Diffusion apparatus, related apparatus and method for measuring diffusion coefficient of rock

Abstract

The application discloses a diffusion device for measuring a diffusion coefficient of rock, a related device and a measuring method, the diffusion device comprising a diffusion assembly and a circulation assembly; an injection assembly is capable of conveying a gas with a preset concentration to a core holder; the core holder is capable of accommodating a rock sample to be measured and applying a preset confining pressure to the rock sample; a gas inlet end of the core holder is provided with a first valve capable of communicating with the atmosphere; a three-way valve is capable of communicating with a gas outlet end of the core holder and a detection device respectively; the circulation assembly comprises a circulation pump and a gas mixing device which are communicated through a circulation pipeline; the circulation pump is capable of communicating with the gas outlet end of the core holder; the gas mixing device is capable of communicating with the three-way valve; the circulation pump is used for driving the gas of the three-way valve and the gas in the core holder into the gas mixing device for mixing, and realizing the circulation of the gas from the gas mixing device, the three-way valve, the core holder and back to the gas mixing device. The measurement precision of the diffusion coefficient of the rock can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of gas development technology, and in particular to a diffusion device, related apparatus, and measurement method for measuring the diffusion coefficient of rocks. Background Technology

[0002] Some gaseous resources, especially helium, are widely used in national defense and high-tech fields and are therefore important resources. With the surge in global demand for helium, helium resource reserves are particularly crucial. To ensure that my country's helium production and supply levels gradually meet the requirements of scientific and technological and industrial development, and given the enormous geological potential of my country's helium storage sites, it is necessary to construct large-scale gas storage facilities to increase helium reserves and address the supply-demand imbalance. The primary task in constructing new gas storage facilities in salt caverns is to quantify the sealing performance of the storage facility. Therefore, it is essential to measure the diffusivity of helium in the salt rock to ensure the sealing of the pillars within the storage facility. For storing helium in interlayered salt caverns, the diffusion mechanism of the gas in the salt rock plays a vital role in evaluating the sealing performance of the salt cavern. The diffusion coefficient, as an important evaluation parameter describing the diffusion rate of small molecule gases between crystals in interlayered salt rock, is an indispensable parameter for describing the amount of gas (e.g., helium) added to and lost from the gas storage facility. Summary of the Invention

[0003] To improve the accuracy of rock diffusion coefficient measurement, this invention provides a diffusion device for measuring the diffusion coefficient of rocks, which is applicable to measuring the diffusion coefficient of different gases in different types of rocks.

[0004] In a first aspect, embodiments of the present invention provide a diffusion device for measuring the diffusion coefficient of rocks, comprising a diffusion component and a circulation component;

[0005] The diffusion assembly includes an injection assembly, a core holder, and a three-way valve connected in sequence via a diffusion pipe;

[0006] The injection component is capable of delivering a preset concentration of gas to the core holder;

[0007] The core holder can hold the rock sample to be tested and apply a preset confining pressure to the rock sample;

[0008] The core holder is equipped with a first valve at the air inlet end that allows it to communicate with the atmosphere.

[0009] The three-way valve can be connected to the air outlet of the core holder and the detection device respectively;

[0010] The circulation assembly includes a circulation pump and a gas mixing device connected via circulation pipes;

[0011] The circulating pump can be connected to the air outlet of the core holder;

[0012] The gas mixing device can be connected to the three-way valve;

[0013] The circulating pump is used to drive the gas from the three-way valve and the gas in the core holder to the gas mixing device for mixing, and to realize the gas circulation from the gas mixing device, the three-way valve, the core holder and back to the gas mixing device.

[0014] Optionally, the three-way valve is provided with a first end, a second end, and a third end;

[0015] The first end is connected to the air outlet end of the core holder;

[0016] The second end is connected to the gas mixing device;

[0017] The third end can be connected to the detection device.

[0018] Optionally, the diffusion assembly further includes a peristaltic pump and a pressure regulating valve connected via a diffusion conduit;

[0019] The peristaltic pump is connected to the injection assembly and is used to regulate the flow rate of the gas;

[0020] The pressure regulating valve is connected to the core holder and is used to regulate the pressure of the gas.

