Diffusion coefficient testing equipment and diffusion coefficient testing method

Abstract

The invention belongs to the technical field of shale reservoir development experiments, and discloses diffusion coefficient testing equipment and a diffusion coefficient testing method.The diffusion coefficient testing equipment comprises a sample holder, a gas injection system, an experimental oil injection system, a confining pressure adjusting device and an oil-gas separation metering system. The sample holder is provided with an air cavity, a sample cavity and an oil cavity which are communicated in sequence; the gas injection system is selectively communicated with the gas cavity, fills experimental gas into the gas cavity and adjusts the pressure of the gas cavity; the experimental oil injection system is selectively communicated with the oil cavity, injects experimental oil into the oil cavity and adjusts the pressure of the oil cavity; the confining pressure adjusting device is communicated with the sample cavity and can adjust the pressure in the sample cavity; and the oil-gas separation metering system is selectively communicated with the oil cavity, is used for containing experimental oil containing experimental gas after an experiment and can be used for carrying out oil-gas separation on the experimental oil. According to the diffusion coefficient testing equipment, the determination accuracy of the gas diffusion coefficient in the porous medium can be improved, and the influence of the diffusion effect in the shale reservoir on the improvement of the recovery efficiency can be accurately described.

Description

Technical Field

[0001] The invention relates to the technical field of shale reservoir development experiments, and in particular to a diffusion coefficient testing device and a diffusion coefficient testing method. Background Art

[0002] At present, the development of tight shale reservoirs faces the problem of rapid production reduction and difficulty in stabilizing production. Due to the small storage space scale, poor permeability and difficulty in injection of tight shale reservoirs, CO2 injection is the main method of development. CO2 has difficulty flowing after injection, and the diffusion capacity determines the speed and scope of CO2 throughput development, which is an important factor in determining CO2 enhanced oil recovery. The diffusion coefficient is the main controlling factor that describes the diffusion capacity of gas in the liquid phase, and its determination is of great significance to improving oil recovery.

[0003] The existing indoor physical simulation methods for measuring diffusion coefficients are mainly based on macroscopic fluid media. When measuring the diffusion coefficient in microscopic porous media, it is difficult to avoid the influence of convection caused by pressure gradient, which leads to inaccurate measurement of the diffusion coefficient in microscopic porous media.

[0004] Therefore, there is an urgent need for a diffusion coefficient testing device and a diffusion coefficient testing method to solve the above problems. Summary of the invention

[0005] According to one aspect of the present invention, an object is to provide a diffusion coefficient testing device, which can improve the measurement accuracy of gas diffusion coefficient in porous media and accurately describe the effect of diffusion in shale reservoirs on improving oil recovery.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] Diffusion coefficient test equipment, including:

[0008] A sample holder, wherein the sample holder is provided with an air cavity, a sample cavity and an oil cavity which are connected in sequence, and the sample cavity is used to accommodate a test sample;

[0009] A gas injection system, the gas injection system is selectively connected to the gas cavity, capable of filling the gas cavity with experimental gas and adjusting the pressure of the gas cavity;

[0010] an experimental oil injection system, the experimental oil injection system being selectively connected to the oil chamber, capable of injecting experimental oil into the oil chamber and adjusting the pressure of the oil chamber;

[0011] a confining pressure regulating device, the confining pressure regulating device being connected to the sample chamber and configured to regulate the pressure in the sample chamber;

[0012] The oil-gas separation metering system is selectively connected to the oil cavity, can receive the experimental oil containing the experimental gas after the experiment, and can perform oil-gas separation on the experimental oil.

[0013] As a preferred solution of the diffusion coefficient testing equipment provided by the present invention, the gas injection system includes a gas intermediate container and a first pump body. The gas intermediate container is selectively connected to the gas cavity and can accommodate experimental gas; the first pump body is connected to the gas intermediate container and can adjust the gas pressure in the gas intermediate container to the experimental pressure.

[0014] As a preferred embodiment of the diffusion coefficient testing equipment provided by the present invention, the experimental oil injection system includes an experimental oil intermediate container and a second pump body. The experimental oil intermediate container is selectively connected to the oil cavity and can accommodate the experimental oil; the second pump body is connected to the experimental oil intermediate container and can pump the experimental oil in the experimental oil intermediate container into the oil cavity.

