Shale gas volume testing method

Abstract

The invention belongs to the field of oil field shale gas exploration and development experiments, and particularly relates to a shale gas volume testing method. According to the invention, after the shale sample is placed in the set test environment, the basic stratum condition corresponding to the shale sample is constructed, and the drilling coring cooling and depressurization process is simulated according to the actual condition of related parameters in the process of pulling out the drill core to test the gas loss; therefore, the testing environment of the lost gas volume is more fit with the actual condition during drilling and coring, large errors generated by theoretical analysis can be avoided, and the accuracy of the testing result of the lost gas volume is effectively improved; the shale sample is recovered to the temperature and pressure conditions of the reservoir by simulating the formation fluid and adjusting the temperature and the pressure, so that the shale is fully saturated and adsorbs the simulated formation fluid, and therefore, the basic formation condition corresponding to the shale sample, which is more fit with the actual formation condition, is constructed and is used for testing the gas volume of the shale; and the accuracy of shale gas volume testing is ensured.

Description

Technical Field

[0001] The invention belongs to the field of oilfield shale gas exploration and development experiments, and in particular relates to a shale gas quantity testing method. Background Art

[0002] As a new field of oil and gas development at home and abroad, shale gas has become a hot spot for oil and gas exploration and development in China in recent years. Compared with foreign exploration and development, the exploration and development of shale gas in China started late, the technology maturity is low, and the exploration area is wider. Since the output of shale gas is mainly methane, it is an efficient and clean energy, and it has received more and more attention under the background of the country's "carbon neutrality". Shale gas is different from ordinary natural gas reservoirs. Because its porosity, permeability and other indicators are far lower than those of conventional gas reservoirs, the state of gas in the formation has also changed from the state of free gas in conventional gas reservoirs to two states of free gas and adsorbed gas in shale reservoirs. Free gas mainly exists in pores or cracks, while adsorbed gas is methane adsorbed on the surface of shale particles. The content of free gas is related to factors such as the size of pores and cracks, formation pressure and formation temperature; the content of adsorbed gas is related to factors such as the gas adsorption capacity of the shale particle surface, formation pressure, formation temperature, etc. Therefore, the shale gas exploration and development industry often needs to test the porosity, formation pressure, formation temperature and adsorbed gas content of reservoir shale.

[0003] On May 17, 2015, Hao Jin published an article entitled "An Improved Method for Estimating Lost Gas Content in Shale Gas" in Modern Geology. He used the lost gas escape geological model to correct the calculation method of loss time and other means, improved the USBM method formed by the US Bureau of Mines based on the coalbed methane diffusion theory, and found the main reason for the small amount of lost gas. As a result, some devices and methods for rapid adsorption gas testing were invented in the industry. These methods are mainly based on the USBM method formed by the US Bureau of Mines based on the coalbed methane diffusion theory. The Chinese invention patent with application publication number CN112964597A pointed out that the accuracy of the results of this method in the shale field is questionable, and from the practical data, due to the limitations of field test time, site and construction process, the calculation of lost gas volume relies on empirical formulas, with large errors, inconsistent starting points of desorption test time, unclear relationship between desorption gas volume and desorption time, difficult to evaluate the accuracy and precision of desorption test results, non-repeatable verification of test results, and lack of free gas volume data. The free space volume of the method shown in the Chinese invention patent with application publication number CN112964597A includes two parts: the desorption tube and the shale pore volume. It can only measure the adsorbed gas volume, but cannot test the lost gas volume.

