Device and method for simulating gas enrichment migration amount of reservoir matrix fractures at different depths

Abstract

The application discloses a device and method for simulating gas enrichment migration amount of matrix fractures in different depth reservoirs. The device comprises a constant pressure displacement system, a first sealed intermediate container, a second sealed intermediate container, a first gas collection system and a second gas collection system, a core holder, a first control valve, a second control valve and a third control valve, etc. The application provides an experimental device for establishing original gas amount of shale matrix and fracture system, which is used for simulating gas migration process in the fracture and matrix system under different pressures of different reservoir depths, obtaining variation law of reservoir matrix gas content and fracture system gas content with pressure coefficient, and determining gas relative migration amount of shale matrix and fracture system under different reservoir pressures, so as to provide a theoretical basis for shale sweet spot area optimization and development technology optimization.

Description

Technical Field

[0001] This invention relates to the field of shale gas exploration and development technology, and in particular to an apparatus and method for simulating gas enrichment and migration in matrix fractures of reservoirs at different depths. Background Technology

[0002] Developed bedding is one of the characteristics that distinguishes shale reservoirs from other conventional reservoirs. Bedding and natural fractures form important reservoir spaces and flow channels in the shale matrix. However, the occurrence state and mobility of gas differ between fractures and the matrix. Gas in fractures is predominantly free gas, with strong flow capacity and easy mobility. In the matrix, micro- and nano-pores are well-developed, and gas exists in both adsorbed and free states, making mobility more difficult. As the burial depth of shale reservoirs increases, reservoir temperature and pressure also increase, and reservoir physical properties change. The enrichment patterns of gas in the matrix and fractures vary with depth. Determining the proportion of gas in the matrix and fractures, and its variation with depth, is of great significance for optimizing development technologies and evaluating the development effect of gas wells. Summary of the Invention

[0003] In view of the above problems, the present invention is proposed to provide an apparatus and method for simulating gas enrichment and migration in reservoir matrix fractures at different depths, in order to overcome or at least partially solve the above problems.

[0004] In a first aspect, embodiments of the present invention provide an apparatus for simulating gas enrichment and migration in matrix fractures of reservoirs at different depths, characterized in that it comprises: a constant pressure displacement system, a first sealed intermediate container, a second sealed intermediate container, a first gas collection system and a second gas collection system, a core holder, a first control valve, a second control valve and a third control valve;

[0005] The core holder includes two chambers for holding two different core samples, and the connection between the two chambers is controlled by the third control valve.

[0006] The constant pressure displacement system is connected to the first sealed intermediate container and the second sealed intermediate container respectively, and is used to provide a first reservoir pressure with a preset pressure value, so as to fill the two chambers with different gases through the first sealed intermediate container and the second sealed intermediate container respectively.

[0007] The first sealed intermediate container and the second sealed intermediate container are respectively connected to the two chambers of the core holder;

[0008] The first gas collection system is connected to the gas pipeline between the core holder and the first sealed intermediate container, and the connection between the first gas collection system and the core holder is controlled by the first valve;

[0009] The second gas collection system is connected to the gas pipeline between the core holder and the second sealed intermediate container, and the connection between the second gas collection system and the core holder is controlled by the second valve.

[0010] The aforementioned device for simulating gas enrichment and migration in reservoir matrix fractures at different depths also includes: a metering pump;

[0011] The metering pump is connected to the core holder and is used to raise the confining pressure of the two chambers in the core holder to a preset pressure.

[0012] In one embodiment, the first control valve and the second control valve are three-way valves.

[0013] In one embodiment, the first gas collection system includes: a water tank, an exhaust pipe, and a gas collection bottle;

[0014] The exhaust pipe is connected to the gas pipeline between the core holder and the first sealed intermediate container;

[0015] The gas collection bottle is used to collect gas delivered through the exhaust pipe by filling it with liquid and placing it upside down below the liquid surface of the water tank.

[0016] In one embodiment, the second gas collection system includes: a water tank, an exhaust pipe, and a gas collection bottle;

[0017] The exhaust pipe is connected to the gas pipeline between the core holder and the second sealed intermediate container;

[0018] The gas collection bottle is used to collect gas delivered through the exhaust pipe by filling it with liquid and placing it upside down below the liquid surface of the water tank.

