Device and method for testing yield of free gas and adsorbed gas of shale gas reservoir

Abstract

The invention discloses a shale gas reservoir free gas and adsorbed gas yield testing device and method, and belongs to the technical field of shale gas reservoir development and productivity evaluation.The shale gas reservoir free gas and adsorbed gas yield testing device is characterized in that the inlet end of a shale holder is connected with the outlet end of a booster pump through a high-pressure pipeline; the inlet end of the booster pump is respectively connected with a methane gas cylinder, a helium gas cylinder and a vacuum pump through a four-way joint; the confining pressure inlet end of the core holder is connected with a confining pressure pump through a high-pressure pipeline; the outlet end of the core holder is connected with a back-pressure valve through a high-pressure pipeline, and a pressure sensor is arranged on the pipeline between the core holder and the back-pressure valve; the outlet end of the back-pressure valve is connected with a gas flowmeter; helium / methane saturation and gas production experiments are respectively carried out based on the test device, and free gas cumulative yield and adsorption gas cumulative yield are obtained according to a relation curve drawn by test data. The method can be used for quantitatively acquiring the free gas, the adsorbed gas and the cumulative yield of the shale gas reservoir, and the accuracy of a measurement result is improved.

Description

Technical Field

[0001] The present invention relates to the field of shale gas reservoir development and productivity evaluation, and in particular to a device and method for testing the production of free gas and adsorbed gas in a shale gas reservoir. Background Art

[0002] There are two main states of methane in shale gas reservoirs: free methane in the pores of shale, called free gas; adsorbed methane on the surface of kerogen and clay minerals and the internal pore walls, called adsorbed gas. Shale gas reservoirs are mostly produced by depressurization. At different depressurization production stages, the accurate splitting of adsorbed gas and free gas in the produced gas is of great significance to the analysis of shale gas reservoir production capacity and the evaluation of remaining reserves.

[0003] At present, the evaluation method for the volume of free gas and adsorbed gas in shale gas reservoir production is mainly calculated through the results of Langmuir isothermal adsorption experiments, or divided according to the change of gas production rate. The initial gas production rate is faster, mainly contributed by free gas, and the gas production rate decreases in the later period, which is mainly adsorbed gas.

[0004] For example, in the prior art, patent CN112394157A discloses a method for measuring the amount of adsorbed gas and free gas in shale. The patent and the measurement method include the following steps: 1) select shale core samples and measure basic physical parameters; 2) conduct exhaustion development experiments and draw the relationship curve between production time and total experimental gas production; 3) set the initial value of the correction coefficient according to the corrected free gas calculation formula and the corrected Langmuir adsorption formula, and draw the relationship curve between production time and calculated total gas production; 4) determine whether the relationship curves obtained in step 2) and step 3) meet the preset conditions, if not, adjust the correction coefficient, repeat step 3) until the preset conditions are met, and enter step 5); 5) draw the relationship curves between the calculated total gas production, the calculated free gas volume, and the calculated adsorbed gas volume and the production time, respectively, to obtain the real-time adsorbed gas volume, the real-time free gas volume and the real-time total gas production. This scheme is to calculate the adsorption amount according to the corrected Langmuir adsorption formula, and then obtain the adsorbed gas and free gas production.

[0005] However, the above method has certain shortcomings. The results of the Langmuir isothermal adsorption experiment reflect the maximum adsorption capacity of shale, and do not consider the dynamic process of desorption, the hysteresis effect and the problem of multi-molecular layer adsorption. Using the results of the isothermal adsorption experiment to calculate the adsorbed gas production is bound to overestimate the adsorbed gas production, so the measured experimental results have errors.

[0006] In addition, due to the simultaneous production of free gas and adsorbed gas during shale gas production, free gas is dominant in the early stage and adsorbed gas is dominant in the later stage. Therefore, the production of gases in different states can only be divided by the change in gas production rate, and the division standard is unclear, so the accuracy of the results is low. Summary of the invention

