A method to quickly set the experimental pressure

Abstract

The invention relates to a method for quickly setting an experimental pressure, comprising a piston-type high-pressure container, an injection pressure gauge, and a capillary model; the top of the piston-type high-pressure container is connected to the inlet end of the capillary model via a pipeline, and the pipeline connecting the piston-type high-pressure container and the capillary model is provided with an injection pressure gauge and an injection valve; the lower part of the piston-type high-pressure container is connected to an electric pump; one end of a four-way valve is connected to a back-pressure pressure gauge, one end is connected to a back-pressure source container via a pipeline, one end is connected to a manual pump via a pipeline, and one end is connected to a pressure relief valve; a branch pipeline is connected to the pipeline between the four-way valve and the manual pump, one end of the branch pipeline is connected to the pipeline between the four-way valve and the manual pump, and the other end is connected to a nitrogen bottle; a back-pressure source inlet valve is provided on the pipeline between the four-way valve and the back-pressure source container, and a gas pressure reducing valve is provided on the branch pipeline; the invention has the characteristics of convenience, rapidity, safety and reliability.

Description

Technical Field

[0001] The present invention relates to a method for quickly setting experimental pressure, in particular to a method for quickly setting experimental pressure used in the petroleum industry to measure the minimum miscible pressure between formation crude oil and injected gas by a capillary method, and belongs to the technical field of conventional oil and gas experiments. Background Art

[0002] Most of my country's oil fields are continental deposits with serious heterogeneity. For such oil fields, the water drive recovery rate is very low, only about 33%, while the comprehensive water content has reached 81%, and some even reach more than 90%. Therefore, it is urgent to develop enhanced oil recovery technology. The basic principle of CO2 drive to enhance oil recovery is to increase production capacity by dissolving CO2 in crude oil to expand the volume of crude oil, reduce crude oil viscosity and interfacial tension to increase fluid mobility, and increase oil recovery by one or more contact miscible phases between CO2 and formation crude oil. Both theory and practice have proved that continuous CO2 injection or CO2 injection plug water and gas alternating drive is another important way to enhance oil recovery after water drive, polymer drive, and steam drive, and is also one of the means of permanent CO2 storage. Therefore, the minimum phase miscibility pressure is an important parameter for selecting reservoir injection schemes. At present, there are two main methods for determining the minimum phase pressure: laboratory determination and theoretical calculation. Laboratory determination methods can be divided into capillary test method, bubble riser method, interfacial tension disappearance method, etc., while theoretical calculations can be divided into empirical formula prediction method, numerical simulation method, etc. Among many experimental measurement methods, the capillary test method is considered to be the most reliable and classic experimental method, because the capillary model provides an ideal porous medium for the formation crude oil and injected gas, which is evenly filled with compacted quartz sand or glass beads of a certain particle size, and eliminates the adverse factors such as mobility ratio, gravity differentiation, and heterogeneity to the greatest extent. This is a condition that other measurement methods cannot have. Under the formation temperature and a certain pressure, the injected fluid and crude oil undergo multiple contacts between the two phases, and sufficient interphase mass transfer such as evaporation or condensation occurs. With the continuous increase of the experimental pressure, the interface between the two phases disappears to form a miscible displacement, and the recovery degree is greatly improved. There are more than three experimental pressure points in the miscible section and the immiscible section to measure their different recovery degrees. The successive approximation method is used to find the lowest miscible pressure value by curve fitting, that is, the pressure value corresponding to the inflection point of the recovery degree. Each pressure point in the experimental design is achieved by adjusting the back pressure valve pressure with a manual pump. The current operating method is that after measuring a certain pressure point at the formation temperature, the inlet valve of the capillary model is slowly opened to empty and relieve the pressure. At the same time, the pressure of the back pressure source container connected to the back pressure valve is slowly reduced by a manual pump to ensure that the inlet and outlet pressures of the capillary model are lower than the back pressure. However, the pressure difference should not exceed 5.0 MPa. If this pressure difference is exceeded or the outlet pressure is higher than the back pressure, the sealing diaphragm of the back pressure valve will deform upward or even be punctured, forming fluid communication between the upper and lower diaphragms, causing equipment damage and even threatening the personal safety of operators. After the pressure of the entire system drops to normal pressure, a high-pressure piston container filled with a cleaning solvent (a mixture of petroleum ether and anhydrous ethanol) is connected to the inlet of the capillary model, and a high-pressure displacement pump is used to clean it at a certain flow rate.Set a new pressure point, continue to displace the cleaning solvent, first pre-fill a certain pressure of nitrogen (2-3MPa) into the back pressure source container connected to the back pressure valve, and then inject liquid (distilled water) into it with a manual pump, and gradually increase the back pressure to gradually increase the pressure of the entire system to the experimental pressure. During the entire pressure building process, the back pressure should always be kept higher than the injection pressure by 2-3 MPa, and the outlet of the capillary model should always keep the liquid out until the entire system reaches the new experimental pressure. During the entire pressure building and pressure relief operation process, you should be careful to avoid large pressure fluctuations to avoid damage to the equipment and threaten the personal safety of the operator. In addition, during the pressure building and pressure relief process, the high-pressure piston container at the inlet end of the capillary tube and the back pressure source container connected to the back pressure valve are both part of the entire system. Their volume is much larger than the pore volume of the capillary model. In order to achieve the effect of easier stabilization of the back pressure, the back pressure source container is pre-filled with a certain pressure of nitrogen. The gas compression is much greater than that of the liquid and is not sensitive to pressure, which adds extra difficulty to the pressure building and pressure relief operations, prolongs the operation time, and affects the progress of the experiment. Summary of the invention