[0019] Secondly, embodiments of the present invention provide a method for simulating gas enrichment and migration in reservoir matrix fractures at different depths using the aforementioned apparatus, comprising:

[0020] Two different core samples are placed in the core holder, and the two chambers are not connected to each other;

[0021] The constant pressure displacement system provides a first reservoir pressure with a preset pressure value. Different gases are injected into the two chambers through the first and second sealed intermediate containers respectively. The same pore pressure and overlying pressure are maintained in the two chambers. The constant pressure displacement system is shut off after saturation.

[0022] The two chambers of the core holder are connected, and the overburden pressure in the two chambers is increased from the first overburden pressure to the preset second overburden pressure by a metering pump;

[0023] Close the third control valve;

[0024] The first control valve and the second control valve are opened respectively, so that the two chambers of the core holder are connected to the first gas collection system and the second gas collection system respectively, and the gas production at different time periods are collected through the first gas collection system and the second gas collection system respectively.

[0025] Based on the gas production collected at different time periods, gas composition analysis was performed to determine the gas cross-flow rate.

[0026] In one embodiment, before placing two different core samples into the core holder, the method further includes:

[0027] The shale core was divided into two sections: one section was used as the shale matrix sample, and the other section was artificially fractured and used as the fracture core sample.

[0028] In one embodiment, filling the two chambers with different gases includes:

[0029] The two chambers are filled with any combination of methane-ethane, methane-carbon dioxide, or methane-nitrogen, and the gases filled into the two chambers are different.

[0030] In one embodiment, collecting the generated gas through a first gas collection system and a second gas collection system includes:

[0031] After filling the gas collection bottle in the first gas collection system with water, invert it below the liquid level in the water tank.

[0032] Place the exhaust pipe into the inverted gas collection bottle, open the outlet end of the core holder, exhaust gas into the gas collection bottle through the exhaust pipe, and record the time and the pressure of the exhaust gas. Seal the gas collection bottle after collecting the gas, replace it with a gas collection bottle filled with water, and invert it again below the liquid surface to collect gas until the core holder no longer discharges gas.

[0033] In one embodiment, the gas collection bottle is sealed after the gas collection is completed when the liquid level in the gas collection bottle drops to a preset height.

[0034] The amount of gas collected in the gas collection bottle is determined by measuring the difference between the remaining water in the gas collection bottle and the total water volume when the gas collection bottle is full.

[0035] In one embodiment, gas composition analysis is performed based on the gas production collected at different time periods to determine the gas cross-flow rate, including:

[0036] Gas chromatography was used to analyze the components of the gases collected by the first gas collection system and the second gas collection system at different time periods to determine the proportion of different gas components in the gases collected by the first gas collection system and the second gas collection system in each time period.

[0037] Based on the proportions of different gas components in the gases collected by different first gas collection systems and second gas collection systems at different time periods, the flow rates of the different gas components from the shale matrix sample to the fracture core sample, and the flow rates of the different gas components from the fracture core sample to the shale matrix sample are determined.

[0038] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0039] The apparatus and method provided in this invention for simulating gas enrichment and migration in reservoir matrix fractures at different depths can simulate the gas flow between the matrix and fracture system under reservoir pressures at different depths. By establishing an experimental apparatus for the original gas volume of the shale matrix and fracture system, the migration process of gas in the fracture and matrix system under different pressures at different reservoir depths can be simulated to obtain the variation law of gas content in the reservoir matrix and fracture system with pressure coefficient, thereby determining the relative gas migration amount between the shale matrix and fracture system under different reservoir pressures, providing a theoretical basis for the selection of shale sweet spots and the optimization of development technology.

[0040] Other features and advantages of the invention will be set forth in the description which follows, 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, claims, and drawings.

[0041] 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

[0042] 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:

[0043] Figure 1 This is a schematic diagram of the device for simulating gas enrichment and migration in reservoir matrix fractures at different depths, as described in this embodiment of the invention.

[0044] Figure 2 This is a flowchart illustrating the method for simulating gas enrichment and migration in reservoir matrix fractures at different depths, as described in this embodiment of the invention.

