A system and method for measuring rock in-situ gas diffusion coefficient and permeability

Abstract

The present invention discloses a system and method for measuring the in-situ gas diffusion coefficient and permeability of rocks. The measurement system includes: a diffusion and permeability measurement unit, which includes: a gas cylinder assembly, including a first target gas cylinder, a reference gas cylinder and a second target gas cylinder connected in parallel with each other; a first diffusion chamber and a second diffusion chamber, the first end of the first diffusion chamber is connected to the first output node, and the second end of the first diffusion chamber is connected to the input port of the high-temperature and high-pressure reactor; the first end of the second diffusion chamber is connected to the second output node, and the second end of the second diffusion chamber is connected to the output port of the high-temperature and high-pressure reactor; a gas chromatograph, configured to detect the gas content and composition information connected thereto; and a pressure difference sensor, configured to detect the pressure difference between a fourth common node and a fifth common node.

Description

Technical Field

[0001] The present invention relates to the field of coal rock monitoring equipment, and in particular to a system and method for measuring the in-situ gas diffusion coefficient and permeability of rocks. Background Art

[0002] In recent years, the effective development of unconventional natural gas resources, such as shale gas and coalbed methane, has greatly alleviated pressure on my country's clean energy supply. With the increasing maturity of shallow shale gas and coalbed methane development and utilization technologies, the effective exploration and development of deep shale gas and coalbed methane resources is becoming a key guarantee for the sustained and efficient development of my country's natural gas industry. Gas migration in unconventional reservoirs, such as shale and coal, is a comprehensive process involving multiple mechanisms within millimeter-, micron-, and nanometer-scale pore-fracture networks. The in-situ high temperatures and high stresses of deep formations complicate gas migration within these reservoirs. Existing triaxial permeability testing devices for rock mostly use hydraulic oil as the pressure transmission medium, which cannot be heated or can only be heated to a relatively low temperature condition, and the achievable confining pressure conditions are relatively low. They cannot simulate the high temperature and high confining pressure environment of reservoirs thousands of meters deep, and their application in the study of gas migration behavior in deep reservoirs is restricted; existing devices only realize the single measurement of rock gas diffusion coefficient and permeability, fail to integrate the diffusion coefficient and permeability measurement functions, and cannot conduct comparative studies on the migration behavior of gas diffusion and seepage under the same conditions, which limits the in-depth analysis of the complex mechanism of gas migration process in rocks. Summary of the Invention

[0003] In response to the problems and needs raised above, this solution proposes a system and method for measuring the in-situ gas diffusion coefficient and permeability of rocks. Due to the adoption of the following technical features, it can achieve the above technical objectives and bring about many other technical effects.

[0004] The present invention provides a rock in-situ gas diffusion coefficient and permeability measurement system, comprising: a high-temperature and high-pressure reactor, a pressure control unit, a temperature control unit, and an external circulation water cooling unit, and further comprising:

[0005] Diffusion and osmosis measurement unit, comprising:

[0006] A gas cylinder assembly, comprising a first target gas cylinder, a reference gas cylinder, and a second target gas cylinder connected in parallel to each other, wherein the first target gas cylinder, the reference gas cylinder, and the second target gas cylinder have a first output node, a second output node, and a third output node;

[0007] a first diffusion chamber and a second diffusion chamber, wherein a first end of the first diffusion chamber is connected to the first output node, and a second end of the first diffusion chamber is connected to the input port of the high-temperature and high-pressure reactor; a first end of the second diffusion chamber is connected to the second output node, and a second end of the second diffusion chamber is connected to the output port of the high-temperature and high-pressure reactor;

[0008] A gas chromatograph having a first common node at its output end, one end of the first common node being connected between the first diffusion chamber and the input port to form a second common node, and the other end of the first common node being connected between the second diffusion chamber and the output port to form a third common node, configured to detect gas content and composition information connected thereto;

[0009] A pressure differential sensor, one end of which is connected between the second common node and the input port to form a fourth common node, and the other end of which is connected between the third common node and the output port to form a fifth common node, is configured to detect the pressure difference between the fourth common node and the fifth common node.

[0010] In addition, the rock in-situ gas diffusion coefficient and permeability measurement system and method according to the present invention may also have the following technical features:

[0011] In one example of the present invention, the invention further includes: a first supercharger and a second supercharger,

[0012] The first booster is disposed between the first output node and the first diffusion chamber and is configured to increase the pressure of the gas output by the first output node;

[0013] The second pressure booster is disposed between the second output node and the second diffusion chamber, and is configured to increase the pressure of the gas outputted from the second output node.

[0014] In one example of the present invention, the present invention further includes: a first gas heater and a second gas heater,

[0015] The first gas heater is disposed between the first supercharger and the first diffusion chamber and is configured to heat the gas pressurized by the first supercharger;

[0016] The second gas heater is disposed between the second supercharger and the second diffusion chamber, and is configured to heat the gas pressurized by the second supercharger.

[0017] In one example of the present invention, it further includes: a vacuum pump,

[0018] A sixth common node is formed at its output end. The sixth common node is arranged between the first common node and the third common node and is configured to perform a vacuum operation on the measurement system.

[0019] In one example of the present invention, the present invention further includes: a first barometer and a second barometer,

[0020] The first barometer is disposed downstream of the output of the first diffusion chamber and is configured to monitor the pressure of the gas flowing out of the first diffusion chamber;

[0021] The second gas pressure gauge is disposed downstream of an output of the second diffusion chamber and is configured to monitor the pressure of the gas flowing out of the second diffusion chamber.

[0022] In one example of the present invention, the present invention further comprises: a first on-off valve, a second on-off valve, a fifth on-off valve and a ninth on-off valve.

[0023] The first on-off valve is arranged at the input port and the fourth common node, the second on-off valve is arranged at the fourth common node and the second common node, the fifth on-off valve is arranged at the output port and the fifth common node, and the ninth on-off valve is arranged between the third common node and the second diffusion chamber.