[0021] Optionally, the rock sample to be tested includes interbedded salt rock;

[0022] The diffusion device also includes a wetting device connected between the pressure stabilizing valve and the core holder;

[0023] The wetting device contains a saturated salt solution for wetting the gas.

[0024] Optionally, the diffusion device for measuring the diffusion coefficient of rocks further includes a control device;

[0025] The control device is connected to the injection assembly, the peristaltic pump, the pressure stabilizing valve, the core holder, the three-way valve, and the circulation pump, respectively.

[0026] Optionally, the air outlet of the core holder is provided with a second valve;

[0027] The circulating pump is connected to the second valve via a circulating pipe.

[0028] Secondly, embodiments of the present invention provide an apparatus for measuring the diffusion coefficient of rocks, including a detection device and the diffusion device described in Embodiment 1.

[0029] Optionally, the detection device includes a gas chromatograph-mass spectrometer.

[0030] Thirdly, embodiments of the present invention provide a method for measuring the diffusion coefficient of rocks, comprising:

[0031] Obtain the dimensions of the rock sample to be tested, and place the rock sample in the core holder;

[0032] Keep the first valve closed and the three-way valve disconnected from the detection device. Keep the three-way valve connected to the air outlet of the core holder and the detection device respectively. Connect the circulation pump to the air outlet of the core holder.

[0033] Start the circulation pump to drive the gas from the three-way valve and the gas in the core holder to the gas mixing device for mixing, and realize the gas circulation from the gas mixing device, the three-way valve, the core holder and back to the gas mixing device until the gas from the three-way valve and the gas in the core holder are in a uniform state.

[0034] Turn off the circulation pump and disconnect the connection between the circulation pump and the gas outlet of the core holder, as well as the connection between the three-way valve and the detection device. Connect the three-way valve and the detection device, and use the detection device to detect the gas concentration to obtain the initial gas concentration value.

[0035] Open the first valve and the injection assembly, and use the injection assembly to deliver a gas of a preset concentration to the core holder until the diffusion pipe between the injection assembly and the core holder and the core holder are filled with the gas of the preset concentration, then close the first valve.

[0036] A preset confining pressure is applied to the rock sample to be tested using the core holder, and the concentration of the gas diffused through the rock sample is detected using the detection device to obtain the diffused gas concentration;

[0037] The diffusion coefficient is calculated based on the size of the rock sample to be tested, the initial gas concentration, the diffusion gas concentration, and the preset gas concentration.

[0038] Optionally, the diffusion assembly further includes a peristaltic pump and a pressure regulating valve connected through a diffusion conduit, wherein the peristaltic pump is connected to the injection assembly and the pressure regulating valve is connected to the core holder;

[0039] The step of opening the first valve and the injection assembly, using the injection assembly to deliver gas of a preset concentration to the core holder, until the diffusion channel between the injection assembly and the core holder and the core holder are filled with gas of the preset concentration, and then closing the first valve, includes:

[0040] Open the injection assembly, the peristaltic pump, and the pressure regulating valve. Use the injection assembly to deliver gas of a preset concentration, use the peristaltic pump to adjust the gas flow rate to a preset flow rate value, and use the pressure regulating valve to adjust the gas pressure to a preset pressure value.

[0041] Open the first valve until all diffusion channels between the injection assembly and the core holder, as well as the core holder, are filled with gas, then close the first valve.

[0042] The beneficial effects of the above-mentioned technical solutions provided in the embodiments of the present invention include at least the following:

[0043] This invention provides a diffusion device for measuring the diffusion coefficient of rocks. The device mainly includes a diffusion component and a circulation component. The diffusion component includes an injection component, a core holder, and a three-way valve connected sequentially via a diffusion pipe. The circulation component includes a circulation pump and a gas mixing device connected via a circulation pipe. The circulation pump is connected to the gas outlet of the core holder, and the gas mixing device is connected to the three-way valve. By using the circulation pump, gas from the three-way valve and gas in the core holder can be driven into the gas mixing device, where it is thoroughly mixed to ensure gas uniformity. Simultaneously, the circulation pump circulates the gas, forming a gas circulation loop from the gas mixing device, the three-way valve, the core holder, and back to the gas mixing device. This helps to uniformly cover the entire core holder, the three-way valve, and the circulation pipe with gas, thereby avoiding the influence of gas inhomogeneity on the diffusion coefficient measurement results.

