A method for experimental testing and prediction of free gas content in shale and coal reservoirs

Abstract

The invention discloses a method for experimental testing and predicting free gas content in shale and coal rock reservoirs, comprising: 1. sample preparation; 2. system calibration; 3. establishing a conversion relationship between nuclear magnetic signal intensity and free methane mass under different temperature conditions; 4. measuring sample nuclear magnetic T2 spectrum; 5. free methane mass calculation; 6. free gas content calculation; 7. free gas content extrapolation under high temperature and high pressure conditions; 8. obtaining parameters P1, P2 and P3 of a single sample; 9. selecting a reservoir as a basic data parameter for calculating parameters P1, P2 and P3 according to the correlation between reservoir parameters and P1, P2 and P3; 10. constructing a prediction model for parameters P1, P2 and P3; 11. completing the prediction of free gas content in reservoirs at different burial depths; the free gas content obtained by the prediction method of the invention is relatively accurate, and the continuous and accurate prediction of free gas content in dense shale and coal rock reservoirs is realized, which has excellent application prospects.

Description

Technical Field

[0001] The invention relates to the field of free gas volume testing of shale and coal rock reservoirs, and in particular to a method for experimental testing and prediction of free gas volume of shale and coal rock reservoirs. Background Art

[0002] Shale gas and coal-rock gas are important components of unconventional natural gas. After nearly 20 years of exploration and development, shale gas has achieved industrial exploitation in multiple layers and regions, such as the Longmaxi Formation, Dalong Formation, and Wujiaping Formation in the Sichuan Basin. At present, the output of coalbed methane is relatively low compared to shale gas, but it also shows a trend of "blooming in multiple places", especially the recent successful high production of deep coal-rock gas in the Sichuan Basin, which has greatly enhanced the confidence in coalbed methane development.

[0003] Exploration and development practices have confirmed that natural gas extracted from shale and coal rock gas is mainly free methane in the formation. At the same time, the amount of free gas is also one of the key parameters for reserve calculation and reservoir evaluation, so it is very important to accurately evaluate the amount of free gas in shale and coal rock reservoirs. At present, the methods for obtaining free gas in these two types of reservoirs are relatively simple, and are mainly calculated using the following formula:

[0004]

[0005] Where n free is the free gas volume, cm 3 / g;T sc is the ground temperature, 298.15K; P sc is the surface pressure, 0.101MPa; Z is the compression factor, constant; T is the formation temperature, K; P is the formation pressure, MPa; S g is gas saturation, %; is the reservoir porosity, %; ρ r is the rock density, g / cm 3 .

[0006] From the above formula, we can see that in order to obtain the free gas volume in the reservoir, we need to know two key parameters, namely the porosity and gas saturation of the reservoir. However, due to the small pores in shale and coal rock reservoirs, the accurate measurement of porosity has always been controversial. Secondly, under formation conditions, there is a large amount of adsorbed gas in the pores, and the adsorbed gas will occupy the corresponding space on the pore wall. If it is not deducted, it will affect the calculation of the free gas saturation. However, there is no consensus on the accurate characterization of the volume of adsorbed phase methane. Secondly, through the test of the newly developed pressure coring technology, it was found that the original method seriously underestimated the total gas content of shale gas reservoirs. According to the average gas content of the pressure coring of the high-quality shale reservoir in the southern Sichuan marine facies, it is 15.31m 3 / t, while the gas content obtained by the traditional method (calculated by equation 1) is usually less than 10m 3 / t. Therefore, the free gas volume calculated by the above formula is seriously low, and a new method needs to be developed for measurement and prediction. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for experimental testing and prediction of free gas content in shale and coal rock reservoirs, comprising: 1. sample preparation; 2. system calibration; 3. establishing a conversion relationship between nuclear magnetic resonance signal intensity and free methane mass under different temperature conditions; 4. measuring sample nuclear magnetic resonance T2 spectrum; 5. free methane mass calculation; 6. free gas volume calculation; 7. free gas volume extrapolation under high temperature and high pressure conditions; 8. obtaining parameters P1, P2, and P3 of a single sample; 9. based on the correlation between reservoir parameters and P1, P2, and P3, selecting the reservoir as the basic data parameter for calculating parameters P1, P2, and P3; 10. constructing a prediction model for parameters P1, P2, and P3; 11. completing the prediction of free gas content in reservoirs at different burial depths; the free gas content obtained by the prediction method of the present invention is relatively accurate, and the continuous and accurate prediction of the free gas content in dense shale and coal rock reservoirs is realized, which has excellent application prospects.