[0024] Another object of the present invention is to provide a method for measuring the in-situ gas diffusion coefficient and permeability of rock as described above, comprising the following steps:

[0025] S10: injecting a first target gas at a target temperature and pressure into the first diffusion chamber from a first target gas cylinder, and then disconnecting the first target gas cylinder; injecting a second target gas at a target temperature and pressure into the second diffusion chamber from a second target gas cylinder, and then disconnecting the second target gas cylinder;

[0026] S20: The first target gas in the first diffusion chamber is circulated into the second diffusion chamber via the high-temperature and high-pressure reactor, wherein gas is collected from the first diffusion chamber and the concentration of the first target gas is detected by a gas chromatograph; gas is collected from the second diffusion chamber and the concentration of the first target gas is detected by a gas chromatograph; the above steps are repeated at specified intervals to collect gas from the first diffusion chamber and the second diffusion chamber, detect gas component characteristics using the gas chromatograph, and record the concentrations of the first target gas in the first diffusion chamber and the second diffusion chamber respectively;

[0027] S30: When the first target gas can be stably detected in the second diffusion chamber and its content increases regularly, after measuring multiple sets of first target gas content data, the diffusion coefficient of the first target gas is obtained by processing the data of the first target gas concentration changing with time.

[0028] In one example of the present invention, the diffusion system expression of the first target gas is:

[0029]

[0030] Where: E = A(1 / V1+1 / V2) / L, D is the diffusion coefficient of gas in shale, cm 2 / s; ΔC0, ΔC i are the initial time (t0) and t i The concentration difference of hydrocarbon gas between the two diffusion chambers at the moment, %; A is the cross-sectional area of ​​the rock sample, cm 2 ; L is the length of the rock sample, cm; V1 and V2 are the volumes of the first and second diffusion chambers, cm 3 .

[0031] Another object of the present invention is to provide a method for measuring the in-situ gas diffusion coefficient and permeability of rock as described above, comprising the following steps:

[0032] W10: Inject the reference gas of the first target pressure into the first diffusion chamber and the second diffusion chamber from the reference gas cylinder and then disconnect the reference gas cylinder;

[0033] W20: Continue to inject the reference gas into the first diffusion chamber to a second target pressure, so that a pressure difference is formed between the first diffusion chamber and the second diffusion chamber at both ends of the high-temperature and high-pressure reactor;

[0034] W30: The pressure difference in the first diffusion chamber and the gas flow rate of the coal rock sample flowing through the high-temperature and high-pressure reactor are obtained by the pressure difference sensor, and the sample permeability is calculated based on the pressure difference and gas flow rate data.

[0035] In one example of the present invention, the expression for the sample permeability is:

[0036]

[0037] Where: k is the permeability of gas in shale, m 2 ; μ is gas viscosity, Pa·s; ΔP0, ΔP i They are the initial time (t0) and time i (t i ) Gas pressure difference between the two diffusion chambers, Pa; P u,0 、P d,0 are the gas pressures in the upstream and downstream diffusion chambers at the initial moment, Pa.

[0038] Hereinafter, the best embodiment of the present invention will be described in more detail with reference to the accompanying drawings so that the features and advantages of the present invention can be easily understood. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention. The drawings are only used to illustrate some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.

[0040] Figure 1 2 is a schematic structural diagram of a system for measuring in-situ gas diffusion coefficient and permeability of rock according to an embodiment of the present invention;

[0041] Figure 2 Flow chart of a gas diffusion coefficient measuring method of a rock in-situ gas diffusion coefficient and permeability measuring system according to an embodiment of the present invention;

[0042] Figure 3 Flowchart of a permeability measurement method of a rock in-situ gas diffusion coefficient and permeability measurement system according to an embodiment of the present invention.

[0043] List of reference numerals:

[0044] Measurement system 1000;

[0045] High temperature and high pressure reactor 400;

[0046] Input port 410;

[0047] Output port 420;

[0048] Diffusion and permeation measurement unit 100;

[0049] Gas cylinder assembly 10;

[0050] First target gas cylinder 11;

[0051] a second target gas cylinder 12;

[0052] Reference gas cylinder 13;

[0053] a first diffusion chamber 20;

[0054] a second diffusion chamber 30;

[0055] Gas chromatograph 40;

[0056] differential pressure sensor 50;

[0057] a first supercharger 60;

[0058] a second supercharger 70;

[0059] a first gas heater 80;

[0060] A second gas heater 90;

[0061] Vacuum pump 110;

[0062] first barometer 120;

[0063] a second barometer 130;

[0064] a third barometer 140;

[0065] fourth barometer 150;

[0066] Flow meter 160;

[0067] First on-off valve 170;

[0068] A second on-off valve 180;

[0069] A third on-off valve 190;

[0070] Fourth on-off valve 200;

[0071] a fifth on-off valve 210;

[0072] a sixth on-off valve 220;

[0073] a seventh on-off valve 230;

[0074] an eighth on-off valve 240;

[0075] Ninth on-off valve 250;

[0076] tenth on-off valve 260;

[0077] eleventh on-off valve 270;

[0078] 12th on-off valve 280;

[0079] 13th on-off valve 290;

[0080] Fourteenth on-off valve 300;

[0081] Fifteenth on-off valve 310;

[0082] sixteenth on-off valve 320;

[0083] A first public node A;

[0084] a second public Node B;

[0085] A third public node C;

[0086] a fourth common node D;

[0087] a fifth public node E;

[0088] a sixth public node F;

[0089] A first output node G;

[0090] A second output node H;