[0015] As a preferred solution of the diffusion coefficient testing device provided by the present invention, the diffusion coefficient testing device further comprises a pressure difference sensor, which is connected to the air cavity and the oil cavity and can sense the pressure difference between the air cavity and the oil cavity.

[0016] As a preferred solution of the diffusion coefficient testing device provided by the present invention, the diffusion coefficient testing device further comprises a constant temperature box, and the sample holder is arranged in the constant temperature box.

[0017] As a preferred solution of the diffusion coefficient testing device provided by the present invention, the air cavity is provided with an air cavity emptying pipeline, the air cavity emptying pipeline is connected to the external space and can be selectively connected to the air cavity.

[0018] As a preferred solution of the diffusion coefficient testing device provided by the present invention, the oil chamber is provided with an oil chamber drain pipeline, the oil chamber drain pipeline is connected to the external space and can be selectively connected to the oil chamber.

[0019] According to another aspect of the present invention, an object is to provide a diffusion coefficient testing method, the diffusion coefficient testing device as described in any one of the above schemes adopts the diffusion coefficient testing method, and the diffusion coefficient testing method comprises:

[0020] S100, adjusting the temperature to the experimental temperature;

[0021] S200, placing a test sample in the sample chamber;

[0022] S300, filling the oil cavity with experimental oil;

[0023] S400, filling the air cavity with experimental gas;

[0024] S500, adjusting the pressures of the oil chamber, the air chamber, and the sample chamber to be equal and equal to the experimental pressure;

[0025] S600, leaving the sample holder still to perform a diffusion experiment;

[0026] S700, sampling and oil-gas separation, and measuring the gas volume and oil volume in the sample;

[0027] S800. Calculate the diffusion coefficient.

[0028] As a preferred solution of the diffusion coefficient testing method provided by the present invention, before step S100, the following steps are also performed:

[0029] The test samples were saturated with oil.

[0030] As a preferred solution of the diffusion coefficient testing method provided by the present invention, step S400 includes:

[0031] S410, increasing the pressure of the sample chamber to make it higher than the initial pressure of the oil chamber;

[0032] S420, raising the pressure of the oil chamber to a test pressure, wherein the test pressure is greater than the pressure of the sample chamber, so that the original accumulated oil in the test sample is discharged through the bypass of the air chamber;

[0033] S430. When the bypass of the air cavity no longer discharges the accumulated oil, the air cavity is filled with experimental gas using a gas injection system.

[0034] Beneficial effects of the present invention:

[0035] The diffusion coefficient testing equipment provided by the present invention includes a sample holder, a gas injection system, an experimental oil injection system, a confining pressure regulating device and an oil-gas separation metering system. The sample holder is provided with an air cavity, a sample cavity and an oil cavity which are connected in sequence, and the sample cavity is used to accommodate a test sample; the gas injection system is selectively connected to the air cavity, and can fill the air cavity with experimental gas and adjust the pressure of the air cavity; the experimental oil injection system is selectively connected to the oil cavity, and can inject experimental oil into the oil cavity and adjust the pressure of the oil cavity; the confining pressure regulating device is connected to the sample cavity and is configured to adjust the pressure in the sample cavity. That is to say, the injection of experimental gas and experimental oil into the sample holder can be realized through the gas injection system and the experimental oil injection system, and the pressure in the air cavity, the sample cavity and the oil cavity can be adjusted by using the above two and the confining pressure regulating device. When the pressure in the air cavity, the sample cavity and the oil cavity is consistent, the influence of convection caused by the pressure gradient can be avoided. The oil-gas separation metering system is selectively connected to the oil chamber, and can receive the experimental oil containing the experimental gas after the experiment, and can perform oil-gas separation on the experimental oil. The diffusion coefficient test equipment can improve the accuracy of the measurement of gas diffusion coefficient in porous media, and accurately describe the effect of diffusion in shale reservoirs on improving recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of a diffusion coefficient testing device provided in an embodiment of the present invention.

