A supercritical carbon dioxide circulation oil recovery experimental system based on multiphase fluid separation

Abstract

The invention discloses a supercritical carbon dioxide circulation oil recovery experimental system based on multiphase fluid separation, wherein a stainless steel pipe in a fluid control and circulation injection subsystem is connected to a pad in a core clamping subsystem, and the pad in the core clamping subsystem is connected to a multiphase fluid separation device in a multiphase fluid separation subsystem through a stainless steel pipe, and the multiphase fluid separation device is respectively connected to a tee and a valve in a fluid injection and circulation control subsystem through a stainless steel pipe; a constant temperature water tank in a temperature control subsystem is connected to a metering pump in a fluid injection and circulation control subsystem through an external water pipe, and a pressure sensor in the fluid injection and circulation control subsystem, a pressure sensor in a core clamping system, and a differential pressure gauge in a multiphase fluid separation subsystem are respectively connected to an acquisition card in a data acquisition subsystem through a cable. The utilization efficiency of supercritical carbon dioxide in the supercritical carbon dioxide oil recovery process is improved, and separation and collection of multiphase fluids are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of gas displacement and multiphase fluid separation in the process of oil recovery enhancement, and more specifically relates to a supercritical carbon dioxide circulation oil recovery experimental system based on multiphase fluid separation. Background Art

[0002] At present, oil is still the main fossil energy consumed in human production activities. Compared with conventional oil extraction methods, supercritical carbon dioxide flooding can increase the oil recovery rate by 15%-25%. Supercritical carbon dioxide flooding technology is increasingly valued in oil field development. In addition, due to the increasingly severe global warming problem caused by the large amount of greenhouse gases emitted by human production and life, reducing carbon emissions is a common challenge facing the world. Therefore, in the process of supercritical carbon dioxide flooding, the utilization efficiency of supercritical carbon dioxide should be improved as much as possible, on the one hand to increase the oil recovery rate, on the other hand to reduce the emission of supercritical carbon dioxide.

[0003] In order to simulate the actual CO2 flooding effect, it is necessary to develop a CO2 flooding experimental system. Currently known CO2 flooding systems are mostly one-way displacement systems, that is, CO2 flows in from the injection end, flows out from the outlet end, and then is discharged into the atmosphere. This experimental system only realizes the single use of the displacement fluid, and the efficiency of the displacement fluid is low, which increases the experimental cost to a certain extent. In addition, in the supercritical CO2 flooding process, the water and oil in the reservoir are often displaced first. As the displacement proceeds, the supercritical CO2 breaks through the sample, and water, oil, and supercritical CO2 coexist at the outlet of the sample. How to separate the phases of fluid and accurately measure the content of each component fluid is the most basic and important process in the experiment. Since the gravity separation process does not require additional power, does not consume reagents, has no secondary pollution, and the operation process is relatively simple, gravity separation is currently the most widely used separation method in experimental oil-water separation devices. In the process of gravity separation, due to density differences, each phase of fluid is naturally stratified in the separation device, but there is currently a lack of simple, efficient and accurate technical means to determine the time when the interface of each phase of fluid moves to the bottom of the separation device and determine the time point when the separation of each phase of fluid is completed. Therefore, it is necessary to develop a supercritical carbon dioxide circulation flooding system to improve the utilization efficiency of supercritical carbon dioxide and the separation efficiency of multiphase fluids. Summary of the invention

