Device and method for measuring permeability of shale under simulated high temperature and high pressure conditions of formation

Abstract

The application provides a shale permeability measurement device and method under simulated high-temperature and high-pressure conditions of a formation, and belongs to the technical field of oil exploration and development. The device comprises: a gas supply system, a gas outlet end of which is connected with an upper end constant container system, and which is used for inputting gas into the upper end constant container system to provide pore pressure required by experiments; the upper end constant container system, a gas inlet end of which is connected with the gas outlet end of the gas supply system, and a gas outlet end of which is connected with a core holder system, and which is used for storing gas with a pressure required by experiments in a quantitative metering volume; a lower end constant container system, a gas inlet end of which is connected with the gas outlet end of the core holder system, and which is used for storing gas with a pressure required by experiments in a quantitative metering volume; the core holder system, a gas inlet end of which is connected with the upper end constant container system, and a gas outlet end of which is connected with the lower end constant container system, and which is used for clamping and sealing a rock sample; an overburden pressure control system, which is in communication with the core holder system, and which is used for applying an overburden pressure required by experiments to the rock sample; and a temperature control system.

Description

Technical Field

[0001] This invention relates to the field of petroleum exploration and development technology, specifically to a shale permeability measurement device and a method for simulating shale permeability under high temperature and high pressure conditions in formations. Background Technology

[0002] In the field of oil and gas field exploration and development, permeability can quantitatively characterize the seepage capacity of oil, gas and water in reservoirs and is one of the important parameters for evaluating reservoir properties. In recent years, with the decrease in the number of conventional oil and gas reservoirs, the development of unconventional oil and gas reservoirs such as tight oil and gas reservoirs and shale oil and gas reservoirs has begun to receive greater attention. Shale oil, in particular, is an important alternative resource for my country's petroleum industry. Developing shale oil has significant strategic and practical implications, as it can not only promote national economic development but also ensure national energy security.

[0003] Shale oil reservoirs are predominantly composed of shale, interbedded with extremely thin layers of siltstone or carbonate rocks. A significant physical characteristic is their low permeability, typically at the Nadasi level. Furthermore, shale reservoirs are primarily located within foliation fractures and matrix pores, and the presence of abundant clay minerals makes them prone to forming overpressured formations with very high pore pressures. Currently, permeability testing for shale primarily employs gas-based methods, typically using nitrogen or helium. These gas-based permeability testing methods can be further divided into steady-state and transient methods.

[0004] The steady-state method, based on Darcy's law, obtains permeability by measuring the flow rate and pressure difference before and after the core sample. For shale, this method has the following three limitations: First, it is difficult to accurately measure the permeability of shale cores due to the low accuracy of flow rate measurement, and the gas flow takes a long time to reach a steady state, resulting in low testing efficiency. Second, the pore pressure is low, generally only 0.1 MPa, making it impossible to measure permeability under high pore pressure. Third, the overlying pressure is low, generally around 1.5 MPa, making it impossible to measure permeability under high overlying pressure conditions. Fourth, the measurement temperature is room temperature, and it cannot be measured at high temperatures.

[0005] Transient methods are suitable for measuring the permeability of shale cores. Their basic principle is to obtain permeability by measuring pressure, and include pulse decay methods, pulse oscillation methods, pressure decay methods, and GRI methods. The most commonly used transient method in laboratories is the pulse decay method, which can meet testing requirements with overlying pressures up to 70 MPa. However, this method also has limitations: firstly, while the pore pressure is higher than that of steady-state methods, reaching a maximum of 14 MPa, it still does not meet the analytical requirements of the actual formation pressure; secondly, the temperature requirements are also not met, and testing and analysis can only be conducted at room temperature or slightly above room temperature.

[0006] Currently, there is no analytical equipment for shale gas permeability testing that can simultaneously meet the testing requirements of overlying pressure, pore pressure, and temperature, and closely approximate the high-temperature and high-pressure conditions of the formation. Summary of the Invention

[0007] The purpose of this invention is to provide a device and method for measuring shale permeability under simulated high-temperature and high-pressure formation conditions. This device provides the required pore pressure through a gas supply system, the required overburden pressure through an overburden pressure control system, and the required experimental temperature through a temperature control system. By simulating actual high-temperature and high-pressure formation conditions through the gas supply system, overburden pressure control system, and temperature control system, the device can measure shale gas permeability under these conditions, meeting the research needs of exploration and development. Furthermore, the device incorporates an upper and lower fixed-container system to precisely set the pressure at the upper and lower ends of the core holder, improving the accuracy of the measured pressure values.

[0008] To achieve the above objectives, embodiments of the present invention provide a shale permeability measurement device simulating high-temperature and high-pressure conditions in formations, the device comprising:

[0009] A gas supply system, the gas supply system having its outlet connected to an upper fixed container system, is used to input gas into the upper fixed container system to provide the pore pressure required for the experiment;

[0010] The upper fixed container system has an air inlet connected to the air outlet of the gas supply system, and the air outlet is connected to the core clamping system. It is used to store the gas required for the experiment at a fixed volume.

[0011] The lower fixed container system has its air inlet connected to the air outlet of the core holder system and its outlet connected to the atmosphere. It is used to store the gas required for the experiment at a fixed volume.

[0012] A core clamping device system, wherein the air inlet of the core clamping device system is connected to the upper fixed container system and the air outlet is connected to the lower fixed container system, for clamping and sealing the rock sample;

[0013] The overburden pressure control system is connected to the core holder system and is used to apply the overburden pressure required for the experiment to the rock sample;

[0014] The temperature control system is used to control the experimental temperature of the upper fixed container system, the lower fixed container system, and the core holder system.

[0015] Based on the aforementioned technical means, this measuring device can provide the required pore pressure through a gas supply system, the required overburden pressure through an overburden pressure control system, and the required experimental temperature through a temperature control system. By combining these systems, it can simulate the actual high-temperature and high-pressure conditions of the formation, thereby enabling the measurement of shale gas permeability under these conditions, meeting the research needs of exploration and development. Furthermore, the measuring device incorporates upper and lower fixed-container systems to precisely set the pressure at the upper and lower ends of the core holder, improving the accuracy of the measured pressure values.

[0016] In some feasible embodiments, the upper fixed container system includes: a pipeline, a second solenoid valve, a safety valve, and multiple upper fixed containers of different volumes. The multiple upper fixed containers of different volumes are connected in parallel on the pipeline. The pipeline is equipped with a second solenoid valve and a safety valve. The inlet end of the pipeline is connected to the gas supply system, and the outlet end of the pipeline is connected to the air inlet end of the core holder system. Each upper fixed container is equipped with a corresponding valve.

[0017] Based on the above technical means, the upper fixed container system is equipped with multiple upper fixed containers of different volumes. Different upper fixed containers can be selected when testing different levels of permeability. The fixed volume of the upper fixed container makes it easy to set the pressure of the core holder.