[0008] In order to achieve the above technical effects, the following technical solutions are adopted:

[0009] A method for experimental testing and prediction of free gas content in shale and coal reservoirs comprises the following steps:

[0010] Step S1: Sample preparation

[0011] The shale sample is prepared into a standard plunger sample, which is then dried and weighed M and measured V before being tested;

[0012] Step S2: System calibration

[0013] Carry out NMR system volume calibration under different pressure conditions to obtain reference chamber volume, pipeline volume and sample chamber volume;

[0014] Step S3: Establish the conversion relationship between the NMR signal intensity and the free methane mass under different temperature conditions

[0015] Select a specific temperature, inject methane gas of different pressures into a sample chamber of known volume, and measure the free methane signal in the sample chamber after the pressure is balanced; calculate the mass of injected methane by different pressures and temperatures, and establish a linear relationship with the nuclear magnetic signal intensity under the corresponding pressure to achieve the conversion relationship between methane mass and nuclear magnetic signal intensity; repeat this step to establish the marking lines at different temperatures;

[0016] Step S4: Sample testing

[0017] The sample is loaded into the sample chamber, pressurized to different pressures under specific temperature conditions, and the NMR T2 spectrum is measured; after the pressure is stable, the NMR T2 spectrum is tested n times continuously, and the above operation is repeated to obtain the NMR T2 spectrum of the sample under different temperature and pressure conditions;

[0018] Step S5: Free methane mass calculation

[0019] Count the nuclear magnetic signal intensity values ​​with nuclear magnetic T2 time greater than 1 ms under different temperature conditions, and convert the nuclear magnetic signal intensity into the mass of methane using the marking line established in step S3;

[0020] Step S6: Calculation of free gas volume

[0021] Using the equation of state:

[0022] PV=ZnRT (1)

[0023] In formula (1), P is the gas pressure, V is the gas volume, R is the gas constant, T is the gas temperature, and Zn is the amount of gas substance;

[0024] Calculate the volume of methane mass under surface conditions at different temperature and pressure conditions; divide the volume by the mass M of the core being tested to obtain the free gas volume under different temperature and pressure conditions;

[0025] Step S7: Extrapolation of free gas volume under high temperature and high pressure conditions

[0026] The correlation between the free gas volume data of the actual test sample in step S6 and the temperature and pressure is established; because there is a negative logarithmic relationship between temperature and free gas volume, and a positive linear relationship between pressure and free gas volume; thus, a nonlinear multiple regression relationship between free gas volume and temperature and pressure is established:

[0027] n free =P1+P2*Ln(T)+P3*P (2)

[0028] In formula (2), n free is the free gas volume; P1, P2, P3 are constants, dimensionless; T is the formation temperature, ℃; P is the formation pressure, MPa.

[0029] Step S8: Obtaining the parameters P1, P2, and P3 of a single sample

[0030] After sorting out the free gas volume of the actual sample measured under different temperature and pressure conditions in step S6, the data is fitted using formula (2) to obtain the parameters P1, P2, and P3;

[0031] Step S9: Based on the correlation between reservoir parameters and P1, P2, P3, the reservoir is selected as the basic data parameter for calculating parameters P1, P2, P3.