[0004] The Chinese invention patent with application publication number CN103822849A discloses an on-site automatic analyzer system for unconventional gas, which shows an on-site automatic analyzer from the perspective of dividing the test analysis into system modules. In principle, it needs the support of fitting theories such as USBM to calculate the lost gas volume. The Chinese invention patent with application publication number CN108982289A discloses a shale gas on-site analysis device and a device that can be transported to the site by a transport vehicle. It mainly solves the problems of the previous desorption device being too large and difficult to carry, the desorption water bath temperature being low, and the interference of water vapor. In principle, it still cannot do without the USBM method. The Chinese invention patent with application publication number CN109540735A describes a shale gas content comprehensive analysis device and method. This method uses a desorption cylinder connected in series with a gas chromatograph to solve the function of online detection of changes in desorption gas components. The test of gas content is still based on the method of fitting curves such as USBM, and the accuracy of measuring gas content needs to be discussed.

[0005] There are also some solutions that involve simulation and experimental methods of the relevant processes of shale gas reservoir exploitation, but do not reflect the measurement method of lost gas volume; for example, the Chinese utility model patent with the authorization announcement number CN208433157U describes a new simulation experimental device for shale gas reservoir exploitation, which mainly simulates the exploitation process of shale gas reservoirs, and does not mention the content of measuring lost gas volume. The Chinese invention patent with the application publication number CN107345890A describes a shale gas adsorption desorption / exploitation simulation experimental device and method. From its disclosed content, it can be seen that the device is still based on Boyle's law and gas state equation to calculate the content of adsorbed gas and gas production law, and does not involve a method for directly obtaining the lost gas volume of shale through testing. Summary of the invention

[0006] The purpose of the present invention is to provide a method for testing shale gas volume, which is used to solve the problem that the existing testing methods related to shale gas volume mainly obtain test results based on theoretical analysis, resulting in poor accuracy of the test results.

[0007] In order to achieve the above object, the present invention provides a method for testing the amount of shale gas, wherein the amount of shale gas includes the amount of lost gas in shale;

[0008] The shale sample is placed in a set test environment, and basic formation conditions corresponding to the shale sample are constructed in the set test environment;

[0009] After constructing the basic formation conditions, within the set coring and drilling cycle, the temperature and pressure in the set test environment are reduced to normal temperature and pressure levels according to the actual conditions of the relevant parameters in the coring process, and the total gas volume discharged in the process of reducing the temperature and pressure to normal temperature and pressure levels is obtained. Based on the total gas volume discharged, the loss of shale gas is obtained to complete the test of the loss of shale gas.

[0010] The beneficial effects of the above technical solution are: after placing the shale sample in the set test environment, the basic formation conditions corresponding to the shale sample are constructed, and the cooling and depressurization process of coring during drilling is simulated according to the actual working conditions corresponding to coring (that is, the actual conditions of the relevant parameters during coring), so that the test environment for lost gas volume is more in line with the actual conditions during coring, and the degassing process of the core coming out of the ground during coring is avoided, thereby avoiding the large errors caused by theoretical analysis and effectively improving the accuracy of the lost gas volume test results; and the test environment and test conditions in the shale gas volume test method are based on the simulated real formation conditions and the parameter changes corresponding to the real working conditions, so while ensuring that the test results are more in line with the actual working conditions and improving the test accuracy, all processes can be reproduced repeatedly, so that the test results can be repeatedly verified.

[0011] Furthermore, the shale gas volume also includes the desorbed gas volume of shale;

[0012] The test environment is set to be inside the desorption device. After the temperature and pressure in the set test environment are reduced to normal temperature and pressure levels according to the actual conditions of relevant parameters in the core drilling process, a desorption gas volume test is performed inside the desorption device at different heating stages to obtain the desorption gas volume of shale, thereby completing the desorption gas volume test of shale.

[0013] The beneficial effects of the above technical solution are: it can make the test environment of the desorption gas volume more in line with the actual formation conditions, effectively improving the accuracy of the test results of the desorption gas volume; and, by setting the test environment to be inside the desorption device, it is possible to directly use the model after the loss gas volume test when testing the desorption gas volume of shale, and there will be no loss of gas volume when the core is taken out from the ground on site during the conventional desorption gas test, thereby improving the test accuracy.

