A method for testing shale gas volume

Abstract

The present application belongs to the field of oilfield shale gas exploration and development experiment, and particularly relates to a shale gas quantity testing method. The present application constructs the basic formation condition corresponding to the shale sample by placing the shale sample into a set testing environment, and tests the lost gas quantity by simulating the drilling core lowering temperature and pressure process according to the actual situation of the related parameters in the process of drilling core taking, so that the testing environment of the lost gas quantity is more consistent with the actual situation when drilling core is taken, thus the large error generated by theoretical analysis can be avoided, and the accuracy of the testing result of the lost gas quantity is effectively improved. Furthermore, the shale sample is restored to the temperature and pressure conditions of the reservoir by adjusting the formation fluid, temperature and pressure, so that the shale is fully saturated and adsorbs the simulated formation fluid, thereby the basic formation condition corresponding to the shale sample which is more consistent with the actual formation condition is constructed, and is used for testing the shale gas quantity, so as to ensure the accuracy of the shale gas quantity testing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of shale gas exploration and development experiment in oil field, and particularly relates to a shale gas quantity testing method. BACKGROUND

[0002] As a new field of oil and gas development at home and abroad, shale gas has become a hot spot in oil and gas exploration and development in recent years. Compared with foreign exploration and development, domestic shale gas exploration and development started late, has low technical maturity, and has a wide exploration field. Because the output of shale gas is mainly methane, which is a highly efficient and clean energy, it is increasingly valued under the background of national "carbon neutralization". Shale gas is different from ordinary natural gas reservoirs. Because the porosity and permeability of shale gas are much lower than those of conventional gas reservoirs, the state of gas in the formation also changes from the state of free gas in conventional gas reservoirs to the state of free gas and adsorbed gas in shale reservoirs. Free gas mainly exists in pores or fractures, while adsorbed gas is methane adsorbed on the surface of shale particles. The content of free gas is related to the size of pores and fractures, formation pressure and formation temperature; the content of adsorbed gas is related to the adsorption capacity of shale particle surface to gas, formation pressure, formation temperature and other factors, so the shale gas exploration and development industry often needs to test the porosity, formation pressure, formation temperature and content of adsorbed gas of the reservoir shale.

[0003] Hao Jin published an article entitled "An Improved Method for Estimating Shale Gas Loss Gas Content" in Modern Geology on May 17, 2015, which improved the USBM method formed by the US Bureau of Mines based on the diffusion theory of coalbed methane by using the loss gas diffusion geological model to correct the calculation method of loss time, and found the main reason for the small loss gas quantity. As a result, some devices and methods for quickly testing adsorbed gas have been invented in the industry, which are mainly based on the USBM method formed by the US Bureau of Mines based on the diffusion theory of coalbed methane. The Chinese invention patent with application publication number CN112964597A points out that the accuracy of the method in the shale field is questionable, and from the practical data, the loss gas quantity calculation relies on empirical formula due to the limitations of site test time, site and construction process conditions, the error is large, the desorption test time starting point is inconsistent, the relationship between desorbed gas quantity and desorption time is not clear, the accuracy and precision of desorption test results are difficult to evaluate, the test results cannot be repeatedly verified, and there is a lack of free gas quantity data. The method shown in the Chinese invention patent with application publication number CN112964597A includes two parts of desorption cylinder and shale pore volume in free space volume, which can only measure adsorbed gas quantity and cannot test loss gas quantity.

[0004] A kind of unconventional gas's field automatic analysis instrument system is disclosed in Chinese invention patent with application publication number CN103822849A, a kind of field automatic analysis instrument is shown from the angle of system module in test analysis division, it needs to be supported by USBM etc. Fitting theory in principle to calculate loss gas amount. A kind of shale gas field analysis device and a device that can be transported to the field by transport vehicle are disclosed in Chinese invention patent with application publication number CN108982289A, mainly solve the desorption device too big in the past, difficult to carry, desorption water bath temperature is low, water vapor interference and other problems, still cannot do without USBM method in principle. A shale gas content comprehensive analysis device and method are described in Chinese invention patent with application publication number CN109540735A, the method uses desorption cylinder and gas chromatograph in series, solves the function of online detection desorption gas component variation, the test of gas content is still based on the method of USBM etc. Fitting curve is realized, and the accuracy of gas content measurement needs to be discussed.

