Production layer injection capacity testing device and method

Abstract

The invention relates to the technical field of petroleum and natural gas underground gas injection construction, in particular to a production layer injection capacity testing device and method.The production layer injection capacity testing device comprises a gas source, a gas pressurization system, a high-pressure storage tank, a buffer tank, a Coriolis flowmeter, a triaxial core holder, a pressure release valve and a sampling device which are sequentially communicated; the device further comprises a constant-speed constant-pressure pump, a temperature control system, a ground stress simulation system, a back pressure system and a pressure monitoring system, and the pressure monitoring system comprises a first pressure gauge, a second pressure gauge, a third pressure gauge, a fourth pressure gauge and a pressure sensor. The injection capacity of the rock core can be determined through data measured by the third pressure gauge, the pressure sensor and the Coriolis flow meter, the injection process is simulated by changing parameters, the injection capacity of different production layers can be obtained, and the high-pressure storage tank can guarantee sufficient high-pressure gas in the experiment process; the buffer tank can prevent the fluctuation of the gas injection pressure in the experiment process from being too large, and the completion quality and accuracy of the experiment are improved.

Description

Technical Field

[0001] The invention relates to the technical field of gas injection construction in oil and natural gas wells, and more specifically, to a device and method for testing the injection capacity of a production layer. Background Art

[0002] How to ensure energy security and effectively control carbon emissions is a top priority for the development of the energy industry. After years of research and practice, CO2 oil and gas flooding and geological storage can not only effectively improve oil recovery, but also achieve in-situ geological storage of CO2 in reservoirs. Among them, the study of the injection capacity of the production layer can provide a scientific basis for the next step of implementing the CO2 geological storage project. In order to effectively evaluate the injection capacity of the production layer, it is particularly important to develop an efficient testing device and method. However, in the current research and development process, there is a problem that it is difficult to fully simulate the actual gas injection development at the laboratory scale.

[0003] The prior art discloses a CO2 displacement simulation test method, and the test device used includes: a model system for containing rock samples and applying pressure pulses, a gas control system for providing test gas to the model system, a temperature control system for controlling the temperature of the model system and keeping it constant, a triaxial loading system for applying confining pressure and axial pressure to the core holder in the model system, a vacuum system for vacuuming the test device, a gas sample collection system for collecting and detecting gas components after the test, and an electrical control and monitoring system. In this scheme, it is necessary to collect pressure data in the upstream reference cylinder, the downstream reference cylinder and the core holder to observe whether the pressure is stable; if the pressure is stable, the gas in the device is released and the confining pressure is unloaded at the same time. If the pressure is not stable, repeat this step. In order to ensure the accuracy of the experiment, the experimental process is cumbersome; and if the pressure in the upstream reference cylinder drops significantly during the test, that is, exceeds 5% of the test design inlet pressure, CO2 is added to the upstream reference cylinder in time, and the pressure fluctuates greatly, making it more difficult to ensure the accuracy of the experiment. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art that it is difficult to ensure the accuracy of the experiment, and to provide a production layer injection capacity testing device and method to ensure that there is sufficient high-pressure gas during the experiment, avoid the reduction of experimental pressure due to insufficient gas volume, and at the same time reduce pressure fluctuations, thereby improving the completion quality and accuracy of the experiment.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] Provided is a production layer injection capacity testing device, comprising a gas source, a gas pressurization system, a high-pressure storage tank, a buffer tank, a Coriolis flowmeter, a three-axis core holder, a pressure relief valve and a sampling device connected in sequence, and also comprising a constant speed and pressure pump, a temperature control system, a ground stress simulation system, a back pressure system and a pressure monitoring system, wherein the constant speed and pressure pump is connected to the buffer tank, the temperature control system and the three-axis core holder are connected to a temperature sensor via a signal line, the ground stress simulation system is connected to the three-axis core holder, and the pressure relief valve is arranged between the three-axis core holder and the back pressure monitoring system. The pressure monitoring system comprises a first pressure gauge, a second pressure gauge, a third pressure gauge, a fourth pressure gauge and a pressure sensor, the first pressure gauge is arranged between the gas source and the gas pressurization system, the second pressure gauge is arranged between the gas pressurization system and the high-pressure storage tank, the third pressure gauge is arranged between the Coriolis flowmeter and the triaxial core holder, the fourth pressure gauge is arranged between the geostress simulation system and the triaxial core holder, and the pressure sensor is arranged between the triaxial core holder and the back pressure system.