[0091] The third output node J. DETAILED DESCRIPTION

[0092] In order to make the purpose, technical solution and advantages of the technical solution of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of specific embodiments of the present invention. The same figure marks in the drawings represent the same parts. It should be noted that the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0093] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by persons of ordinary skill in the field to which the invention belongs. The words "first", "second" and similar terms used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "a" or "an" do not necessarily indicate a quantity limitation. Words such as "include" or "comprising" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0094] According to the first aspect of the present invention, a rock in-situ gas diffusion coefficient and permeability measurement system 1000 is provided. Figure 1 As shown, it includes: a high-temperature and high-pressure reactor 400, a pressure control unit (including a confining pressure control unit and an axial pressure control unit), a temperature control unit and an external circulation water cooling unit, and also includes:

[0095] Diffusion and permeation measurement unit 100, comprising:

[0096] The gas cylinder assembly 10 includes a first target gas cylinder 11, a reference gas cylinder 13, and a second target gas cylinder 12 connected in parallel to each other, wherein the first target gas cylinder 11, the reference gas cylinder 13, and the second target gas cylinder 12 have a first output node G, a second output node H, and a third output node J;

[0097] A first diffusion chamber 20 and a second diffusion chamber 30, wherein a first end of the first diffusion chamber 20 is connected to the first output node G, and a second end of the first diffusion chamber 20 is connected to the input port 410 of the high-temperature and high-pressure reactor 400; a first end of the second diffusion chamber 30 is connected to the second output node H, and a second end of the second diffusion chamber 30 is connected to the output port 420 of the high-temperature and high-pressure reactor 400;

[0098] The gas chromatograph 40 has a first common node A at its output end. One end of the first common node A is connected between the first diffusion chamber 20 and the input port 410 to form a second common node B. The other end of the first common node A is connected between the second diffusion chamber 30 and the output port 420 to form a third common node C. The gas chromatograph 40 is configured to detect the gas content and composition information connected thereto.

[0099] a differential pressure sensor 50, one end of which is connected between the second common node B and the input port 410 to form a fourth common node D, and the other end of which is connected between the third common node C and the output port 420 to form a fifth common node E, configured to detect a pressure difference between the fourth common node D and the fifth common node E;

[0100] When determining the diffusion coefficient of a sample:

[0101] A first target gas at a target temperature and pressure is injected into the first diffusion chamber 20 from a first target gas cylinder 11, and then the first target gas cylinder 11 is disconnected. A second target gas at a target temperature and pressure is injected into the second diffusion chamber 30 from a second target gas cylinder 12, and then the second target gas cylinder 12 is disconnected. The first target gas in the first diffusion chamber 20 flows into the second diffusion chamber 30 via a high-temperature and high-pressure reactor 400, wherein gas is collected from the first diffusion chamber 20 and sent to a gas chromatograph 40 to detect the concentration of the first target gas. Gas is also collected from the second diffusion chamber 30 and sent to a gas chromatograph 40 to detect the concentration of the first target gas. The above steps are repeated at specified intervals to collect gas from the first diffusion chamber 20 and the second diffusion chamber 30, detect gas component characteristics using the gas chromatograph 40, and record the concentrations of the first target gas in the first diffusion chamber 20 and the second diffusion chamber 30, respectively. When the first target gas can be stably detected in the second diffusion chamber 30 and its content increases regularly, after measuring multiple sets of first target gas content data, the diffusion coefficient of the first target gas is determined by processing the data on the change in the first target gas concentration over time.

[0102] When determining the permeability of a sample:

[0103] After the reference gas cylinder 13 is used to inject reference gas of a first target pressure into the first diffusion chamber 20 and the second diffusion chamber 30, the reference gas cylinder 13 is disconnected; the reference gas is continued to be injected into the first diffusion chamber 20 to the second target pressure, so that a pressure difference is formed between the first diffusion chamber 20 and the second diffusion chamber 30 at both ends of the high-temperature and high-pressure reactor 400; the pressure difference value of the first diffusion chamber 20 and the gas flow rate of the coal rock sample flowing through the high-temperature and high-pressure reactor 400 are obtained by the pressure difference sensor 50, and the sample permeability is calculated based on the pressure difference value and the airflow flow rate data.

[0104] The present invention can achieve temperature and pressure conditions of 800MPa axial pressure, 300MPa confining pressure and 500°C, and can better simulate geological conditions such as high temperature, high confining pressure and high differential stress in deep strata; the present invention can realize single / synchronous loading and unloading of axial pressure and confining pressure conditions, and the cooperation between the two can realize the simulation of complex stress evolution paths in geological history periods; based on the rock triaxial deformation test system, the present invention integrates the gas diffusion coefficient / permeability measurement function, and can realize the simulation and characterization of gas migration behavior at different deformation stages during the high-temperature and high-pressure deformation process of rocks; the present invention has a more optimized and reasonable structure, higher efficiency and safety factor.

[0105] It should be noted that the high-temperature and high-pressure reactor 400, the pressure control unit (including the confining pressure control unit and the axial pressure control unit) (not shown in the figure), the temperature control unit (not shown in the figure) and the external circulation water cooling unit (not shown in the figure) are all existing technologies.

[0106] In one example of the present invention, the first supercharger 60 and the second supercharger 70 are further included.

[0107] The first booster 60 is disposed between the first output node G and the first diffusion chamber 20 and is configured to increase the pressure of the gas outputted from the first output node G;

[0108] The second booster 70 is disposed between the second output node H and the second diffusion chamber 30 and is configured to increase the pressure of the gas outputted from the second output node H.

[0109] That is to say, when measuring the diffusion coefficient and permeability of the sample, it is necessary to inject gas of the target pressure. By setting the first booster 60 and the second booster 70, the first target gas of the target pressure can be injected into the first diffusion chamber 20 and the second target gas of the target pressure can be injected into the second diffusion chamber 30, or the reference gas of the target pressure can be injected into the first diffusion chamber 20 and the second diffusion chamber 30; by setting the first booster 60 and the second booster 70, the gas in the gas cylinder assembly 10 connected thereto can be pressurized to reach the pressure set in the test, so as to simulate the deep formation pressure environment more realistically and accurately.