[0018] In some feasible embodiments, the upper fixed container system further includes an explosion-proof plate disposed on the pipeline between the safety valve and the second solenoid valve.

[0019] Based on the above technical means, an explosion-proof plate is installed in the upper fixed container system. The explosion-proof plate can release the pressure medium when the pressure difference between the two sides reaches a set threshold, ensuring the safety of equipment and personnel and preventing safety accidents caused by high temperature and high pressure during the measurement process.

[0020] In some feasible embodiments, the lower fixed container system includes: a pipeline, a third solenoid valve, a fourth solenoid valve, a throttle valve, and multiple lower fixed containers of different volumes. The multiple lower fixed containers of different volumes are connected in parallel on the pipeline. The inlet end of the pipeline is connected to the fourth solenoid valve and then to the outlet end of the core holder system. The throttle valve is located at the outlet end of the pipeline. The third solenoid valve is located on the pipeline, between the lower fixed containers and the throttle valve. The number and volume of the lower fixed containers are the same as those of the upper fixed containers. Each lower fixed container is equipped with a corresponding valve.

[0021] Based on the above technical means, the lower fixed container system is equipped with multiple lower fixed containers of different volumes. Different lower fixed containers can be selected when testing different levels of permeability. The fixed volume of the lower fixed container, in conjunction with the upper fixed container, can more accurately set the pressure of the core holder.

[0022] In some feasible embodiments, there are three upper fixed containers and three lower fixed containers.

[0023] Based on the aforementioned technical methods, the three upper-end fixed containers and the corresponding three lower-end fixed containers can be applied to rock samples with low permeability, medium permeability, and high permeability, respectively, with a lower permeability limit of 10. -6 mD.

[0024] In some feasible embodiments, the core holder system includes: a pipeline, a core holder, a fifth solenoid valve, a sixth solenoid valve, a seventh solenoid valve, an eighth solenoid valve, a first pressure gauge, a second pressure gauge, a differential pressure sensor, and a first control valve; the core holder includes a sample chamber and an overburden pressure chamber, the sample chamber being located at the center of the overburden pressure chamber, the overburden pressure chamber being connected to an overburden pressure control system via an overburden pressure pipeline, and the overburden pressure pipeline connecting the overburden pressure chamber and the overburden pressure control system is equipped with a first control valve; the upper end of the core holder is connected to an upper fixed container system via an inlet pipeline, and the inlet pipeline is equipped with a fifth solenoid valve and a first pressure gauge; the inlet end of the fifth solenoid valve is connected to the outlet end of a fourth solenoid valve via a bypass pipeline; the bypass pipeline is equipped with a second pressure gauge, a sixth solenoid valve, a seventh solenoid valve, an eighth solenoid valve, and a differential pressure sensor, the differential pressure sensor being located between the sixth and seventh solenoid valves, and the eighth solenoid valve being connected in parallel with the sixth and seventh solenoid valves and the differential pressure sensor via a parallel pipeline; the second pressure gauge is located between the seventh and fourth solenoid valves.

[0025] Based on the above technical means, the core holder system is equipped with a bypass pipeline, which connects the upper fixed container system and the lower fixed container system. During the process of applying pore pressure to the rock sample, the pressure of the upper fixed container and the lower fixed container can be increased simultaneously to saturate the rock sample with gas, thereby increasing the gas saturation rate.

[0026] In some feasible embodiments, the gas supply system includes: a gas cylinder, a gas cylinder pressure gauge, a gas cylinder control valve, a gas booster pump, a first solenoid valve, an air pressure gauge, an air compressor, a vent valve, and a booster pressure gauge. The gas booster pump is connected to the gas cylinder via a first pipeline, and the first pipeline is equipped with a gas cylinder pressure gauge and a gas cylinder control valve. The gas booster pump is connected to the air compressor via a second pipeline, and the second pipeline is equipped with a first solenoid valve and an air pressure gauge. The first solenoid valve is located between the air pressure gauge and the gas booster pump. The gas booster pump is connected to a fixed container system at the lower end of a third pipeline, and the third pipeline is equipped with a booster pressure gauge. The gas booster pump is also connected to the atmosphere via a third pipeline, and a vent valve is installed on the pipeline connecting the gas booster pump to the atmosphere.

[0027] Based on the above technical means, an air compressor and a gas booster pump are used to increase the gas pressure in the pipeline. A booster pressure gauge can be set up to detect the pressure of the gas supplied by the gas supply system in real time, ensuring that the gas pressure entering the upper fixed container system meets the experimental requirements.

[0028] In some feasible embodiments, the gas supply system further includes a pressure regulating valve disposed between the air compressor and the air pressure gauge.

[0029] Based on the above technical means, a pressure regulating valve is added between the air compressor and the air pressure gauge. The pressure regulating valve can more accurately adjust the amount of gas pressurized by the air compressor in the pipeline.

[0030] In some feasible embodiments, the overburden pressure control system includes a pressurizing pump and a second control valve. The pressurizing pump is connected to the overburden pressure chamber of the core holder system via a pipeline, and the second control valve is located on the pipeline.

[0031] Based on the aforementioned technical means, the overlying pressure control system can provide stable overlying pressure for rock samples, ensuring measurement accuracy. The system features automatic pressurization and automatic energy replenishment functions, and the pressurization pump boasts high precision.

[0032] In some feasible embodiments, the pressurizing pump is a constant speed and constant pressure pump.

[0033] Based on the above technical means, a constant speed and constant pressure pump can provide a maximum overburden pressure of 70MPa, and has automatic pressurization and automatic energy replenishment functions, with high pressure control accuracy.

[0034] In some feasible embodiments, the temperature control system includes a heater and a thermostat made of 316L stainless steel. The thermostat is resistant to high temperature and high pressure.

[0035] A second aspect of this application provides a method for measuring shale permeability under simulated high-temperature and high-pressure formation conditions, the method comprising:

[0036] Place the rock sample into the core holder system;

[0037] Activate the overburden pressure control system to provide and maintain the required overburden pressure to the rock sample in the core clamping system;

[0038] Turn on the temperature control system to provide and maintain the required experimental temperature for the upper fixed container system, the lower fixed container system, and the core holder system;

[0039] Turn on the gas supply system and adjust the pore pressure to the pressure value required for the experiment.

[0040] Pore ​​pressure is supplied to the upper fixed container system, the core holder system and the lower fixed container system to saturate the sample chambers in the upper fixed container system, the core holder system and the lower fixed container system with gas until the pressure of the three systems stabilizes, and this continues for a preset time.