[0007] The production layer injection capacity testing device of the present invention is as follows: during the experiment, the core is loaded into the three-axis core holder, and the gas source can provide simulated multi-component CO2 experimental gas, and the gas booster system and the constant speed and pressure pump can transport the experimental gas to the three-axis core holder; the core in the three-axis core holder can simulate the injection channel of the production layer; the ground stress is simulated by the ground stress simulation system, and the confining pressure of the three-axis core holder is accurately adjusted by the fourth pressure gauge; the formation pressure is simulated by the back pressure system, and the back pressure can be accurately controlled by the pressure sensor; the formation temperature is simulated by the temperature control system, and the temperature of the three-axis core holder is monitored in real time by the temperature sensor; thereby simulating the gas injection process; if the outlet pressure of the three-axis core holder is greater than the back pressure, the pressure relief valve is pushed open, the gas flows into the sampling device, and the liquid therein is discharged, thereby ensuring the safety of the experiment, and the volume of the discharged liquid is the volume of the gas outflow; in the simulated gas injection process, the third pressure gauge, the pressure The sensor and the Coriolis flowmeter can measure the pressure at both ends of the three-axis core holder and the gas flow through the three-axis core holder. The injection capacity of the core can be determined based on the measured data. By changing the core permeability, injection gas composition, formation pressure, formation temperature, injection pressure difference and other parameters to simulate the injection process, different production layer injection capacities can be obtained, thereby obtaining the changing law of the production layer injection capacity; wherein, the gas boosting system boosts the experimental gas provided by the gas source, and uses the first pressure gauge to monitor the pressure of the gas source in real time. The boosted gas enters the high-pressure storage tank, and the second pressure gauge is used to monitor the pressure of the gas in the high-pressure storage tank, and then flows into the buffer tank, and the injection gas is displaced by a constant speed and constant pressure pump. The high-pressure storage tank can ensure that there is sufficient high-pressure gas during the experiment, avoid the reduction of the experimental pressure due to insufficient gas volume, and improve the completion quality of the experiment. The buffer tank can avoid excessive fluctuations in the gas injection pressure during the experiment, thereby reducing experimental errors.

[0008] Furthermore, a first control valve is provided between the first pressure gauge and the gas pressurization system, a second control valve is provided between the high-pressure storage tank and the buffer tank, a third control valve is provided between the buffer tank and the Coriolis flowmeter, and a fourth control valve is provided between the three-axis core clamp and the pressure relief valve.

[0009] Furthermore, a first vent valve is provided between the high-pressure storage tank and the second control valve, a second vent valve is provided between the buffer tank and the third control valve, and a third vent valve is provided between the fourth control valve and the pressure relief valve.

[0010] Furthermore, one end of the geostress simulation system is connected to the first hydraulic oil storage tank through a fifth control valve, and the other end of the geostress simulation system is connected to the fourth pressure gauge through a sixth control valve.

[0011] Furthermore, one end of the back pressure system is connected to the second hydraulic oil storage tank through a seventh control valve, and the other end of the back pressure system is connected to a pressure sensor through an eighth control valve.

[0012] Furthermore, the gas source is provided with a safety valve.

[0013] Furthermore, the constant speed and constant pressure pump is connected to a water storage container.

[0014] Furthermore, it also includes a computer device, and the Coriolis flowmeter, the third pressure gauge, the pressure sensor, the temperature control system, and the constant speed and pressure pump are respectively connected to the computer device for communication.