[0045] Figure 3This is a graph showing the change in gas outflow from the shale matrix and fracture system over time in an embodiment of the present invention.

[0046] 1-Constant pressure displacement system; 2-First sealed intermediate container; 11-Sealed intermediate container; 3-First control valve; 9-Second control valve; 4-First gas collection system; 10-Second gas collection system; 5, 7-Two different experimental cores; 6-Third control valve; 8-Core holder; 12-Metering pump. Detailed Implementation

[0047] 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.

[0048] This invention provides an apparatus for simulating gas enrichment and migration in reservoir matrix fractures at different depths, with reference to... Figure 1 As shown, it includes: a constant pressure displacement system 1, a first sealed intermediate container 2, a second sealed intermediate container 11, a first gas collection system 4 and a second gas collection system 10, a core holder 8, a first control valve 3, a second control valve 9, and a third control valve 6; wherein:

[0049] The core holder 8 includes two chambers for placing two different core samples (core sample 5 and core sample 7), and the connection between the two chambers is controlled by the third control valve 6.

[0050] The constant pressure displacement system 1 is connected to the first sealed intermediate container 2 and the second sealed intermediate container 11 respectively, and is used to provide a first reservoir pressure with a preset pressure value, so as to fill the two chambers with different gases through the first sealed intermediate container 2 and the second sealed intermediate container 11 respectively.

[0051] The first sealed intermediate container 2 and the second sealed intermediate container 11 are respectively connected to the two chambers of the core holder 8;

[0052] The first gas collection system 4 is connected to the gas pipeline between the core holder 8 and the first sealed intermediate container 2, and the connection between the first gas collection system 4 and the core holder 8 is controlled by the first valve.

[0053] The second gas collection system 10 is connected to the gas pipeline between the core holder 8 and the second sealed intermediate container 11, and the connection between the second gas collection system 10 and the core holder 8 is controlled by a second valve.

[0054] The constant pressure displacement system 1 is used to keep the first sealed intermediate container 2 and the first sealed intermediate container 11 in a constant pressure state during the displacement process; for example, the constant pressure displacement system 1 can be a set of constant pressure displacement pumps with a constant pressure injection mode and a pressure range of 0-50MPa.

[0055] In one embodiment, the core holder 8 is used to hold two different core samples, such as a matrix core sample and a fracture core sample (for simulating a reservoir).

[0056] In the first sealed intermediate container 2 and the second sealed intermediate container 11, the experimental gas and distilled water can be separated by a movable metal piston for filling any one of the gas combinations such as methane-ethane, methane-CO2, and methane-nitrogen. The two sealed intermediate containers (the first sealed intermediate container 2 and the second sealed intermediate container 11) provide gas sources for the matrix rock sample and the fracture rock sample in the core holder 8, respectively.

[0057] The first sealed intermediate container 2 and the second sealed intermediate container 11 may be made of stainless steel (e.g., 316L stainless steel) with a pressure resistance range of 0-70 MPa.

[0058] The aforementioned core holder 8 includes a cavity for placing two different types of core samples, and a third control valve 6 controls whether the two are connected.

[0059] The core holder 8 can be, for example, a core holder with a diameter of 2.5cm, 3.8cm or 10cm and a pressure resistance of 0-50MPa.

[0060] The aforementioned third control valve 6 can be, for example, a high-pressure control valve.

[0061] In one embodiment, refer to Figure 1 The device shown also includes: a metering pump;

[0062] The metering pump is connected to the core holder 8 and is used to raise the confining pressure of the two chambers in the core holder 8 to a preset pressure.

[0063] In practice, the metering pump can be a manual metering pump.

[0064] The pressure range of the manual metering pump is 0-70 MPa.

[0065] Furthermore, the first control valve 3 and the second control valve mentioned above can be, for example, three-way valves.

[0066] The first control valve 3 and the second control valve are used to connect the two sides of the core holder 8, the first sealed intermediate container 2 and the second sealed intermediate container 11, the first gas collection system 4 and the second gas collection system 10, and can switch the port of the core holder 8 to either the state of filling the first sealed intermediate container 2 and the second sealed intermediate container 11 with gas or the state of venting the first gas collection system 4 and the second gas collection system 10.