[0014] Furthermore, the shale gas volume also includes the gas production of shale;

[0015] After constructing the basic formation conditions corresponding to the shale sample in the set test environment, the temperature of the set test environment is kept unchanged, and the pressure of the set test environment is gradually reduced. In the process, the values ​​of the changing parameters of the corresponding gas reservoir development process are obtained in real time. According to the changes in the changing parameters, the change law of the gas production of shale under different pressure drop conditions is obtained to complete the test of the gas production of shale.

[0016] The beneficial effect of the above technical solution is that it can more realistically simulate the constant temperature and pressure reduction conditions of the formation during formation development, thereby obtaining more accurate test results of the relationship between gas production and formation pressure during the pressure reduction development of shale gas reservoirs.

[0017] Furthermore, the shale sample is stored in the following manner before being placed in the set test environment and constructing the basic formation conditions corresponding to the shale sample:

[0018] If the test environment is set up in the laboratory, the two ends of the collected shale samples are cut flat, wrapped with plastic wrap and then sealed with paraffin for preservation;

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

[0020] The beneficial effect of the above technical solution is that it can prevent the volatilization of the remaining water in the core and ensure that the state of the shale sample is as consistent as possible with its state in the formation.

[0021] Furthermore, after placing the shale sample in the set test environment, the method of constructing the basic formation conditions corresponding to the shale sample includes: after placing the shale sample in the set test environment, simulating the formation fluid and adjusting the temperature and pressure so that the temperature and pressure of the set test environment meet the basic formation conditions corresponding to the shale sample.

[0022] Furthermore, after placing the shale sample in the set test environment, the temperature and pressure of the set test environment are adjusted by simulating the formation fluid and adjusting the temperature and pressure to meet the basic formation conditions corresponding to the shale sample in the following manner:

[0023] After placing the shale sample in a set test environment under normal temperature and pressure conditions, the simulated formation fluid is injected into the set test environment to keep the pressure of the set test environment within the set pressure range;

[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 continues to be 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 temperature and pressure levels of the current set test environment are maintained for a set time.

[0025] The beneficial effects of the above technical solution are as follows: by simulating formation fluid and adjusting temperature and pressure, pressurizing first and then heating can reduce the evaporation of water in the core of the shale sample caused by heating, and restore the temperature and pressure conditions of the reservoir to the shale sample, so that the shale is fully saturated and adsorbs the simulated formation fluid, and establishes a model with formation temperature, formation pressure and full saturation, adsorption, and rebalance, thereby constructing basic formation conditions corresponding to shale samples that are more in line with actual formation conditions, which are used for testing the shale gas volume and can ensure the accuracy of the shale gas volume test.

[0026] Furthermore, the changing parameters corresponding to the gas reservoir development process include the gas production corresponding to the current shale sample, the pressure of the currently set test environment, and the current time; if the shale sample corresponds to the presence of condensate oil, it also includes the current condensate oil quality.

[0027] Furthermore, the simulated formation fluid is compounded according to the composition of the produced gas of the target well, and is stored in a container whose humidity value reaches a set threshold value, so that the formation fluid has a certain humidity.

[0028] The beneficial effects of the above technical scheme are as follows: the simulated formation fluid is compounded according to the composition of the gas produced by the target well, which can ensure that the test environment set during the test is as close as possible to the actual formation conditions; and the simulated formation fluid is stored in a container whose humidity value reaches a set threshold value, 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] Furthermore, the relevant parameters in the process of drilling and coring include the temperature gradient, pressure gradient and drilling speed in the wellbore.