[0041] Close the core holder system and open the lower fixed container to vent air, so that a pressure difference of less than the first preset value is generated between the upper and lower ends of the rock sample;

[0042] Close the exhaust gas from the lower fixed container, connect the core holder system to the lower fixed container, and allow the gas at the upper end of the core holder to flow through the sample chamber to the lower end of the core holder. Record the values ​​of the first pressure gauge, the second pressure gauge, and the differential pressure sensor at preset intervals until the pressure difference between the upper and lower ends of the sample is less than the second preset value.

[0043] Adjust the pore pressure and repeatedly measure and record the values ​​of the first pressure gauge, the second pressure gauge, and the differential pressure sensor.

[0044] The core permeability is calculated based on the recorded pressure value, the volume of the upper and lower fixed containers used.

[0045] Based on the above-mentioned technical means, during the measurement process, the overlying pressure required for the experiment is provided by the overlying pressure control system, the experimental temperature is controlled by the temperature control system, and the pore pressure required for the experiment is provided by the gas supply system, thereby simulating the actual high temperature and high pressure conditions of the formation. It is possible to measure the permeability of shale gas under the actual high temperature and high pressure conditions of the formation, which meets the research needs of exploration and development. The pressure at the upper and lower ends of the core holder is accurately set by the upper and lower fixed container systems, which improves the accuracy of the measured pressure value. Finally, the core permeability is calculated based on the recorded pressure value and the volume of the upper and lower fixed containers used, making the calculation method simpler.

[0046] In some feasible embodiments, the core permeability is calculated based on the recorded pressure value, the volume of the upper fixed container, and the volume of the lower fixed container, including:

[0047] The initial differential pressure and the differential pressure at each moment are determined based on the recorded pressure values;

[0048] The core permeability is calculated based on the initial pressure difference, the pressure difference at each moment, and the volumes of the upper and lower fixed containers used. The calculation formula is as follows:

[0049] ΔP=ΔP0e -αt ;

[0050]

[0051] Where V1 is the volume of the upper fixed container, V2 is the volume of the lower fixed container, ΔP is the real-time pressure difference between the upper and lower ends of the core holder, ΔP0 is the initial pressure difference, k is the permeability, A is the cross-sectional area of ​​the rock sample, μ is the viscosity of the gas, β is the compressibility coefficient of the gas, L is the length of the rock sample, and t is the time corresponding to the pressure difference.

[0052] Based on the above technical means, the upper and lower fixed container volumes are fixed values. The measured values ​​in the calculation only include the initial pressure difference and the real-time pressure difference. Since there are fewer measured values, the error introduced by the measurement is smaller, and the calculated value is more accurate.

[0053] In some feasible embodiments, the method further includes:

[0054] Before calculating the core permeability, the compressibility and viscosity of the gas under the experimental temperature and pressure conditions are determined.

[0055] Core permeability was calculated using the compressibility and viscosity of the gas under experimental temperature and pressure conditions.

[0056] Based on the above technical means, the compressibility and viscosity of the gas under experimental temperature and pressure conditions are used to calculate the core permeability. This fully considers the characteristic that the viscosity and compressibility of the gas will change with temperature and pressure, thereby improving the accuracy of the calculation results.

[0057] In some feasible embodiments, the first preset value is 1000 kPa, the second preset value is 5 kPa, and the preset time is 5-10 seconds.

[0058] Through the above technical solution, the measuring device can provide the required pore pressure through a gas supply system, the required overburden pressure through an overburden pressure control system, and the required experimental temperature through a temperature control system. By simulating the actual high-temperature and high-pressure conditions of the formation through these systems, the measuring device can measure shale gas permeability under these conditions, meeting the research needs of exploration and development. Furthermore, the measuring device incorporates upper and lower fixed-container systems to precisely set the pressure at the upper and lower ends of the core holder, improving the accuracy of the measured pressure values.

[0059] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0060] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0061] Figure 1 This is a structural block diagram of a shale permeability measurement device under simulated high temperature and high pressure conditions in a formation, provided in an embodiment of this application.

[0062] Figure 2 This is a detailed structural schematic diagram of the shale permeability measurement device under simulated high temperature and high pressure conditions provided in the embodiments of this application;

[0063] Figure 3 This is a flowchart of a shale permeability measurement method under simulated high temperature and high pressure conditions provided in the embodiments of this application;

[0064] Figure 4 This is a curve showing the relationship between gas viscosity and pressure at a temperature of 100°C, provided in an embodiment of this application.

[0065] Figure 5 This is a graph showing the change of pore pressure at both ends of the core holder provided in this application over time;

[0066] Figure 6 This is a graph showing the permeability as a function of pore pressure under an overlying pressure of 60 MPa and a temperature of 100°C, provided in an embodiment of this application.

[0067] Explanation of reference numerals in the attached figures

[0068] 1-Gas supply system, 2-Upper fixed container system, 3-Lower fixed container system, 4-Core clamping device system, 5-Overburden pressure control system, 6-Temperature control system, 7-Gas cylinder, 8-Gas cylinder pressure gauge, 9-Gas cylinder control valve, 10-Gas booster pump, 11-First solenoid valve, 12-Air pressure gauge, 13-Pressure regulating valve, 14-Air compressor, 15-Vent valve, 16-Booster pressure gauge, 17-Upper fixed container, 18-Second solenoid valve 19-Safety valve, 20-Explosion-proof disc, 21-Lower fixed container, 22-Third solenoid valve, 23-Throttle valve, 24-Fourth solenoid valve, 25-Rock sample chamber, 26-Overlapping pressure chamber, 27-Fifth solenoid valve, 28-First pressure gauge, 29-Second pressure gauge, 30-Sixth solenoid valve, 31-Differential pressure sensor, 32-Seventh solenoid valve, 33-Eighth solenoid valve, 34-First control valve, 35-Pressure pump, 36-Second control valve. Detailed Implementation

[0069] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0070] It should be noted that the acquisition, transmission, storage, use, and processing of data in the technical solution of this application all comply with the relevant provisions of national laws and regulations. In the embodiments of this application, certain existing industry solutions such as software, components, and models may be mentioned. These should be considered exemplary, intended only to illustrate the feasibility of implementing the technical solution of this application, and do not imply that the applicant has already used or necessarily used such solutions.

[0071] Currently, permeability analysis of shale primarily employs gas permeation methods. These methods consider three main indicators: overburden pressure (confining pressure), pore pressure (test pressure), and temperature. However, current gas permeability analysis equipment in laboratories both domestically and internationally can only meet the requirements for overburden pressure testing, which can reach up to 70 MPa. Pore pressure and temperature, however, are insufficient for research needs. Specifically, the steady-state method typically achieves pore pressures around 0.2 MPa; the pulse decay method theoretically achieves pore pressures between 3.5 and 14 MPa, but in actual testing, it is generally around 7 MPa; and the pressure decay method typically achieves around 1.5 MPa. All three methods—steady-state, pulse decay, and pressure decay—are tested at room temperature. Under current technological conditions, it is not possible to fully meet the permeability analysis requirements of shale under actual high temperature and high pressure conditions in formations. Taking the Daqing area as an example, at a formation depth of 2500m, the overburden pressure is about 60MPa, and the pore pressure of the reservoir is about 25MPa. If the formation is overpressured, the pore pressure can reach 40MPa or even higher, and the formation temperature is about 100℃. However, the current technological conditions can only meet the overburden pressure index, while the pore pressure and temperature indices cannot meet the testing requirements. Current testing and research do not provide strong support for the study of shale formation and reservoir mechanisms and development guidance.