[0015] The present invention also provides a method for testing the injection capacity of a production layer, comprising the following steps:

[0016] S1: Collect core parameters and source gas parameters, connect the above-mentioned production layer injection capacity test device, and check the sealing of the pipeline;

[0017] S2: The triaxial core holder is heated to a specified temperature through the temperature control system, the confining pressure is increased to a specified confining pressure through the in-situ stress simulation system, and the back pressure is increased to a specified back pressure through the back pressure system;

[0018] S3: Inflate the gas boosting system through the gas source, pressurize the gas to the high-pressure storage tank through the gas boosting system, and inject high-pressure gas into the buffer tank;

[0019] S4: Use a constant speed and constant pressure pump to displace the gas in the buffer tank into the core to simulate the gas injection process. After the pressure of the constant speed and constant pressure pump is stable, record the experimental data.

[0020] S5: Turn off the temperature control system, wait for the triaxial core holder to cool to room temperature, remove the injection pipeline, unload the confining pressure and back pressure, vent the system gas to the outside, take out the rock sample, and the experiment ends;

[0021] S6: Calculate the core injection index to characterize the injection capacity of the production layer.

[0022] The production layer injection capacity testing method of the present invention can simulate the formation environment to perform gas injection simulation, pressurize and transport the experimental gas through the gas source and the gas booster system, use the high-pressure storage tank to ensure that there is sufficient experimental gas, and use the buffer tank to inject gas to reduce gas injection fluctuations, improve the quality of experimental completion, and reduce experimental errors; by changing the core permeability, injection gas components, formation pressure, formation temperature, injection pressure difference and other parameters to simulate the injection process, different production layer injection capacities can be obtained, thereby obtaining the changing law of the production layer injection capacity.

[0023] Preferably, in step S6, the injection capacity of the production layer is evaluated by using an injection index, which is the fluid injection volume per unit cross section and unit pressure difference. The injection index is calculated by recording the injection velocity, cross-sectional area and injection pressure difference, and the calculation formula is:

[0024]

[0025] In the formula, I represents the injection index; Q represents the injection velocity; A represents the cross-sectional area; ΔP represents the injection pressure difference,

[0026] Compared with the prior art, the device and method for testing the injection capacity of production layers of the present invention have the following beneficial effects:

[0027] 1. During the simulated gas injection process, the pressure at both ends of the triaxial core holder and the gas flow through the triaxial core holder can be measured through the third pressure gauge, pressure sensor and Coriolis flowmeter to calculate the injection capacity of the production layer;

[0028] 2. The high-pressure storage tank can ensure sufficient high-pressure experimental gas, avoid the reduction of experimental pressure due to insufficient gas volume, and improve the completion quality of the experiment;

[0029] 3. The buffer tank can avoid excessive fluctuations in gas injection pressure during the experiment, reduce experimental errors and improve experimental accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic structural diagram of a device for testing the injection capacity of a production layer in a first embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the structure of a production layer injection capacity testing device according to Embodiment 2 of the present invention;

[0032] Figure 3 This is a flow chart of a method for testing the injection capacity of a production layer in Embodiment 3 of the present invention.

[0033] In the attached figure: 1-gas source; 2-gas boosting system; 3-high-pressure storage tank; 4-buffer tank; 5-constant speed and constant pressure pump; 6-Coriolis flowmeter; 7-three-axis core clamp; 8-ground stress simulation system; 9-back pressure system; 10-temperature control system; 11-temperature sensor; 12-pressure relief valve; 13-sampling device; 14-first pressure gauge; 15-second pressure gauge; 16-third pressure gauge; 17-fourth pressure gauge; 18-pressure sensor; 19-first control valve; 20-second control valve; 21-third control valve; 22-fourth control valve; 23-fifth control valve; 24-sixth control valve; 25-seventh control valve; 26-eighth control valve; 27-first vent valve; 28-second vent valve; 29-third vent valve; 30-water storage container; 31-first hydraulic oil storage tank; 32-second hydraulic oil storage tank; 33-computer equipment. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0035] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] Embodiment 1