[0007] The present invention aims to solve the problem in the prior art that the accuracy of shale gas reservoir capacity analysis results is poor due to the inability to accurately split adsorbed gas and free gas, proposes a testing device and method for the free gas and adsorbed gas production of shale gas reservoirs, designs experiments to quantitatively obtain the cumulative production of free gas and adsorbed gas in shale gas reservoirs, and improves the accuracy of measurement results.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0009] A testing device for the production of free gas and adsorbed gas in shale gas reservoirs, characterized in that it comprises a shale clamp, wherein the inlet end of the core clamp is connected to the outlet end of a booster pump through a high-pressure pipeline; the inlet end of the booster pump is respectively connected to a methane gas cylinder, a helium gas cylinder and a vacuum pump through a four-way connection; the confining pressure inlet end of the core clamp is connected to the confining pressure pump through a high-pressure pipeline; the outlet end of the core clamp is connected to a back pressure valve through a high-pressure pipeline, and a pressure sensor is arranged on the pipeline between the core clamp and the back pressure valve; the outlet end of the back pressure valve is connected to a gas flow meter.

[0010] Furthermore, a fourth stop valve is provided on the pipeline between the core clamp and the booster pump, and a first stop valve, a second stop valve and a third stop valve are respectively provided on the pipelines between the methane cylinder, the helium cylinder, the vacuum pump and the cross-way.

[0011] Furthermore, the confining pressure pump is used to inject water into the core holder to establish a required confining pressure value, and a fifth stop valve is provided on the pipeline between the confining pressure pump and the core holder.

[0012] Furthermore, a sixth stop valve is arranged on the pipeline between the back pressure valve and the gas flow meter.

[0013] Furthermore, the entire test device is placed in a constant temperature box to control the temperature; the temperature control range of the constant temperature box is 20°C-200°C, and the temperature control accuracy is 0.1°C.

[0014] Furthermore, the control accuracy of the back pressure valve is 0.01 MPa, and the accuracy of the gas flow meter is 0.5%.

[0015] A method for testing the free gas and adsorbed gas production of shale gas reservoirs, according to the above-mentioned testing device, is characterized in that it comprises the following steps:

[0016] S1. Open the thermostat, set the insulation temperature of the test device, place the shale core into the shale holder, and close all the stop valves in the test device.

[0017] S2. Conduct helium saturation and gas production experiments; during the experiment, at the same interval of pressure difference, measure the cumulative helium gas production corresponding to the pressure difference from the initial moment to when gas production stops through a gas flowmeter, and denote it as V He_i ;

[0018] S3. Conduct methane saturation and gas production experiments; at the same interval of pressure difference, measure the cumulative methane gas production corresponding to the pressure difference from the initial moment to when gas production stops through a gas flowmeter, and denote it as V CH4_i ;

[0019] S4. According to the test results, with the pressure difference as the abscissa and the cumulative gas production as the ordinate, respectively plot the relationship curves between the cumulative gas production of methane and helium and the pressure.

[0020] S5. Obtain the cumulative free gas production and the cumulative adsorbed gas production based on the relationship curves.

[0021] Furthermore, the specific operation steps of the helium saturation and gas production experiments are as follows:

[0022] S21. Open the stop valve between the confining pressure pump and the core holder, apply confining pressure to the shale core in the core holder through the confining pressure pump to the set pressure P f , and then close the stop valve on this pipeline.

[0023] S22. Open the stop valve on the pipeline from the self - vacuum pump, through the booster pump to the core holder, extract vacuum through the vacuum pump, and then close the stop valve on this pipeline.

[0024] S23. Open the stop valve on the pipeline from the helium gas cylinder, through the booster pump to the core holder, saturate the shale core with helium gas. When the final equilibrium pressure reaches the set value P0, close the stop valve on this pipeline.

[0025] S24. Control the pressure at the outlet end of the core holder to be P1 through the back - pressure valve, and P1 < P0. Denote the pressure difference between the initial pressure and the outlet pressure as △P1 = P0 - P1. Measure the cumulative helium gas production corresponding to the pressure difference from the initial moment to when gas production stops through a gas flowmeter, and denote it as V He_1 ;

[0026] S25. Repeat step S24, gradually reduce the outlet pressure through the back - pressure valve, which are P i , i = 2, 3, …, n, and P i +1 < P i , P n≥0; the cumulative helium production corresponding to the corresponding pressure difference from the initial moment to the moment when no more gas is produced is measured by a gas flow meter and recorded as V He_i ;

[0027] S26. End the helium saturation and gas production experiments and close all stop valves.