[0110] In one example of the present invention, the first gas heater 80 and the second gas heater 90 are further included.

[0111] The first gas heater 80 is disposed between the first supercharger 60 and the first diffusion chamber 20 and is configured to heat the gas pressurized by the first supercharger 60 ;

[0112] The second gas heater 90 is disposed between the second supercharger 70 and the second diffusion chamber 30 and is configured to heat the gas pressurized by the second supercharger 70 ;

[0113] That is to say, when measuring the diffusion coefficient and permeability of the sample, it is necessary to inject gas of the target temperature. By setting the first gas heater 80 and the second gas heater 90, the first target gas of the target temperature can be injected into the first diffusion chamber 20 and the second target gas of the target temperature can be injected into the second diffusion chamber 30, or the reference gas of the target temperature can be injected into the first diffusion chamber 20 and the second diffusion chamber 30; by setting the first gas heater 80 and the second gas heater 90, the gas in the gas cylinder assembly 10 connected thereto can be pressurized to reach the temperature set in the test, so as to simulate the temperature environment of the deep formation more realistically and accurately.

[0114] In one example of the present invention, it further includes: a vacuum pump 110,

[0115] A sixth common node F is formed at its output end, and the sixth common node F is arranged between the first common node A and the third common node C, and is configured to perform a vacuuming operation on the measurement system 1000;

[0116] The role of setting the vacuum pump 110 is mainly reflected in two aspects:

[0117] One aspect is that before conducting the high-temperature and high-pressure rock triaxial deformation test, the entire air circuit is first tested for air tightness; specifically, the vacuum pump 110 is run to the target negative pressure value; the vacuum pump 110 is turned off, and the pressure gauge reading of the vacuum pump 110 is continuously recorded. If the negative pressure value can be maintained, the air circuit system of the entire test device is airtight.

[0118] Another aspect is that during the diffusion coefficient and permeability tests, vacuum pump 110 is operated after the diffusion coefficient measurement is completed to clear residual gas in the gas path. During the permeability measurement, vacuum pump 110 is operated to reduce the gas pressure in the sample to the pressure a1 in the gas path before the diffusion coefficient measurement. The triaxial deformation test is then continued to the next measurement point to measure the diffusion coefficient and permeability of the sample at this deformation stage.

[0119] In one example of the present invention, the first barometer 120 and the second barometer 130 are further included.

[0120] The first barometer 120 is disposed downstream of the output of the first diffusion chamber 20 and is configured to monitor the pressure of the gas flowing out of the first diffusion chamber 20 ;

[0121] The second barometer 130 is disposed downstream of the output of the second diffusion chamber 30 and is configured to monitor the pressure of the gas flowing out of the second diffusion chamber 30 ;

[0122] By setting up the first barometer 120, the pressure of the gas flowing out of the first diffusion chamber 20 can be accurately monitored in real time; by setting up the second barometer 130, the pressure of the gas flowing out of the second diffusion chamber 30 can be accurately monitored in real time, so as to obtain the pressure of the gas in the first diffusion chamber 20 and the second diffusion chamber 30 in real time, so as to more accurately simulate the geological pressure environment.

[0123] In one example of the present invention, it further includes:

[0124] A third barometer 140 and a fourth barometer 150, wherein the third barometer 140 is provided at the first supercharger and the first air pressure heater, and is configured to measure the pressure of the gas after being pressurized by the first supercharger; the fourth barometer 150 is provided at the second supercharger and the second air pressure heater, and is configured to measure the pressure of the gas after being pressurized by the second supercharger.

[0125] In one example of the present invention, the flow meter 160 is further included.

[0126] It is disposed between the output port 420 and the second diffusion chamber 30 and is configured to measure the flow rate of the gas flowing out through the output port 420;

[0127] By providing the flow meter 160 , the flow rate of the gas flowing out through the output port 420 of the high-temperature and high-pressure reactor 400 can be measured, thereby facilitating the calculation of the permeability and diffusion coefficient.

[0128] In one example of the present invention, it also includes: a first on-off valve 170, a second on-off valve 180, a third on-off valve 190, a fourth on-off valve 200, a fifth on-off valve 210, a sixth on-off valve 220, a seventh on-off valve 230, an eighth on-off valve 240, a ninth on-off valve 250, a tenth on-off valve 260, an eleventh on-off valve 270, a twelfth on-off valve 280, a thirteenth on-off valve 290, a fourteenth on-off valve, a fifteenth on-off valve 310 and a sixteenth on-off valve 320.

[0129] The first on-off valve 170 is provided at the input port 410 and the fourth common node D, and is configured to control the on-off of the gas between the fourth common node D and the input port 410; the second on-off valve 180 is provided at the fourth common node D and the second common node B, and is configured to control the on-off of the gas between the second common node B and the fourth common node D; the third on-off valve 190 is provided between the fourth common node D and the pressure differential sensor 50, and is configured to control the on-off of the gas between the fourth common node D and the pressure differential sensor 50; the fourth on-off valve 200 is provided between the pressure differential sensor 50 and the fifth common node E, and is configured to control the on-off of the gas between the fifth common node E and the pressure differential sensor 50; the fifth on-off valve 210 is provided at the output port 420 and the fifth common node E, and is configured to control the on-off of the gas between the output port 420 and the fifth common node E; the sixth on-off valve 220 is provided between the second common node B and the first common node A, and is configured to control the on-off of the gas between the second common node B and the first common node A; the seventh on-off valve 230 is provided between the first common node A and the sixth common node F, and is configured to control the on-off of the gas between the first common node A and the sixth common node F; the eighth on-off valve 240 is provided between the sixth common node F and the third common node C, and is configured to control the on-off of the gas The on-off between the sixth common node F and the third common node C; the ninth on-off valve 250 is provided between the third common node C and the second diffusion chamber 30, and is configured to control the on-off of the gas between the third common node C and the second diffusion chamber 30; the tenth on-off valve 260 is provided between the first output node G and the first target gas cylinder 11, and is configured to control the on-off between the first target gas cylinder 11 and the first output node G; the eleventh on-off valve 270 is provided between the first output node G and the first supercharger 60, and is configured to control the on-off of the gas between the first output node G and the first supercharger 60; the twelfth on-off valve 280 is provided between the second target gas cylinder 12 and the first A third output node J between the output node G and the second output node H is configured to control the flow of gas between the second target gas cylinder 12 and the third output node J. A thirteenth on-off valve 290 is provided between the reference gas cylinder and the second output node H, and is configured to control the flow of gas between the reference gas cylinder and the second output node H. A fourteenth on-off valve 300 is provided between the second output node H and the second supercharger 70, and is configured to control the flow of gas between the second output node H and the second supercharger 70. A fifteenth on-off valve 310 is provided between the first supercharger 60 and the first gas heater 80, and is configured to control the flow of gas between the first supercharger 60 and the first gas heater 80.The sixteenth on-off valve 320 is provided between the second supercharger 70 and the second gas heater 90 and is configured to control the on-off of the gas between the second supercharger 70 and the second gas heater 90.