[0037] This embodiment is the first embodiment of the production layer injection capacity testing device. Figure 1As shown, it includes a gas source 1, a gas boosting system 2, a high-pressure storage tank 3, a buffer tank 4, a Coriolis flowmeter 6, a three-axis core holder 7, a pressure relief valve 12 and a sampling device 13 connected in sequence, and also includes a constant speed and pressure pump 5, a temperature control system 10, a ground stress simulation system 8, a back pressure system 9 and a pressure monitoring system. The constant speed and pressure pump 5 is connected to the buffer tank 4, the temperature control system 10 and the three-axis core holder 7 are connected to a temperature sensor 11 through a signal line, the ground stress simulation system 8 is connected to the three-axis core holder 7, and the pressure relief valve 12 is provided between the three-axis core holder 7 and the back pressure The pressure monitoring system includes a first pressure gauge 14, a second pressure gauge 15, a third pressure gauge 16, a fourth pressure gauge 17 and a pressure sensor 18. The first pressure gauge 14 is arranged between the gas source 1 and the gas boosting system 2, the second pressure gauge 15 is arranged between the gas boosting system 2 and the high-pressure storage tank 3, the third pressure gauge 16 is arranged between the Coriolis flowmeter 6 and the triaxial core holder 7, the fourth pressure gauge 17 is arranged between the geostress simulation system 8 and the triaxial core holder 7, and the pressure sensor 18 is arranged between the triaxial core holder 7 and the back pressure system 9.

[0038] The above-mentioned production layer injection capacity test device, during the experiment, the core is loaded into the triaxial core holder 7, the gas source 1 can provide simulated multi-component CO2 experimental gas, the gas booster system 2 and the constant speed and constant pressure pump 5 can transport the experimental gas to the triaxial core holder 7; the core in the triaxial core holder 7 can simulate the injection channel of the production layer; the ground stress is simulated by the ground stress simulation system 8, and the confining pressure of the triaxial core holder 7 is accurately controlled by the fourth pressure gauge 17; the formation pressure is simulated by the back pressure system 9, and the back pressure can be accurately controlled by the pressure sensor 18; the formation temperature is simulated by the temperature control system 10, and the temperature of the triaxial core holder 7 is monitored in real time by the temperature sensor 11; thereby simulating the gas injection process; if the outlet pressure of the triaxial core holder 7 is greater than the back pressure, the pressure relief valve 12 is opened, the gas flows into the sampling device 13, and the liquid therein is discharged, thereby ensuring the safety of the experiment, and the volume of the discharged liquid is the volume of the gas outflow; in the simulated gas injection process, the third pressure gauge 16 is used , the pressure sensor 18 and the Coriolis flowmeter 6 can measure the pressure at both ends of the three-axis core holder 7 and the gas flow through the three-axis core holder 7, and the injection capacity of the core can be determined based on the measured data. By changing the core permeability, injection gas composition, formation pressure, formation temperature, injection pressure difference and other parameters to simulate the injection process, different production layer injection capacities can be obtained, thereby obtaining the changing law of the production layer injection capacity; wherein, the gas boosting system 2 boosts the experimental gas provided by the gas source 1, and uses the first pressure gauge 14 to monitor the pressure of the gas source 1 in real time. The boosted gas enters the high-pressure storage tank 3, and the second pressure gauge 15 is used to monitor the pressure of the gas in the high-pressure storage tank 3, and then flows into the buffer tank 4, and the injection gas is displaced by the constant speed and constant pressure pump 5. The high-pressure storage tank 3 can ensure that there is sufficient high-pressure gas during the experiment, avoid the reduction of the experimental pressure due to insufficient gas volume, and improve the completion quality of the experiment. The buffer tank 4 can avoid excessive fluctuations in the gas injection pressure during the experiment, thereby reducing the experimental error.