[0030] Furthermore, according to the total amount of gas discharged, the lost gas volume of shale is obtained as follows:

[0031] According to the ideal gas state equation, the total amount of gas discharged is corrected to the gas volume under standard conditions and is taken as the loss of gas in shale. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic flow chart of a method for testing shale gas volume in an embodiment of the method for testing shale gas volume of the present invention;

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

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0035] Example of a method for testing shale gas volume

[0036] This embodiment provides a technical solution for a method for testing shale gas volume. Figure 1 ,When testing is conducted, the shale sample needs to be placed in the set test environment first, and the basic formation conditions corresponding to the shale sample are constructed in the set test environment;

[0037] In order to prevent the volatilization of the remaining water in the core and ensure that the state of the shale sample is as consistent as possible with the state in the formation, in this embodiment, the shale sample is stored in the following manner before being placed in the set test environment and constructing the basic formation conditions corresponding to the shale sample:

[0038] If the test environment is set in the laboratory, the two ends of the collected shale samples are cut flat at the collection site, wrapped with plastic wrap and then sealed with paraffin for preservation; if the test environment is set at the collection site, the two ends of the collected shale samples are cut flat at the collection site and directly placed in the set test environment for standby use; in this embodiment, the test environment is set inside the desorption device, and the sample is directly loaded into the analysis cylinder of the desorption device for standby use.

[0039] After placing the shale sample in the set test environment, the methods for constructing the basic formation conditions corresponding to the shale sample include:

[0040] After the shale sample is placed in the set test environment, the temperature and pressure of the set test environment are adjusted by simulating formation fluid and adjusting temperature and pressure to meet the basic formation conditions corresponding to the shale sample; specifically, 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 to keep the pressure of the set test environment within the set pressure range; in this embodiment, in order to facilitate the subsequent desorption test, the test environment is set to the inside of the high-temperature and high-pressure desorption device; the shale sample is weighed after the net weight is recorded (the mass of the shale is recorded as m, such as Figure 2 The shale mass shown is 4.4 kg), and is placed in a high-temperature and high-pressure desorption device under normal temperature and pressure conditions, and the set pressure range is set at about 10 MPa; that is, the simulated formation fluid is filled into the high-temperature and high-pressure desorption device to maintain the pressure inside the desorption device at about 10 MPa.

[0041] Then, the temperature of the set test environment is adjusted to a level consistent with the formation temperature corresponding to the shale sample, and then 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 temperature and pressure level of the current set test environment are maintained for a set time. In this embodiment, the desorption device is heated to the formation temperature T0, and after the temperature is stable, the simulated formation fluid is continuously filled into the desorption device to increase the pressure in the desorption device to the formation pressure P0. The set time is set to 7d×24h, that is, the constant temperature and pressure state of the formation pressure and formation temperature maintained inside the desorption device is stable for 7d×24h. During this period, when pressure fluctuations are caused by adsorption or desorption, the simulated formation fluid is added to the desorption device or discharged from the desorption device to keep the pressure in the desorption device constant. If the pressure fluctuation within 24h is less than 0.5MPa, it can be considered that the adsorption and desorption of the formation conditions have reached equilibrium, and if it is maintained for 7d (7 days), it can be considered that the basic formation conditions corresponding to the shale sample (i.e., Figure 1 The high-temperature and high-pressure reservoir model shown in the figure was completed.

[0042] Among them, the simulated formation fluid is compounded according to the composition of the gas produced by the target well to ensure that the test environment set during the test is as close as possible to the actual formation conditions; and the simulated formation fluid is stored in a container whose humidity value reaches a set threshold value, 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 too low humidity of the formation fluid when adjusting the temperature of the set test environment. In this embodiment, the container whose humidity value reaches the set threshold value is a sample dispenser with water. In order to facilitate the filling of the simulated formation fluid, the working parameters of the sample dispenser are set to the formation temperature and formation pressure.

[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 simulating formation fluid and high-temperature and high-pressure desorption device, so that the shale is fully saturated and adsorbs the simulated formation fluid, and establishes a model with formation temperature, formation pressure and full saturation, adsorption, and rebalance, thereby constructing basic formation conditions corresponding to shale samples that are more in line with actual formation conditions, which are used for testing the shale gas volume and can ensure the accuracy of the shale gas volume test.