[0003] The present invention aims to provide a method for quickly setting the test pressure in view of the above-mentioned shortcomings.

[0004] The object of the present invention is achieved as follows: a device for quickly setting the experimental pressure, in the capillary experiment process, a four-way valve and components are installed between the back pressure source container and the manual pump and the nitrogen bottle. The capillary experiment process includes a piston-type high-pressure container, an injection pressure gauge, and a capillary model; the top of the piston-type high-pressure container is connected to the inlet end of the capillary model through a pipeline, and the pipeline connecting the piston-type high-pressure container and the capillary model is installed with an injection pressure gauge and an injection valve; the lower part of the piston-type high-pressure container is connected to an electric pump;

[0005] Its characteristics are: it is also equipped with a four-way valve, a manual pump, a nitrogen bottle, a back pressure source container, a back pressure valve, and a high pressure window;

[0006] One end of the four-way valve is connected to a back pressure gauge, one end is connected to a back pressure source container via a pipeline, one end is connected to a manual pump via a pipeline, and one end is connected to a pressure relief valve; a branch pipeline is connected to the pipeline between the four-way valve and the manual pump, one end of the branch pipeline is connected to the pipeline between the four-way valve and the manual pump, and the other end is connected to a nitrogen bottle; a back pressure source inlet valve is installed on the pipeline between the four-way valve and the back pressure source container, and a gas pressure reducing valve is installed on the branch pipeline;

[0007] The four-way valve is equipped with an upper valve and a lower valve, and the upper valve controls the pipeline between the four-way valve and the manual pump; the preset pressure interface on the top of the back-pressure valve is connected to the pipeline between the pressure relief valve and the lower valve through the pipeline, and the lower valve and the pressure relief valve are opened, and the four-way valve is connected to the back-pressure valve through the pipeline;

[0008] The bottom of the back-pressure source container is connected to the preset pressure interface at the top of the back-pressure valve through a back-pressure source outlet valve;

[0009] The two ends of the high-pressure window are respectively connected to the lower outlet of the capillary model and the inlet of the back-pressure valve; the outlet of the back-pressure valve is connected to the gas-liquid separator and the gas meter; wherein the capillary model, the high-pressure window and the back-pressure valve are all placed in a heating constant temperature box.

[0010] The four-way valve, back pressure source container, injection valve, pressure relief valve, upper valve, four-way valve, gas pressure reducing valve, lower valve, back pressure source inlet valve, back pressure source outlet valve, back pressure valve and branch pipelines, and various connecting pipelines are made of 316 stainless steel with a pressure resistance of 70.0 MPa.

[0011] The manual pump pressure range is 0-50 MPa, the back pressure gauge working pressure is 0-50 MPa, and the accuracy is 0.1% FS.