[0039] like Figure 1 As shown, a first control valve 19 is provided between the first pressure gauge 14 and the gas boosting system 2, a second control valve 20 is provided between the high-pressure storage tank 3 and the buffer tank 4, a third control valve 21 is provided between the buffer tank 4 and the Coriolis flowmeter 6, and a fourth control valve 22 is provided between the triaxial core holder 7 and the pressure relief valve 12. The flow state of the gas can be regulated by regulating the opening and closing of the first control valve 19, the second control valve 20, the third control valve 21 and the fourth control valve 22 respectively. Specifically, the first control valve 19 can control the flow of gas from the gas source 1 to the gas boosting system 2, the second control valve 20 can control the flow of gas from the high-pressure storage tank 3 to the buffer tank 4, the third control valve 21 can control the flow of gas from the buffer tank 4 to the triaxial core holder 7, and the fourth control valve 22 can control the flow of gas from the triaxial core holder 7 to the sampling device 13.

[0040] like Figure 1As shown, a first vent valve 27 is provided between the high-pressure storage tank 3 and the second control valve 20, a second vent valve 28 is provided between the buffer tank 4 and the third control valve 21, and a third vent valve 29 is provided between the fourth control valve 22 and the pressure relief valve 12. The first vent valve 27 is used to discharge the residual gas in the high-pressure storage tank 3 and the pipeline after the experiment is completed, the second vent valve 28 is used to discharge the residual gas in the buffer tank 4 and the pipeline after the experiment is completed, and the third vent valve 29 is used to discharge the residual gas in the triaxial core holder 7 and the pipeline.

[0041] The core holder is divided into an inner ring and an outer ring by a rubber seal; the inner ring is used to place core samples and simulate the injection channel of the production layer, and the inner ring is an independent void environment; the outer ring is used to inject hydraulic oil, and the confining pressure is applied through the ground stress simulation system 8 to simulate the average absolute ground stress, and the temperature of the hydraulic oil is controlled by the temperature control system 10 to set the experimental temperature. The hydraulic oil heating method can ensure that the triaxial core holder 7 is heated evenly, thereby ensuring the accuracy of the experiment, and the hydraulic oil has a good anti-corrosion effect on the triaxial core holder 7.

[0042] like Figure 1 As shown, one end of the ground stress simulation system 8 is connected to the first hydraulic oil storage tank 31 through the fifth control valve 23, and the other end of the ground stress simulation system 8 is connected to the fourth pressure gauge 17 through the sixth control valve 24; one end of the back pressure system 9 is connected to the second hydraulic oil storage tank 32 through the seventh control valve 25, and the other end of the back pressure system 9 is connected to the pressure sensor 18 through the eighth control valve 26. The flow of hydraulic oil is controlled by the fifth control valve 23, the sixth control valve 24, the seventh control valve 25 and the eighth control valve 26, and the pressure is monitored by the fourth pressure gauge 17 and the pressure sensor 18 respectively.

[0043] Gas source 1 is equipped with a safety valve to ensure experimental safety.

[0044] Gas source 1 uses a standard gas cylinder. Both single-component gas and multi-component gas are configured standard gases to ensure the standard of gas source 1 and avoid affecting the experiment due to problems with gas component content.

[0045] The gas boosting system 2 is equipped with a gas booster, an air compressor, an air dryer, a boosting controller, a gas concentration monitoring and alarm system, and a gas pressure reducer. It can accurately pressurize the gas during the experiment, monitor the experimental gas concentration in the air at any time, improve the accuracy of the experiment, and ensure the safety of the experiment.

[0046] like Figure 1 As shown, the constant speed and constant pressure pump 5 is connected to a water storage container 30 for providing water required for displacing gas.