[0005] There are still some solutions that involve simulation and experimental methods of shale gas reservoir exploitation related processes, but do not embody the measurement method of loss gas amount; such as Chinese utility model patent with authorization announcement number CN208433157U describes a new shale gas reservoir exploitation simulation experiment device mainly simulates the exploitation process of shale gas reservoir, and does not mention the measurement of loss gas amount. A shale gas adsorption / desorption exploitation simulation experiment device and method are described in Chinese invention patent with application publication number CN107345890A, from the disclosed content, it can be seen that the device is still based on Boyle's law, gas state equation to calculate the content of adsorbed gas and gas production law, does not involve the method of directly obtaining the loss gas amount of shale by testing. SUMMARY

[0006] The purpose of the present application is to provide a shale gas amount test method, to solve the problem of poor accuracy of test results caused by the existing shale gas amount test method based on theoretical analysis.

[0007] To achieve the above purpose, the present application provides a shale gas amount test method, the shale gas amount includes the loss gas amount of shale;

[0008] Place the shale sample in a set test environment, and construct the corresponding basic formation conditions of the shale sample in the set test environment;

[0009] After the basic formation condition is constructed, the temperature and pressure in the set test environment are reduced to normal temperature and pressure level according to the actual situation of the related parameters in the coring drilling process within the set coring drilling period, and the total gas amount discharged in the process of reducing the temperature and pressure to normal temperature and pressure level is obtained, and the lost gas amount of the shale is obtained according to the total gas amount, so as to complete the test of the lost gas amount of the shale.

[0010] The beneficial effects of the above technical solution are that: after the shale sample is placed in the set test environment, the basic formation condition corresponding to the shale sample is constructed, and the drilling core temperature and pressure reduction process is simulated according to the actual working condition (i.e. the actual situation of the related parameters in the coring drilling process), so that the test environment of the lost gas amount is more in line with the actual situation during drilling core taking, and the degassing process of the ground core is avoided during drilling core taking, thus avoiding the large error caused by theoretical analysis, effectively improving the accuracy of the test result of the lost gas amount; and the test environment and test condition in the shale gas amount test method are obtained based on the simulated real formation condition and the parameter changes corresponding to the real working condition, so that the test result is more in line with the actual working condition and the test accuracy is improved, and all processes can be reproduced, so that the test result can be repeatedly verified.

[0011] Further, the shale gas amount further includes a desorbed gas amount of the shale;

[0012] The set test environment is inside the desorption device, after the temperature and pressure in the set test environment are reduced to normal temperature and pressure level according to the actual situation of the related parameters in the coring drilling process, the desorbed gas amount test is performed in different temperature rising stages inside the desorption device, the desorbed gas amount of the shale is obtained, and the test of the desorbed gas amount of the shale is completed.

[0013] The beneficial effects of the above technical solution are that: the test environment of the desorbed gas amount is more in line with the actual formation condition, and the accuracy of the test result of the desorbed gas amount is effectively improved; and the set test environment is inside the desorption device, so that the model after the test of the lost gas amount can be directly used when the test of the desorbed gas amount of the shale is performed, and the lost gas amount during the conventional desorbed gas test process when the core is taken out on the ground is avoided, and the test accuracy is improved.

[0014] Further, the shale gas amount further includes a desorbed gas amount of the shale;

[0015] After the basic formation condition corresponding to the shale sample is constructed in the set test environment, the temperature of the set test environment is kept unchanged, the pressure of the set test environment is gradually reduced, and the value of the change parameter corresponding to the gas reservoir development process is obtained in real time in the process, the change rule of the gas production amount of the shale under different pressure reduction conditions is obtained according to the change of the change parameter, and the test of the gas production amount of the shale is completed.

[0016] The beneficial effects of the above technical solution are that the constant temperature and pressure reduction of the formation during the formation development process can be simulated more realistically, and thus more accurate test results of the relationship between the gas production and the formation pressure during the pressure reduction development of the shale gas reservoir can be obtained.