[0032] Since the free gas volume is affected by various reservoir parameters, the multiple reservoir parameters of the sample are respectively correlated with the parameters P1, P2, and P3 obtained in step S8, and the correlation coefficients between the reservoir parameters and the parameters P1, P2, and P3 are counted; the parameters P1, P2, and P3 respectively select the two reservoir parameters with the best correlation as the basic data for calculating the parameters P1, P2, and P3;

[0033] Step S10: Parameter P1, P2, P3 prediction model construction

[0034] The two selected reservoir parameters and parameters P1, P2, and P3 were fitted with the Macquart + general global optimization method to obtain:

[0035] P1=a1+b1*K1+c1 / (K2) 2 (3)

[0036] P2=a2+b2*H1+c2*H2 (4)

[0037] P3=a3+b3*G1+c3*G2+d*G2 2 (5)

[0038] Wherein, a1, a2, a3, b1, b2, b3, c1, c2, c3, d are all constants; K1 and K2 are the two reservoir parameter contents with the best correlation with parameter P1, %; H1 and H2 are the two reservoir parameter contents with the best correlation with parameter P2, %; G1 and G2 are the two reservoir parameter contents with the best correlation with parameter P3, %;

[0039] Step S11: Prediction of free gas in reservoirs with different properties

[0040] The free gas content parameters P1, P2, and P3 of reservoirs at different burial depths are calculated using the content values ​​of the reservoir parameters selected in step S10. On this basis, the temperature and pressure of the formation are calculated in combination with the burial depth of the shale reservoir, and the free gas content of the reservoir is calculated using formula (2), thereby realizing the continuous prediction calculation of the free gas content of a single well reservoir.

[0041] Furthermore, the drying temperature in step S1 is 60-150°C.

[0042] Furthermore, the drying time in step S1 is 12-24 hours.

[0043] Furthermore, in step S3, the test temperature is 40-100° C., with 4 or more temperature values; the test pressure is 1-12 MPa, with 7 or more pressure values.

[0044] Furthermore, the specific method of continuously testing the nuclear magnetic T2 spectrum n times in step S4 is: when the repetition rate is higher than 98%, it is considered that the methane reaches an equilibrium state in the core under this pressure.

[0045] Furthermore, n≥3.

[0046] Furthermore, in step S4, the test temperature is 40-100° C., with 4 or more temperature values; the test pressure is 15-35 MPa, with 4 or more pressure values.

[0047] Furthermore, the reservoir parameters in step S9 include porosity, TOC content, and mineral composition.

[0048] The above method is applied to the testing and prediction of free gas volume in shale and coal reservoirs.

[0049] The beneficial effects of the present invention are:

[0050] The invention discloses a method for experimental testing and predicting free gas content in shale and coal rock reservoirs, comprising: 1. sample preparation; 2. system calibration; 3. establishing a conversion relationship between nuclear magnetic signal intensity and free methane mass under different temperature conditions; 4. measuring sample nuclear magnetic T2 spectrum; 5. free methane mass calculation; 6. free gas content calculation; 7. free gas content extrapolation under high temperature and high pressure conditions; 8. obtaining parameters P1, P2 and P3 of a single sample; 9. selecting a reservoir as a basic data parameter for calculating parameters P1, P2 and P3 according to the correlation between reservoir parameters and P1, P2 and P3; 10. constructing a prediction model for parameters P1, P2 and P3; 11. completing the prediction of free gas content in reservoirs at different burial depths; the free gas content obtained by the prediction method of the invention is relatively accurate, and the continuous and accurate prediction of free gas content in dense shale and coal rock reservoirs is realized, which has excellent application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A line graph showing the relationship between the mass of methane and the amount of nuclear magnetic resonance signal under different temperature conditions according to an embodiment of the present invention;

[0052] Figure 2 The NMR T2 spectra at different pressures at 40° C. described in the embodiments of the present invention;

[0053] Figure 3 The NMR T2 spectra at different pressures at 60° C. described in the embodiments of the present invention;

[0054] Figure 4 This is the NMR T2 spectrum at different pressures at 80°C described in the embodiments of the present invention;

[0055] Figure 5 The NMR T2 spectra at different pressures at 100° C. described in the embodiments of the present invention;

[0056] Figure 6 A graph showing the relationship between temperature and free gas volume according to an embodiment of the present invention;

[0057] Figure 7 is a diagram showing the relationship between pressure and free gas volume according to an embodiment of the present invention;

[0058] Figure 8 is a correlation diagram between the reservoir parameters and the parameter P1 according to an embodiment of the present invention;

[0059] Fig. 9 is a correlation diagram between the reservoir parameters and the parameter P2 according to an embodiment of the present invention;

[0060] Fig.10 It is a correlation diagram between the reservoir parameters and the parameter P3 described in the embodiment of the present invention. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0062] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0063] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0064] Embodiment 1:

[0065] Step S1: Sample preparation. Prepare the shale sample into a standard plunger sample, dry it, weigh it (m), measure its volume v, and then test it;

[0066] Step S2: System calibration. Carry out NMR system volume calibration under different pressure conditions to obtain the reference chamber volume, pipeline volume and sample chamber volume;

[0067] Step S3: Establish the conversion relationship between the nuclear magnetic signal intensity and the mass of free methane under different temperature conditions. That is, select a specific temperature, inject methane gas of different pressures into a sample chamber of known volume, and measure the free methane signal in the sample chamber after the pressure is balanced. Calculate the mass of injected methane by different pressures and temperatures, and establish a linear relationship with the nuclear magnetic signal intensity under the corresponding pressure to achieve the conversion relationship between the methane mass and the nuclear magnetic signal intensity. Repeat this step to establish the markings at different temperatures. This time, the markings were tested at 4 temperature points (40°C, 60°C, 80°C, 100°C), and the pressures were set to 1MPa, 2MPa, 4MPa, 6MPa, 8MPa, 10MPa, and 12MPa. The specific results are as follows: Figure 1 As shown:

[0068] Step S4: Sample testing. Load the sample into the sample chamber, pressurize it to different pressures under specific temperature conditions, and measure the NMR T2 spectrum. After the pressure stabilizes, test the NMR T2 spectrum three times in succession, with a repetition rate of more than 98%. It is considered that methane reaches equilibrium in the core under this pressure. Repeat the above operation to obtain the NMR T2 spectrum of the sample under different temperature and pressure conditions. This time, the methane NMR T2 spectra at four temperature points (40°C, 60°C, 80°C, 100°C) and four pressure points (15MPa, 25MPa, 30MPa, 35MPa) were tested, as shown in the figure. Figure 2-Figure 5 shown.

[0069] Step S5: Calculation of free methane mass: Count the NMR signal intensity values ​​with NMR T2 time greater than 1 ms under different temperature conditions, and convert the NMR signal intensity into the mass of methane using the scale established in step S3.

[0070] Step S6: Calculation of free gas volume. Using the state equation PV=ZnRT, calculate the volume of methane mass under different temperature and pressure conditions corresponding to surface conditions. Divide the volume by the mass M of the core being tested to obtain the free gas volume under different temperature and pressure conditions.

[0071] Step S7: Extrapolation of free gas content under high temperature and high pressure conditions. Use the actual test sample gas content data and the correlation between temperature and pressure, such as Figure 6-Figure 7 As shown. From the measurement data of the actual test samples, it can be seen that there is a negative logarithmic relationship between temperature and free gas volume, and a positive linear relationship between pressure and free gas volume. Therefore, a nonlinear multiple regression relationship between free gas volume and temperature and pressure is established:

[0072] n free =P1+P2*Ln(T)+P3*P (1)

[0073] Where P1, P2, and P3 are constants and dimensionless; T is the formation temperature, °C; and P is the formation pressure, MPa.

[0074] Step S8: Obtaining the parameters P1, P2, and P3 of a single sample. After sorting out the free gas volume measured for the actual sample under different temperature and pressure conditions, equation (1) is used to perform data fitting to obtain the parameters P1, P2, and P3.

[0075] Step S9: Parameter optimization of reservoir parameters P1, P2, P3 predicted by different properties. Since the free gas volume is affected by reservoir parameters such as porosity, TOC content, mineral composition, etc., the reservoir parameters (porosity, TOC content, mineral composition, etc.) of multiple samples are respectively subjected to correlation analysis with the parameters P1, P2, P3 obtained in step S8, and the correlation coefficients between the reservoir parameters and the parameters P1, P2, P3 are statistically analyzed. The two reservoir parameters with the best correlation are selected as the basic data for calculating the parameters P1, P2, P3. Figure 8-Figure 10 Correlation analysis shown.