[0047] The constant speed and constant pressure pump 5 is provided with a first control panel, which can adjust the injection parameters in real time during the experiment; the third pressure gauge 16 can form a control loop with the constant speed and constant pressure pump 5 to realize the control of the working pressure. If the pressure measured by the third pressure gauge 16 is greater than the set working pressure, the pressure can be adjusted by the constant speed and constant pressure pump 5 until the pressure measured by the third pressure gauge 16 is no greater than the set working pressure.

[0048] The temperature control system 10 is provided with a second control panel, which can adjust the temperature of the triaxial core holder 7 for simulating different formation temperatures.

[0049] Specifically, the maximum working pressure of the gas boosting system 2 is set to 60MPa; the volume of the high-pressure storage tank 3 is 6L; the volume of the buffer tank 4 is 3L, and the design pressure is 100MPa, to ensure that the experiment has sufficient high-pressure gas; the design size of the core sample of the triaxial core holder 7 is 1 inch, the length of the core sample is 50mm~100mm, the design pressure is 20MPa, the design temperature is 100℃, and the ground stress simulation system 8 simulates a maximum ground stress of 60MPa.

[0050] The production layer injection capacity test device of this embodiment is used to simulate the gas injection process of an offshore gas field. The permeability of the core sample is 1mD, the gas source 1 is a multi-component gas containing CO2, N2, and CH4, the injection pressure of the simulated reservoir is 15.2MPa, the temperature of the simulated reservoir is 60, and the simulated reservoir pressure is 15MPa. The simulation experiment found that when supercritical injection is performed, the higher the CO2 content in the component, the lower the viscosity of the multi-component CO2 fluid, the stronger the fluidity of the fluid, and the stronger the production layer injection capacity. The experimental results provide good support for the optimization of the gas injection process of the offshore gas field.

[0051] Embodiment 2

[0052] This embodiment is a second embodiment of a production layer injection capacity testing device. This embodiment is similar to the first embodiment, except that: Figure 2As shown, it also includes a computer device 33, a Coriolis flowmeter 6, a third pressure gauge 16, a pressure sensor 18, a temperature control system 10, and a constant speed and pressure pump 5, which are respectively connected to the computer device 33 for communication. Specifically, the pressure sensor 18 monitors the pressure at the outlet of the three-axis core holder 7, and after converting it into a standard signal through a pressure transmitter, the standard signal is sent to the computer device 33; the Coriolis flowmeter 6 has a flow monitoring capability, and can output a gas flow under standard conditions, such as detecting the gas flow through the Coriolis flowmeter 6, converting it into a gas flow under standard conditions through a flow transmitter, and sending the gas flow to the computer device 33; the temperature sensor 11 detects the temperature of the liquid in the annulus of the three-axis core holder 7, and after converting it into a standard signal through a temperature transmitter, the standard signal is sent to the computer device 33, and the computer device 33 automatically calculates the injection capacity of the production layer.

[0053] In this embodiment, the constant speed and constant pressure pump 5 can be remotely controlled through the computer device 33, the temperature control system 10 can be remotely controlled, the pressure and flow changes can be monitored in real time, and the pressure and flow change curves can be obtained, which greatly improves the experimental efficiency and safety and reduces the experimental risks.

[0054] Embodiment 3

[0055] This embodiment is the first embodiment of the method for testing the injection capacity of a production layer. Figure 3 As shown, the following steps are included:

[0056] S1: Collect core parameters and gas parameters of gas source 1, connect the production layer injection capacity testing device of embodiment 1 or embodiment 2, and check the sealing of the pipeline;

[0057] S2: heating the triaxial core holder 7 to a specified temperature through the temperature control system 10, increasing the confining pressure to a specified confining pressure through the in-situ stress simulation system 8, and increasing the back pressure to a specified back pressure through the back pressure system 9;

[0058] S3: Inflate the gas boosting system 2 through the gas source 1, boost the gas to the high-pressure storage tank 3 through the gas boosting system 2, and inject the high-pressure gas into the buffer tank 4;

[0059] S4: The gas in the buffer tank 4 is driven into the core by the constant speed and constant pressure pump 5 to simulate the gas injection process. After the pressure of the constant speed and constant pressure pump 5 is stabilized, the experimental data is recorded;

[0060] S5: Turn off the temperature control system 10, wait for the triaxial core holder 7 to cool to room temperature, remove the injection pipeline, unload the confining pressure and back pressure, vent the system gas to the outside, take out the rock sample, and the experiment ends;

[0061] S6: Calculate the core injection index to characterize the injection capacity of the production layer.