[0028] Furthermore, the specific operating steps of the helium saturation and gas production experiment are as follows:

[0029] S31, repeat step S23 to evacuate the device and perform air tightness test;

[0030] S32, open the stop valve on the pipeline from the methane cylinder to the core holder via the booster pump, saturate the shale core with methane through the booster pump, and read the final equilibrium pressure through the pressure sensor to be consistent with the helium saturation pressure, which is P0; then close the stop valve on the pipeline;

[0031] S33, for the shale core saturated with methane, repeat steps S24 to S25 to obtain the cumulative methane production when the pressure difference is △Pi, recorded as V CH4_i ;

[0032] S34, methane saturation and gas production experiments are completed, and all stop valves are closed;

[0033] Furthermore, the set equilibrium pressure value P0=18 MPa.

[0034] In summary, the present invention has the following advantages:

[0035] 1. The present invention respectively conducts saturation and pressure reduction mining experiments of helium and methane in shale, measures the cumulative production of helium and methane under different pressure reduction amplitudes, and calculates the volume and proportion of free gas and adsorbed gas in the output gas by comparing the production of the two gases; the present invention has a clear principle, and by comparing the production of methane and helium without adsorption, the production of free gas and adsorbed gas in the shale gas reservoir is quantitatively obtained, thereby improving the accuracy of the measurement results;

[0036] 2. The present invention has the advantages of being easy to promote and implement, and provides important parameters and basis for the development of shale gas reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a structural schematic diagram of the device of the present invention;

[0038] In the figure:

[0039] 1. Core holder, 2. Shale core, 3. Confining pressure pump, 4. Vacuum pump, 5. Methane cylinder, 6. Helium cylinder, 7. Booster pump, 8. Pressure sensor, 9. Back pressure valve, 10. Gas flow meter, 11. Constant temperature box, 12. High pressure pipeline, 101. First stop valve, 102. Second stop valve, 103. Third stop valve, 104. Fourth stop valve, 105. Fifth stop valve, 106. Sixth stop valve, 201. Four-way valve, 202. Three-way valve. DETAILED DESCRIPTION

[0040] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments and drawings. It should be understood by those skilled in the art that the content described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0041] The present invention provides a testing device for the production of free gas and adsorbed gas in shale gas reservoirs, such as Figure 1 As shown, the testing device includes a core holder 1, and the core holder 1 is used to clamp a shale core 2. In this embodiment, the diameter of the core holder 1 is preferably 26 mm, and the core holder 1 includes an inlet end, an outlet end and a confining pressure inlet end.

[0042] The inlet end of the core holder 1 is connected to the outlet end of the booster pump 7 through a high-pressure pipeline 12. A fourth stop valve 104 is provided on the pipeline between the core holder 1 and the booster pump 7. The inlet end of the booster pump 7 is respectively connected to a methane gas cylinder 5, a helium gas cylinder 6 and a vacuum pump 4 through a four-way 201. The upper limit of the boosting pressure of the booster pump 7 is 40 MPa, the vacuum degree of the vacuum pump 4 is 0.1 Pa, and a first stop valve 101, a second stop valve 102 and a third stop valve 103 are respectively provided on the pipelines between the methane gas cylinder 5, the helium gas cylinder 6, the vacuum pump 4 and the four-way 201.

[0043] The confining pressure inlet of the core holder 1 is connected to the confining pressure pump 3 through a high-pressure pipeline 12. The confining pressure pump 3 can inject water into the core holder 1 to establish the required confining pressure value. The pressurization range of the confining pressure pump 3 is 60MPa and the accuracy is 0.01MPa. A fifth stop valve 105 is provided on the pipeline between the confining pressure pump 3 and the core holder 1.

[0044] The outlet of the core holder 1 is connected to a back pressure valve 9 through a high pressure pipeline 12, and the control accuracy of the back pressure valve 9 is 0.01 MPa. A pressure sensor 8 is provided on the pipeline between the core holder 1 and the back pressure valve 9 through a tee 202, and the range of the pressure sensor 8 is 45 MPa and the accuracy is 0.01 MPa. The outlet of the back pressure valve 9 is connected to a gas flow meter 10 through a high pressure pipeline 12, and the accuracy of the gas flow meter 10 is 0.5%. A sixth stop valve 106 is provided on the pipeline between the back pressure valve 9 and the gas flow meter 10.