[0067] Furthermore, the first gas collection system 4 and the second gas collection system 10 are used to collect the gas production at the port of the core holder 8 at different time periods.

[0068] Furthermore, the first gas collection system 4 includes: a water tank, an exhaust pipe, and a gas collection bottle;

[0069] The gas collection bottle can be, for example, a glass bottle with a volume of 0.25L, or a suitable volume can be selected according to the amount of gas produced. This embodiment of the invention does not limit this.

[0070] The exhaust pipe is connected to the gas pipeline between the core holder 8 and the first sealed intermediate container 2;

[0071] The gas collection bottle is used to collect gas delivered through the exhaust pipe by filling it with liquid and placing it upside down below the liquid surface of the water tank.

[0072] Furthermore, the second gas collection system 10 has a similar structure to the first gas collection system 4, and the second gas collection system 10 includes: a water tank, an exhaust pipe, and a gas collection bottle;

[0073] The exhaust pipe is connected to the gas pipeline between the core holder 8 and the second sealed intermediate container 11;

[0074] The gas collection bottle is used to collect gas delivered through the exhaust pipe by filling it with liquid and placing it upside down below the surface of the water tank.

[0075] This invention provides a method for simulating gas enrichment and migration in reservoir matrix fractures at different depths using the aforementioned apparatus, with reference to... Figure 2 As shown, it includes the following steps:

[0076] S21. Two different core samples are placed in the core holder, and the two chambers are not connected to each other;

[0077] S22. The constant pressure displacement system provides a first reservoir pressure with a preset pressure value, and different gases are injected into the two chambers through the first and second sealed intermediate containers respectively. The same pore pressure and overburden pressure are maintained in the two chambers, and the constant pressure displacement system is shut off after saturation.

[0078] S23. Connect the two chambers of the core holder and use a metering pump to increase the overburden pressure in the two chambers from the first overburden pressure to a preset second overburden pressure;

[0079] S24. Close the third control valve;

[0080] S25. Open the first control valve and the second control valve respectively, so that the two chambers of the core holder are connected to the first gas collection system and the second gas collection system respectively, and collect the gas production at different time periods through the first gas collection system and the second gas collection system respectively.

[0081] S26. Based on the gas production collected at different time periods, perform gas composition analysis to determine the gas cross-flow rate.

[0082] In one embodiment, before steps S21-S26 above, the shale core needs to be divided into two segments: one segment as a shale matrix sample and the other segment after artificial fracture as a fracture core sample.

[0083] In one embodiment, in step S22 above, it is necessary to fill the two chambers with any one of the following combinations: methane-ethane, methane-carbon dioxide, or methane-nitrogen, and the gases filled into the two chambers are different.

[0084] Furthermore, in step S25 above, the generated gas is collected through the first gas collection system and the second gas collection system, which can be achieved, for example, in the following manner:

[0085] After filling the gas collection bottle in the first gas collection system with water, invert it below the liquid level in the water tank.

[0086] Place the exhaust pipe into the inverted gas collection bottle, open the outlet end of the core holder, exhaust gas into the gas collection bottle through the exhaust pipe, and record the time and the pressure of the exhaust gas. Seal the gas collection bottle after collecting the gas, replace it with a gas collection bottle filled with water, and invert it again below the liquid surface to collect gas until the core holder no longer discharges gas.

[0087] In one embodiment, in step S25 above, the gas collection bottle is sealed after the gas collection is completed when the liquid level in the gas collection bottle drops to a preset height.

[0088] The amount of gas collected in the gas collection bottle is determined by measuring the difference between the remaining water in the gas collection bottle and the total water volume when the gas collection bottle is full.

[0089] In one embodiment, in step S26 above, the gas composition analysis based on the gas production collected at different time periods to determine the gas cross-flow rate can be achieved through the following steps:

[0090] Gas chromatography was used to analyze the components of the gases collected by the first gas collection system and the second gas collection system at different time periods to determine the proportion of different gas components in the gases collected by the first gas collection system and the second gas collection system in each time period.