[0012] A method for quickly setting experimental pressure, characterized by:

[0013] Operations to establish experimental pressure: After heating the thermostat to keep the temperature of the entire system constant at the experimental temperature, the electric pump drives the cleaning solvent in the piston-type high-pressure container to continuously inject into the capillary model. The back pressure gauge displays normal pressure. After the gas-liquid separator discharges liquid evenly and the gas meter has no reading, confirm that the capillary model has been cleaned and there is no residual gas, then close the pressure relief valve, upper valve, gas pressure reducing valve, lower valve, back pressure source inlet valve, and back pressure source outlet valve;

[0014] After confirming that the entire system is operating normally and meets the requirements for establishing pressure, open the upper valve and the back pressure source inlet valve in sequence, open the nitrogen bottle, adjust the gas pressure reducing valve, control the gas pressure entering the back pressure source container at 2-3MPa, close the nitrogen bottle, and continue to inject liquid into the back pressure source container with a manual pump. When the pressure value displayed on the back pressure gauge reaches the experimental pressure and remains stable, stop injecting and close the back pressure source inlet valve;

[0015] Retract the manual pump and observe the back pressure gauge at the same time. After the pressure drops to normal pressure, open the pressure relief valve and the lower valve in sequence to relieve the residual pressure in the four-way valve and the pipeline connected to the back pressure valve, and then close the pressure relief valve. At this time, the manual pump is connected to the preset pressure on the top of the back pressure valve, and liquid is injected into the back pressure valve. Observe the back pressure gauge and stop injecting liquid after the pressure reaches 2-3 MPa. After the gas-liquid separator discharges liquid evenly and there is no reading on the gas meter, the fluid in the entire process including the capillary model is single-phase. Close the electric pump and injection valve at the inlet of the capillary model. The manual pump continues to inject liquid into the back-pressure valve. The sealing diaphragm of the back-pressure valve is deformed downward by force, compressing the fluid at the bottom of the back-pressure valve. Since the fluid in the system flow is single-phase at this time, the compression ratio is extremely small, and the pressure in the capillary model increases rapidly. When it is 0.5MPa away from the preset experimental pressure, the back-pressure source outlet valve is opened and the upper valve is closed. At this time, the pressure in the pre-set back-pressure source container directly acts on the back-pressure valve, and the upper gas plays a role in stabilizing the pressure, controlling the experimental pressure to be constant at the preset pressure. The lower single-phase liquid fills the cavity above the sealing diaphragm of the back-pressure valve and the connecting pipeline. The electric pump first uses constant pressure control to quickly increase the pressure of the solvent in the piston-type high-pressure container to the experimental pressure, and then changes to constant speed mode control, sets a reasonable injection speed, opens the injection valve to inject the fluid into the capillary model, and after the gas-liquid separator is evenly discharged, the formation temperature and the experimental pressure at this pressure point are established;

[0016] Operation of unloading experimental pressure: After the experiment of this pressure point is completed, because the capillary model, high-pressure window and connecting pipeline are full of free injection gas and a small amount of residual oil, the pressure of the entire system needs to be reduced to normal pressure for degassing, and then repeatedly cleaned with organic solvent. First close the outlet valve of the back pressure source, open the upper valve, and slowly open the inlet valve of the capillary model to relieve pressure. At this time, the sealing diaphragm of the back pressure valve is deformed downward under pressure, expanding the volume of the cavity and connecting pipeline above the back pressure valve sealing diaphragm. Because of its small volume and single-phase liquid inside, it is extremely sensitive to pressure, so that the back pressure valve pressure and the pore pressure in the capillary model are synchronously reduced. When the back pressure pressure cannot be reduced, it is gradually adjusted to normal pressure by the manual pump. Finally, the electric pump and the piston high-pressure container are opened to adjust to the appropriate pressure and flow rate, and the injection valve is opened to inject organic solvent into the process for cleaning. Throughout the entire pressure relief process, the pressure of the upper and lower parts of the back pressure valve sealing diaphragm drops synchronously, and the lower pressure will never be higher than the upper pressure, so the back pressure valve is not easy to be damaged. In addition, there is no need to relieve the pressure of the back pressure source container and the high-pressure piston container, thus saving operation time.

[0017] Adjust the operation of the next experimental pressure point: without affecting the equipment process cleaning working conditions, close the lower valve, open the back pressure source inlet valve and upper valve in turn, observe the pressure value displayed on the back pressure gauge, operate the manual pump, adjust the back pressure source container pressure to the next experimental pressure point, and close the back pressure source inlet valve for standby use.