[0062] The above-mentioned production layer injection capacity test method can simulate the formation environment to perform gas injection simulation, and the experimental gas is pressurized and transported through the gas source 1 and the gas booster system 2. The high-pressure storage tank 3 can ensure that there is sufficient experimental gas, and the buffer tank 4 is used to inject gas to reduce gas injection fluctuations, improve the quality of experimental completion, and reduce experimental errors. By changing the core permeability, injection gas composition, formation pressure, formation temperature, injection pressure difference and other parameters to simulate the injection process, different production layer injection capacities can be obtained, thereby obtaining the changing law of the production layer injection capacity.

[0063] In step S1, before the gas injection simulation process is carried out, experimental design and sample preparation can be carried out. The experimental design includes designing injection conditions for the production layer injection capacity test, core rotation, ground stress conditions, gas source 1 selection, parallel experiments, and the purpose of production layer injection capacity analysis according to the characteristics of the offshore gas reservoir.

[0064] In step S2, in order to prevent cross-flow during the experiment, the confining pressure is generally 6 MPa greater than the injection pressure.

[0065] The specific process of step S3 is: open the valve of the gas cylinder of gas source 1, inflate 3MPa~5MPa into the gas boosting system 2, turn on the gas concentration monitoring and alarm system, adjust the boosting pointer to the design value, slowly open the boosting valve switch, and after the boosting is completed, inject the gas in the high-pressure storage tank 3 into the buffer tank 4.

[0066] The specific process of step S4 is: turn on the injection switch of the constant speed and constant pressure pump 5 to displace the gas in the buffer tank 4 into the core. After the pressure of the constant speed and constant pressure pump 5 is stable, read the data of the third pressure gauge 16 and record the data of the pressure sensor 18 and the Coriolis flowmeter 6.

[0067] In step S6, the injection capacity of the production layer is evaluated by the injection index, which is the fluid injection volume per unit cross section and unit pressure difference. The larger the injection index, the better the injection performance, and vice versa. The injection index is calculated by recording the injection speed, cross-sectional area and injection pressure difference, and the calculation formula is:

[0068]

[0069] Where I represents the injection index; Q represents the injection velocity; A represents the cross-sectional area; and ΔP represents the injection pressure difference.

[0070] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] 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, other different forms of changes or modifications can be made based on the above description. 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. A production layer injection capacity testing device, characterized in that: The invention comprises a gas source (1), a gas pressurizing system (2), a high-pressure storage tank (3), a buffer tank (4), a Coriolis flowmeter (6), a triaxial core holder (7), a pressure relief valve (12) and a sampling device (13) which are connected in sequence, and also comprises a constant speed and pressure pump (5), a temperature control system (10), a geostress simulation system (8), a back pressure system (9) and a pressure monitoring system, wherein the constant speed and pressure pump (5) is connected to the buffer tank (4), the temperature control system (10) and the triaxial core holder (7) are connected to a temperature sensor (11) via a signal line, the geostress simulation system (8) is connected to the triaxial core holder (7), and the pressure relief valve (12) is arranged between the triaxial core holder (7) and the back pressure system (9). The pressure monitoring system comprises a first pressure gauge (14), a second pressure gauge (15), a third pressure gauge (16), a fourth pressure gauge (17) and a pressure sensor (18); the first pressure gauge (14) is arranged between the gas source (1) and the gas pressurizing system (2); the second pressure gauge (15) is arranged between the gas pressurizing system (2) and the high-pressure storage tank (3); the third pressure gauge (16) is arranged between the Coriolis flowmeter (6) and the triaxial core holder (7); the fourth pressure gauge (17) is arranged between the geostress simulation system (8) and the triaxial core holder (7); and the pressure sensor (18) is arranged between the triaxial core holder (7) and the back pressure system (9).