[0004] In view of the problems existing in the prior art, in order to better improve the utilization efficiency of supercritical carbon dioxide in the supercritical carbon dioxide flooding process and effectively separate and collect the mixed fluid (supercritical carbon dioxide, oil, water), the purpose of the present invention is to provide a supercritical carbon dioxide circulation flooding experimental system based on multiphase fluid separation, which realizes the recycling of supercritical carbon dioxide by rationally arranging relevant pipelines. In addition, the experimental system can separate immiscible fluids of different densities, and judge the positions of the oil-water interface and the oil-carbon dioxide interface in the process of collecting each phase fluid by the change of the differential pressure gauge reading over time.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] In order to improve the utilization efficiency of supercritical carbon dioxide and effectively separate and collect supercritical carbon dioxide, oil and water, the present invention develops a supercritical carbon dioxide circulation oil recovery experimental system based on multiphase fluid separation. A supercritical carbon dioxide circulation oil recovery experimental system based on multiphase fluid separation, the experimental system includes: a fluid injection and circulation control subsystem, a core clamping subsystem, a multiphase fluid separation subsystem, a data acquisition subsystem, a temperature control subsystem and a fluid collection subsystem. It is characterized in that: the stainless steel pipe in the fluid control and circulation injection subsystem is connected to the first end pad in the core clamping subsystem to provide injection fluid for the sample; the second end pad in the core clamping subsystem is connected to the multiphase fluid separation device in the multiphase fluid separation subsystem through a stainless steel pipe, so that the displaced phases of fluid are separated in the multiphase fluid separation device; the multiphase fluid separation device is respectively connected to the second three-way and the fourth valve in the fluid injection and circulation control subsystem through stainless steel pipes; part of the pipelines in the fluid injection and circulation control subsystem, the core clamping subsystem and the multiphase fluid separation subsystem are placed in the temperature control subsystem. The temperature of the constant temperature water tank in the subsystem is kept constant to ensure that the carbon dioxide is in a supercritical state; the constant temperature water tank in the temperature control subsystem is connected to the first metering pump and the second metering pump in the fluid injection and circulation control subsystem through an external water pipe to achieve temperature control of the fluid injection metering pump; the first pressure sensor, the second pressure sensor in the fluid injection and circulation control subsystem, the pressure sensor in the core clamping system, and the differential pressure gauge in the multiphase fluid separation subsystem are connected to the acquisition card in the data acquisition subsystem through the first cable, the second cable, the third cable and the fourth cable respectively to achieve real-time recording of experimental data. The fluid injection and circulation control subsystem includes gas cylinders, pressure reducing valves, filters (two in total), fluid injection metering pumps (two in total), stainless steel pipes, tees (two in total), valves (four in total), four-way valves (two in total), pressure sensors (two in total), and vacuum pumps; the core clamping subsystem includes pressure chambers, confining pressure liquids, end pads (two in total), porous gaskets (two in total), specimens, sealing materials, tees, pressure sensors, and confining pressure pumps; the phase fluid separation subsystem includes differential pressure gauges, multiphase fluid separation devices, multiphase fluids (three phases in total), and back pressure valves; the data acquisition subsystem includes computers, USB data cables, acquisition cards, and cables (four in total); the temperature control subsystem includes a constant temperature water tank and an external circulating water pipe; the fluid collection subsystem includes tees, valves (two in total), and fluid collection containers (two in total). The specific structural connection relationships of each component are as follows:

[0007] Fluid injection and circulation control subsystem: the gas cylinder is connected to the pressure reducing valve for adjusting the pressure of carbon dioxide flowing out of the gas cylinder; the pressure reducing valve is connected to the first filter; the first filter is connected to the first metering pump; the first fluid metering pump is connected to one end of the first three-way through a stainless steel pipe; the other two ends of the first three-way are respectively connected to the first valve and the third valve; the third valve is connected to one end of the second three-way; the other two ends of the second three-way are respectively connected to the differential pressure gauge and the multiphase fluid separation device in the multiphase fluid separation subsystem; the first valve is connected to one end of the first four-way; the other three ends of the first four-way are respectively connected to the second valve, the first pressure sensor, and the first end pad in the core clamping subsystem; the second valve is connected to one end of the second four-way; the other three ends of the second four-way are respectively connected to the fourth valve, the second pressure sensor, and the second metering pump; the fourth valve is connected to the multiphase fluid separation device in the multiphase fluid separation subsystem; the second metering pump is connected to the second filter; the second filter is connected to the vacuum pump.

[0008] Core clamping subsystem: both ends of the sample are in contact with the first porous gasket and the second porous gasket respectively to ensure that the fluid flows into and out of the sample evenly; the first porous gasket and the second porous gasket are in contact with the first end gasket and the second end gasket respectively; the sealing material tightly wraps the first end gasket, the first porous gasket, the sample, the second porous gasket, and the second end gasket; the first end gasket is connected to one end of the first four-way in the fluid injection and circulation control subsystem through a stainless steel pipe; the second end gasket is connected to the multiphase fluid separation device in the multiphase fluid separation subsystem through a stainless steel pipe; the confining pressure pump is connected to one end of the three-way; the other two ends of the three-way are connected to the pressure chamber and the pressure sensor respectively; and the confining pressure liquid is injected into the pressure chamber through the confining pressure pump.