[0037] In the figure:

[0038] 100, sample holder; 110, air cavity; 111, air cavity exhaust pipeline; 112, first exhaust valve; 120, sample cavity; 130, oil cavity; 131, oil cavity exhaust pipeline; 132, second exhaust valve;

[0039] 200, gas injection system; 210, gas intermediate container; 211, ventilation pipe; 212, first valve; 220, first pump body; 221, first pipeline; 222, first control valve;

[0040] 300, experimental oil injection system; 310, experimental oil intermediate container; 311, oil pipe; 312, second valve; 320, second pump body; 321, second pipeline; 322, second control valve;

[0041] 400. Confining pressure regulating device;

[0042] 500. Oil and gas separation metering system;

[0043] 600, differential pressure sensor;

[0044] 700. Constant temperature box. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0046] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0048] In the description of this embodiment, the terms "upper", "lower", "right", "left" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0049] Figure 1 Schematic diagram of a diffusion coefficient testing device provided by an embodiment of the present invention is shown. Figure 1 This embodiment provides a diffusion coefficient testing device, which includes a sample holder 100 , a gas injection system 200 , an experimental oil injection system 300 , a confining pressure regulating device 400 , and an oil-gas separation metering system 500 .

[0050] Specifically, the sample holder 100 is provided with an air cavity 110, a sample cavity 120 and an oil cavity 130 which are connected in sequence, and the sample cavity 120 is used to accommodate the test sample. The air cavity 110 and the oil cavity 130 are respectively located on both sides of the sample cavity 120, and the air cavity 110 can accommodate the test gas, and in this embodiment, the test gas is CO2. The oil cavity 130 can accommodate the test oil, and in this embodiment, the test oil is degassed crude oil.

[0051] More specifically, the gas injection system 200 is selectively connected to the gas cavity 110, and can fill the gas cavity 110 with experimental gas and adjust the pressure of the gas cavity 110. Similarly, the experimental oil injection system 300 is selectively connected to the oil cavity 130, and can inject experimental oil into the oil cavity 130 and adjust the pressure of the oil cavity 130. The confining pressure regulating device 400 is connected to the sample cavity 120, and is configured to adjust the pressure in the sample cavity 120. The oil-gas separation metering system 500 is selectively connected to the oil cavity 130, and can receive the experimental oil containing the experimental gas after the experiment, and can perform oil-gas separation on the experimental oil.

[0052] Continue to refer to Figure 1 The gas injection system 200 includes a gas intermediate container 210 and a first pump body 220. The gas intermediate container 210 is selectively connected to the gas cavity 110 through a vent pipe 211, and can accommodate experimental gas. The vent pipe 211 is provided with a first valve 212, and the first pump body 220 is connected to the gas intermediate container 210 through a first pipeline 221. The first pipeline 221 is arranged with a first control valve 222, and the first control valve 222 can control the connection and disconnection between the first pump body 220 and the gas intermediate container 210. By adjusting the opening of the first control valve 222 and using the first pump body 220, the gas pressure in the gas intermediate container 210 can be adjusted to the experimental pressure.

[0053] Furthermore, the experimental oil injection system 300 includes an experimental oil intermediate container 310 and a second pump body 320. The experimental oil intermediate container 310 is selectively connected to the oil chamber 130 through an oil pipe 311, and can accommodate experimental oil. The oil pipe 311 is provided with a second valve 312, and the second pump body 320 is connected to the experimental oil intermediate container 310 through a second pipeline 321. The second pipeline 321 is arranged with a second control valve 322, and the second control valve 322 can control the connection and disconnection between the second pump body 320 and the experimental oil intermediate container 310. By adjusting the opening of the second control valve 322 and using the second pump body 320, the experimental oil in the experimental oil intermediate container 310 can be pumped to the oil chamber 130, and the oil quantity and pressure can be controlled.

[0054] Furthermore, the diffusion coefficient testing device further includes a thermostat 700. The sample holder 100, the gas intermediate container 210 and the experimental oil intermediate container 310 are respectively arranged in the thermostat 700. The thermostat 700 can ensure that the experimental gas and the experimental oil are kept at a certain experimental temperature during the experiment.

[0055] Furthermore, the diffusion coefficient testing device further includes a differential pressure sensor 600, which is connected to the air cavity 110 and the oil cavity 130 and can sense the pressure difference between the air cavity 110 and the oil cavity 130. The differential pressure sensor 600 is a prior art, and its structure and principle are not described in detail in this embodiment.