[0045] All the components mentioned in the above test device are placed in the constant temperature box 11 to control the constant temperature. The temperature control range of the constant temperature box 11 is 20°C - 200°C, and the temperature control accuracy is 0.1°C.

[0046] Based on the above test device for the production of free gas and adsorbed gas in shale gas reservoirs, this embodiment also proposes a test method for the production of free gas and adsorbed gas in shale gas reservoirs, including the following steps:

[0047] Step 1: Open the constant temperature box and set the heat preservation temperature to T, and this temperature range is preferably 50°C - 100°C;

[0048] Step 2: Close all the stop valves of the test device, put the shale core with a mass of m0 into the core holder; open the stop valve between the confining pressure pump and the core holder, and apply a confining pressure to the shale core in the core holder to the set pressure P f , and then close the stop valve on this pipeline; the set confining pressure in this step is 20 MPa;

[0049] Step 3: Open the stop valve on the pipeline from the self-vacuum pump, via the booster pump to the core holder, extract vacuum through the vacuum pump, and when the vacuum degree reaches 0.1 Pa, close the stop valve on this pipeline; the pressure value of the pressure sensor is stable for 6 hours, which is regarded as meeting the airtightness requirement;

[0050] Step 4: Open the stop valve on the pipeline from the self-helium gas cylinder, via the booster pump to the core holder, saturate the shale core with helium gas; read the final equilibrium pressure as P0 through the pressure sensor, and then close the stop valve on this pipeline; in this step, the equilibrium pressure P0 is 18 MPa;

[0051] Step 5: Control the pressure at the outlet end of the core holder to be P1 through the back pressure valve, and P1 < P0. The pressure difference between the initial pressure and the outlet pressure is recorded as △P1 = P0 - P1. Measure the cumulative helium gas production volume corresponding to the corresponding pressure difference from the initial moment to when no gas is produced through the gas flowmeter, and record it as V He_1 ;

[0052] Step 6: Repeat Step 5, gradually reduce the outlet pressure through the back pressure valve, at the same pressure difference interval, measure the cumulative helium gas production volume corresponding to the corresponding pressure difference from the initial moment to when no gas is produced through the gas flowmeter, and record it as V He_i ;

[0053] Step 7: After the helium gas saturation and gas production experiment are completed, close all the stop valves;

[0054] Step 8: Repeat Step 3 to evacuate the device and detect the airtightness;

[0055] Step 9: Open the stop valve on the pipeline from the methane cylinder to the core holder via the booster pump, saturate the shale core with methane through the booster pump, and read the final equilibrium pressure through the pressure sensor to be consistent with the helium saturation pressure, which is P0; then close the stop valve on the pipeline;

[0056] Step 10: For the shale core saturated with methane, repeat steps 5 and 6 to obtain the cumulative methane production when the pressure difference is △Pi, recorded as V CH4_i ;

[0057] Step 11: After the methane saturation and gas production experiments are completed, close all stop valves;

[0058] According to the experimental results, in the same coordinate system, the pressure difference △P i V is plotted as the horizontal axis and the cumulative gas production as the vertical axis. CH4_i —P i 、V He_i —P i The relationship curve of

[0059] When the pressure difference is △P i When the cumulative helium production is equal to the free gas cumulative production V fi , expressed as:

[0060] V fi = V He_i ; (1)

[0061] Cumulative adsorption gas production V ai It is the difference between the cumulative production of methane and the cumulative production of helium under the same pressure difference, expressed as:

[0062] V ai = V CH4_i - V He_i ; (2)

[0063] When the pressure difference is △P i When the free gas cumulative production accounts for R fi for:

[0064] R fi = V fi / V CH4_i ; (3)

[0065] The proportion of adsorption gas cumulative production in total production R ai for:

[0066] R ai = V ai / V CH4_i (4)

[0067] Example 1

[0068] The following is a description of a method for testing the production of free gas and adsorbed gas in a shale gas reservoir according to the present invention using specific test data.