[0009] Multiphase fluid separation subsystem: one end of the differential pressure gauge is connected to the lower left end of the multiphase fluid separation device, and the other end is connected to the second three-way connection in the fluid injection and circulation control subsystem; one end of the back pressure valve is connected to the lower right end of the multiphase fluid separation device, and the other end is connected to the three-way connection in the fluid collection subsystem; the top of the multiphase fluid separation device is connected to the second end pad in the core clamping subsystem through a stainless steel pipe; supercritical carbon dioxide, oil and water are layered in the multiphase fluid separation device due to their different densities.

[0010] Data acquisition subsystem: The acquisition card is connected to the computer via a USB data cable;

[0011] Temperature control subsystem: an external circulating water pipe connects the constant temperature water tank with the first metering pump and the second metering pump in the fluid injection and circulation control subsystem.

[0012] Fluid collection subsystem: one end of the three-way is connected to the back pressure valve in the multiphase fluid separation subsystem; the other two ends are connected to the first valve and the second valve respectively; the first valve is connected to the first fluid collection container; the second valve is connected to the second fluid collection container.

[0013] In summary, the relative positions of the first three-way, the first valve, the first four-way, the second valve, the third valve, the fourth valve and the second four-way constitute a circulation injection system, so that the supercritical carbon dioxide fluid in the experiment can be recycled; the two ends of the differential pressure gauge are respectively connected to the upper and lower ends of the separation device, so as to realize the monitoring of the liquid level in the separation device. In the process of fluid collection, the time point of completion of oil and water separation can be accurately judged by the change of the differential pressure gauge reading over time, and the quantitative measurement of the separated fluid can be completed. The ideal experiment is used to illustrate the workflow of separation and collection of each phase fluid in the present invention, such as Figure 5 Assume that the density of water, oil, and supercritical carbon dioxide is 1g / cm 3 , 0.7g / cm 3 and 0.6gcm 3 After the displacement is completed, the height of the liquid column of oil and water in the separation device is 10cm. At this time, the differential pressure gauge shows 1.7kPa, which is displayed as a horizontal straight line. When water separation begins, the differential pressure gauge reading decreases. When the slope of the differential pressure gauge reading decreases suddenly, it indicates that the water phase separation is completed and the oil phase separation begins. When the differential pressure gauge reading becomes 0, it indicates that the oil phase separation is completed and the separation device is full of supercritical carbon dioxide. At this point, the separation of each phase of fluid is completed.

[0014] Through the above experimental system design, the supercritical carbon dioxide fluid is fully utilized; through the change of the differential pressure gauge reading, the time point when the separation of each phase fluid is completed can be accurately judged, thereby improving the accuracy of the measurement of the total displacement amount of each phase fluid and the separation efficiency.

[0015] The method for separating and collecting multiphase fluids in the supercritical carbon dioxide circulation oil recovery process using the present invention is as follows:

[0016] 1. Make a device according to the present invention.

[0017] 2. Prepare the test samples saturated with oil and water, and wrap them with plastic wrap to prevent the oil and water from evaporating.

[0018] 3. Neatly stack the first end gasket, the first porous gasket and the sample, the second porous gasket and the second end gasket together, and tightly wrap and seal them with sealing materials to isolate the sample from the confining pressure liquid.

[0019] 4. Connect the first cross-piece in the fluid injection and circulation control subsystem to the first end pad in the core clamping subsystem through a stainless steel pipe; connect the second end pad in the core clamping subsystem to the multiphase fluid separation device in the multiphase fluid separation subsystem;

[0020] 5. Inject confining pressure liquid into the pressure chamber through the confining pressure pump. When the pressure of the confining pressure liquid in the pressure chamber reaches the pressure required for the experiment (determined by the pressure sensor reading), stop injecting and maintain the pressure stable.

[0021] 6. Open the valve of the gas cylinder, fill the first metering pump with carbon dioxide, and adjust the pressure of the first metering pump and the temperature of the constant temperature water tank to make the carbon dioxide in a supercritical state.