[0017] Further, the preservation method of the shale sample before being placed in the set test environment and the corresponding basic formation condition of the shale sample is constructed, and the preservation method is:

[0018] If the set test environment is set in the laboratory, the collected shale sample is cut flat at both ends, wrapped with preservative film, and then sealed with paraffin for preservation.

[0019] If the set test environment is set in the collection site, the collected shale sample is cut flat at both ends and directly placed in the set test environment for use.

[0020] The beneficial effects of the above technical solution are that the evaporation of the remaining water in the core can be prevented, and the state of the shale sample can be ensured to be consistent with the state in the formation as much as possible.

[0021] Further, after the shale sample is placed in the set test environment, the method for constructing the corresponding basic formation condition of the shale sample includes: after the shale sample is placed in the set test environment, the temperature and pressure of the set test environment are adjusted by simulating the formation fluid and the temperature and pressure, so that the temperature and pressure of the set test environment meet the corresponding basic formation condition of the shale sample.

[0022] Further, after the shale sample is placed in the set test environment, the method for constructing the corresponding basic formation condition of the shale sample includes: after the shale sample is placed in the set test environment, the temperature and pressure of the set test environment are adjusted by simulating the formation fluid and the temperature and pressure, so that the temperature and pressure of the set test environment meet the corresponding basic formation condition of the shale sample.

[0023] After the shale sample is placed in the set test environment under normal temperature and pressure conditions, the simulated formation fluid is filled into the set test environment, and the pressure of the set test environment is maintained within the set pressure interval.

[0024] Then, the temperature of the set test environment is adjusted to a level consistent with the formation temperature corresponding to the shale sample, and the simulated formation fluid is continuously filled into the set test environment until the pressure of the set test environment reaches a level consistent with the formation pressure corresponding to the shale sample, and then the current temperature and pressure levels of the set test environment are maintained for a set period of time.

[0025] The beneficial effects of the above technical solution are: through the simulation of formation fluid and the adjustment of temperature and pressure, the pressurization before heating can reduce the evaporation of water in the core of the shale sample caused by heating, the shale sample is restored to the temperature and pressure conditions of the reservoir, the shale is fully saturated and adsorbs the simulated formation fluid, a model with formation temperature, formation pressure and full saturation, adsorption and rebalancing is established, and thus the basic formation conditions corresponding to the shale sample are constructed, which are more consistent with the actual formation conditions, and are used for testing the shale gas volume, so that the accuracy of the shale gas volume test can be ensured.

[0026] Further, the change parameters corresponding to the gas reservoir development process include the current shale sample corresponding gas production, the pressure of the current test environment, and the current time; if the shale sample corresponds to condensate oil, the current condensate oil quality is also included.

[0027] Further, the simulated formation fluid is compounded according to the composition of the target well output gas, and is stored in a container with a humidity value reaching a set threshold, so that the formation fluid has a certain humidity.

[0028] The beneficial effects of the above technical solution are: the simulated formation fluid is compounded according to the composition of the target well output gas, which can ensure that the set test environment in the test process is as close as possible to the actual formation working condition; and the simulated formation fluid is stored in a container with a humidity value reaching a set threshold, so that the formation fluid has a certain humidity, thereby preventing the evaporation of water in the core of the shale sample caused by heating or insufficient humidity of the formation fluid when adjusting the temperature of the set test environment.

[0029] Further, the related parameters in the coring process include the temperature gradient, the pressure gradient and the tripping speed in the wellbore.

[0030] Further, the way to obtain the lost gas volume of the shale according to the total discharged gas volume is:

[0031] According to the ideal gas state equation, the total discharged gas volume is corrected to the gas volume at standard conditions as the lost gas volume of the shale. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a flowchart of the shale gas volume test method in the shale gas volume test method embodiment of the present application.

[0033] Figure 2 It is a schematic diagram of the test results of the lost gas volume of the shale and the total gas volume test results of the shale in different heating stages in the shale gas volume test method embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions, and advantages of the present application clearer, further detailed description will be given to the present application in combination with the accompanying drawings and examples.