[0044] By setting a first valve that can communicate with the atmosphere at the air inlet end of the core holder, and simultaneously opening the injection component and the first valve, exhaust gas is vented through the first valve to remove impurities from the core holder and diffusion pipe. This ensures the purity of the gas entering the core holder during subsequent diffusion experiments, thereby effectively guaranteeing the accuracy of diffusion coefficient measurement.

[0045] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0046] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0047] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0048] Figure 1 This is a schematic diagram of the structure of a diffusion device for measuring the diffusion coefficient of rocks, provided in an embodiment of the present invention.

[0049] Figure 2 This is a schematic flowchart of a method for measuring the diffusion coefficient of gas in rock according to an embodiment of the present invention;

[0050] Explanation of reference numerals in the attached figures:

[0051] 1. Injection assembly; 2. Peristaltic pump; 3. Pressure regulating valve; 4. Wetting device; 5. Core holder; 6. Rock sample to be tested; 7. Circulation pump; 8. Three-way valve; 9. Gas mixing device; 10. Control device; 11. Diffusion pipe; 12. First valve; 13. Second valve; 14. Circulation pipe; 15. Control circuit; 16. First end; 17. Second end; 18. Third end. Detailed Implementation

[0052] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0053] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "far," "near," "front," and "rear," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0054] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0055] The inventors discovered that in existing technologies, domestic and international laboratories studying the diffusion coefficient of gases, especially helium, periodically verify the concentration of the gas to be measured during diffusion to determine the rock's diffusion coefficient. In existing devices for measuring the diffusion coefficient of gases in rocks, such as the shale single-component gas diffusion coefficient testing device and method disclosed in Chinese patent application CN116973275A, a micro-pressure difference method is used to reduce the Darcy flow rate in the total flow. Two intermediate chambers filled with single-component gas are connected to opposite sides of the core sample. Initially, a small pressure difference is maintained between the two intermediate chambers. As the gas flows through the core, the pressure difference gradually decreases until it approaches zero. Under near-equilibrium conditions, the total flow rate and Darcy flow rate are calculated using the volume subtraction method and the Darcy formula to obtain the convection flow rate and diffusion flow rate results, thus achieving the testing of shale diffusion flow rate under single-component gas conditions. However, other impurities may exist in the pipes connecting to the intermediate chambers in this device. The presence of these impurities can affect the measurement of single-component gases, ultimately impacting the accuracy of the diffusion coefficient measurement.

[0056] Chinese patent application CN115979899B discloses a device for testing the effective diffusion coefficient of helium in helium-containing natural gas. The diffusion system simulates the diffusion process of helium-containing natural gas in a formation and uses a true triaxial apparatus to simulate formation pressure and temperature. The gas pressure in the upstream and downstream diffusion chambers is equal to ensure accurate simulation of the diffusion process and thus accurate measurement of diffusion data. A gas sampling and analysis system repeatedly acquires gas samples from the upstream and downstream diffusion chambers at regular intervals during the diffusion process and analyzes the gas components in both chambers using a chromatograph to obtain multiple sets of gas component data. However, this scheme does not consider the inhomogeneity of the gas after diffusion, which will affect the accuracy of the diffusion coefficient measurement.

[0057] To address the aforementioned issues, the inventors developed a diffusion device, related apparatus, and measurement method for measuring the diffusion coefficient of rocks. This method is applicable to measuring the diffusion coefficient of different gases in different types of rocks and ensures the accuracy of the diffusion coefficient measurement.

[0058] Example 1

[0059] See Figure 1 This embodiment proposes a diffusion device for measuring the diffusion coefficient of rocks. The diffusion device is used in the apparatus for measuring the diffusion coefficient of rocks to obtain the diffusion coefficient of rocks.

[0060] The diffusion device mainly includes a diffusion assembly and a circulation assembly. The diffusion assembly includes an injection assembly 1, a core holder 5, and a three-way valve 8, which are connected in sequence through a diffusion pipe 11. The injection assembly 1 can deliver a gas of a preset concentration to the core holder 5. Here, the gas can be helium or a mixture of helium and carbon dioxide, etc. The core holder 5 can hold the rock sample 6 to be tested and apply a preset confining pressure to the rock sample 6. The gas inlet end of the core holder 5 is equipped with a first valve 12 that can communicate with the atmosphere. The three-way valve 8 can be connected to the gas outlet end of the core holder 5 and a detection device (not shown in the figure) respectively, so as to guide the gas passing through the rock sample 6 from the core holder 5 to the detection device for concentration analysis to obtain the diffusion coefficient of the rock sample 6.