2. The production layer injection capacity testing device according to claim 1, characterized in that: A first control valve (19) is provided between the first pressure gauge (14) and the gas boosting system (2), a second control valve (20) is provided between the high-pressure storage tank (3) and the buffer tank (4), a third control valve (21) is provided between the buffer tank (4) and the Coriolis flowmeter (6), and a fourth control valve (22) is provided between the three-axis core holder (7) and the pressure relief valve (12).

3. The production layer injection capacity testing device according to claim 2, characterized in that: A first vent valve (27) is provided between the high-pressure storage tank (3) and the second control valve (20), a second vent valve (28) is provided between the buffer tank (4) and the third control valve (21), and a third vent valve (29) is provided between the fourth control valve (22) and the pressure relief valve (12).

4. The production layer injection capacity testing device according to claim 1, characterized in that: One end of the geostress simulation system (8) is connected to the first hydraulic oil storage tank (31) via a fifth control valve (23), and the other end of the geostress simulation system (8) is connected to the fourth pressure gauge (17) via a sixth control valve (24).

5. The production layer injection capacity testing device according to claim 1, characterized in that: One end of the back pressure system (9) is connected to the second hydraulic oil storage tank (32) through the seventh control valve (25), and the other end of the back pressure system (9) is connected to the pressure sensor (18) through the eighth control valve (26).

6. The production layer injection capacity testing device according to claim 1, characterized in that: The gas source (1) is provided with a safety valve.

7. The production layer injection capacity testing device according to claim 1, characterized in that: The constant speed and constant pressure pump (5) is connected to a water storage container (30).

8. The production layer injection capacity testing device according to claim 1, characterized in that: It also includes a computer device (33), and the Coriolis flowmeter (6), the third pressure gauge (16), the pressure sensor (18), the temperature control system (10), and the constant speed and constant pressure pump (5) are respectively connected to the computer device (33) for communication.

9. A method for testing the injection capacity of a production layer, characterized in that: The following steps are involved: S1: Collect core parameters and gas parameters of the gas source (1), connect the production layer injection capacity testing device according to any one of claims 1 to 8, and check the sealing of the pipeline; S2: heating the triaxial core holder (7) to a specified temperature through a temperature control system (10), applying confining pressure to a specified confining pressure through a geostress simulation system (8), and applying back pressure to a specified back pressure through a back pressure system (9); S3: Inflate the gas boosting system (2) through the gas source (1), boost the gas pressure to the high-pressure storage tank (3) through the gas boosting system (2), and inject the high-pressure gas into the buffer tank (4); S4: The gas in the buffer tank (4) is driven into the core by a constant speed and constant pressure pump (5) to simulate the gas injection process, and after the pressure of the constant speed and constant pressure pump (5) is stabilized, the experimental data is recorded; S5: Turn off the temperature control system (10), wait for the triaxial core holder (7) to cool to room temperature, remove the injection pipeline, unload the confining pressure and back pressure, vent the system gas to the outside, take out the rock sample, and end the experiment; S6: Calculate the core injection index to characterize the injection capacity of the production layer.

10. The method for testing the injection capacity of a production layer according to claim 9, characterized in that: In step S6, the injection capacity of the production layer is evaluated by using the injection index, which is the fluid injection volume per unit cross section and unit pressure difference. The injection index is calculated by recording the injection speed, cross-sectional area and injection pressure difference. The calculation formula is: Where I represents the injection index; Q represents the injection velocity; A represents the cross-sectional area; and ΔP represents the injection pressure difference.

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