[0091] Based on the proportions of different gas components in the gases collected by different first gas collection systems and second gas collection systems at different time periods, the flow rates of the different gas components from the shale matrix sample to the fracture core sample, and the flow rates of the different gas components from the fracture core sample to the shale matrix sample are determined.

[0092] To illustrate the method for simulating gas enrichment and migration in reservoir matrix fractures at different depths, an example is provided, which includes the following steps:

[0093] 1. Select a shale core of appropriate length and split it in half. One half serves as the matrix system, and the other half is used to create artificial fractures, producing 2-4 through fractures. Use sealing tape to maintain the integrity of the core. This step generates two different types of core samples.

[0094] 2. Different gases are introduced into the first sealed intermediate container and the second sealed intermediate container respectively. These gases can be any combination of methane-ethane, methane-CO2, or methane-nitrogen.

[0095] 3. Place the shale matrix and fractured core into the two ends of the core holder respectively, and use a manual metering pump to uniformly increase the confining pressure to the reservoir overlying pressure. Then close the third control valve in the middle of the core holder.

[0096] 4. The constant pressure displacement system maintains the first reservoir pressure and simultaneously saturates the matrix core and fracture core with any combination of gases through the first and second sealed intermediate containers, maintaining the same pore pressure and overlying pressure. After saturation, the constant pressure displacement system is shut off. At this time, the third control valve is closed, and the first and second control valves control the first and second sealed intermediate containers to connect with the core holder, while the first and second gas collection systems are not connected to the core holder.

[0097] 5. Open the third control valve in the middle of the core holder and increase the confining pressure from the first overburden pressure to the second overburden pressure using a manual metering pump. Increase the overburden pressure and allow different gases to cross-flow between the matrix and fractures. Once equilibrium is reached, close the third control valve in the middle of the core holder.

[0098] 6. Open both ends of the core holder to release gas. Use the first gas collection system and the second gas collection system to mark and record the gas production at different time periods until gas production stops.

[0099] 7. Perform gas composition analysis on the gas production at different time periods using gas chromatography to determine the gas cross-flow rate.

[0100] The shale cores selected in step 1 above should meet the following requirements: length ≥ 5cm, no cracks, permeability (0.1 > X > 0.00001mD), and porosity > 2%.

[0101] In step 2 above, the methane content is 99.999% and the nitrogen content is 99.999%.

[0102] In step 3 above, ensure that the confining pressure is added at a uniform rate using the manual metering pump;

[0103] In step 4 above, a constant pressure displacement system 1 is used to simultaneously saturate the matrix core and fracture core with 30MPa methane and nitrogen gas from the two sealed intermediate containers 2 and 11.

[0104] In step 5 above, the third control valve 6 in the middle of the core holder 8 is slowly opened, and the confining pressure is increased from 35MPa to 50MPa at a constant speed by the manual metering pump 12.

[0105] The gas collection system 4 and 10 described in step 6 above includes a water tank, an exhaust pipe, and a glass bottle. The specific operation is as follows: pour about 2 / 3 of the volume of distilled water into the water tank, fill the glass bottle with distilled water, and then invert it below the surface of the water tank, ensuring that no air enters the glass bottle during the inversion process. Insert the exhaust pipe into the glass bottle filled with distilled water that is inverted below the surface of the water tank. Then open the outlet end of the core holder and exhaust gas into the glass bottle through the exhaust pipe. Record the time and pressure at any time. When the gas in the glass bottle reaches 4 / 5, seal and mark the glass bottle. Replace the exhaust pipe with the next glass bottle filled with distilled water that is inverted below the surface of the water tank to continue collecting gas. Repeat this process until the pressure is 0 and no more gas is produced.

[0106] In step 7 above, the amount of water in the glass bottle at different time periods is measured, and the total amount of water in the glass bottle is also measured. The difference between the two is used to obtain the amount of gas produced in the glass bottle at different time periods.

[0107] After measuring the gas production at different time periods, the method for measuring gas enrichment and migration in matrix cores and fracture cores described above also requires obtaining the saturated gas volume of each core through the basic parameters of the core samples, and obtaining the ratio of methane and nitrogen at different time periods through gas composition analysis; the basic parameters of the core samples include length, diameter and porosity.