[0072] To address the issue that laboratory shale gas permeability analysis equipment cannot fully simulate formation conditions, this invention provides a shale core permeability measurement device and method that can meet the requirements of actual shale formations under high temperature and high pressure conditions. The experimental device can withstand overburden pressure of up to 70 MPa, pore pressure of up to 40 MPa, and temperature of up to 100°C. The lower limit of permeability analysis can reach 10⁻⁶ mD. It can measure shale gas permeability under actual formation high temperature and high pressure conditions, meeting the research needs of exploration and development. Furthermore, it can correctly understand the stress sensitivity variation law of permeability under formation overpressure with overburden pressure and pore pressure. The analytical equipment can meet the analytical requirements of gas permeability under high temperature and high pressure conditions in shale formations.

[0073] like Figure 1 The image shows a shale permeability measurement device under simulated high temperature and high pressure conditions in a formation, as provided in this application. The device includes:

[0074] Gas supply system 1, the gas supply system 1 is connected to the upper fixed container system 2 at its outlet end, and is used to input gas into the upper fixed container system 2 to provide the pore pressure required for the experiment;

[0075] The upper fixed container system 2 has an air inlet connected to the air outlet of the gas supply system 1 and an air outlet connected to the core clamping system. It is used to store the gas required for the experiment at a fixed volume.

[0076] The lower fixed container system 3 has its air inlet end connected to the air outlet end of the core clamping device system 4, and its outlet end connected to the atmosphere. It is used to store the gas required for the experiment at a fixed volume.

[0077] The core clamping device system 4 has an air inlet connected to the upper fixed container system 2 and an air outlet connected to the lower fixed container system 3, which is used to clamp and seal the rock sample.

[0078] The overburden pressure control system 5 is connected to the core holder system 4 and is used to apply the overburden pressure required for the experiment to the rock sample.

[0079] Temperature control system 6 is used to control the experimental temperature of upper fixed container system 2, lower fixed container system 3 and core clamping device system 4.

[0080] Based on the aforementioned technical means, this measuring device can provide the pore pressure required for the experiment through the gas supply system 1, the overburden pressure control system 5, and the experimental temperature through the temperature control system 6. The gas supply system 1, the overburden pressure control system 5, and the temperature control system 6 can simulate the actual high-temperature and high-pressure conditions of the formation, thereby enabling the measurement of shale gas permeability under these conditions, meeting the research needs of exploration and development. Simultaneously, the measuring device is designed with an upper fixed-container system 2 and a lower fixed-container system 3 to precisely set the pressure at the upper and lower ends of the core holder, improving the accuracy of the measured pressure values.

[0081] In some feasible embodiments, such as Figure 2As shown, the upper fixed container system 2 includes: a pipeline, a second solenoid valve 18, a safety valve 19, and multiple upper fixed containers 17 of different volumes. The multiple upper fixed containers 17 of different volumes are connected in parallel on the pipeline. The pipeline is equipped with the second solenoid valve 18 and the safety valve 19. The inlet end of the pipeline is connected to the gas supply system 1, and the outlet end of the pipeline is connected to the air inlet end of the core clamping device system 4. Each upper fixed container 17 is equipped with a corresponding gas cylinder control valve 9. During the measurement process, the second solenoid valve 18 is opened, allowing gas meeting the required pore pressure to flow from the gas supply system 1 into the upper fixed container system 2 through the pipeline. The gas cylinder control valve 9 corresponding to the upper fixed container 17 used in this test is then opened, thus filling the corresponding upper fixed container 17 with gas meeting the required pore pressure.

[0082] Based on the above technical means, the upper fixed container system 2 is equipped with multiple upper fixed containers 17 of different volumes. Different upper fixed containers 17 can be selected when testing different levels of permeability. The fixed volume of the upper fixed container 17 makes it easy to set the pressure of the core holder.

[0083] In some feasible embodiments, the upper fixed container system 2 further includes an explosion-proof plate 20, which is disposed on the pipeline between the safety valve 19 and the second solenoid valve 18.

[0084] Based on the above technical means, an explosion-proof disc 20 is installed in the upper fixed container system 2. The explosion-proof disc 20 can release the pressure medium when the pressure difference between the two sides reaches a set threshold, so as to ensure the safety of equipment and personnel and prevent safety accidents caused by high temperature and high pressure during the measurement process.

[0085] In some feasible embodiments, the lower fixed container system 3 includes: a pipeline, a third solenoid valve 22, a fourth solenoid valve 24, a throttle valve 23, and multiple lower fixed containers 21 of different volumes. The multiple lower fixed containers 21 of different volumes are connected in parallel on the pipeline. The inlet end of the pipeline is connected to the fourth solenoid valve 24 and then connected to the outlet end of the core holder system 4. The throttle valve 23 is located at the outlet end of the pipeline. The third solenoid valve 22 is located on the pipeline, between the lower fixed container 21 and the throttle valve 23. The number and volume of the lower fixed containers 21 are the same as those of the upper fixed container 17. Each lower fixed container 21 is equipped with a corresponding gas cylinder control valve 9. During the measurement process, the eighth solenoid valve 33 in the fixed container system is opened, connecting the upper fixed container system 2 and the lower fixed container system 3. The gas with the required pore pressure flows into the lower fixed container system 3 through the bypass pipeline. The control valve 9 of the gas cylinder corresponding to the lower fixed container 21 used in this test is opened, thus filling the corresponding lower fixed container 21 with the gas that meets the required pore pressure. The third solenoid valve 22 is opened, and the gas with the required pore pressure flows into the core holder system 4 from the bottom through the pipeline.

[0086] Based on the above technical means, the lower fixed container system 3 is equipped with multiple lower fixed containers 21 of different volumes. Different lower fixed containers 21 can be selected when testing different levels of permeability. The fixed volume of the lower fixed container 21, together with the upper fixed container 17, can more accurately set the pressure of the core holder.

[0087] In some feasible embodiments, there are three upper fixed containers 17 and three lower fixed containers 21.

[0088] In one feasible embodiment, the three fixed containers have volumes of 20ml, 48ml, and 100ml, respectively, which can be used for rock samples with low permeability, medium permeability, and high permeability, with a lower permeability limit of 10. -6 mD.