[0069] A test device for the production of free gas and adsorbed gas in a shale gas reservoir is provided with a constant temperature box 11 at a temperature of 50°C, a shale core having a length of 5.65 cm, a diameter of 2.51 cm, a porosity of 4.908%, and a mass of 284.04 g. All stop valves are closed, a shale core 2 is placed in a core holder 1, a fifth stop valve 105 is opened, and a confining pressure P is applied to the shale core 2 in the core holder 1 through a confining pressure pump 3. f to 20MPa, close the fifth stop valve 105; after vacuuming and performing airtightness inspection, open the second stop valve 102 and the fourth stop valve 104, saturate the shale core 2 with helium through the booster pump 7, read the final equilibrium pressure P0 as 18MPa through the pressure sensor 8, close the second stop valve 102 and the fourth stop valve 104; control the outlet pressure P1 to 16MPa through the back pressure valve 9, and the difference between the initial pressure and the outlet pressure is △P1=2MPa, open the sixth stop valve 106, and when the outlet end of the core holder 1 no longer produces gas, the cumulative helium production V measured by the gas flowmeter 10 He_1 =340.6cm 3 The pressure reduction production experiment process was repeated, and the pressure difference between the initial pressure and the outlet pressure was set to 4MPa, 6MPa, 8MPa, 10MPa, 12MPa, 14MPa, and 16MPa in turn. The cumulative helium production under the corresponding pressure difference was measured to be 590.1cm 3 、734.2cm 3 、806.4cm 3 、839.9cm 3 、854.9cm 3 、861.5cm 3 、864.4cm 3 .

[0070] The gas used in the experiment was replaced with methane, and the above steps were repeated to measure the cumulative methane production when the pressure difference was 2MPa, 4MPa, 6MPa, 8MPa, 10MPa, 12MPa, 14MPa, and 16MPa, respectively. 3 、599.0cm 3 、761.0cm 3 、873.1cm 3 、961.5cm 3 、1016.6cm 3 、1041.0cm 3 、1050.0cm 3 .

[0071] According to formulas (1)-(4), the production pressure difference △P is calculated i Cumulative production of free gas downstream V fi and its proportion R fi , Cumulative adsorption gas production V ai and its proportion R ai , as shown in the following table:

[0072] <![CDATA[△P i (MPa)]]> <![CDATA[V fi (cm 3 )]]> <![CDATA[V ai (cm 3 )]]> <![CDATA[R fi (%)]]> <![CDATA[R ai (%)]]> 2 340.6 2.8 99.2 0.8 4 590.1 8.9 98.5 1.5 6 734.2 26.7 96.5 3.5 8 806.4 66.8 92.3 7.7 10 839.9 121.6 87.4 12.6 12 854.9 161.7 84.1 15.9 14 861.5 179.5 82.8 17.2 16 864.4 185.6 82.3 17.7

[0073] The present invention respectively conducts saturation and pressure reduction mining experiments of helium and methane in shale, measures the cumulative production of helium and methane under different pressure reduction amplitudes, and calculates the volume and proportion of free gas and adsorbed gas in the output gas by comparing the production of the two gases. The present invention can quantitatively obtain the free gas and adsorbed gas and the cumulative production of shale gas reservoirs, thereby improving the accuracy of the measurement results.

[0074] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A testing device for the production of free gas and adsorbed gas in shale gas reservoirs, characterized in that: The invention comprises a shale clamp, wherein the inlet end of the core clamp (1) is connected to the outlet end of a booster pump (7) through a high-pressure pipeline (12); the inlet end of the booster pump (7) is respectively connected to a methane gas cylinder (5), a helium gas cylinder (6) and a vacuum pump (4) through a four-way (201); the confining pressure inlet end of the core clamp (1) is connected to the confining pressure pump (3) through a high-pressure pipeline (12); the outlet end of the core clamp (1) is connected to a back pressure valve (9) through a high-pressure pipeline (12); a pressure sensor (8) is arranged on the pipeline between the core clamp (1) and the back pressure valve (9); and the outlet end of the back pressure valve (9) is connected to a gas flow meter (10).

2. A shale gas reservoir free gas and adsorbed gas production testing device according to claim 1, characterized in that: A fourth stop valve (104) is provided on the pipeline between the core holder (1) and the booster pump (7), and a first stop valve (101), a second stop valve (102) and a third stop valve (103) are respectively provided on the pipelines between the methane gas cylinder (5), the helium gas cylinder (6), the vacuum pump (4) and the cross-connection (201).

3. A testing device for the production of free gas and adsorbed gas in shale gas reservoirs according to claim 1, characterized in that: The confining pressure pump (3) is used to inject water into the core holder (1) to establish a required confining pressure value, and a fifth stop valve (105) is provided on the pipeline between the confining pressure pump (3) and the core holder (1).