[0108] Example 1:

[0109] This embodiment provides a method for gas enrichment and migration in the matrix and fracture system at different depths of a reservoir. This method uses, for example... Figure 1 The device shown is implemented by including the following steps:

[0110] 1) Select a shale core from a well in a certain location, cut it vertically from the middle 1 / 2 and one end 1 / 4 respectively, and glue the two 1 / 4 cores together to form a fractured core; the other part is used as the shale matrix core;

[0111] 2) Introduce 30 MPa of methane and nitrogen into the first and second sealed intermediate containers respectively;

[0112] 3) Place the shale matrix and fractured core into the two ends of the core holder respectively, and use a manual metering pump to uniformly increase the confining pressure to 35MPa, then close the third control valve in the middle of the core holder;

[0113] 4) The constant pressure displacement system is set at a constant pressure of 30MPa. Through the first and second sealed intermediate containers, methane and nitrogen are simultaneously saturated at 30MPa at both ends of the core holder to maintain the same pore pressure and overlying pressure. Saturated methane is introduced into the matrix core on the left and saturated nitrogen is introduced into the fracture core on the right. After saturation, the constant pressure displacement system is shut off.

[0114] 5) Open the third control valve in the middle of the core holder, and at the same time increase the confining pressure from 35MPa to 50MPa by manually metering pumping to increase the overlying pressure. Different gases will cross-flow between the matrix core and the fracture core and reach equilibrium after 48 hours. Then close the third control valve in the middle of the core holder to prevent the two from connecting.

[0115] 6) Release gas by opening both ends of the core holder. Use the first and second gas collection systems to collect 10 bottles of gas produced from the left matrix core and 9 bottles of gas produced from the right fracture core. Mark and record the gas production at different time points. After the pressure inside the core holder drops to 0 MPa, the average gas production rate within one week should be less than 10 cm³ / min. 3 The measurement ends at / d;

[0116] 7) Gas chromatography was used to analyze the gas components of 19 bottles from different time periods on both sides to obtain the ratio of methane to nitrogen in each bottle. The water volume in the glass bottles at different time periods was measured, and the gas volume of each glass bottle was obtained by subtracting the water volume from the total volume of the glass bottles. 216 ml of matrix (CH4) was supplied to the fracture system (i.e., the side with the fractured rock sample), and 141 ml of fracture (N2) diffused into the matrix. After deducting the convective diffusion flow rate, the matrix supplied 75 ml of gas to the fracture, accounting for 7% of the total matrix gas volume. The final results are statistically shown below. Figure 3 As shown.

[0117] The apparatus and method provided in this invention for simulating gas enrichment and migration in reservoir matrix fractures at different depths can simulate the gas flow between the matrix and fracture system under reservoir pressures at different depths. By establishing an experimental apparatus for the original gas volume of the shale matrix and fracture system, the migration process of gas in the fracture and matrix system under different pressures at different reservoir depths can be simulated to obtain the variation law of gas content in the reservoir matrix and fracture system with pressure coefficient, thereby determining the relative gas migration volume between the shale matrix and fracture system under different reservoir pressures, providing a theoretical basis for the selection of shale sweet spots and the optimization of development technology.

[0118] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A device for simulating gas enrichment and migration in reservoir matrix fractures at different depths, characterized in that, include: The system comprises a constant pressure displacement system, a first sealed intermediate container, a second sealed intermediate container, a first gas collection system and a second gas collection system, a core holder, a first control valve, a second control valve and a third control valve; The core holder includes two chambers for holding two different core samples, and the connection between the two chambers is controlled by the third control valve. The constant pressure displacement system is connected to the first sealed intermediate container and the second sealed intermediate container respectively, and is used to provide a first reservoir pressure with a preset pressure value, so as to fill the two chambers with different gases through the first sealed intermediate container and the second sealed intermediate container respectively. The first sealed intermediate container and the second sealed intermediate container are respectively connected to the two chambers of the core holder; The first gas collection system is connected to the gas pipeline between the core holder and the first sealed intermediate container, and the connection between the first gas collection system and the core holder is controlled by the first valve; The second gas collection system is connected to the gas pipeline between the core holder and the second sealed intermediate container, and the connection between the second gas collection system and the core holder is controlled by the second valve.