[0035] Embodiment of shale gas volume testing method

[0036] The embodiment provides a technical scheme of a shale gas volume testing method, referring to Figure 1 When testing, the shale sample needs to be first placed in a set testing environment, and the basic formation condition corresponding to the shale sample is constructed in the set testing environment;

[0037] To prevent the volatilization of residual water in the core and ensure that the state of the shale sample is as consistent as possible with the state of the shale sample in the formation, in the embodiment, the shale sample is stored in the following manner before being placed in the set testing environment and the basic formation condition corresponding to the shale sample is constructed:

[0038] If the set testing environment is set in a laboratory, the shale sample collected in the field is cut flat at both ends, wrapped with preservative film, and then sealed with paraffin for storage; if the set testing environment is set in the collection site, the shale sample collected in the field is cut flat at both ends and directly placed in the set testing environment for use; since the set testing environment in the embodiment is the interior of a desorption device, the sample is directly loaded into the analysis cylinder of the desorption device for use.

[0039] After the shale sample is placed in the set testing environment, the basic formation condition corresponding to the shale sample is constructed in the following manner:

[0040] After the shale sample is placed in the set testing environment, the temperature and pressure of the set testing environment are adjusted by simulating the formation fluid, temperature, and pressure, so that the temperature and pressure of the set testing environment meet the basic formation condition corresponding to the shale sample; specifically, after the shale sample is placed in the set testing environment under normal temperature and pressure conditions, the set testing environment is filled with simulated formation fluid, so that the pressure of the set testing environment is maintained within the set pressure interval; in the embodiment, to facilitate subsequent desorption testing, the set testing environment is the interior of a high-temperature and high-pressure desorption device; after the shale sample is weighed (the shale mass is recorded as m, such as the shale mass of 4.4 kg shown in the figure), the shale sample is placed in the high-temperature and high-pressure desorption device under normal temperature and pressure conditions, and the set pressure interval is set at about 10 MPa; that is, the high-temperature and high-pressure desorption device is filled with simulated formation fluid, so that the pressure in the interior of the desorption device is maintained at about 10 MPa. Figure 2

[0041] ​Then, the temperature of the setting test environment is adjusted to a level consistent with the formation temperature corresponding to the shale sample, and the simulated formation fluid is continuously filled into the setting test environment until the pressure of the setting test environment reaches a level consistent with the formation pressure corresponding to the shale sample, and then the current temperature and pressure level of the setting test environment are maintained for a set duration; in this embodiment, the desorption device is warmed to the formation temperature T0, and after the temperature is stabilized, the simulated formation fluid is continuously filled into the desorption device to raise the pressure in the desorption device to the formation pressure P0; the set duration is set to 7d x 24h, that is, the constant temperature and constant pressure state of the formation pressure and the formation temperature maintained in the desorption device is stabilized for 7d x 24h; during this period, if the pressure fluctuates due to adsorption or desorption, the simulated formation fluid is supplemented into the desorption device or discharged out of the desorption device, so as to keep the pressure in the desorption device constant; if the pressure fluctuation is less than 0.5MPa within 24h, it is considered that the adsorption and desorption of the formation condition reach equilibrium, and if the 7d (7 days) are maintained, it is considered that the basic formation condition (i.e., the high temperature and high pressure reservoir model as shown in Figure 1 indicated) corresponding to the shale sample is constructed.

[0042] In this embodiment, the container with a humidity value reaching the set threshold is a sample preparation device with water, and the working parameters of the sample preparation device are set to the formation temperature and the formation pressure for the convenience of filling the simulated formation fluid.

[0043] It can be seen that the shale gas volume testing method of this embodiment restores the shale sample to the temperature and pressure conditions of the reservoir through the simulated formation fluid and the high temperature and high pressure desorption device, so that the shale is fully saturated and adsorbs the simulated formation fluid, establishes a model with the formation temperature, the formation pressure and the fully saturated, adsorbed and rebalanced, and thus constructs the basic formation condition corresponding to the shale sample which is more consistent with the actual formation condition, for testing the shale gas volume, which can ensure the accuracy of the shale gas volume testing.