4. A testing device for the production of free gas and adsorbed gas in shale gas reservoirs according to claim 1, characterized in that: A sixth stop valve (106) is provided on the pipeline between the back pressure valve (9) and the gas flow meter (10).

5. The testing device for free gas and adsorbed gas production in shale gas reservoirs according to claim 1, characterized in that: The entire test device is placed in a constant temperature box (11) to control the temperature; the temperature control range of the constant temperature box (11) is 20°C-200°C, and the temperature control accuracy is 0.1°C.

6. A testing device for the production of free gas and adsorbed gas in shale gas reservoirs according to claim 1, characterized in that: The control accuracy of the back pressure valve (9) is 0.01 MPa, and the accuracy of the gas flow meter (10) is 0.5%.

7. A method for testing the free gas and adsorbed gas production in shale gas reservoirs, according to the device according to any one of claims 1 to 6, characterized in that: The steps include: S1. Open the thermostat, set the insulation temperature of the test device, put the shale core into the shale holder, and close all the stop valves in the test device; S2. Conduct helium saturation and gas production experiments. During the experiment, at the same pressure difference, the gas flow meter measures the cumulative helium production corresponding to the corresponding pressure difference from the initial moment to the moment when no more gas is produced, and records it as V Hei ; S3. Carry out methane saturation and gas production experiments; at the same pressure difference interval, use a gas flow meter to measure the cumulative methane gas production corresponding to the corresponding pressure difference from the initial moment to the moment when no gas is produced, and record it as V CH4_i ; S4. Based on the test results, the relationship curves between the cumulative gas production and pressure of methane and helium are drawn respectively, with the pressure difference as the horizontal axis and the cumulative gas production as the vertical axis; S5. Obtain the free gas cumulative production and the adsorbed gas cumulative production based on the relationship curve.

8. A method for testing the free gas and adsorbed gas production of shale gas reservoirs according to claim 7, characterized in that: The specific operating steps of the helium saturation and gas production experiment are as follows: S21, open the stop valve between the confining pressure pump and the core holder, and apply confining pressure to the shale core in the core holder through the confining pressure pump to the set pressure P f , and then close the stop valve on the pipeline; S22, opening the stop valve on the pipeline from the vacuum pump to the core holder via the booster pump, extracting vacuum through the vacuum pump, and then closing the stop valve on the pipeline; S23, opening the stop valve on the pipeline from the helium cylinder to the core holder via the booster pump, and injecting saturated helium into the shale core. When the final equilibrium pressure reaches the set value P0, closing the stop valve on the pipeline; S24. Control the pressure at the outlet end of the core holder to be P1 through a back-pressure valve, where P1 < P0. Denote the pressure difference between the initial pressure and the outlet pressure as △P1 = P0 - P1. Measure the cumulative helium gas production corresponding to the pressure difference from the initial moment until gas production stops through a gas flowmeter, and denote it as V He_1 ; S25, repeat step S24, and gradually reduce the outlet pressure through the back pressure valve, respectively P i , i=2,3,…,n, and P i +1 <P i , P n ≥0; the cumulative helium production corresponding to the corresponding pressure difference from the initial moment to the moment when no more gas is produced is measured by a gas flow meter and recorded as V He_i ; S26. End the helium saturation and gas production experiments and close all stop valves.

9. A method for testing the free gas and adsorbed gas production of shale gas reservoirs according to claim 8, characterized in that: The specific operating steps of the helium saturation and gas production experiment are as follows: S31, repeat step S23 to evacuate the device and perform air tightness test; S32, open the stop valve on the pipeline from the methane cylinder to the core holder via the booster pump, saturate the shale core with methane through the booster pump, and read the final equilibrium pressure through the pressure sensor to be consistent with the helium saturation pressure, which is P0; then close the stop valve on the pipeline; S33, for the shale core saturated with methane, repeat steps S24 to S25 to obtain the cumulative methane production when the pressure difference is △Pi, recorded as V CH4_i ; S34. After the methane saturation and gas production experiments are completed, close all stop valves.

10. A method for testing the free gas and adsorbed gas production of shale gas reservoirs according to claim 9, characterized in that: The equilibrium pressure reaches the set value P0=18MPa.

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