[0044] In this embodiment, the testable shale gas volume includes the lost gas volume of shale, and the test of the lost gas volume is carried out by simulating the cooling and depressurization process of coring during drilling; thus, after constructing the basic formation conditions, within the set coring and drilling cycle, the temperature and pressure in the set test environment are reduced to normal temperature and pressure levels according to the actual conditions of the relevant parameters in the coring process, and the total gas volume discharged in the process of reducing the temperature and pressure to normal temperature and pressure levels is obtained, and the lost gas volume of shale is obtained based on the total gas volume discharged to complete the test of the lost gas volume of shale; wherein, the method of obtaining the lost gas volume of shale based on the total gas volume discharged is: according to the ideal gas state equation, the total gas volume discharged is corrected to the gas volume under standard conditions, as the lost gas volume of shale.

[0045] In this embodiment, the relevant parameters in the process of drilling and coring include the temperature gradient, pressure gradient and drilling speed in the wellbore; Figure 2 In the curve portion corresponding to the temperature reduction and pressure reduction stage in the present embodiment, according to the values ​​of the temperature gradient, pressure gradient and drilling speed in the wellbore under actual working conditions, the temperature and pressure in the set test environment are reduced to room temperature and atmospheric pressure (specifically adjusted by setting the temperature and pressure reduction program in the test environment), the room temperature and atmospheric pressure are recorded, the total gas volume discharged during the entire temperature reduction and pressure reduction process is collected, and the total gas volume discharged is corrected to the volume V1 under standard conditions according to the ideal gas state equation, then V1 is the gas loss volume of shale obtained through the test; Figure 2 As shown in the figure, the gas loss of shale obtained in the test in this embodiment is 16500mL, and the gas loss per ton of shale is 16500mL / 4.4kg=3.75Sm 3 / t.

[0046] The testable shale gas volume also includes the desorbed gas volume of shale. The test of the desorbed gas volume is carried out non-destructively after the loss gas volume test is completed. Since the test of the desorbed gas volume of shale requires the corresponding working conditions after the temperature and pressure reduction of the core after drilling, the test environment is set to the inside of the desorption device, which means that the model after the loss gas volume test can be directly used, and there will be no loss of gas volume when the core is taken out of the field during the conventional desorption gas test, so the test accuracy can be improved. According to the actual situation of the relevant parameters in the process of drilling and coring, the temperature and pressure in the set test environment are reduced to the normal temperature and pressure level, and the desorbed gas volume test is carried out in the desorption device according to different heating stages to obtain the desorbed gas volume of shale, so as to complete the test of the desorbed gas volume of shale. Since the specific method of the desorbed gas volume test belongs to the existing technology, the detailed method can be found in SY / T 6490 The method for determining the gas content of shale will not be described in detail here; in addition, the testable shale gas content also includes the total gas content of the shale. The total gas content of the shale is determined based on the loss gas content and the desorbed gas content obtained by the above tests (i.e., the test of the loss gas content and the test of the desorbed gas content). In this embodiment, the total gas content of the shale is obtained based on the sum of the loss gas content and the desorbed gas content.

[0047] Specifically, refer to Figure 2 , perform desorption gas volume test according to the method of testing adsorption gas volume, and obtain the desorption gas volume V2 of shale under standard conditions, Figure 2 The desorption stage is divided into a 50℃ heating desorption stage and an 80℃ heating desorption stage. Based on the shale gas loss V1 and desorption gas volume V2 obtained from the above test, the total gas content V of the shale can also be calculated. t =V1+V2; for example, Figure 2 The total gas content per ton of shale measured in is 22221 mL; and the total gas abundance of shale can be expressed as the ratio of the total gas content of shale to the mass of shale, that is, V t / m, unit is Sm 3 / t, Figure 2 The example is 2221mL / 4.4kg=5.05Sm 3 / t; Furthermore, combined with shale density ρ, reservoir thickness H, reservoir area A and other parameters, the total reserves of regional shale gas G = V t ×ρ×H×A; In summary, the gas loss and desorption volumes of shale obtained from the test can be used to calculate various parameters of shale gas volume and make the calculation results of these parameters more accurate; simulating the cooling and pressure reduction process after drilling and coring can obtain a more accurate relationship between the desorption gas volume and desorption time based on the accurate measurement of the gas loss.

