressure of 2 ℃, and keeping the pressure difference between the confining pressure and the pore pressure at 2MPa by using a confining pressure tracking system. And setting a high-pressure pump, increasing the pore pressure to 5MPa by injecting water, and measuring the T2 distribution and the nuclear magnetic resonance imaging of the saturated water core at the moment.

And step 400, reducing the pore pressure of the rock core to atmospheric pressure, injecting methane gas into the rock core by using a gas booster pump, and monitoring the moisture change in the injection process.

In step 400, the specific steps of monitoring the moisture change are:

step 401, if the moisture change is small, and meanwhile, the gas can pass through the rock core to reach the outlet end, the experiment can be continued, and the gas is continuously and slowly pressurized until the experimental required pore pressure of 5Mpa is reached.

Step 402, if the moisture changes greatly under the gas displacement and a large amount of moisture is lost, sample loading needs to be carried out again, or a water pump is used for injecting water to saturate the sample.

And 403, if the gas can not pass through the rock core while keeping the moisture, connecting the inlet and the outlet of the holder by using the gas path, and injecting the gas from the inlet and the outlet simultaneously to slowly dissolve the gas into the rock core.

And 500, when the temperature and the pressure meet the experimental requirements, performing T2 spectrum test after the temperature and the pressure are stable, acquiring the water signal quantity of the rock core as initial experimental data, and acquiring nuclear magnetic resonance imaging data.

In step 500, the specific values of temperature, pressure and pressure required to be achieved by the experiment are:

the experiment requires that the temperature to be reached is 2 ℃, and the core pore pressure to be reached is 5 MPa.

Step 600, collecting a T2 spectrum in the experiment process, and acquiring nuclear magnetic image data when hydrate synthesis is obvious.

And 700, when the water signal amount of the core is not reduced any more, considering that the hydrate synthesis reaches the maximum saturation, and acquiring the T2 spectrum and nuclear magnetic imaging data at the moment.

And 800, changing the pressure value of the back pressure valve at the outlet end to gradually reduce the pore pressure of the rock core to atmospheric pressure, observing the nuclear magnetic water signal quantity of the rock core, and when the signal quantity begins to increase, indicating that the hydrate in the rock core begins to decompose, as shown in fig. 4, representing the generation of the hydrate and the decomposition of a nuclear magnetic imaging graph of the rock core.

And 900, collecting a T2 spectrum in the hydrate decomposition process until the water signal quantity of the core does not change obviously, and obtaining the T2 spectrum and nuclear magnetic imaging data when the hydrate is considered to be completely decomposed.

The above embodiments are only exemplary embodiments of the present application, and are not intended to limit the present application, and the protection scope of the present application is defined by the claims. Various modifications and equivalents may be made by those skilled in the art within the spirit and scope of the present application and such modifications and equivalents should also be considered to be within the scope of the present application.