[0044] In the embodiment, the shale gas amount to be tested includes the lost gas amount of the shale, and the lost gas amount is tested by simulating the coring and pressure-reducing process of the well. Thus, after the basic formation condition is established, the temperature and pressure in the set testing environment are reduced to normal temperature and pressure according to the actual situation of the related parameters in the coring and pressure-reducing process in the set coring and tripping period, the total gas amount discharged in the process of reducing the temperature and pressure to normal temperature and pressure is obtained, the lost gas amount of the shale is obtained according to the total gas amount, and the testing of the lost gas amount of the shale is completed. The way of obtaining the lost gas amount of the shale according to the total gas amount is: the total gas amount is corrected to the gas volume under the standard condition according to the ideal gas state equation, and the gas volume is taken as the lost gas amount of the shale.

[0045] In the embodiment, the related parameters in the coring and tripping process include the temperature gradient, the pressure gradient and the tripping speed in the wellbore. Referring to the curve part corresponding to the temperature-reducing and pressure-reducing stage in Figure 2 , the temperature and pressure in the set testing environment are reduced to room temperature and atmospheric pressure according to the values of the temperature gradient, the pressure gradient and the tripping speed in the wellbore under the actual working condition (the temperature and pressure are adjusted by setting the temperature and pressure reduction program in the set testing environment), the room temperature and atmospheric pressure are recorded, the total gas amount discharged in the whole temperature-reducing and pressure-reducing process is collected, the total gas amount is corrected to the volume V1 under the standard condition according to the ideal gas state equation, and then V1 is taken as the lost gas amount of the shale obtained by testing. As shown in Figure 2 , the lost gas amount of the shale obtained by testing in the embodiment is 16500 mL, and the lost gas amount of each ton of shale is 16500 mL / 4.4 kg=3.75 Sm 3 / t.

[0046] The testable shale gas amount also includes the desorbed gas amount of the shale, and the test of the desorbed gas amount is carried out without loss after the test of the lost gas amount is completed; since the test of the desorbed gas amount of the shale needs to adopt the corresponding working condition after the drilling coring is cooled and depressurized, the test environment is set to the inside of the desorption device, that is, the model after the test of the lost gas amount can be directly used, and the lost gas amount in the process of the conventional desorbed gas test when the core is taken out on the ground does not occur, so that the test accuracy can be improved; after the temperature and the pressure in the set test environment are reduced to the normal temperature and pressure level according to the actual situation of the related parameters in the process of the coring, the desorbed gas amount test is carried out in the desorption device according to different temperature rising stages, the desorbed gas amount of the shale is obtained, and the test of the desorbed gas amount of the shale is completed; since the specific way of the desorbed gas amount test belongs to the prior art, the detailed method can be referred to the shale gas content determination method SY / T 6490, which will not be described here. In addition, the testable shale gas amount also includes the total gas content of the shale, and the total gas content of the shale is determined according to the lost gas amount and the desorbed gas amount obtained by the above tests (i.e., the test of the lost gas amount and the test of the desorbed gas amount). In this embodiment, the total gas content of the shale is obtained according to the sum of the lost gas amount and the desorbed gas amount.

[0047] Specifically, with reference to Figure 2 , the desorbed gas amount test is carried out according to the method of testing the adsorbed gas amount, and the desorbed gas amount V2 of the shale under the standard condition is obtained, Figure 2 In the embodiment, the temperature rising desorption stage is divided into a 50℃ temperature rising desorption stage and an 80℃ temperature rising desorption stage. According to the lost gas amount V1 and the desorbed gas amount V2 of the shale obtained by the above tests, the total gas content V of the shale can also be calculated. t = V1 + V2; for example, Figure 2 The total gas content of each ton of shale measured in the embodiment is 22221 mL; and the shale total gas abundance can be expressed as the ratio of the total gas content of the shale to the mass of the shale, that is, V t / m, the unit is Sm 3 / t, Figure 2 The example in the embodiment is 2221 mL / 4.4 kg = 5.05 Sm 3 / t; further, combined with the parameters such as the shale density ρ, the reservoir thickness H, and the reservoir area A, the total reserves G of the regional shale gas can also be more accurately calculated, that is, G = V t × ρ × H × A; in summary, the lost gas amount and the desorbed gas amount of the shale obtained by the test can be used to calculate various parameters of the shale gas amount, and the calculation results of these parameters are more accurate; the simulation of the drilling coring and the subsequent cooling and depressurization process can obtain a more accurate relationship between the desorbed gas amount and the desorption time on the basis of accurately measuring the lost gas amount.