[0048] Since the shale gas volume testing method of this embodiment can also simulate the shale gas production process after constructing the basic formation conditions, the shale gas volume that can be tested also includes the gas production of shale, that is, the relationship between the gas production and the formation pressure during the depressurization development of the shale gas reservoir is tested; in this embodiment, refer 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 in the manner of the test of the gas loss of shale), and then the temperature of the set test environment is kept unchanged, and the pressure of the set test environment (i.e., the pressure in the desorption device) is gradually reduced, and the values ​​of the changing parameters corresponding to the gas reservoir development process are obtained in real time during the process. According to the changes in the changing parameters, the changing law of the gas production of the shale under different pressure drop conditions is obtained to complete the simulation of the production process, that is, to complete the test of the gas production of the shale; in this embodiment, the changing parameters corresponding to the gas reservoir development process include the gas production V corresponding to the current shale sample i 、The current set test environment pressure P i and the current time t i etc. (where i represents the sequence number of the time scale, with 0, 1, 2, 3, etc. representing different stages under the same time scale); if condensate oil exists in the corresponding shale sample, it also includes the current condensate oil mass m oi According to the 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 changing law of gas production under different pressure drops (i.e. the relationship between gas production and formation pressure during the depressurization development of shale gas reservoirs) according to the characteristics of different change curves.

[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 ratio of cumulative gas production to reserves of shale gas reservoirs at different pressure drop levels, that is, the degree of shale gas recovery, thereby indirectly improving the accuracy of shale gas recovery estimation.

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

[0051] The present invention has the following characteristics:

[0052] 1) After placing the shale sample in the set test environment, the basic formation conditions corresponding to the shale sample are constructed, and according to the actual conditions of the relevant parameters in the process of drilling and coring, that is, the actual working conditions corresponding to drilling and coring, the cooling and pressure reduction process of drilling and coring is simulated, so that the test environment of gas loss is more in line with the actual conditions during drilling and coring, and the degassing process of the core coming out of the ground during drilling and coring is avoided, so that the large errors caused by theoretical analysis can be avoided, and the accuracy of the test results of gas loss can be effectively improved.

[0053] 2) By simulating the formation fluid and adjusting the temperature and pressure, pressurizing first and then heating can reduce the evaporation of water in the core of the shale sample caused by heating, and restore the temperature and pressure conditions of the reservoir to the shale sample, so that the shale is fully saturated and adsorbs the simulated formation fluid, and establishes a model with formation temperature, formation pressure and full saturation, adsorption, and rebalance, thereby constructing the basic formation conditions corresponding to the shale sample that is more in line with the actual formation conditions, which is used for the test of shale gas volume and can ensure the accuracy of the test of shale gas volume.

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

[0055] 4) It can make the test environment of desorption gas volume more in line with the actual formation conditions, effectively improving the accuracy of the test results of desorption gas volume; and, by setting the test environment to be inside the desorption device, the model after the loss gas volume test (such as the simulation results of cooling and depressurization of drilling coring) can be directly used when testing the desorption gas volume of shale, and the loss of gas volume when coring on the ground during the conventional desorption gas test will not occur, thereby improving the test accuracy.

[0056] 5) The simulated formation fluid is compounded according to the composition of the gas produced by the target well to ensure that the test environment set during the test is as close as possible to the actual formation conditions; and the simulated formation fluid is stored in a container whose humidity value reaches 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.

[0057] 6) It can simulate the constant temperature and pressure reduction of the formation in a more realistic manner, thereby obtaining more accurate test results of the relationship between gas production and formation pressure during the pressure reduction development of shale gas reservoirs.