[0018] The invention aims to provide a method for quickly setting an experimental pressure, wherein the pressure of a back pressure source is preset, that is, nitrogen with a certain pressure is injected into a back pressure source container in advance, and distilled water is continuously injected into the back pressure source container by a manual pump, and the pressure is adjusted to be stable for standby use, and then the back pressure valve at the end of a capillary model is pressurized by a manual pump, and the system pressure is gradually increased to 0.5 MPa lower than the preset back pressure source pressure, and the back pressure source container and the back pressure valve are connected to complete the new construction of the experimental pressure. When the pressure is released and cleaned after the experiment is completed, the valve connecting the back pressure valve and the back pressure source is closed first, and the inlet valve of the capillary model is opened to slowly release the pressure, and then the residual pressure of the back pressure valve is released by the manual pump, that is, the manual pump directly acts on the back pressure valve during the unloading and pressure building process, because the space in its valve body is much smaller than the volume of the back pressure source container, the pressure building and unloading speeds are significantly accelerated, and in the pressure building process, the upper and lower parts of the back pressure valve diaphragm are liquids with extremely small compression ratios, the pressure is easy to balance, and the sealing diaphragm is not easy to be damaged; in the pressure unloading process, the pressures of the upper and lower parts of the back pressure valve sealing diaphragm decrease synchronously, and the pressure of the lower part is never higher than the pressure of the upper part, so it is not easy to be damaged. During the process of setting up and releasing pressure, there is no need to operate the large back pressure source container and the piston type high pressure container simultaneously, which saves operation time. This method of quickly setting the test pressure is convenient, fast, safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention.

[0020] Among them: 1 electric pump, 2 piston high pressure container, 3 injection pressure gauge, 4 injection valve, 5 heating thermostat, 6 capillary model, 7 pressure relief valve, 8 upper valve, 9 back pressure pressure gauge, 10 four-way valve, 11 manual pump, 12 gas pressure reducing valve, 13 nitrogen bottle, 14 lower valve, 15 back pressure source inlet valve, 16 back pressure source container, 17 back pressure source outlet valve, 18 gas meter, 19 gas-liquid separator, 20 back pressure valve, 21 high pressure window. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and the accompanying descriptions.

[0022] As shown in the figure, the relevant devices used in the method for quickly setting the experimental pressure in the capillary experiment of the present invention include: a four-way valve 10, a manual pump 11, a nitrogen bottle 13, a back pressure source container 16, and a back pressure valve 20.

[0023] The four-way valve 10 is connected at both ends axially, one end is connected to the back pressure pressure gauge 9, and the other end is connected to the back pressure source container 16 through the back pressure source inlet valve 15. The four-way valve 10 is radially divided into two upper and lower passages, and the upper valve 8 controls the radial fluid in this direction to communicate with the two axial ends, and is parallelly connected to the manual pump 11, the nitrogen bottle 13 and the gas pressure reducing valve 12 respectively. The lower valve 14 controls the radial fluid in this direction to communicate with the two axial ends, and is connected to the pressure relief valve 7 and the back pressure valve 20; the bottom of the back pressure source container 16 is connected to the prefabricated pressure interface on the top of the back pressure valve 20 through the back pressure source outlet valve 17. The rest are all existing processes of the capillary experiment, that is, the upper part of the piston-type high-pressure container 2 is connected to the injection pressure gauge 3, the injection valve 4 is connected to the inlet end of the capillary model 6, and the lower part is connected to the electric pump 1; the two ends of the high-pressure window 21 are respectively connected to the lower outlet end of the capillary model 6 and the inlet of the back pressure valve 20, and the outlet of the back pressure valve 20 is connected to the gas-liquid separator 19 and the gas meter 18 of the terminal collection system, wherein the capillary model 6, the high-pressure window 21, the back pressure valve 20 and the accessories such as the connecting pipeline are all placed in the heating thermostatic box 5. The four-way valve 10, the back pressure source container 16 and the connecting pipeline, and each valve are made of 316 stainless steel, with a pressure resistance of 70.0MPa, the pressure range of the manual pump 11 is 0-50 MPa, the working pressure of the back pressure gauge 9 is 0-50MPa, and the accuracy is 0.1%FS, and the nitrogen cylinder 13 and the accessory gas pressure reducing valve 12 are all existing products. The parameters such as materials, pressure and temperature ranges, and control accuracy of equipment, pressure gauges, models, pipelines, valves and other accessories in the existing process all meet the relevant technical requirements of the SY / T 6573-2016 industry standard.