[0048] Since the shale gas quantity testing method in this embodiment can simulate the shale gas production process after establishing basic formation conditions, the testable shale gas quantity also includes the shale gas production, that is, testing the relationship between gas production and formation pressure during the depressurization development of a shale gas reservoir; in this embodiment, referring to Figure 1 First, the basic formation conditions corresponding to the shale sample are constructed (in this embodiment, the basic formation conditions corresponding to the shale sample are constructed in a set test environment according to the method used in the test of shale gas loss). Then, while keeping the temperature of the set test environment constant, the pressure of the set test environment (i.e., the pressure inside the desorption device) is gradually reduced. During this process, the values ​​of the changing parameters of the corresponding gas reservoir development process are acquired in real time. Based on the changes in the changing parameters, the variation law of shale gas production under different pressure drop conditions is obtained to complete the simulation of the production process, that is, to complete the test of shale gas production. In this embodiment, the changing parameters of the corresponding gas reservoir development process include the gas production V corresponding to the current shale sample. i The current test environment stress P i and the current time t i Data such as i (where i represents the time scale number, with 0, 1, 2, 3... representing different stages at the same time scale); if the shale sample corresponds to condensate oil, it also includes the current condensate oil mass m. oi According to formula V i -V i-1 / P i -P i-1 V i -V i-1 / t i -t i-1 m oi -m oi-1 / P i -P i-1 m oi -m oi-1 / t i -t i-1 The corresponding change curves (where i-1 represents the value of the corresponding parameter in the previous time scale) can be used to study the change law of gas production under different pressure drops based on the characteristics of different change curves (i.e., the relationship between gas production and formation pressure during the depressurization development of shale gas reservoirs).

[0049] The relationship between gas production and formation pressure during the depressurization development of shale gas reservoirs obtained from the test can be used to calculate the proportion of cumulative gas production to reserves of shale gas reservoirs under different pressure drop levels, i.e. the degree of shale gas recovery, thereby indirectly improving the accuracy of shale gas recovery degree estimation.

[0050] Since the test environment and test conditions in the shale gas volume testing method of the embodiment are basically obtained based on simulated basic formation conditions and formation changes corresponding to different working conditions, the test results are more in line with actual working conditions and the testing accuracy is improved, and all processes can be reproduced, so that the test results can be repeatedly verified.

[0051] The present application has the following features:

[0052] 1) After placing the shale sample in the set test environment, the basic formation conditions corresponding to the shale sample are constructed, and the actual situation of the relevant parameters in the coring process, i.e., the actual working conditions corresponding to the coring, is simulated to simulate the coring temperature and pressure reduction process, so that the test environment of the lost gas volume is more in line with the actual situation during the coring, and the degassing process of the ground core is avoided during the coring, thus avoiding the large error caused by theoretical analysis and effectively improving the accuracy of the test results of the lost gas volume.

[0053] 2) By simulating the adjustment of the formation fluid, temperature and pressure, the water evaporation in the core of the shale sample caused by heating can be reduced by heating after pressurizing, the temperature and pressure conditions of the reservoir are restored to the shale sample, the shale is fully saturated and adsorbs the simulated formation fluid, a model with formation temperature, formation pressure and full saturation, adsorption and rebalancing is established, and the basic formation conditions corresponding to the shale sample which are more in line with the actual formation conditions are constructed for testing the shale gas volume, so as to ensure the accuracy of the shale gas volume testing.

[0054] 3) After constructing the basic formation conditions corresponding to the shale sample, the shale gas volume in various aspects (such as the lost gas volume, the desorbed gas volume, the total gas content of the shale and the gas production) can be tested, and the applicability is stronger.

[0055] 4) The test environment of the desorbed gas volume can be made more in line with the actual formation conditions, and the accuracy of the test results of the desorbed gas volume can be effectively improved; and the set test environment is the inside of the desorption device, so that the model (such as the simulation results of the coring temperature and pressure reduction) after the lost gas volume test can be directly used when testing the desorbed gas volume of the shale, and the lost gas volume during the conventional desorbed gas test process when the core is taken out on the ground can be avoided, and the testing accuracy is improved.