[0076] At this time, the porosity and reservoir clay mineral content are the two reservoir parameter contents with the best correlation with parameter P1, %; the porosity and reservoir quartz mineral content are the two reservoir parameter contents with the best correlation with parameter P2, %; the porosity and reservoir quartz mineral content are the two reservoir parameter contents with the best correlation with parameter P3, %;

[0077] Step S10: Parameter P1, P2, P3 prediction model construction. The two selected reservoir parameters and parameters P1, P2, P3 are fitted with the Macquart + general global optimization method to obtain:

[0078]

[0079]

[0080]

[0081] In the formula, a1, a2, a3, b1, b2, b3, c1, c2, c3, and d are all constants. is the porosity, %; C clay is the clay mineral content of the reservoir, %; C q is the reservoir quartz mineral content, %.

[0082] Step S11: Prediction of free gas in reservoirs with different properties. Using the reservoir parameters ( C clay , C qThe free gas content at different burial depths (such as reservoir parameters) is calculated respectively by calculating the free gas volume parameters P1, P2, and P3 of reservoirs at different burial depths. On this basis, the temperature and pressure of the formation are calculated in combination with the burial depth of the shale reservoir, and equation (1) is used to calculate the free gas volume of the reservoir, thereby realizing the continuous prediction calculation of the free gas volume of the single well reservoir.

[0083] In summary, the present invention discloses a method for experimental testing and prediction of free gas content in shale and coal reservoirs, comprising: 1. sample preparation; 2. system calibration; 3. establishing a conversion relationship between nuclear magnetic signal intensity and free methane mass under different temperature conditions; 4. measuring sample nuclear magnetic T2 spectrum; 5. free methane mass calculation; 6. free gas content calculation; 7. free gas content extrapolation under high temperature and high pressure conditions; 8. obtaining parameters P1, P2, and P3 of a single sample; 9. selecting a reservoir as a basic data parameter for calculating parameters P1, P2, and P3 based on the correlation between reservoir parameters and P1, P2, and P3; 10. constructing a prediction model for parameters P1, P2, and P3; 11. completing the prediction of free gas content in reservoirs at different burial depths; the free gas content obtained by the prediction method of the present invention is relatively accurate, and the continuous and accurate prediction of free gas content in dense shale and coal reservoirs is realized, which has excellent application prospects.

[0084] At this point, those skilled in the art recognize that, although the embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived based on the contents disclosed in the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.