[0130] The process of the rock in-situ gas diffusion coefficient and permeability measurement system 1000 of the present invention is as follows:

[0131] (1) Before conducting the high-temperature and high-pressure rock triaxial deformation test, the entire gas path is first tested for air tightness.

[0132] (1-1) After loading the sample, close the tenth on-off valve 260, the twelfth on-off valve 280, and the thirteenth on-off valve 290, open the remaining on-off valves, and operate the vacuum pump 110 to the target negative pressure value;

[0133] (1-2) Turn off the vacuum pump 110 and continuously record the pressure gauge reading of the vacuum pump 110. If the negative pressure value can be maintained, the air tightness of the gas system of the entire test device is good.

[0134] (1-3) Open the first on-off valve 170, the second on-off valve 180, the sixth on-off valve 220 and the seventh on-off valve 230, and keep the remaining on-off valves closed.

[0135] (2) The triaxial deformation test process simulates the in-situ formation environment at the target depth and conducts rock deformation tests with different stress evolution paths. When the target temperature and pressure conditions are reached, the confining pressure, axial pressure, and temperature conditions are maintained, and the diffusion coefficient and permeability of the sample are measured. It should be noted that simulating the in-situ formation environment at the target depth and conducting rock deformation tests with different stress evolution paths are existing mature technologies.

[0136] (3) Real-time recording of gas concentration changes upstream and downstream of the sample and calculation of the diffusion coefficient; for example, the first target gas is methane, the second target gas is nitrogen, and the reference gas is helium;

[0137] (3-1) Record the reading a1 of the first barometer 120 as the pressure value in the sample during the deformation stage, and operate the vacuum pump 110 to clear the gas in the gas path that may be generated during the rock deformation process;

[0138] (3-2) Close the first on-off valve 170, the second on-off valve 180, the sixth on-off valve 220 and the seventh on-off valve 230; open the tenth on-off valve 260, the eleventh on-off valve and the fifteenth on-off valve 310, open the first booster 60 and the first gas heater 80, and fill the first diffusion chamber 20 with methane gas at the target temperature and pressure, then close the tenth on-off valve 260, the eleventh on-off valve 270 and the fifteenth on-off valve 310, and turn off the gas source; open the twelfth on-off valve 280, the fourteenth on-off valve 300 and the sixteenth on-off valve 320, open the second booster 70 and the second gas heater 90, and fill the second diffusion chamber 30 with nitrogen gas at the target temperature and pressure, then close the twelfth on-off valve 280, the fourteenth on-off valve 300 and the sixteenth on-off valve 320, and disconnect the gas source;

[0139] (3-3) Open the first diffusion chamber 20, the second diffusion chamber 30, and the first on-off valve 170, the second on-off valve 180, the fifth on-off valve 210, and the ninth on-off valve 250; open the sixth on-off valve 220, collect gas from the first diffusion chamber 20, and detect the CH4 gas concentration using the gas chromatograph 40, and then close the sixth on-off valve 220; open the seventh on-off valve 230 and the eighth on-off valve 240, collect gas from the second diffusion chamber 30, and detect the CH4 gas concentration using the gas chromatograph 40, and then close the seventh on-off valve 230 and the eighth on-off valve 240; repeat the above steps every 0.5 hours to collect gas from the two diffusion chambers, detect the gas component characteristics using the gas chromatograph 40, and record the methane concentration information in the two diffusion chambers;

[0140] (3-4) When methane can be stably detected in the nitrogen diffusion chamber and its content increases regularly, after measuring eight sets of gas content data, the shale methane diffusion coefficient can be calculated by processing the change of hydrocarbon gas concentration in the diffusion chamber over time according to the formula:

[0141]

[0142] Where: E = A(1 / V1+1 / V2) / L

[0143] Where: D is the diffusion coefficient of gas in shale, cm 2 / s; ΔC0, ΔC i are the initial time (t0) and t i The concentration difference of hydrocarbon gas between the two diffusion chambers at the moment, %; A is the cross-sectional area of ​​the rock sample, cm 2 ; L is the length of the rock sample, cm; V1 and V2 are the volumes of diffusion chambers 1 and 2, cm 3 .

[0144] (3-5) Open the first on-off valve 170, the second on-off valve 180, the fifth on-off valve 210, the sixth on-off valve 220, the seventh on-off valve 230, the eighth on-off valve 240 and the ninth on-off valve 250, run the vacuum pump 110, clean the residual gas in the gas circuit, and then close the sixth on-off valve 220, the seventh on-off valve 230 and the eighth on-off valve 240.

[0145] (4) Apply a pressure difference to the upstream and downstream of the sample, and record the upstream and downstream pressure change information in real time to measure the sample permeability.