[0056] 5) The simulated formation fluid is compounded according to the composition of the target well output gas to ensure that the set test environment is as close as possible to the actual formation working condition during the test; and the simulated formation fluid is stored in a container with a humidity value reaching a set threshold, so that the formation fluid has a certain humidity, thereby preventing the water evaporation in the core of the shale sample caused by heating or insufficient humidity of the formation fluid when adjusting the temperature of the set test environment.

[0057] 6) can more closely simulate the constant temperature and pressure reduction of the formation in the process of formation development, so as to obtain more accurate test results of the relationship between the gas production and the formation pressure in the process of shale gas reservoir pressure reduction development.

[0058] It should be understood that the above specific embodiments of the present application are only used for illustrative or explanatory purposes of the principles of the present application, and do not constitute a limitation on the present application.

Claims

1. A method for testing shale gas volume, characterized in that, The shale gas volume includes the gas loss from shale formation; After placing the shale sample into the set test environment under normal temperature and pressure conditions, simulated formation fluid is injected into the set test environment to keep the pressure of the set test environment within the set pressure range. Then, adjust the temperature of the set test environment to the same level as the formation temperature corresponding to the shale sample, and continue to fill the set test environment with simulated formation fluid until the pressure of the set test environment reaches the same level as the formation pressure corresponding to the shale sample. Then maintain the current temperature and pressure level of the set test environment for the set duration. After establishing the basic geological conditions, within the set core drilling cycle, the temperature and pressure in the set test environment are reduced to normal temperature and pressure levels based on the actual situation of relevant parameters during the core drilling process. The total amount of gas discharged during the process of reducing the temperature and pressure to normal temperature and pressure levels is obtained. Based on the total amount of gas discharged, the gas loss of shale is obtained to complete the test of the gas loss of shale.

2. The method for testing shale gas volume according to claim 1, characterized in that, The shale gas volume also includes the desorbed gas volume from the shale; The test environment is set inside the desorption device. Based on the actual situation of relevant parameters during the core drilling process, the temperature and pressure in the set test environment are reduced to normal temperature and pressure levels. Inside the desorption device, the desorption gas volume is tested according to different heating stages to obtain the desorption gas volume of the shale, thus completing the test of the desorption gas volume of the shale.

3. The method for testing shale gas volume according to claim 1, characterized in that, The shale gas volume also includes the gas production of shale; After establishing the basic formation conditions corresponding to the shale sample in the set test environment, the temperature of the set test environment is kept constant, and the pressure of the set test environment is gradually reduced. During this process, the values ​​of the changing parameters of the corresponding gas reservoir development process are acquired in real time. Based on the changes in the changing parameters, the variation law of shale gas production under different pressure drop conditions is obtained to complete the test of shale gas production.

4. The method for testing shale gas volume according to claim 1, characterized in that, The method for preserving the shale samples before placing them in the designated test environment and constructing the corresponding basic geological conditions for the shale samples is as follows: If the test environment is set in a laboratory, the two ends of the collected shale sample are cut flat, wrapped in plastic wrap, and then sealed with paraffin wax for preservation. If the test environment is set at the collection site, the two ends of the collected shale sample are cut flat and placed directly into the set test environment for later use.

5. The method for testing shale gas volume according to claim 4, characterized in that, The parameters corresponding to the changes in the gas reservoir development process include the gas production of the current shale sample, the pressure of the current test environment, and the current time; if the shale sample contains condensate oil, the current condensate oil quality is also included.

6. The method for testing shale gas volume according to claim 1, characterized in that, The simulated formation fluid is prepared by blending the components of the gas produced from the target well and stored in a container with a humidity value reaching a set threshold so that the formation fluid has a certain humidity.

7. The method for testing shale gas volume according to any one of claims 1-4, characterized in that, The relevant parameters during the core extraction process include the temperature gradient, pressure gradient, and drilling speed within the wellbore.

8. The method for testing shale gas volume according to any one of claims 1-4, characterized in that, The method for determining the gas loss of shale based on the total gas volume discharged is as follows: According to the ideal gas law, the total amount of gas discharged is corrected to the gas volume under standard conditions, which is taken as the gas loss of the shale.

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