[0089] In some feasible embodiments, the core holder system 4 includes: a pipeline, a core holder, a fifth solenoid valve 27, a sixth solenoid valve 30, a seventh solenoid valve 32, an eighth solenoid valve 33, a first pressure gauge 28, a second pressure gauge 29, a differential pressure sensor 31, and a first control valve 34; the core holder includes a sample chamber 25 and an overburden pressure chamber 26, the sample chamber 25 being located at the center of the overburden pressure chamber 26, the overburden pressure chamber 26 being connected to the overburden pressure control system 5 via an overburden pressure pipeline, and the first control valve 34 being provided on the overburden pressure pipeline connecting the overburden pressure chamber 26 and the overburden pressure control system 5; the upper end of the core holder is connected to the upper fixed container system 2 via an inlet pipeline. The inlet pipeline is equipped with a fifth solenoid valve 27 and a first pressure gauge 28; the inlet end of the fifth solenoid valve 27 is connected to the outlet end of the fourth solenoid valve 24 through a bypass pipeline; the bypass pipeline is equipped with a second pressure gauge 29, a sixth solenoid valve 30, a seventh solenoid valve 32, an eighth solenoid valve 33 and a differential pressure sensor 31, the differential pressure sensor 31 is located between the sixth solenoid valve 30 and the seventh solenoid valve 32, and the eighth solenoid valve 33 is connected in parallel with the sixth solenoid valve 30, the seventh solenoid valve 32 and the differential pressure sensor 31 through a parallel pipeline; the second pressure gauge 29 is located between the seventh solenoid valve 32 and the fourth solenoid valve 24, wherein the first control valve 34 is used to open when pressure relief is required.

[0090] In one feasible embodiment, the differential pressure sensor 31 is a high-precision differential pressure sensor with an accuracy of up to 0.1 kPa, which improves the accuracy of the test results.

[0091] During the test, the fifth solenoid valve 27 is opened, and the gas that meets the required pore pressure flows into the core holder system 4 from the upper end through the pipeline. The eighth solenoid valve 33 on the bypass pipeline is opened, which connects the upper fixed container system 2 and the lower fixed container system 3. The gas that meets the required pore pressure will flow into the lower fixed container system 3 through the bypass pipeline. Thus, the core holder system 4 is equipped with a bypass pipeline, which connects the upper fixed container system 2 and the lower fixed container system 3. During the process of applying pore pressure to the rock sample, the pressure of the upper fixed container 17 and the lower fixed container 21 can be increased simultaneously to saturate the rock sample with gas, thereby increasing the gas saturation rate.

[0092] In some feasible embodiments, the gas supply system 1 includes: a gas cylinder 7, a gas cylinder pressure gauge 8, a gas cylinder control valve 9, a gas booster pump 10, a first solenoid valve 11, an air pressure gauge 12, an air compressor 14, a vent valve 15, and a booster pressure gauge 16. The gas booster pump 10 is connected to the gas cylinder 7 via a first pipeline, and the first pipeline is equipped with the gas cylinder pressure gauge 8 and the gas cylinder control valve 9. The gas booster pump 10 is connected to the air compressor 14 via a second pipeline, and the second pipeline is equipped with the first solenoid valve 11 and the air pressure gauge 12. The first solenoid valve 11 is located between the air pressure gauge 12 and the gas booster pump 10. The gas booster pump 10 is connected to a fixed container system 3 at the lower end of a third pipeline, and the third pipeline is equipped with a booster pressure gauge 16. The gas booster pump 10 is also connected to the atmosphere via a third pipeline, and the connection pipeline between the gas booster pump 10 and the atmosphere is equipped with a vent valve 15.

[0093] During the test, the first solenoid valve 11, the gas cylinder control valve 9, the gas booster pump 10, and the air compressor 14 are opened sequentially. This pressurizes the gas flowing out of the gas cylinder 7 to the required pore pressure. The air pressure gauge 12 detects the pressure of the air compressor 14, and the booster pressure gauge 16 detects the pressurized gas pressure. The vent valve 15 is used to open when pressure needs to be released. The air compressor 14 and the gas booster pump 10 are used to increase the gas pressure in the pipeline. The booster pressure gauge 16 can detect the pressure of the gas supplied by the gas supply system 1 in real time, ensuring that the gas pressure entering the upper fixed container system 2 meets the experimental requirements. The gas booster pump 10 enables the pore pressure of the gas permeability test to reach 40 MPa, with a pore pressure accuracy of 0.1 kPa.

[0094] In some feasible embodiments, the gas supply system 1 further includes a pressure regulating valve 13 disposed between the air compressor 14 and the air pressure gauge 12.

[0095] Based on the above technical means, a pressure regulating valve 13 is added between the air compressor 14 and the air pressure gauge 12. The pressure regulating valve 13 can more accurately adjust the amount of gas pressurized by the air compressor 14 in the pipeline.

[0096] In some feasible embodiments, the overburden pressure control system 5 includes a pressurizing pump 35 and a second control valve 36. The pressurizing pump 35 is connected to the overburden pressure chamber 26 of the core holder system 4 via a pipeline, and the second control valve 36 is located on the pipeline. During testing, opening the second control valve 36 and the pressurizing pump 35 can pressurize other parts within the overburden pressure chamber 26.

[0097] Based on the aforementioned technical means, the overburden pressure control system 5 can provide stable overburden pressure for rock samples, ensuring the accuracy of measurements. This system features automatic pressurization and automatic energy replenishment functions, and the pressurization pump 35 has high precision.

[0098] In some feasible embodiments, the pressurizing pump 35 is a constant-speed, constant-pressure pump. In one feasible embodiment, the pressurizing pump 35 is a high-precision constant-speed, constant-pressure pump with a flow rate range of 0.0001-30 ml / min, a maximum pressure of 70 MPa, and a pressure accuracy of 0.001 MPa. All operating parameters of the constant-speed, constant-pressure pump are displayed on a 10.2-inch LCD screen configured on the equipment. It has a pressure measurement and overpressure / underpressure protection system, ensuring safe and reliable operation of the pump system; it also has an automatic compression compensation program control, ensuring stable flow accuracy when the pump operates under high pressure. The constant-speed, constant-pressure pump can provide a maximum overpressure of 70 MPa, and has automatic pressurization and automatic energy replenishment functions, with high pressure regulation accuracy.

[0099] In some feasible embodiments, the temperature control system 6 includes a heater and a thermostat made of 316L stainless steel. The thermostat is resistant to high temperature and high pressure.

[0100] In one feasible embodiment, the size of the constant temperature chamber is designed based on the dimensions of the upper fixed container system 2, the core clamping device system 4, and the lower fixed container system 3. Its compact structure and small size make it easier to maintain a constant temperature. An opening is provided on the side of the constant temperature chamber for pipes and other connecting parts to pass through; the small opening ensures a constant gas temperature. The constant temperature chamber can reach 120℃ with a temperature control accuracy of ±0.1℃ and uses internal hot air circulation.