[0146] (4-1) Open the first on-off valve 170, the second on-off valve 180, the fifth on-off valve 210, the ninth on-off valve 250, the eleventh on-off valve 270, the thirteenth on-off valve 290, the fourteenth on-off valve 300, the fifteenth on-off valve 310, and the sixteenth on-off valve 320, operate the first booster 60, the second booster 70, the first gas heater 80, and the second gas heater 90, and fill the first diffusion chamber 20, the second diffusion chamber 30, and the sample with helium (or other gas) to the target pressure P d,0 ;

[0147] (4-2) Close the first on-off valve 170, the second on-off valve 180, the fifth on-off valve 210, the ninth on-off valve 250, the fourteenth on-off valve 300, and the sixteenth on-off valve 320, and operate the first booster 60 and the first gas heater 80 to continue filling the first diffusion chamber 20 with helium (or other gases as needed) to the target pressure P u,0 , then closing the eleventh on-off valve, the thirteenth on-off valve 290 and the fifteenth on-off valve 310 to form a pressure difference between the first diffusion chamber 20 and the second diffusion chamber 30 upstream and downstream of the sample;

[0148] (4-3) Open the first on-off valve 170, the second on-off valve 180, the third on-off valve 190, the fourth on-off valve 200, the fifth on-off valve 210 and the ninth on-off valve 250, and use the pressure differential sensor 50 to record the gas pressure difference between the upstream and downstream first diffusion chambers 20 and the second diffusion chamber 30 in real time. Run the flow meter 160 to record the gas flow through the sample in real time. Based on the pressure difference at both ends of the sample and the gas flow data, calculate the sample permeability according to formula (2).

[0149]

[0150] Where: k is the permeability of gas in shale, m 2 ; μ is gas viscosity, Pa·s; ΔP0, ΔP i They are the initial time (t0) and time i (t i ) Gas pressure difference between the two diffusion chambers, Pa; P u,0 、P d,0are the gas pressures in the upstream and downstream diffusion chambers at the initial moment, Pa.

[0151] (5) Close the third on-off valve 190 and the fourth on-off valve 200, open the sixth on-off valve 220, the seventh on-off valve 230, and the eighth on-off valve 240, and operate the vacuum pump 110 to reduce the gas pressure in the sample to the pressure a1 in the gas path before the diffusion coefficient is measured; continue the triaxial deformation test to the next measurement point, and repeat steps (3) and (4) to test the diffusion coefficient and permeability of the sample at this deformation stage;

[0152] (6) Repeat step 5 to complete the diffusion coefficient and permeability of the sample at each deformation stage; then unload the sample from the diffusion and permeability measuring device.

[0153] According to the second aspect of the present invention, a gas diffusion coefficient measuring method of the rock in-situ gas diffusion coefficient and permeability measuring system 1000 as described above is as follows: Figure 2 As shown, the following steps are included:

[0154] S10: Injecting a first target gas at a target temperature and pressure into the first diffusion chamber 20 from the first target gas cylinder 11 and then disconnecting the first target gas cylinder 11; injecting a second target gas at a target temperature and pressure into the second diffusion chamber 30 from the second target gas cylinder 12 and then disconnecting the second target gas cylinder 12;

[0155] S20: The first target gas in the first diffusion chamber 20 is circulated into the second diffusion chamber 30 via the high-temperature and high-pressure reactor 400, wherein gas is collected from the first diffusion chamber 20 and sent to the gas chromatograph 40 to detect the concentration of the first target gas; and gas is collected from the second diffusion chamber 30 and sent to the gas chromatograph 40 to detect the concentration of the first target gas. The above steps are repeated at specified intervals to collect gas from the first diffusion chamber 20 and the second diffusion chamber 30, detect gas component characteristics using the gas chromatograph 40, and record the concentrations of the first target gas in the first diffusion chamber 20 and the second diffusion chamber 30 respectively.

[0156] S30: When the first target gas can be stably detected in the second diffusion chamber 30 and its content increases regularly, after measuring multiple sets of first target gas content data, the diffusion coefficient of the first target gas is obtained by processing the data of the first target gas concentration changing with time.

[0157] Record the concentration changes of gases upstream and downstream of the sample in real time and calculate the diffusion coefficient; for example, the first target gas is methane, the second target gas is nitrogen, and the reference gas is helium;

[0158] Record the reading a1 of the first barometer 120 as the pressure value in the sample at this deformation stage, and operate the vacuum pump 110 to clear the gas in the gas path that may be generated during the rock deformation process;

[0159] Close the first on-off valve 170, the second on-off valve 180, the sixth on-off valve 220 and the seventh on-off valve 230; open the tenth on-off valve 260, the eleventh on-off valve and the fifteenth on-off valve 310, open the first supercharger 60 and the first gas heater 80, and fill the first diffusion chamber 20 with methane gas at the target temperature and pressure, then close the tenth on-off valve 260, the eleventh on-off valve 270 and the fifteenth on-off valve 310, and cut off the gas source; open the twelfth on-off valve 280, the fourteenth on-off valve 300 and the sixteenth on-off valve 320, open the second supercharger 70 and the second gas heater 90, and fill the second diffusion chamber 30 with nitrogen gas at the target temperature and pressure, then close the twelfth on-off valve 280, the fourteenth on-off valve 300 and the sixteenth on-off valve 320, and cut off the gas source;

[0160] Open the first diffusion chamber 20, the second diffusion chamber 30, and the first on-off valve 170, the second on-off valve 180, the fifth on-off valve 210, and the ninth on-off valve 250; open the sixth on-off valve 220, collect gas from the first diffusion chamber 20, and detect the CH4 gas concentration using the gas chromatograph 40, then close the sixth on-off valve 220; open the seventh on-off valve 230 and the eighth on-off valve 240, collect gas from the second diffusion chamber 30, and detect the CH4 gas concentration using the gas chromatograph 40, then close the seventh on-off valve 230 and the eighth on-off valve 240; repeat the above steps every 0.5 hours to collect gas from the two diffusion chambers, detect the gas component characteristics using the gas chromatograph 40, and record the methane concentration information in the two diffusion chambers;

[0161] When methane can be stably detected in the nitrogen diffusion chamber and its content increases regularly, after eight sets of gas content data are measured, the shale methane diffusion coefficient can be calculated according to the formula by processing the change of hydrocarbon gas concentration in the diffusion chamber over time.