[0024] Operations for establishing experimental pressure: After heating the thermostat 5 to keep the temperature of the entire system constant at the experimental temperature, the electric pump 1 displaces the cleaning solvent in the piston-type high-pressure container 2 and continuously injects it into the capillary model 6. The back pressure gauge 9 shows normal pressure, the gas-liquid separator 19 discharges liquid evenly, and the gas meter 18 has no reading. Close the pressure relief valve 7, the upper valve 8, the gas pressure reducing valve 12, the lower valve 14, the back pressure source inlet valve 15, and the back pressure source outlet valve 17. After confirming that the entire system is operating normally and meets the requirements for establishing pressure, open the upper valve 8, the back pressure source inlet valve 15 in sequence, open the nitrogen bottle 13, adjust the gas pressure reducing valve 12, control the gas pressure entering the back pressure source container 16 to 2-3MPa, close the nitrogen bottle 13, and continue to inject liquid into the back pressure source container 16 with the manual pump 11. After the pressure value displayed on the back pressure gauge 9 reaches the experimental pressure and remains stable, stop the injection and close the back pressure source inlet valve 15. Manual pump 11 is retracted, and back pressure gauge 9 is observed at the same time. After the pressure drops to normal pressure, pressure relief valve 7 and lower valve 14 are opened in sequence. After the residual pressure in four-way valve 10 and the pipeline connected to back pressure valve 20 is released, pressure relief valve 7 is closed, and manual pump 11 is continued to inject liquid into back pressure valve 20. Back pressure gauge 9 is observed, and the pressure reaches 2-3 MPa, stop injecting liquid. When the gas-liquid separator 19 discharges liquid evenly and the gas meter 18 has no reading, the fluid in the entire process including the capillary model 6 is now a single-phase liquid. Close the electric pump 1 and the injection valve 4. The manual pump 11 continues to inject liquid into the back-pressure valve 20. The sealing diaphragm of the back-pressure valve is deformed downward under the force, and the fluid under the diaphragm is continuously compressed. At this time, the fluid in the entire system including the capillary model 6 is single-phase, with a very small compression ratio, and the system pressure increases rapidly. When the pressure is 0.5 MPa away from the preset experimental pressure, open the back-pressure source outlet valve 17, close the upper valve 8, and the liquid at the bottom of the back-pressure source container 16 contacts the back-pressure valve 20. The gas at the top stabilizes the pressure and keeps the pressure of the entire system constant at the experimental pressure. At this point, the experimental pressure is established.

[0025] Operation of unloading experimental pressure: After the recovery degree measurement experiment at this pressure point is completed, since the capillary model 6, high-pressure window 21 and connecting pipelines are full of free injection gas and a small amount of residual oil, the pressure needs to be reduced to normal pressure and then repeatedly cleaned with organic solvent. First close the back pressure source outlet valve 17, open the upper valve 8, open the injection valve 4 to slowly unload the pressure. At this time, the pressure of the entire system including the capillary model 6 and the back pressure pressure will drop synchronously. After observing that the pressure value displayed by the back pressure pressure gauge 9 no longer changes, that is, the back pressure pressure no longer drops, operate the manual pump 11 to gradually reduce the pressure of the back pressure valve 20 to normal pressure, open the electric pump 1, and adjust the piston high pressure container 2 to the appropriate pressure and flow rate, open the injection valve 4, and inject the organic solvent into the process for cleaning.

[0026] Adjust the operation of the next experimental pressure point: without affecting the equipment process cleaning working condition, close the lower valve 14, open the back pressure source inlet valve 15 and the upper valve 8 in turn, observe the pressure value displayed on the back pressure pressure gauge 9, operate the manual pump 11, adjust the pressure of the back pressure source container 16 to the next experimental pressure point and close the back pressure source inlet valve 15 for standby use.

[0027] In the present invention, Figure 1 As shown, the four-way valve 10 is made of stainless steel and is an existing product. The upper and lower parts thereof are respectively connected to the back pressure gauge 9, the back pressure source container 16, the connecting pipeline and the back pressure source inlet valve 15. The upper and lower pipelines inside the four-way valve are always in a normally open state and cannot be closed.