[0101] It adopts computer control and display screen control; it is equipped with a large backlit LCD screen that can set and display the temperature in real time. It has safety measures such as sensor fault alarm, over-temperature alarm, independent over-temperature protector, and overcurrent trip protection.

[0102] In one feasible embodiment, in order to meet the high temperature and high pressure requirements during the measurement process, a dedicated high temperature and high pressure resistant gas cylinder control valve 9 and connector are designed for the upper fixed container system 2 and the lower fixed container system 3.

[0103] The second aspect of this application provides a method for measuring shale permeability under simulated high-temperature and high-pressure conditions in formations, such as... Figure 3As shown, the method includes:

[0104] S1: Place the rock sample into the core holder system 4;

[0105] S2: Activate the overburden pressure control system 5 to provide and maintain the required overburden pressure for the rock sample in the core clamping system;

[0106] S3: Activate the temperature control system 6 to provide and maintain the required experimental temperature for the upper fixed container system 2, the lower fixed container system 3, and the core holder system 4;

[0107] S4: Turn on the gas supply system 1 and adjust the pore pressure to the pressure value required for the experiment;

[0108] S5: Provide pore pressure to the upper fixed container system 2, the core holder system 4 and the lower fixed container system 3 to saturate the sample chamber 25 in the upper fixed container system 2, the core holder system 4 and the lower fixed container system 3 with gas until the pressure of the three systems stabilizes, for a preset time.

[0109] S6: Close the core clamping device system 4, open the lower fixed container 21 to vent, so that the pressure difference between the upper and lower ends of the rock sample is less than the first preset value;

[0110] S7: Close the exhaust of the lower fixed container 21, connect the core holder system 4 and the lower fixed container 21, so that the gas at the upper end of the core holder flows through the sample chamber 25 to the lower end of the core holder. Record the values ​​of the first pressure gauge 28, the second pressure gauge 29 and the differential pressure sensor 31 at preset time intervals until the pressure difference between the upper and lower ends of the sample is less than the second preset value.

[0111] S8: Adjust the pore pressure and repeatedly measure and record the values ​​of the first pressure gauge 28, the second pressure gauge 29, and the differential pressure sensor 31;

[0112] S9: Calculate the core permeability based on the recorded pressure value, the volume of the upper fixed container 17, and the volume of the lower fixed container 21.

[0113] Based on the above-mentioned technical means, during the measurement process, the overburden pressure control system 5 provides the overburden pressure required for the experiment, the temperature control system 6 controls the experimental temperature, and the gas supply system 1 provides the pore pressure required for the experiment, thereby simulating the actual high temperature and high pressure conditions of the formation. It is possible to measure the shale gas permeability under the actual high temperature and high pressure conditions of the formation, which meets the research needs of exploration and development. The pressure at the upper end and the lower end of the core holder is accurately set by the upper fixed container system 2 and the lower fixed container system 3, which improves the accuracy of the measured pressure value. Finally, the core permeability is calculated based on the recorded pressure value, the volume of the upper fixed container 17 and the volume of the lower fixed container 21 used, and the calculation method is simpler.

[0114] In some feasible embodiments, the core permeability is calculated based on the recorded pressure value, the volume of the upper fixed container 17, and the volume of the lower fixed container 21, including:

[0115] The initial differential pressure and the differential pressure at each moment are determined based on the recorded pressure values. In some embodiments, the differential pressure at each moment can be determined by subtracting the value of the second pressure gauge 29 from the value of the first pressure gauge 28 at the same moment. The initial differential pressure is obtained by subtracting the value of the second pressure gauge 29 from the value of the first pressure gauge 28 at the initial moment. In other embodiments, the measurement value of the differential pressure sensor at the initial moment can be directly used as the initial differential pressure, and the measurement value of the differential pressure sensor at each moment can be used as the differential pressure at each moment. The differential pressure sensor has higher accuracy, more accurate measurement results, and is more suitable for applications with high accuracy requirements.

[0116] The core permeability is calculated based on the initial pressure difference, the pressure difference at each moment, and the volumes of the upper fixed container 17 and the lower fixed container 21. The calculation formula is as follows:

[0117] ΔP=ΔP0e -αt ;

[0118]

[0119] Where V1 is the volume of the upper fixed container 17, V2 is the volume of the lower fixed container 21, ΔP is the real-time pressure difference between the upper and lower ends of the core holder, ΔP0 is the initial pressure difference, k is the permeability, A is the cross-sectional area of ​​the rock sample, μ is the viscosity of the gas, β is the compressibility coefficient of the gas, L is the length of the rock sample, and t is the time corresponding to the pressure difference.

[0120] According to the above technical means, the volumes of the upper fixed container 17 and the lower fixed container 21 are fixed values. The measured values ​​in the calculation only include the initial pressure difference and the real-time pressure difference. Since there are fewer measured values, the error introduced by the measurement is smaller, and the calculated value is more accurate.

[0121] Traditional instruments operate under ambient temperature and pressure conditions, where the viscosity and compressibility of gases are relatively fixed. The calculation models use fixed, unchangeable values. However, under high temperature and pressure conditions, the viscosity and compressibility of gases change significantly. Using the viscosity and compressibility of gases under ambient temperature and pressure conditions for calculations will result in substantial errors. Therefore, in some feasible embodiments, the method further includes:

[0122] Before calculating the core permeability, the compressibility and viscosity of the gas under the experimental temperature and pressure conditions are determined based on the experimental temperature and pressure conditions. Then, the core permeability is calculated using the compressibility and viscosity of the gas under the experimental temperature and pressure conditions.

[0123] In one feasible embodiment, the compressibility and viscosity of the gas under experimental temperature and pressure conditions can be determined by querying the viscosity and compressibility curves of the gas under different temperature and pressure conditions. Figure 4 The graph shows the relationship between gas viscosity and pressure at a temperature of 100°C. It can be seen from the graph that the higher the pressure, the higher the gas viscosity.

[0124] Based on the above technical means, the compressibility and viscosity of the gas under experimental temperature and pressure conditions are used to calculate the core permeability. This fully considers the characteristic that the viscosity and compressibility of the gas will change with temperature and pressure, thereby improving the accuracy of the calculation results.

[0125] In some feasible embodiments, the first preset value is 1000 kPa, the second preset value is 5 kPa, and the preset time is 5-10 seconds.

[0126] The following section describes how the measuring device of this application is used in the permeability measurement process, using a specific rock sample measurement procedure as an example.

[0127] (I) Sample Preparation

[0128] Cylindrical shale samples were prepared using wire cutting technology. The diameter of the cylindrical samples was 2.5 cm and the length was 2-5 cm.