[0162] In one example of the present invention, the diffusion system expression of the first target gas is:

[0163]

[0164] Where: E = A(1 / V1+1 / V2) / L, D is the diffusion coefficient of gas in shale, cm 2 / s; ΔC0, ΔC i are the initial time (t0) and t i The concentration difference of hydrocarbon gas between the two diffusion chambers at the moment, %; A is the cross-sectional area of ​​the rock sample, cm 2 ; L is the length of the rock sample, cm; V1 and V2 are the volumes of the first diffusion chamber 20 and the second diffusion chamber 30, cm 3 .

[0165] According to the third aspect of the present invention, a method for measuring permeability of a rock in-situ gas diffusion coefficient and permeability measuring system 1000 as described above is provided. Figure 3 As shown, the following steps are included:

[0166] W10: The reference gas cylinder 13 is disconnected after injecting the reference gas of the first target pressure into the first diffusion chamber 20 and the second diffusion chamber 30;

[0167] W20: Continue to inject the reference gas into the first diffusion chamber 20 to a second target pressure, so that a pressure difference is formed between the first diffusion chamber 20 and the second diffusion chamber 30 at both ends of the high-temperature and high-pressure reactor 400;

[0168] W30: The pressure difference sensor 50 obtains the pressure difference of the first diffusion chamber 20 and the gas flow rate of the coal rock sample flowing through the high-temperature and high-pressure reactor 400, and calculates the sample permeability based on the pressure difference and gas flow rate data.

[0169] Apply a pressure difference to the upstream and downstream of the sample, and record the upstream and downstream pressure change information in real time to measure the sample permeability.

[0170] Open the first on-off valve 170, the second on-off valve 180, the fifth on-off valve 210, the ninth on-off valve 250, the eleventh on-off valve 270, the thirteenth on-off valve 290, the fourteenth on-off valve 300, the fifteenth on-off valve 310 and the sixteenth on-off valve 320, operate the first booster 60, the second booster 70 and the first gas heater 80, the second gas heater 90, and fill the first diffusion chamber 20, the second diffusion chamber 30 and the sample with helium (or other gas) to the target pressure P d,0 ;

[0171] Close the first on-off valve 170, the second on-off valve 180, the fifth on-off valve 210, the ninth on-off valve 250, the fourteenth on-off valve 300, and the sixteenth on-off valve 320, and operate the first booster 60 and the first gas heater 80 to continue filling the first diffusion chamber 20 with helium (or other gases as needed) to the target pressure P u,0 , then closing the eleventh on-off valve, the thirteenth on-off valve 290 and the fifteenth on-off valve 310 to form a pressure difference between the first diffusion chamber 20 and the second diffusion chamber 30 upstream and downstream of the sample;

[0172] Open the first on-off valve 170, the second on-off valve 180, the third on-off valve 190, the fourth on-off valve 200, the fifth on-off valve 210 and the ninth on-off valve 250, and use the pressure differential sensor 50 to record the gas pressure difference between the upstream and downstream first diffusion chambers 20 and the second diffusion chamber 30 in real time. Run the flow meter 160 to record the gas flow through the sample in real time. Based on the pressure difference at both ends of the sample and the gas flow data, calculate the sample permeability according to formula (2).

[0173] In one example of the present invention, the expression for the sample permeability is:

[0174]

[0175] Where: k is the permeability of gas in shale, m 2 ; μ is gas viscosity, Pa·s; ΔP0, ΔP i They are the initial time (t0) and time i (t i ) Gas pressure difference between the two diffusion chambers, Pa; P u,0 、P d,0 are the gas pressures in the upstream and downstream diffusion chambers at the initial moment, Pa.

[0176] The exemplary implementation scheme of the rock in-situ gas diffusion coefficient and permeability measurement system 1000 and method proposed in the present invention is described in detail above with reference to the preferred embodiments. However, it can be understood by those skilled in the art that, without departing from the concept of the present invention, various modifications and variations can be made to the above-mentioned specific embodiments, and various technical features and structures proposed in the present invention can be combined in various ways without exceeding the scope of protection of the present invention, which is determined by the appended claims.

Claims

1. A rock in-situ gas diffusion coefficient and permeability measurement system, comprising: The high-temperature and high-pressure reactor (400), the pressure control unit, the temperature control unit and the external circulation water cooling unit are characterized by further comprising: A diffusion and permeation measurement unit (100), comprising: A gas cylinder assembly (10) comprises a first target gas cylinder (11), a reference gas cylinder (13) and a second target gas cylinder (12) connected in parallel to each other, wherein the first target gas cylinder (11), the reference gas cylinder (13) and the second target gas cylinder (12) have a first output node (G), a second output node (H) and a third output node (J); A first diffusion chamber (20) and a second diffusion chamber (30), wherein the first end of the first diffusion chamber (20) is connected to the first output node (G), and the second end of the first diffusion chamber (20) is connected to the input port (410) of the high-temperature and high-pressure reactor (400); the first end of the second diffusion chamber (30) is connected to the second output node (H), and the second end of the second diffusion chamber (30) is connected to the output port (420) of the high-temperature and high-pressure reactor (400); A gas chromatograph (40), having a first common node (A) at its output end, one end of the first common node (A) being connected between the first diffusion chamber (20) and the input port (410) to form a second common node (B), and the other end of the first common node (A) being connected between the second diffusion chamber (30) and the output port (420) to form a third common node (C), configured to detect gas content and composition information connected thereto; A pressure differential sensor (50) having one end connected between the second common node (B) and the input port (410) to form a fourth common node (D), and having the other end connected between the third common node (C) and the output port (420) to form a fifth common node (E), is configured to detect a pressure difference between the fourth common node (D) and the fifth common node (E).