[0061] The circulation assembly includes a circulation pump 7 and a gas mixing device 9 connected via a circulation pipe 14. The circulation pump 7 can be connected to the gas outlet of the core holder 5, and the gas mixing device 9 can be connected to a three-way valve 8. The circulation pump 7 is used to drive the gas from the three-way valve 8 and the gas in the core holder 5 into the gas mixing device 9 for mixing, and to realize the gas circulation from the gas mixing device 9, the three-way valve 8, the core holder 5 and back to the gas mixing device 9.

[0062] In use, the core holder 5 clamps the rock sample 6 to be tested, and a preset confining pressure is applied to the rock sample 6 to simulate the stress situation of the rock sample 6 in a real environment, which helps to more accurately measure the diffusion performance of the rock sample 6. The injection component 1 delivers gas into the core holder 5, and the gas diffuses in the rock sample 6. The diffused gas enters the three-way valve 8 through the diffusion pipe 11. The three-way valve 8 guides the gas into the detection device, where the detection device performs concentration analysis to accurately measure the concentration of each component in the gas. If the injected gas contains helium, the detection device can be calibrated to detect helium and measure the concentration of helium in the diffused gas. Based on the size of the rock sample 6 and the concentration of helium in the gas delivered by the injection component 1, the diffusion coefficient of the rock sample 6 can be calculated using Fick's diffusion law.

[0063] This embodiment enables precise quantification of gas diffusion performance in underground salt cavern gas (helium) storage, thereby providing technical support for the development of underground salt cavern gas (helium) storage and filling a gap in related research in this field. Simultaneously, the gas delivered by the injection component 1 and the rock sample 6 to be tested can be customized according to experimental requirements. This embodiment is applicable to measuring the diffusion coefficients of different gases in different types of rocks, enhancing the flexibility and wide applicability of the device.

[0064] In this embodiment, to improve the accuracy of diffusion coefficient measurement, impurity gas removal and gas mixing operations can be performed before conducting the gas diffusion experiment. During gas mixing, after the rock sample 6 to be tested is loaded into the core holder 5, with the three-way valve 8 connected to the gas mixing device 9, the circulation pump 7 drives the gas from the three-way valve 8 and the gas in the core holder 5 into the gas mixing device 9. The gas mixing device 9 performs thorough gas mixing to ensure gas uniformity. At the same time, the circulation pump 7 circulates the gas, forming a gas circulation loop from the gas mixing device 9, the three-way valve 8, the core holder 5, and back to the gas mixing device 9. This helps to uniformly cover the entire core holder 5, the three-way valve 8, and the circulation pipe 14 with gas, thereby avoiding the influence of gas non-uniformity on the diffusion coefficient measurement results.

[0065] During the venting of impurities, the injection assembly 1 and the first valve 12 are opened, and the first valve 12 is used to vent the gas, thereby removing impurities from the core holder 5 and the diffusion pipe 11. The venting time should be determined according to the experimental requirements and the length of the diffusion pipe 11, ensuring that all impurities are completely removed. During the venting process, the concentration of the vented gas can be monitored using a gas detection device. When the detected gas concentration matches the concentration of the gas delivered by the injection assembly 1, the venting operation is considered complete. By venting impurities, the situation where impurities affect gas measurements, as is common in existing technologies, can be avoided. This embodiment ensures the purity of the gas entering the core holder 5 during subsequent diffusion experiments, thereby effectively guaranteeing the accuracy of the diffusion coefficient measurement.

[0066] In one specific embodiment, the core holder 5 can be adopted as follows: Figure 1 The sleeve structure shown has an inner cavity (not labeled in the figure) to accommodate the rock sample 6 to be tested. A rubber sleeve surrounds the rock sample 6, and confining pressure fluid is placed inside the sleeve. The presence of the rubber sleeve effectively prevents the confining pressure fluid from seeping into the rock sample 6 and affecting the experimental results. The core holder 5 can apply confining pressure and use the confining pressure fluid to transfer the pressure to the rock sample 6, thus replicating the stress conditions of the rock sample 6 in a real environment and helping to more accurately measure the diffusion properties of the rock sample 6.