[0022] 7. Set the first metering pump and the second metering pump to constant pressure mode respectively, open the first valve and the fourth valve in the fluid injection and circulation control subsystem, close the second valve and the third valve, and the first metering pump injects fluid into the sample at a pressure slightly higher than that of the second metering pump to carry out the supercritical carbon dioxide oil recovery experiment.

[0023] 8. When the fluid volume in the first metering pump is insufficient, close the first valve and the fourth valve in the injection and circulation control subsystem, and readjust the pressure of the first metering pump and the second metering pump. After the pressure stabilizes, open the second valve and the third valve to achieve the circulation displacement of supercritical carbon dioxide.

[0024] 9. When the differential pressure gauge reading in the multiphase fluid separation subsystem does not change, the displacement is considered complete. Open the first valve in the fluid collection subsystem and adjust the back pressure valve pressure to allow the water in the multiphase fluid separation device to flow into the first fluid collection container in the fluid collection subsystem. Observe the change in the differential pressure gauge reading in the multiphase fluid separation subsystem. When the slope of the differential pressure gauge reading decreases significantly over time ( Figure 5 ), close the first valve in the fluid collection subsystem, open the second valve in the fluid collection subsystem, and allow the oil in the multiphase fluid separation device to flow into the second fluid collection container in the fluid collection subsystem. When the differential pressure gauge reading drops to zero, indicating that the oil and water phases are separated, close the second valve in the fluid collection subsystem. At this point, the displacement and fluid collection work is completed.

[0025] Compared with the prior art, the present invention has the following advantages and positive effects:

[0026] The device realizes the recycling of supercritical carbon dioxide by rationally arranging the relevant pipelines; the principle is simple and the structure is clear. The utilization efficiency of supercritical carbon dioxide in the supercritical carbon dioxide flooding process is improved, and the position of the multiphase fluid interface is determined by the change in the differential pressure gauge reading, so as to realize the separation and collection of multiphase fluids. The device uses the immiscible characteristics and density differences of different fluids to separate multiphase fluids, and uses the law of change of the differential pressure gauge reading over time to determine the time point when the oil-water interface and the oil-carbon dioxide interface move to the bottom of the separation device, so as to realize the collection of different fluids. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the structure of a supercritical carbon dioxide circulation oil recovery experimental system based on multiphase fluid separation.

[0028] Figure 2 is a schematic diagram of a first fluid displacement system;

[0029] Figure 3 is a schematic diagram of a second fluid displacement system;

[0030] Figure 4 Schematic diagram of a multiphase fluid separation device;

[0031] Figure 5 This is a typical curve of the differential pressure gauge reading changing with time during the separation and collection of multiphase fluids.

[0032] in:

[0033] 1—Fluid injection and circulation control subsystem (including gas cylinder 1.1, pressure reducing valve 1.2, filter (including first filter 1.3a, second filter 1.3b, two in total), fluid injection metering pump (first metering pump 1.4a, second metering pump 1.4b, two in total), stainless steel pipe 1.5, tee (first tee 1.6a, second tee 1.6b, two in total), valve (first valve 1.7a, second valve 1.7b, third valve 1.7c, and fourth valve 1.7e, four in total), four-way (first four-way 1.8a, second four-way 1.8b, two in total), pressure sensor (conventional pressure sensor can be used, with a range of up to 10MPa, no other special requirements) (first pressure sensor 1.9a, second pressure sensor 1.9b, two in total), vacuum pump 1.10);

[0034] 2—core clamping subsystem (including pressure chamber 2.1, confining pressure liquid 2.2, end pads (first end pad 2.3a, second end pad 2.3b, 2 in total), porous gaskets (first porous gasket 2.4a, second porous gasket 2.4b, 2 in total), specimen 2.5, sealing material 2.6, core clamping subsystem tee 2.7, core clamping subsystem pressure sensor 2.8 (any conventional pressure sensor can be used, with a range of up to 10 MPa, no other special requirements), confining pressure pump 2.9);

[0035] 3—Multiphase fluid separation subsystem {including differential pressure gauge 3.1, multiphase fluid separation device 3.2, separation fluid (supercritical carbon dioxide 3.3a, oil 3.3b and water 3.3c, three phases in total), back pressure valve 3.4);

[0036] 4—Data acquisition subsystem (including computer 4.1, USB data cable 4.2, acquisition card 4.3, cables (first cable 4.4a, second cable 4.4b, third cable 4.4c, fourth cable 4.4d, four in total)); temperature control subsystem (including constant temperature water tank 5.1, external circulating water pipe 5.2).