[0129] (II) Sample washing and drying

[0130] The prepared shale samples were cleaned with dichloromethane as a cleaning solvent for at least 72 hours, and the fluorescence detection level of the shale samples after cleaning was less than level 3. After the oil was washed off, the samples were dried under vacuum at 60°C for 8 hours. The shale samples were then transferred to a desiccator for storage in preparation for subsequent experimental analysis.

[0131] (III) Sample Testing

[0132] 1. Measure the length and diameter of the shale sample using vernier calipers: The length of shale sample A-1 was measured to be 2.52 cm and the diameter to be 2.49 cm. Record the data.

[0133] 2. Place the shale core into the sample chamber 25 of the core holder system 4, and tighten the gas cylinder control valve 9 to prevent gas leakage;

[0134] 3. Turn on the pressurization pump 35 and the second control valve 36 to set the overlying pressure of the overlying pressure chamber 26 to 60MPa and keep the pressure constant;

[0135] 4. Start the constant temperature chamber and set the temperature to 100℃. Preheat the temperature of all parts of the device for no less than 1 hour until the temperature is constant.

[0136] 5. Sequentially open the first solenoid valve 11, gas cylinder control valve 9, air compressor 14 and gas booster pump 10 on the upper fixed container system 2 and gas booster pump 10 pipelines. When the pore pressure rises to 5MPa, stop the gas booster pump 10 and air compressor 14 to maintain pressure stability.

[0137] 6. Close the first solenoid valve 11 on the upper fixed container system 2 and the gas booster pump 10 pipeline, and open the second solenoid valve 18 in the upper fixed container system 2, the fifth solenoid valve 27, the sixth solenoid valve 30, the seventh solenoid valve 32 and the eighth solenoid valve 33 on the core holder pipeline to saturate the sample chamber 25 in the pipeline, the upper fixed container system 2, the lower fixed container system 3 and the core holder system 4 with gas. Observe the first pressure gauge 28 at the upper end of the core holder and the second pressure gauge 29 at the lower end of the core holder until the pressure stabilizes and the saturation time is not less than 30 minutes.

[0138] 7. Close the eighth solenoid valve 33 of the connecting pipeline between the upper and lower ends of the core holder, open the third solenoid valve 22 of the lower fixed container 21 to exhaust air, reduce the pressure of the lower fixed container 21, so that a pressure difference is generated between the upper and lower ends of the rock sample, and the pressure difference is not higher than 1000 kPa.

[0139] 8. Close the third solenoid valve 22 for exhaust, allowing the gas at the top of the core holder to flow through the sample chamber 25 to the bottom of the core holder. Automatically record the values ​​of the first pressure gauge 28 at the top of the core holder, the second pressure gauge 29 at the bottom of the core holder, and the differential pressure sensor 31 every 10 seconds.

[0140] 9. After a period of time, when the pressure difference between the upper end of the core holder and the lower end of the core holder is less than 5 kPa, stop collecting data. At this point, the permeability test procedure with an overburden pressure of 60 MPa, a pore pressure of 5 MPa, and a temperature of 100℃ is completed.

[0141] 10. Repeat steps 5-9, and measure the permeability at pore pressures of 10, 15, 20, 25, 30, 35, and 38 MPa respectively.

[0142] 11. Calculate core permeability:

[0143] The pressure at the upper and lower ends of the core holder is precisely set by using the upper fixed container 17 and the lower fixed container 21. The pressure is simultaneously increased in both containers to saturate the sample with gas. Then, the pressure at the lower end of the core holder is reduced by opening the gas cylinder control valve 9 in the lower fixed container 21. Both containers maintain a constant volume. The pressure difference between the upper and lower ends of the core holder is recorded to obtain a pressure differential decay curve. The pore pressure at the upper and lower ends of the core holder changes over time as shown in the figure. Figure 5 As shown.

[0144] The penetration rate is calculated using the following formula:

[0145] ΔP=ΔP0e -αt ;

[0146]

[0147] Where V1 is the volume of the upper fixed container 17, V2 is the volume of the lower fixed container 21, ΔP is the real-time pressure difference between the upper and lower ends of the core holder, ΔP0 is the initial pressure difference, k is the permeability, A is the cross-sectional area of ​​the rock sample, μ is the viscosity of the gas, β is the compressibility coefficient of the gas, L is the length of the rock sample, and t is the time corresponding to the pressure difference.

[0148] Calculations show that, under an overburden pressure of 60 MPa and a temperature of 100 °C, the permeability as a function of pore pressure is as follows: Figure 6 As shown, the permeability is 3.64 x 10⁻⁶ when the pore pressure is 5, 10, 15, 20, 25, 30, 35, and 38 MPa. -5 mD, 1.60x10 -5 mD, 1.02x10- 5 mD, 2.36x10 -5 mD, 2.51x10 -5 mD, 3.17x10 -5 mD.

[0149] It should be noted that in this experimental example, the gas in cylinder 7 is helium. In other feasible embodiments, the gas in cylinder 7 may be carbon dioxide, nitrogen, etc.

[0150] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0151] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0152] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0153] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0154] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0155] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0156] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0157] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0158] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A device for measuring shale permeability under simulated high temperature and high pressure conditions in geological formations, characterized in that, The device includes: A gas supply system, the gas supply system having its outlet connected to an upper fixed container system, is used to input gas into the upper fixed container system to provide the pore pressure required for the experiment; The upper fixed container system has an air inlet connected to the air outlet of the gas supply system, and the air outlet is connected to the core clamping system. It is used to store the gas required for the experiment at a fixed volume. The lower fixed container system has its air inlet connected to the air outlet of the core holder system and its outlet connected to the atmosphere. It is used to store the gas required for the experiment at a fixed volume. A core clamping device system, wherein the air inlet of the core clamping device system is connected to the upper fixed container system and the air outlet is connected to the lower fixed container system, for clamping and sealing the rock sample; The overburden pressure control system is connected to the core holder system and is used to apply the overburden pressure required for the experiment to the rock sample; The temperature control system is used to control the experimental temperature of the upper fixed container system, the lower fixed container system, and the core holder system.

2. The shale permeability measuring device under simulated high temperature and high pressure conditions according to claim 1, characterized in that, The upper fixed container system includes: a pipeline, a second solenoid valve, a safety valve, and multiple upper fixed containers of different volumes. The multiple upper fixed containers of different volumes are connected in parallel on the pipeline. The pipeline is equipped with a second solenoid valve and a safety valve. The inlet end of the pipeline is connected to the gas supply system, and the outlet end of the pipeline is connected to the air inlet end of the core holder system. Each upper fixed container is equipped with a corresponding valve.

3. The shale permeability measuring device under simulated high temperature and high pressure conditions according to claim 2, characterized in that, The upper fixed container system also includes an explosion-proof plate, which is installed on the pipeline between the safety valve and the second solenoid valve.