[0067] In one specific embodiment, see [reference] Figure 1The core holder 5 has a second valve 13 at its outlet, and the circulation pump 7 is connected to the second valve 13 via a circulation pipe 14. When the second valve 13 is open, gas can flow out from the outlet of the core holder 5, and the circulation pump 7 realizes the gas circulation process, forming a gas circulation loop from the gas mixing device 9, the three-way valve 8, the core holder 5, and back to the gas mixing device 9; when the second valve 13 is closed, the circulation loop is cut off. The opening of the circulation loop can be controlled by the second valve 13, and the circulation flow rate can be controlled by adjusting the opening degree of the second valve 13, which improves the flexibility and controllability of the experiment.

[0068] In one specific embodiment, see [reference] Figure 1 The three-way valve 8 has a first end 16, a second end 17, and a third end 18. The first end 16 is connected to the gas outlet of the core holder 5, the second end 17 is connected to the gas mixing device 9, and the third end 18 can be connected to the detection device. By properly configuring the ports of the three-way valve 8, precise control and monitoring of the gas diffusion experiment can be achieved, thereby improving the accuracy and reliability of the diffusion coefficient measurement.

[0069] In one specific embodiment, see [reference] Figure 1 The diffusion assembly also includes a peristaltic pump 2 and a pressure regulating valve 3 connected via a diffusion conduit 11. The peristaltic pump 2 is connected to the injection assembly 1 and pumps gas by squeezing the diffusion conduit 11 to precisely regulate the gas flow rate. The pressure regulating valve 3 is connected to the core holder 5 and is used to regulate the gas pressure, ensuring that the gas pressure inside the core holder 5 remains at a preset value. Through the peristaltic pump 2 and the pressure regulating valve 3, the flow rate and pressure of the gas delivered by the injection assembly 1 can be kept stable, enabling more precise control of experimental conditions and thus improving the accuracy and reliability of diffusion coefficient measurements.

[0070] In one specific embodiment, see [reference] Figure 1The rock sample 6 to be tested includes interbedded salt rocks. These interbedded salt rocks are typically in a brine environment in real strata. Due to the high underground temperature, the brine evaporates, and the evaporated brine adheres to the surface of the interbedded salt rocks. Because interbedded salt rocks can self-heal from damage, the brine does not affect their diffusion coefficient. To simulate the self-healing process of interbedded salt rocks in a brine environment in real strata, a wetting device 4 is connected between the pressure stabilizing valve 3 and the core holder 5. The wetting device 4 contains a saturated salt solution to wet the gas. The gas carries the salt solution into the core holder 5, where the salt solution crystallizes on the surface and in the pores of the rock sample 6. During the diffusion experiment, the concentration of the diffused gas is detected at preset time intervals using a detection device, and the diffusion coefficient is calculated. By comparing the diffusion coefficient values ​​measured at different time intervals, if the measured diffusion coefficient values ​​are relatively stable, it is considered that the rock sample 6 can self-heal from damage under the long-term action of the salt solution, and the salt solution has no significant effect on the diffusion coefficient. Furthermore, by adjusting the preset time interval, the relationship between the damage self-healing effect of the rock sample 6 and time can be studied. By setting the wetting device 4, the brine environment of interbedded salt rocks in real strata can be simulated more accurately, and its damage self-healing process can be studied, providing experimental data support for the study of the mechanical properties and seepage characteristics of interbedded salt rocks.

[0071] In one specific embodiment, see [reference] Figure 1 The diffusion device also includes a control device 10, which is connected to the injection assembly 1, peristaltic pump 2, pressure regulating valve 3, core holder 5, three-way valve 8, and circulation pump 7. The connection can be wired via control line 15 or wireless, using technologies such as LoRa or RF (radio frequency). A control program is written to implement wireless communication and control logic. The control device 10 controls the operating status of each component. Compared to manual control, this embodiment effectively reduces human error. By precisely controlling these components, the experimental process is automated and precise, significantly improving the automation level and reliability of the experiment.

[0072] Example 2

[0073] Based on the same inventive concept, this embodiment proposes an apparatus for measuring the diffusion coefficient of rocks, including a detection device and the diffusion device in Embodiment 1.