[0037] 6—Fluid collection subsystem (including fluid collection subsystem tee 6.1, fluid collection subsystem first valve 6.2a, fluid collection subsystem second valve 6.2b, first fluid collection container 6.3a, second fluid collection container 6.3b)

[0038] The remaining parts mentioned above can all be purchased on the market. DETAILED DESCRIPTION

[0039] Embodiment 1:

[0040] according to Figure 1 , Figure 2 , Figure 3 It can be seen that a supercritical carbon dioxide circulation oil recovery experimental system based on multiphase fluid separation, the experimental system includes: a fluid injection and circulation control subsystem 1, a core clamping subsystem 2, a multiphase fluid separation subsystem 3, a data acquisition subsystem 4, a temperature control subsystem and a fluid collection subsystem 6, characterized in that: the stainless steel pipe 1.5 in the fluid injection and circulation control subsystem 1 is connected to the first end pad 2.3a in the core clamping subsystem 2 to provide injection fluid for the sample 2.5; the second end pad 2.3 in the core clamping subsystem 2 is connected to the multiphase fluid separation device 3.2 in the multiphase fluid separation subsystem 3 through the stainless steel pipe 1.5, so that the displaced phases of fluid are separated in the multiphase fluid separation device 3.2; the multiphase fluid separation device 3.2 is respectively connected to the second three-way 1.6b and the fourth valve 1.7e in the fluid injection and circulation control subsystem 1 through the stainless steel pipe 1.5; the fluid injection and circulation control subsystem 1 is connected to the first end pad 2.3a in the core clamping subsystem 2 to provide injection fluid for the sample 2.5; the second end pad 2.3 in the core clamping subsystem 2 is connected to the multiphase fluid separation device 3.2 in the multiphase fluid separation subsystem 3 through the stainless steel pipe 1.5, so that the displaced phases of fluid are separated in the multiphase fluid separation device 3.2; the multiphase fluid separation device 3.2 is respectively connected to the second three-way 1.6b and the fourth valve 1.7e in the fluid injection and circulation control subsystem 1 through the stainless steel pipe 1. The stainless steel pipe 1.5, the core clamping subsystem 2 and the multiphase fluid separation subsystem 3 in the control subsystem 1 are placed in a constant temperature water tank 5.1 in the temperature control subsystem to keep the temperature constant, so as to ensure that the carbon dioxide is in a supercritical state; the constant temperature water tank 5.1 in the temperature control subsystem 5 is connected to the first metering pump 1.4a and the second metering pump 1.4b in the fluid injection and circulation control subsystem 1 through an external circulating water pipe 5.2, so as to realize the temperature control of the fluid injection metering pump; the first pressure sensor 1.9a, the second pressure sensor 1.9b in the fluid injection and circulation control subsystem 1, the core clamping subsystem pressure sensor 2.8 in the core clamping subsystem 2, and the differential pressure gauge 3.1 in the multiphase fluid separation subsystem 3 are connected to the acquisition card 4.3 in the data acquisition subsystem 4 through the first cable 4.4a, the second cable 4.4b, the third cable 4.4c and the fourth cable 4.4d, respectively, so as to realize the real-time recording of the experimental data.