4. The shale permeability measuring device under simulated high temperature and high pressure conditions according to claim 2, characterized in that, The lower fixed container system includes: a pipeline, a third solenoid valve, a fourth solenoid valve, a throttle valve, and multiple lower fixed containers of different volumes. The multiple lower fixed containers of different volumes are connected in parallel on the pipeline. The inlet end of the pipeline is connected to the fourth solenoid valve and then to the outlet end of the core holder system. The throttle valve is located at the outlet end of the pipeline. The third solenoid valve is located on the pipeline, between the lower fixed containers and the throttle valve. The number and volume of the lower fixed containers are the same as those of the upper fixed containers. Each lower fixed container is equipped with a corresponding valve.

5. The shale permeability measuring device under simulated high temperature and high pressure conditions according to claim 4, characterized in that, There are three upper fixed containers and three lower fixed containers.

6. The shale permeability measuring device under simulated high temperature and high pressure conditions according to claim 4, characterized in that, The core holder system includes: pipelines, a core holder, a fifth solenoid valve, a sixth solenoid valve, a seventh solenoid valve, an eighth solenoid valve, a first pressure gauge, a second pressure gauge, a differential pressure sensor, and a first control valve. The core holder includes a sample chamber and an overlying pressure chamber. The sample chamber is located at the center of the overlying pressure chamber. The overlying pressure chamber is connected to the overlying pressure control system via an overlying pipeline. The overlying pipeline connecting the overlying pressure chamber and the overlying pressure control system is equipped with a first control valve. The upper end of the core holder is connected to an upper fixed container system via an inlet pipeline. The inlet pipeline is equipped with a fifth solenoid valve and a first pressure gauge. The inlet end of the fifth solenoid valve is connected to the outlet end of a fourth solenoid valve via a bypass pipeline. The bypass pipeline is equipped with a second pressure gauge, a sixth solenoid valve, a seventh solenoid valve, an eighth solenoid valve, and a differential pressure sensor. The differential pressure sensor is located between the sixth and seventh solenoid valves. The eighth solenoid valve is connected in parallel with the sixth and seventh solenoid valves and the differential pressure sensor via a parallel pipeline. The second pressure gauge is located between the seventh and fourth solenoid valves.

7. The shale permeability measuring device under simulated high temperature and high pressure conditions according to claim 1, characterized in that, The gas supply system includes: a gas cylinder, a gas cylinder pressure gauge, a gas cylinder control valve, a gas booster pump, a first solenoid valve, an air pressure gauge, an air compressor, a vent valve, and a booster pressure gauge. The gas booster pump is connected to the gas cylinder via a first pipeline, and the first pipeline is equipped with a gas cylinder pressure gauge and a gas cylinder control valve. The gas booster pump is connected to the air compressor via a second pipeline, and the second pipeline is equipped with a first solenoid valve and an air pressure gauge. The first solenoid valve is located between the air pressure gauge and the gas booster pump. The gas booster pump is connected to a fixed container system at the lower end of a third pipeline, and the third pipeline is equipped with a booster pressure gauge. The gas booster pump is also connected to the atmosphere via a third pipeline, and a vent valve is installed on the pipeline connecting the gas booster pump to the atmosphere.

8. The shale permeability measuring device under simulated high temperature and high pressure conditions according to claim 7, characterized in that, The gas supply system also includes a pressure regulating valve, which is located between the air compressor and the air pressure gauge.

9. The shale permeability measuring device under simulated high temperature and high pressure conditions according to claim 1, characterized in that, The overburden pressure control system includes a pressurizing pump and a second control valve. The pressurizing pump is connected to the overburden pressure chamber of the core holder system via a pipeline, and the second control valve is located on the pipeline.

10. The shale permeability measuring device under simulated high temperature and high pressure conditions according to claim 9, characterized in that, The pressurizing pump is a constant speed and constant pressure pump.

11. The shale permeability measuring device under simulated high temperature and high pressure conditions according to claim 1, characterized in that, The temperature control system includes a constant temperature chamber, which is made of 316L stainless steel.

12. A method for measuring shale permeability under simulated high temperature and high pressure conditions in geological formations, characterized in that, The method includes: Place the rock sample into the core holder system; Activate the overburden pressure control system to provide and maintain the required overburden pressure to the rock sample in the core clamping system; Turn on the temperature control system to provide and maintain the required experimental temperature for the upper fixed container system, the lower fixed container system, and the core holder system; Turn on the gas supply system and adjust the pore pressure to the pressure value required for the experiment. Pore ​​pressure is supplied to the upper fixed container system, the core holder system and the lower fixed container system to saturate the sample chambers in the upper fixed container system, the core holder system and the lower fixed container system with gas until the pressure of the three systems stabilizes, and this continues for a preset time. Close the core holder system and open the lower fixed container to vent air, so that a pressure difference of less than the first preset value is generated between the upper and lower ends of the rock sample; Close the exhaust gas from the lower fixed container, connect the core holder system to the lower fixed container, and allow the gas at the upper end of the core holder to flow through the sample chamber to the lower end of the core holder. Record the values ​​of the first pressure gauge, the second pressure gauge, and the differential pressure sensor at preset intervals until the pressure difference between the upper and lower ends of the sample is less than the second preset value. Adjust the pore pressure and repeatedly measure and record the values ​​of the first pressure gauge, the second pressure gauge, and the differential pressure sensor. The core permeability is calculated based on the recorded pressure value, the volume of the upper and lower fixed containers used.

13. The method for measuring shale permeability under simulated high temperature and high pressure conditions in strata according to claim 12, characterized in that, The core permeability is calculated based on the recorded pressure values, the volume of the upper and lower fixed containers used, including: The initial differential pressure and the differential pressure at each moment are determined based on the recorded pressure values; The core permeability is calculated based on the initial pressure difference, the pressure difference at each moment, and the volumes of the upper and lower fixed containers used. The calculation formula is as follows: ΔP=ΔP0e -αt ; Where V1 is the volume of the upper fixed container, V2 is the volume of the lower fixed container, ΔP is the real-time pressure difference between the upper and lower ends of the core holder, ΔP0 is the initial pressure difference, k is the permeability, A is the cross-sectional area of ​​the rock sample, μ is the viscosity of the gas, β is the compressibility coefficient of the gas, L is the length of the rock sample, and t is the time corresponding to the pressure difference.

14. The method for measuring shale permeability under simulated high temperature and high pressure conditions in strata according to claim 13, characterized in that, The method further includes: Before calculating the core permeability, the compressibility and viscosity of the gas under the experimental temperature and pressure conditions are determined. Core permeability was calculated using the compressibility and viscosity of the gas under experimental temperature and pressure conditions.

15. The method for measuring shale permeability under simulated high temperature and high pressure conditions in strata according to claim 12, characterized in that, The first preset value is 1000 kPa, the second preset value is 5 kPa, and the preset time is 5-10 seconds.

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