[0074] In one specific embodiment, the detection device includes a gas chromatograph-mass spectrometer.

[0075] The device for measuring the diffusion coefficient of rocks provided in this embodiment of the invention has a similar implementation principle and technical effect to that in Embodiment 1, and will not be described again here.

[0076] Example 3

[0077] Based on the same inventive concept, see [reference] Figure 2 This embodiment proposes a method for measuring the diffusion coefficient of gas in rock, including:

[0078] Step S1: Obtain the dimensions of the rock sample to be tested and place the rock sample in the core holder;

[0079] Step S2: Keep the first valve closed and the three-way valve disconnected from the detection device. Keep the three-way valve connected to the air outlet of the core holder and the detection device respectively. Connect the circulation pump to the air outlet of the core holder.

[0080] Step S3: Start the circulation pump. Use the circulation pump to drive the gas from the three-way valve and the gas in the core holder to the gas mixing device for mixing. This will achieve gas circulation from the gas mixing device, the three-way valve, the core holder, and back to the gas mixing device until the gas from the three-way valve and the gas in the core holder are in a uniform state.

[0081] Step S4: Turn off the circulation pump and disconnect the connection between the circulation pump and the gas outlet of the core holder, as well as the connection between the three-way valve and the detection device. Connect the three-way valve and the detection device, and use the detection device to detect the gas concentration to obtain the initial gas concentration value.

[0082] Step S5: Open the first valve and the injection assembly, and use the injection assembly to deliver gas of a preset concentration to the core holder until the diffusion pipe between the injection assembly and the core holder and the core holder are filled with gas of the preset concentration, then close the first valve.

[0083] Step S6: Apply a preset confining pressure to the rock sample to be tested using a core holder, and use a detection device to detect the concentration of the gas diffused through the rock sample to obtain the diffused gas concentration.

[0084] Step S7: Calculate the diffusion coefficient based on the size of the rock sample to be tested, the initial gas concentration value, the diffusion gas concentration, and the preset gas concentration.

[0085] In step S4 above, since the gas composition in the circulation pipe and the three-way valve may include the composition of the gas input by the injection component, it is necessary to use a detection device to detect the gas concentration in the circulation pipe and the three-way valve to obtain the initial gas concentration value in order to ensure the accuracy of the experimental data.

[0086] In step S7 above, the actual diffuse gas concentration is obtained based on the difference between the diffuse gas concentration and the initial gas concentration. Then, the diffusion coefficient is calculated using Fick's diffusion law based on the size of the rock sample to be tested and the preset gas concentration.

[0087] In one specific embodiment, the diffusion assembly further includes a peristaltic pump and a pressure regulating valve connected via a diffusion conduit, wherein the peristaltic pump is connected to the injection assembly, and the pressure regulating valve is connected to the core holder. In step S5 above, the impurity removal process may specifically include the following steps:

[0088] Open the injection assembly, peristaltic pump, and pressure regulating valve. Use the injection assembly to deliver gas of a preset concentration, use the peristaltic pump to adjust the gas flow rate to a preset flow rate value, and use the pressure regulating valve to adjust the gas pressure to a preset pressure value.

[0089] Open the first valve until all diffusion channels between the injection assembly and the core holder, as well as the core holder itself, are filled with gas, then close the first valve.

[0090] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. This disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims. Thus, if these modifications and variations of the invention fall within the scope of the claims of the invention and their equivalents, the invention is also intended to include these modifications and variations.

Claims

1. A diffusion device for measuring the diffusion coefficient of rocks, characterized in that, Includes diffusion components and circulation components; The diffusion assembly includes an injection assembly, a core holder, and a three-way valve connected in sequence via a diffusion pipe; The injection component is capable of delivering a preset concentration of gas to the core holder; The core holder can hold the rock sample to be tested and apply a preset confining pressure to the rock sample; The core holder is equipped with a first valve at the air inlet end that allows it to communicate with the atmosphere. The three-way valve can be connected to the air outlet of the core holder and the detection device respectively; The circulation assembly includes a circulation pump and a gas mixing device connected via circulation pipes; The circulating pump can be connected to the air outlet of the core holder; The gas mixing device can be connected to the three-way valve; The circulating pump is used to drive the gas from the three-way valve and the gas in the core holder to the gas mixing device for mixing, and to realize the gas circulation from the gas mixing device, the three-way valve, the core holder and back to the gas mixing device.