[0028] The four-way valve 10 is connected to other components through the upper valve 8 and the lower valve 14 on the left and right sides, which are part of the valve body of the four-way valve. The valve stem is manually rotated counterclockwise or clockwise to control the smoothness or closure of the pipeline connected to the valve. If the valve stem is rotated counterclockwise to open the upper valve 8, the manual pump 11, the nitrogen bottle 13 and the connecting pipelines and valves and other components will communicate with the pipelines of the back pressure gauge 9 and the back pressure source container 16 connected to the four-way valve 10. If the lower valve 14 is opened again, it will also communicate with the pipeline of the back pressure valve 20 and the pressure relief valve 7. The upper valve 8 and the lower valve 14 of the four-way valve 10 control the connection state of the corresponding pipelines and components with the pipelines in the upper and lower normally open state in the four-way valve.

[0029] The injection valve 4 is a high-pressure three-way valve, and the pressure relief valve 7, the back-pressure source inlet valve 15, and the back-pressure source outlet valve 17 are all high-pressure horizontal flow valves, all of which are made of stainless steel and are existing products. The valve stem is manually rotated counterclockwise or clockwise to control the connection or closure of the pipeline connected to the valve. The different names are just for the convenience of distinguishing their different uses. The horizontal flow valve refers to straight-line parallel flow, which controls whether the fluid can flow out smoothly from the other end after entering from one end; the three-way valve means that different fluids can flow in from two different directions, and controls whether any one of the fluids can flow out smoothly from the third-party outlet.

[0030] The injection valve 4 connects the piston type high pressure container 2 and the capillary model 6. If the solvent in the piston type high pressure container 2 is to be injected into the capillary model 6, the valve is opened, otherwise it is closed. If the capillary model needs to be depressurized, another way is opened to the atmosphere.

[0031] The pressure relief valve 7, when opened, releases the fluid pressure in the connected pipeline to normal pressure.

[0032] After the back pressure of the back pressure source inlet valve 15 is established and the pressure is stable, that is, after the experimental pressure of the next point is established, the valve is closed to cut off the connection between the back pressure source container 16 and the four-way valve 10.

[0033] After the back pressure source outlet valve 17 is adjusted to the next experimental pressure by the manual pump 11, the valve is opened when it is 0.5MPa away from the experimental pressure to connect the back pressure source container 16 and the back pressure valve 20. Since the back pressure source container 16 has been adjusted to the experimental pressure in advance and its upper part is nitrogen, its compression ratio is not of the same order of magnitude as that of the liquid, which can play a role in stabilizing the pressure and ensure that the experimental pressure remains constant during the experiment. After the pressure point extraction degree measurement experiment is completed, the pressure relief and cleaning are prepared. The lower part of the back pressure source container 16 is liquid (distilled water) in contact with the back pressure valve 20. The back pressure source outlet valve 17 is closed first, and then the injection valve 4 is opened to slowly relieve the pressure. Since the valve cavity and the connecting pipeline above the sealing diaphragm of the back pressure valve 20 are small in volume and are all single-phase liquids, the back pressure can be reduced synchronously with the pressure in the capillary model. Finally, the manual pump 11 is used to gradually adjust the back pressure to normal pressure.

[0034] The gas pressure reducing valve 12 is an existing device, through which the gas in the gas cylinder with a maximum pressure of more than ten MPa can be reduced to the required pressure (2-3 MPa) and injected into the back-pressure source container 16. Due to gravity differentiation, the gas is always at the top of the back-pressure source container 16 and does not directly contact the back-pressure valve 20, and only plays a role in stabilizing the pressure.

[0035] The back pressure valve 20 is a device that plays the role of increasing or decreasing the experimental pressure of the entire system. Because its function is similar to that of a valve, we figuratively call it a valve. It is also an existing product, and its main body is made of stainless steel. According to different principles, it can be divided into piston type, diaphragm type, etc. Diaphragm back pressure valves are generally used for those with higher pressure accuracy requirements. The general structure of the valve body is as follows: there is a very thin circular metal diaphragm (or other polymer materials such as polytetrafluoroethylene) in the valve body. There is a small space between the top of the metal diaphragm and the top of the valve body. It is connected to the bottom of the back pressure source container 16 through the pressure preset port. There is a slightly smaller annular groove below the metal diaphragm, and a sealing rubber "O" ring of suitable size is built in. Two small holes are opened at the bottom of the valve body, both below the metal diaphragm. One is inside the "O" ring (back pressure valve inlet) and connected to the high pressure window 21, and the other is outside the "O" ring (back pressure valve outlet) and connected to the gas-liquid separator 19.