[0056] Continue to refer to Figure 1 The air cavity 110 is provided with an air cavity drain pipeline 111, which is connected to the external space and can be selectively connected to the air cavity 110. The air cavity drain pipeline 111 is provided with a first drain valve 112. The first drain valve 112 can control the connection and disconnection of the air cavity drain pipeline 111 and the air cavity 110. Similarly, the oil cavity 130 is provided with an oil cavity drain pipeline 131, which is connected to the external space and can be selectively connected to the oil cavity 130. The oil cavity drain pipeline 131 is provided with a second drain valve 132. The second drain valve 132 can control the connection and disconnection of the oil cavity drain pipeline 131 and the oil cavity 130.

[0057] This embodiment also provides a diffusion coefficient testing method. The diffusion coefficient testing device provided in this embodiment adopts the diffusion coefficient testing method, and the diffusion coefficient testing method includes:

[0058] First, the test sample is saturated with oil. The specific steps are as follows: the test sample is cleaned and dried, the length and diameter of the test sample are measured, and then the test sample is saturated with oil under high pressure, and the saturated test sample is placed in the experimental oil for immersion and waits for the next step of treatment. In this embodiment, the test sample is a dense sandstone with a permeability of 0.16md, a length of 2mm and a diameter of 2.5mm.

[0059] Step S100, adjusting the temperature of the thermostat 700 to the experimental temperature. In this embodiment, the experimental temperature is 76°C. At this experimental temperature, the viscosity of the experimental oil is 0.89 mPa·s.

[0060] Specifically, after step S100, the following steps need to be performed: transfer the experimental oil required for the experiment into the experimental oil intermediate container 310, transfer the experimental gas into the gas intermediate container 210 according to the experimental pressure, and check the air tightness. In this embodiment, the experimental pressure is 33Mpa.

[0061] Step S200 , placing a test sample in the sample chamber 120 .

[0062] Step S300 , fill the oil chamber 130 with the experimental oil. During this process, open the second drain valve 132 to discharge the air in the oil chamber 130 through the oil chamber drain pipe 131 , so that the oil chamber 130 is filled with the experimental oil.

[0063] Step S400: Fill the air cavity 110 with the experimental gas.

[0064] Specifically, step S400 includes:

[0065] Step S410 , increasing the pressure of the sample chamber 120 to be higher than the initial pressure of the oil chamber 130 . The pressure value of the sample chamber 120 is 2-3 MPa higher than the initial pressure of the oil chamber 130 .

[0066] Step S420, raising the pressure of the oil chamber 130 to the experimental pressure, which is greater than the pressure of the sample chamber 120, so that the original accumulated oil in the test sample is discharged through the bypass of the gas chamber 110, and at the same time, the first drain valve 112 is opened and purged with experimental gas.

[0067] Step S430: When the bypass of the air cavity 110 no longer discharges the accumulated oil, close the first drain valve 112, and use the gas injection system 200 to fill the air cavity 110 with experimental gas, and increase the pressure of the air cavity 110 to the experimental pressure.

[0068] Step S500: adjust the pressures of the oil chamber 130, the air chamber 110 and the sample chamber 120 to be equal and equal to the experimental pressure. Use the pressure difference sensor 600 to monitor the pressure difference between the air chamber 110 and the oil chamber 130, and make the pressure difference between the air chamber 110 and the oil chamber 130 zero.

[0069] Step S600 , leaving the sample holder 100 still to perform a diffusion experiment.

[0070] Specifically, in step S600, firstly, the first control valve 222, the second control valve 322, the first drain valve 112 and the second drain valve 132 are closed, and the static diffusion experiment is performed according to the experimental setting time. In this embodiment, the experimental setting time is 7 days.

[0071] After the experiment is completed, proceed as follows:

[0072] Step S700: using the oil-gas separation metering system 500 to sample the experimental oil, perform oil-gas separation, and measure the gas volume and oil volume in the sample.

[0073] Step S800, according to the experimental pressure, experimental temperature, the experimental gas volume after separation and the experimental oil volume after separation, the concentration and total volume of the experimental gas in the oil chamber 130 are calculated, and the diffusion coefficient is calculated according to Fick's law in combination with the length and diameter of the test sample.