2. The apparatus as claimed in claim 1, characterized in that, Also includes: Metering pump; The metering pump is connected to the core holder and is used to raise the confining pressure of the two chambers in the core holder to a preset pressure.

3. The apparatus as described in claim 1, characterized in that, The first control valve and the second control valve are three-way valves.

4. The apparatus as claimed in claim 1, characterized in that, The first gas collection system includes: a water tank, an exhaust pipe, and a gas collection bottle; The exhaust pipe is connected to the gas pipeline between the core holder and the first sealed intermediate container; The gas collection bottle is used to collect gas delivered through the exhaust pipe by filling it with liquid and placing it upside down below the liquid surface of the water tank.

5. The apparatus as claimed in claim 1, characterized in that, The second gas collection system includes: a water tank, an exhaust pipe, and a gas collection bottle; The exhaust pipe is connected to the gas pipeline between the core holder and the second sealed intermediate container; The gas collection bottle is used to collect gas delivered through the exhaust pipe by filling it with liquid and placing it upside down below the liquid surface of the water tank.

6. A method for simulating gas enrichment and migration in reservoir matrix fractures at different depths using the apparatus described in any one of claims 1-5, characterized in that, include: Two different core samples are placed in the core holder, and the two chambers are not connected to each other; The constant pressure displacement system provides a first reservoir pressure with a preset pressure value. Different gases are injected into the two chambers through the first and second sealed intermediate containers respectively. The same pore pressure and overlying pressure are maintained in the two chambers. The constant pressure displacement system is shut off after saturation. The two chambers of the core holder are connected, and the overburden pressure in the two chambers is increased from the first overburden pressure to the preset second overburden pressure by a metering pump; Close the third control valve; The first control valve and the second control valve are opened respectively, so that the two chambers of the core holder are connected to the first gas collection system and the second gas collection system respectively, and the gas production at different time periods are collected through the first gas collection system and the second gas collection system respectively. Based on the gas production collected at different time periods, gas composition analysis was performed to determine the gas cross-flow rate.

7. The method as described in claim 6, characterized in that, Before placing the two different core samples into the core holder, the process also includes: The shale core was divided into two sections: one section was used as the shale matrix sample, and the other section was artificially fractured and used as the fracture core sample.

8. The method as described in claim 6, characterized in that, The process of filling the two chambers with different gases includes: The two chambers are filled with any combination of methane-ethane, methane-carbon dioxide, or methane-nitrogen, and the gases filled into the two chambers are different.

9. The method as described in claim 6, characterized in that, The generated gas is collected through a first gas collection system and a second gas collection system, including: After filling the gas collection bottle in the first gas collection system with water, invert it below the liquid level in the water tank. Place the exhaust pipe into the inverted gas collection bottle, open the outlet end of the core holder, exhaust gas into the gas collection bottle through the exhaust pipe, and record the time and the pressure of the exhaust gas. Seal the gas collection bottle after collecting the gas, replace it with a gas collection bottle filled with water, and invert it again below the liquid surface to collect gas until the core holder no longer discharges gas.

10. The method as described in claim 9, characterized in that, When the liquid level in the gas collection bottle drops to a preset height, the gas collection bottle, after collecting all the gas, is sealed. The amount of gas collected in the gas collection bottle is determined by measuring the difference between the remaining water in the gas collection bottle and the total water volume when the gas collection bottle is full.

11. The method as described in claim 7, characterized in that, Based on the gas production collected at different time periods, gas composition analysis was performed to determine the gas cross-contamination rate, including: Gas chromatography was used to analyze the components of the gases collected by the first gas collection system and the second gas collection system at different time periods to determine the proportion of different gas components in the gases collected by the first gas collection system and the second gas collection system in each time period. Based on the proportions of different gas components in the gases collected by different first gas collection systems and second gas collection systems at different time periods, the flow rates of the different gas components from the shale matrix sample to the fracture core sample, and the flow rates of the different gas components from the fracture core sample to the shale matrix sample are determined.

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