[0036] Working principle: First, a certain safety pressure is applied to the top of the metal diaphragm through the pressure preset port. The metal diaphragm fits tightly with the "O"-shaped sealing ring below it. When the outflow of the capillary is driven to the inlet of the back pressure valve through the high-pressure window 21 and enters the back pressure valve body, when the injection pressure is greater than the preset pressure above the metal diaphragm, the metal diaphragm gradually breaks away from the seal of the "O"-shaped ring below it, and the fluid passes through the gap between the "O"-shaped ring and the metal diaphragm, communicates with the outlet of the back pressure valve outside the "O"-shaped ring, flows out of the back pressure valve and enters the gas-liquid separator 19 for gas-liquid separation, and the oil and gas are measured separately. After the back pressure valve outlet is evenly discharged, the preset pressure is gradually increased until the experimental pressure. What you need to pay attention to during operation is: the fluid pressure above and below the back-pressure valve sealing diaphragm is suddenly agitated, or the pressure difference exceeds the tolerance range of the diaphragm, especially during the pressure relief operation. Once the pressure below the back-pressure valve sealing diaphragm is greater than the pressure above it, the diaphragm will be deformed by force. If the force is uneven and the deformation in each direction is different, the diaphragm will be damaged or even punctured, causing the liquid above and below the diaphragm to communicate, damaging the equipment and even causing personal injury.