[0074] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. Diffusion coefficient testing equipment, characterized in that, include: A sample holder (100), wherein the sample holder (100) is provided with an air cavity (110), a sample cavity (120) and an oil cavity (130) which are connected in sequence, and the sample cavity (120) is used to accommodate a test sample; a gas injection system (200), the gas injection system (200) being selectively connected to the gas cavity (110), capable of filling the gas cavity (110) with experimental gas and adjusting the pressure of the gas cavity (110); an experimental oil injection system (300), the experimental oil injection system (300) being selectively connected to the oil chamber (130), capable of injecting experimental oil into the oil chamber (130) and adjusting the pressure of the oil chamber (130); a confining pressure regulating device (400), the confining pressure regulating device (400) being connected to the sample chamber (120) and configured to regulate the pressure in the sample chamber (120); An oil-gas separation metering system (500) is selectively connected to the oil chamber (130), capable of receiving experimental oil containing experimental gas after the experiment, and capable of performing oil-gas separation on the experimental oil.

2. The diffusion coefficient testing device according to claim 1, characterized in that: The gas injection system (200) comprises a gas intermediate container (210) and a first pump body (220); the gas intermediate container (210) is selectively connected to the gas cavity (110) and is capable of containing the experimental gas; the first pump body (220) is connected to the gas intermediate container (210) and is capable of adjusting the gas pressure in the gas intermediate container (210) to the experimental pressure.

3. The diffusion coefficient testing device according to claim 1, characterized in that: The experimental oil injection system (300) comprises an experimental oil intermediate container (310) and a second pump body (320). The experimental oil intermediate container (310) is selectively connected to the oil chamber (130) and is capable of containing the experimental oil. The second pump body (320) is connected to the experimental oil intermediate container (310) and is capable of pumping the experimental oil in the experimental oil intermediate container (310) into the oil chamber (130).

4. The diffusion coefficient testing device according to claim 1, characterized in that: The diffusion coefficient testing device further comprises a differential pressure sensor (600), wherein the differential pressure sensor (600) is connected to the air cavity (110) and the oil cavity (130) and is capable of sensing the differential pressure between the air cavity (110) and the oil cavity (130).

5. The diffusion coefficient testing device according to claim 1, characterized in that: The diffusion coefficient testing device further comprises a constant temperature box (700), and the sample holder (100) is arranged in the constant temperature box (700).

6. The diffusion coefficient testing device according to claim 1, characterized in that: The air cavity (110) is provided with an air cavity emptying pipeline (111), and the air cavity emptying pipeline (111) is connected to the external space and can be selectively connected to the air cavity (110).

7. The diffusion coefficient testing device according to claim 1, characterized in that: The oil chamber (130) is provided with an oil chamber drain pipeline (131), and the oil chamber drain pipeline (131) is connected to the external space and can be selectively connected to the oil chamber (130).

8. A diffusion coefficient test method, characterized in that: The diffusion coefficient testing device according to any one of claims 1 to 7 adopts the diffusion coefficient testing method, and the diffusion coefficient testing method comprises: S100, adjusting the temperature to the experimental temperature; S200, placing a test sample in the sample chamber (120); S300, filling the oil chamber (130) with experimental oil; S400, filling the air cavity (110) with experimental gas; S500, adjusting the pressures of the oil chamber (130), the air chamber (110), and the sample chamber (120) to be equal and equal to the experimental pressure; S600, leaving the sample holder (100) still to perform a diffusion experiment; S700, sampling and oil-gas separation, and measuring the gas volume and oil volume in the sample; S800. Calculate the diffusion coefficient.

9. The diffusion coefficient testing method according to claim 8, characterized in that: Before step S100, the following steps are also performed: The test samples were saturated with oil.

10. The diffusion coefficient testing method according to claim 8, characterized in that: Step S400 includes: S410, increasing the pressure of the sample chamber (120) to be higher than the initial pressure of the oil chamber (130); S420, raising the pressure of the oil chamber (130) to a test pressure, wherein the test pressure is greater than the pressure of the sample chamber (120), so that the original accumulated oil in the test sample is discharged through the bypass of the air chamber (110); S430. When the bypass of the air cavity (110) no longer discharges the accumulated oil, the gas injection system (200) is used to fill the air cavity (110) with experimental gas.

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