[0058] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, but do not constitute a limitation to the present invention.

Claims

1. A method for testing shale gas volume, characterized in that: The shale gas volume includes the lost gas volume of shale; The shale sample is placed in a set test environment, and basic formation conditions corresponding to the shale sample are constructed in the set test environment; After constructing the basic formation conditions, within the set coring and drilling cycle, the temperature and pressure in the set test environment are reduced to normal temperature and pressure levels according to the actual conditions of the relevant parameters in the coring process, and the total gas volume discharged in the process of reducing the temperature and pressure to normal temperature and pressure levels is obtained. Based on the total gas volume discharged, the loss of shale gas is obtained to complete the test of the loss of shale gas.

2. The shale gas volume testing method according to claim 1, characterized in that: The shale gas volume also includes the desorbed gas volume of shale; The test environment is set to be inside the desorption device. After the temperature and pressure in the set test environment are reduced to normal temperature and pressure levels according to the actual conditions of relevant parameters in the core drilling process, a desorption gas volume test is performed inside the desorption device at different heating stages to obtain the desorption gas volume of shale, thereby completing the desorption gas volume test of shale.

3. The shale gas volume testing method according to claim 1, characterized in that: The shale gas volume also includes the gas production of shale; After constructing the basic formation conditions corresponding to the shale sample in the set test environment, the temperature of the set test environment is kept unchanged, and the pressure of the set test environment is gradually reduced. In the process, the values ​​of the changing parameters of the corresponding gas reservoir development process are obtained in real time. According to the changes in the changing parameters, the change law of the gas production of shale under different pressure drop conditions is obtained to complete the test of the gas production of shale.

4. The method for testing shale gas volume according to claim 1, characterized in that: The shale samples are stored in the following manner before being placed in the set test environment and establishing the basic formation conditions corresponding to the shale samples: If the test environment is set up in the laboratory, the two ends of the collected shale samples are cut flat, wrapped with plastic wrap and then sealed with paraffin for preservation; If the test environment is set at the collection site, the two ends of the collected shale samples are cut flat and directly placed in the set test environment for use.

5. The method for testing shale gas volume according to any one of claims 1 to 4, characterized in that: After placing the shale sample in the set test environment, the method of constructing the basic formation conditions corresponding to the shale sample includes: after placing the shale sample in the set test environment, simulating the formation fluid and adjusting the temperature and pressure so that the temperature and pressure of the set test environment meet the basic formation conditions corresponding to the shale sample.

6. The method for testing shale gas volume according to claim 5, characterized in that: After placing the shale sample in the set test environment, the temperature and pressure of the set test environment are adjusted by simulating the formation fluid and adjusting the temperature and pressure to meet the basic formation conditions corresponding to the shale sample in the following manner: After placing the shale sample in a set test environment under normal temperature and pressure conditions, the 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, 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 continues to be 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 temperature and pressure levels of the current set test environment are maintained for a set time.

7. The method for testing shale gas volume according to claim 4, characterized in that: The changing parameters corresponding to the gas reservoir development process include the gas production corresponding to the current shale sample, the pressure of the current set test environment and the current time; if the shale sample corresponds to the presence of condensate oil, it also includes the current condensate oil quality.

8. The method for testing shale gas volume according to claim 5, characterized in that: The simulated formation fluid is compounded according to the composition of the produced gas of the target well, and is stored in a container whose humidity value reaches a set threshold value, so that the formation fluid has a certain humidity.

9. The method for testing shale gas volume according to any one of claims 1 to 4, characterized in that: The relevant parameters in the process of drilling and coring include the temperature gradient, pressure gradient and drilling speed in the wellbore.

10. The method for testing shale gas volume according to any one of claims 1 to 4, characterized in that: According to the total gas volume discharged, the lost gas volume of shale is obtained as follows: According to the ideal gas state equation, the total amount of gas discharged is corrected to the gas volume under standard conditions and is taken as the loss of gas in shale.

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