2. The rock in-situ gas diffusion coefficient and permeability measurement system according to claim 1, characterized in that: It also includes: a first supercharger (60) and a second supercharger (70), The first booster (60) is disposed between the first output node (G) and the first diffusion chamber (20), and is configured to increase the pressure of the gas outputted from the first output node (G); The second booster (70) is disposed between the second output node (H) and the second diffusion chamber (30), and is configured to increase the pressure of the gas output from the second output node (H).

3. The rock in-situ gas diffusion coefficient and permeability measurement system according to claim 2, characterized in that: Also included: a first gas heater (80) and a second gas heater (90), The first gas heater (80) is disposed between the first supercharger (60) and the first diffusion chamber (20), and is configured to heat the gas pressurized by the first supercharger (60); The second gas heater (90) is disposed between the second supercharger (70) and the second diffusion chamber (30), and is configured to heat the gas pressurized by the second supercharger (70).

4. The rock in-situ gas diffusion coefficient and permeability measurement system according to claim 1, characterized in that: Also included: a vacuum pump (110), A sixth common node (F) is formed at its output end. The sixth common node (F) is arranged between the first common node (A) and the third common node (C) and is configured to perform a vacuum operation on the measurement system.

5. The rock in-situ gas diffusion coefficient and permeability measurement system according to claim 1, characterized in that: Also included: a first barometer (120) and a second barometer (130), The first barometer (120) is disposed downstream of the output of the first diffusion chamber (20) and is configured to monitor the pressure of the gas flowing out of the first diffusion chamber (20); The second gas pressure gauge (130) is disposed downstream of the output of the second diffusion chamber (30) and is configured to monitor the pressure of the gas flowing out of the second diffusion chamber (30).

6. The rock in-situ gas diffusion coefficient and permeability measurement system according to claim 1, characterized in that: It also includes: a first on-off valve (170), a second on-off valve (180), a fifth on-off valve (210) and a ninth on-off valve (250), The first on-off valve (170) is provided at the input port (410) and the fourth common node (D), the second on-off valve (180) is provided at the fourth common node (D) and the second common node (B), the fifth on-off valve (210) is provided at the output port (420) and the fifth common node (E), and the ninth on-off valve (250) is provided between the third common node (C) and the second diffusion chamber (30).

7. A method for measuring the in-situ gas diffusion coefficient and permeability of rock according to any one of claims 1 to 6, characterized in that: The steps include: S10: injecting a first target gas at a target temperature and pressure into the first diffusion chamber (20) from a first target gas cylinder (11), and then disconnecting the first target gas cylinder (11); injecting a second target gas at a target temperature and pressure into the second diffusion chamber (30) from a second target gas cylinder (12), and then disconnecting the second target gas cylinder (12); S20: The first target gas in the first diffusion chamber (20) is circulated into the second diffusion chamber (30) via the high-temperature and high-pressure reactor (400), wherein gas is collected from the first diffusion chamber (20) and sent to the gas chromatograph (40) to detect the concentration of the first target gas; gas is collected from the second diffusion chamber (30) and sent to the gas chromatograph (40) to detect the concentration of the first target gas; the above steps are repeated at specified intervals to collect gas from the first diffusion chamber (20) and the second diffusion chamber (30), detect gas component characteristics using the gas chromatograph (40), and record the concentrations of the first target gas in the first diffusion chamber (20) and the second diffusion chamber (30), respectively; S30: When the first target gas can be stably detected in the second diffusion chamber (30) and its content increases regularly, after measuring multiple sets of first target gas content data, the diffusion coefficient of the first target gas is obtained by processing the data of the first target gas concentration changing with time.

8. The rock in-situ gas diffusion coefficient and permeability measurement method according to claim 7, characterized in that: The diffusion system expression of the first target gas is: Where: E = A(1 / V1+1 / V2) / L, D is the diffusion coefficient of gas in shale, cm 2 / s; ΔC0, ΔC i are the initial time (t0) and t i The concentration difference of hydrocarbon gas between the two diffusion chambers at the moment, %; A is the cross-sectional area of ​​the rock sample, cm 2 ; L is the length of the rock sample, cm; V1 and V2 are the volumes of the first diffusion chamber (20) and the second diffusion chamber (30), cm 3 .

9. A method for measuring the in-situ gas diffusion coefficient and permeability of rock according to any one of claims 1 to 6, characterized in that: The steps include: W10: injecting a reference gas of a first target pressure into the first diffusion chamber (20) and the second diffusion chamber (30) from the reference gas cylinder (13), and then disconnecting the reference gas cylinder (13); W20: continuously injecting the reference gas into the first diffusion chamber (20) to a second target pressure, so that a pressure difference is formed between the first diffusion chamber (20) and the second diffusion chamber (30) at both ends of the high-temperature and high-pressure reactor (400); W30: The pressure difference value of the first diffusion chamber (20) and the gas flow rate of the coal rock sample flowing through the high-temperature and high-pressure reactor (400) are obtained by the pressure difference sensor (50), and the sample permeability is calculated based on the pressure difference value and the gas flow rate data.

10. The rock in-situ gas diffusion coefficient and permeability measurement method according to claim 9, characterized in that: The expression of sample permeability is: Where: k is the permeability of gas in shale, m 2 ; μ is gas viscosity, Pa·s; ΔP0, ΔP i They are the initial time (t0) and time i (t i ) Gas pressure difference between the two diffusion chambers, Pa; P u,0 、P d,0 are the gas pressures in the upstream and downstream diffusion chambers at the initial moment, Pa.

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