Claims

1. A method for quickly setting an experimental pressure device, comprising a piston-type high-pressure container (2), an injection pressure gauge (3), and a capillary model (6); the top of the piston-type high-pressure container (2) is connected to the inlet end of the capillary model (6) via a pipeline, and the injection pressure gauge (3) and an injection valve (4) are installed on the pipeline connecting the piston-type high-pressure container (2) and the capillary model (6); the bottom of the piston-type high-pressure container (2) is connected to an electric pump (1); Its characteristics are: It is also provided with a four-way valve (10), a manual pump (11), a nitrogen bottle (13), a back-pressure source container (16), a back-pressure valve (20), and a high-pressure window (21); One end of the four-way valve (10) is connected to a back pressure gauge (9), one end is connected to a back pressure source container (16) via a pipeline, one end is connected to a manual pump (11) via a pipeline, and one end is connected to a pressure relief valve (7); a branch pipeline is connected to the pipeline between the four-way valve (10) and the manual pump (11), one end of the branch pipeline is connected to the pipeline between the four-way valve (10) and the manual pump (11), and the other end is connected to a nitrogen bottle (13); a back pressure source inlet valve (15) is installed on the pipeline between the four-way valve (10) and the back pressure source container (16), and a gas pressure reducing valve (12) is installed on the branch pipeline; The four-way valve (10) is provided with an upper valve (8) and a lower valve (14), and the upper valve (8) controls the pipeline between the four-way valve (10) and the manual pump (11); the preset pressure interface at the top of the back-pressure valve (20) is connected to the pipeline between the pressure relief valve (7) and the lower valve (14) through the pipeline, and when the lower valve (14) and the pressure relief valve (7) are opened, the four-way valve (10) is connected to the back-pressure valve (20) through the pipeline; The bottom of the back pressure source container (16) is connected to the preset pressure interface at the top of the back pressure valve (20) via the back pressure source outlet valve (17); The two ends of the high-pressure window (21) are respectively connected to the lower outlet of the capillary model (6) and the inlet of the back-pressure valve (20); the outlet of the back-pressure valve (20) is connected to the gas-liquid separator (19) and the gas meter (18); wherein the capillary model (6), the high-pressure window (21) and the back-pressure valve (20) are all placed in a heating thermostatic box (5); The following steps are included when setting the experimental pressure quickly: Operations for establishing the experimental pressure: After the temperature of the entire system is kept constant at the experimental temperature by heating the thermostatic box (5), the electric pump (1) displaces the cleaning solvent in the piston-type high-pressure container (2) and continuously injects it into the capillary model (6). The back pressure gauge (9) displays normal pressure, the gas-liquid separator (19) discharges liquid evenly, and the gas meter (18) has no reading. The pressure relief valve (7), the upper valve (8), the gas pressure reducing valve (12), the lower valve (14), the back pressure source inlet valve (15), and the back pressure source outlet valve (17) are closed. After confirming that the entire system is operating normally and meets the requirements for establishing pressure, open the upper valve (8) and the back pressure source inlet valve (15) in sequence, open the nitrogen bottle (13), adjust the gas pressure reducing valve (12), control the gas pressure entering the back pressure source container (16) to be 2-3 MPa, close the nitrogen bottle (13), and continue to inject liquid into the back pressure source container (16) with the manual pump (11). After the pressure value displayed on the back pressure gauge (9) reaches the experimental pressure and remains stable, stop injecting and close the back pressure source inlet valve (15); The manual pump (11) is turned off and the back pressure gauge (9) is observed at the same time. When the pressure drops to normal pressure, the pressure relief valve (7) and the lower valve (14) are opened in sequence to relieve the residual pressure in the four-way valve (10) and the pipeline connected to the back pressure valve (20). The pressure relief valve (7) is then closed and the manual pump (11) is used to inject liquid into the back pressure valve (20) through the preset pressure interface at the top of the back pressure valve (20). The back pressure gauge (9) is observed and the pressure reaches 2-3 MPa, stop injecting liquid. When the gas-liquid separator (19) evenly discharges liquid and the gas meter (18) has no reading, the fluid in the entire process including the capillary model (6) is now a single-phase liquid. The manual pump (11) continues to inject liquid into the back-pressure valve (20). The sealing diaphragm of the back-pressure valve is deformed downward by force, and the fluid under the diaphragm is continuously compressed. At this time, the fluid in the entire system including the capillary model (6) is single-phase, the compression ratio is extremely small, and the system pressure increases rapidly. When the pressure is 0.5 MPa away from the preset experimental pressure, open the back-pressure source outlet valve (17) and close the upper valve (8). The liquid at the bottom of the back-pressure source container (16) contacts the back-pressure valve (20), and the gas at the top stabilizes the pressure and keeps the pressure of the entire system constant at the experimental pressure. At this point, the experimental pressure is established. Operation of removing the experimental pressure: After the recovery degree measurement experiment at this pressure point is completed, since the capillary model (6), the high-pressure window (21) and the connecting pipeline are filled with free injection gas and a small amount of residual oil, the pressure needs to be reduced to normal pressure and then repeatedly cleaned with an organic solvent; first close the back pressure source outlet valve (17), open the upper valve (8), open the injection valve (4) to slowly release the pressure, at this time, the pressure of the entire system including the capillary model (6) and the back pressure pressure decrease synchronously, and wait until the back pressure pressure gauge (9) shows that the pressure value no longer changes, that is, the back pressure pressure no longer decreases, and then operate the manual pump (11) to gradually reduce the pressure of the back pressure valve (20) to normal pressure; open the electric pump (1), adjust the piston high pressure container to a suitable pressure and flow rate, open the injection valve (4), and inject the organic solvent into the process for cleaning; Adjust the operation of the next experimental pressure point: without affecting the equipment process cleaning working conditions, close the lower valve (14), open the back pressure source inlet valve (15) and the upper valve (8) in turn, observe the pressure value displayed on the back pressure gauge (9), operate the manual pump (11), adjust the pressure of the back pressure source container (16) to the next experimental pressure point, and close the back pressure source inlet valve for standby use.

2. The method according to claim 1, characterized in that: The four-way valve (10), the back-pressure source container (16), the injection valve (4), the pressure relief valve (7), the upper valve (8), the four-way valve (10), the gas pressure reducing valve (12), the lower valve (14), the back-pressure source inlet valve (15), the back-pressure source outlet valve (17), the back-pressure valve (20), the branch pipelines, and the various connecting pipelines are made of 316 stainless steel with a pressure resistance of 70.0 MPa.

3. The method according to claim 1, characterized in that: The operating pressure range of the manual pump (11) is 0-50 MPa, and the working pressure of the back pressure gauge (9) is 0-50 MPa with an accuracy of 0.1% FS.

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