2. The diffusion device for measuring the diffusion coefficient of rock according to claim 1, characterized in that, The three-way valve is provided with a first end, a second end, and a third end; The first end is connected to the air outlet end of the core holder; The second end is connected to the gas mixing device; The third end can be connected to the detection device.

3. The diffusion device for measuring the diffusion coefficient of rock according to claim 2, characterized in that, The diffusion assembly also includes a peristaltic pump and a pressure regulating valve connected via a diffusion conduit; The peristaltic pump is connected to the injection assembly and is used to regulate the flow rate of the gas; The pressure regulating valve is connected to the core holder and is used to regulate the pressure of the gas.

4. The diffusion device for measuring the diffusion coefficient of rock according to claim 3, characterized in that, The rock samples to be tested include interbedded salt rocks; The diffusion device also includes a wetting device connected between the pressure stabilizing valve and the core holder; The wetting device contains a saturated salt solution for wetting the gas.

5. The diffusion apparatus for measuring the diffusion coefficient of rock according to claim 3 or 4, characterized in that, It also includes control devices; The control device is connected to the injection assembly, the peristaltic pump, the pressure stabilizing valve, the core holder, the three-way valve, and the circulation pump, respectively.

6. The diffusion apparatus for measuring the diffusion coefficient of rock according to claim 5, characterized in that, The core holder is equipped with a second valve at its air outlet. The circulating pump is connected to the second valve via a circulating pipe.

7. An apparatus for measuring the diffusion coefficient of rocks, characterized in that, It includes a detection device and a diffusion device as described in any one of claims 1-6.

8. The apparatus for measuring the diffusion coefficient of rock according to claim 7, characterized in that, The detection device includes a gas chromatograph-mass spectrometer.

9. A method for measuring the diffusion coefficient of rocks, characterized in that, include: Obtain the dimensions of the rock sample to be tested, and place the rock sample in the core holder; Keep the first valve closed and the three-way valve disconnected from the detection device. Keep the three-way valve connected to the air outlet of the core holder and the detection device respectively. Connect the circulation pump to the air outlet of the core holder. Start the circulation pump to drive the gas from the three-way valve and the gas in the core holder to the gas mixing device for mixing, and realize the gas circulation from the gas mixing device, the three-way valve, the core holder and back to the gas mixing device until the gas from the three-way valve and the gas in the core holder are in a uniform state. Turn off the circulation pump and disconnect the connection between the circulation pump and the gas outlet of the core holder, as well as the connection between the three-way valve and the detection device. Connect the three-way valve and the detection device, and use the detection device to detect the gas concentration to obtain the initial gas concentration value. Open the first valve and the injection assembly, and use the injection assembly to deliver a gas of a preset concentration to the core holder until the diffusion pipe between the injection assembly and the core holder and the core holder are filled with the gas of the preset concentration, then close the first valve. A preset confining pressure is applied to the rock sample to be tested using the core holder, and the concentration of the gas diffused through the rock sample is detected using the detection device to obtain the diffused gas concentration; The diffusion coefficient is calculated based on the size of the rock sample to be tested, the initial gas concentration, the diffusion gas concentration, and the preset gas concentration.

10. The method for measuring the diffusion coefficient of rock according to claim 9, characterized in that, The diffusion assembly also includes a peristaltic pump and a pressure regulating valve connected via a diffusion conduit, wherein the peristaltic pump is connected to the injection assembly and the pressure regulating valve is connected to the core holder; The step of opening the first valve and the injection assembly, using the injection assembly to deliver gas of a preset concentration to the core holder, until the diffusion channel between the injection assembly and the core holder and the core holder are filled with gas of the preset concentration, and then closing the first valve, includes: Open the injection assembly, the peristaltic pump, and the pressure regulating valve. Use the injection assembly to deliver gas of a preset concentration, use the peristaltic pump to adjust the gas flow rate to a preset flow rate value, and use the pressure regulating valve to adjust the gas pressure to a preset pressure value. Open the first valve until all diffusion channels between the injection assembly and the core holder, as well as the core holder, are filled with gas, then close the first valve.

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