Claims

1. A method for experimental testing and prediction of free gas content in shale and coal reservoirs, characterized in that: The experimental test and prediction method comprises the following steps: Step S1: Sample preparation The shale sample is prepared into a standard plunger sample, which is then dried and weighed M and measured V before being tested; Step S2: System calibration Carry out NMR system volume calibration under different pressure conditions to obtain reference chamber volume, pipeline volume and sample chamber volume; Step S3: Establish the conversion relationship between the nuclear magnetic signal intensity and the free methane mass under different temperature conditions Select the test temperature, inject methane gas of different pressures into the sample chamber of known volume, and measure the free methane signal in the sample chamber after the pressure is balanced; calculate the injected methane mass by different pressures and temperatures, and establish a linear relationship with the nuclear magnetic signal intensity under the corresponding pressure to achieve the conversion relationship between methane mass and nuclear magnetic signal intensity; repeat this step to establish the marking lines at different temperatures; Step S4: Sample testing The sample is loaded into the sample chamber, pressurized to different pressures under the test temperature conditions, and the nuclear magnetic T2 spectrum is measured; after the pressure is stable, the nuclear magnetic T2 spectrum is tested n times continuously, and the above operation is repeated to obtain the nuclear magnetic T2 spectrum of the sample under different temperature and pressure conditions; Step S5: Free methane mass calculation Count the nuclear magnetic signal intensity values ​​with nuclear magnetic T2 time greater than 1 ms under different temperature conditions, and convert the nuclear magnetic signal intensity into the mass of methane using the marking line established in step S3; Step S6: Calculation of free gas volume Using the equation of state: PV=ZnRT (1) In formula (1), P is the gas pressure, V is the gas volume, R is the gas constant, T is the gas temperature, and Zn is the amount of gas substance; Calculate the volume of methane mass under surface conditions at different temperature and pressure conditions; divide the volume by the mass M of the core being tested to obtain the free gas volume under different temperature and pressure conditions; Step S7: Extrapolation of free gas volume under high temperature and high pressure conditions The correlation between the free gas volume data of the actual test sample in step S6 and the temperature and pressure is established; because there is a negative logarithmic relationship between temperature and free gas volume, and a positive linear relationship between pressure and free gas volume; thus, a nonlinear multiple regression relationship between free gas volume and temperature and pressure is established: n free = P1+P2*Ln(T)+P3*P (2) In formula (2), n free is the free gas volume; P1, P2, P3 are constants, dimensionless; T is the formation temperature, °C; P is the formation pressure, MPa; Step S8: Obtaining the parameters P1, P2, and P3 of a single sample After sorting out the free gas volume of the actual sample measured under different temperature and pressure conditions in step S6, the data is fitted using formula (2) to obtain the parameters P1, P2, and P3; Step S9: Based on the correlation between the reservoir parameters and P1, P2, and P3, the reservoir parameters with the best correlation are selected as the basic data parameters for calculating the parameters P1, P2, and P3. Since the free gas volume is affected by various reservoir parameters, the multiple reservoir parameters of the sample are respectively correlated with the parameters P1, P2, and P3 obtained in step S8, and the correlation coefficients between the reservoir parameters and the parameters P1, P2, and P3 are counted; the parameters P1, P2, and P3 respectively select the two reservoir parameters with the best correlation as the basic data for calculating the parameters P1, P2, and P3; Step S10: Parameter P1, P2, P3 prediction model construction The two selected reservoir parameters and parameters P1, P2, and P3 were fitted with the Macquart + general global optimization method to obtain: P1=a1+b1*K1+c1 / (K2) 2 (3) P2=a2+ b2* H1 + c2* H2 (4) P3=a3+ b3* G1+ c3* G2 + d* G2 2 (5) Wherein, a1, a2, a3, b1, b2, b3, c1, c2, c3, d are all constants; K1 and K2 are the two reservoir parameter contents with the best correlation with parameter P1, %; H1 and H2 are the two reservoir parameter contents with the best correlation with parameter P2, %; G1 and G2 are the two reservoir parameter contents with the best correlation with parameter P3, %; Step S11: Prediction of free gas in reservoirs with different properties The reservoir parameters selected in step S10 at different burial depths are used to calculate the free gas parameters P1, P2, and P3 of reservoirs at different burial depths. On this basis, the temperature and pressure of the formation are calculated in combination with the burial depth of the shale reservoir, and the free gas volume of the reservoir is calculated using formula (2), thereby realizing the continuous prediction calculation of the free gas volume of a single well reservoir.

2. The method for experimental testing and prediction of free gas content in shale and coal reservoirs according to claim 1, characterized in that: The drying temperature in step S1 is 60-150°C.

3. The method for experimental testing and prediction of free gas content in shale and coal reservoirs according to claim 1, characterized in that: The drying time in step S1 is 12-24 hours.

4. The method for experimental testing and prediction of free gas content in shale and coal reservoirs according to claim 1, characterized in that: In step S3, the test temperature is 40-100° C., and the temperature values ​​are 4 or more; the test pressure is 1-12 MPa, and the pressure values ​​are 7 or more.

5. The method for experimental testing and prediction of free gas content in shale and coal reservoirs according to claim 1, characterized in that: The specific method of continuously testing the nuclear magnetic T2 spectrum n times in step S4 is: when the repetition rate is higher than 98%, it is considered that the methane reaches an equilibrium state in the core under this pressure.

6. A method for experimental testing and prediction of free gas content in shale and coal reservoirs as claimed in claim 5, characterized in that: Said n≥3.

7. The method for experimental testing and prediction of free gas content in shale and coal reservoirs according to claim 1, characterized in that: In step S4, the test temperature is 40-100° C., and the temperature value is 4 or more; the test pressure is 15-35 MPa, and the pressure value is 4 or more.

8. The method for experimental testing and prediction of free gas content in shale and coal reservoirs according to claim 1, characterized in that: The reservoir parameters in step S9 include porosity, TOC content, and mineral composition.

9. A method for experimental testing and prediction of free gas content in shale and coal reservoirs according to any one of claims 1 to 8, characterized in that: The method is applied to the testing and prediction of free gas volume in shale and coal reservoirs.

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