[0041] The fluid injection and circulation control subsystem 1 includes a gas cylinder 1.1, a pressure reducing valve 1.2, a first filter 1.3a, a second filter 1.3b, a first metering pump 1.4a, a second metering pump 1.4b, a stainless steel pipe 1.5, a first three-way 1.6a, a second three-way 1.6b, a first valve 1.7a, a second valve 1.7b, a third valve 1.7c, a fourth valve 1.7e, a first four-way 1.8a, a second four-way 1.8b, and a first pressure sensor 1.9a. , a second pressure sensor 1.9b, and a vacuum pump 1.10; the connection relationship is as follows: the gas cylinder 1.1 in the fluid injection and circulation control subsystem 1 is connected to the pressure reducing valve 1.2, which is used to adjust the pressure of carbon dioxide flowing out of the gas cylinder 1.1; the pressure reducing valve 1.2 is connected to the first filter 1.3a; the first filter 1.3a is connected to the first metering pump 1.4a; the first fluid metering pump 1.4a is connected to one end of the first tee 1.6a through the stainless steel pipe 1.5; the first tee 1.6a The other two ends are connected to the first valve 1.7a and the third valve 1.7c respectively; the third valve 1.7c is connected to one end of the second three-way valve 1.6b; the other two ends of the second three-way valve 1.6b are connected to the differential pressure gauge 3.1 and the multiphase fluid separation device 3.2 in the multiphase fluid separation subsystem 3; the first valve 1.7a is connected to one end of the first four-way valve 1.8a; the other three ends of the first four-way valve 1.8a are connected to the second valve 1.7b, the first pressure sensor 1.9a, and the core clamping subsystem 3 respectively. The first end gasket 2.3a in the system 2 is connected; the second valve 1.7b is connected to one end of the second four-way valve 1.8b; the other three ends of the second four-way valve 1.8b are respectively connected to the fourth valve 1.7e, the second pressure sensor 1.9b, and the second metering pump 1.4b; the fourth valve 1.7e is connected to the multiphase fluid separation device 3.2 in the multiphase fluid separation subsystem 3; the second metering pump 1.4b is connected to the second filter 1.3b; the second filter 1.3b is connected to the vacuum pump 1.10.

[0042] The core clamping subsystem 2 comprises a pressure chamber 2.1, a confining pressure liquid 2.2, a first end pad 2.3a, a second end pad 2.3b, a first porous gasket 2.4a, a second porous gasket 2.4b, a sample 2.5, a sealing material 2.6, a core clamping subsystem tee 2.7, a core clamping subsystem pressure sensor 2.8, and a confining pressure pump 2.9; the connection relationship is: the two ends of the sample 2.5 are respectively in contact with the first porous gasket 2.4a and the second porous gasket 2.4b to ensure that the fluid flows into and out of the sample 2.5 evenly; the first porous gasket 2.4a and the second porous gasket 2.4b are respectively in contact with the first porous gasket 2.4a and the second porous gasket 2.4b. The sealing material 2.6 tightly wraps the first end pad 2.3a, the first porous gasket 2.4a, the sample 2.5, the second porous gasket 2.4b, and the second end pad 2.3b; the first end pad 2.3a is connected to one end of the first four-way 1.8a in the fluid injection and circulation control subsystem 1 through the stainless steel pipe 1.5; the second end pad 2.3b is connected to the multiphase fluid separation device 3.2 in the multiphase fluid separation subsystem 3 through the stainless steel pipe 1.5; the confining pressure pump 2.9 is connected to one end of the three-way 2.7 of the core clamping subsystem;

[0043] The other two ends of the core clamping subsystem tee 2.7 are respectively connected to the pressure chamber 2.1 and the core clamping subsystem pressure sensor 2.8; the confining pressure liquid 2.2 is injected into the pressure chamber 2.1 through the confining pressure pump 2.9.

[0044] The multiphase fluid separation subsystem 3 comprises a differential pressure gauge 3.1, a multiphase fluid separation device 3.2, a supercritical carbon dioxide 3.3a phase, an oil 3.3b phase, a water 3.3c phase, and a back pressure valve 3.4; the connection relationship thereof is as follows: one end of the differential pressure gauge 3.1 is connected to the lower left end of the multiphase fluid separation device 3.2, and the other end of the differential pressure gauge 3.1 is connected to the second three-way connection 1.6b in the fluid injection and circulation control subsystem 1; one end of the back pressure valve 3.4 is connected to the lower right end of the multiphase fluid separation device 3.2, and the other end of the back pressure valve 3.4 is connected to the fluid collection subsystem three-way connection 6.1 in the fluid collection subsystem 6; the top of the multiphase fluid separation device 3.2 is connected to the second end pad 2.3b in the core clamping subsystem 2 through a stainless steel pipe 1.5; the supercritical carbon dioxide 3.3a, the oil 3.3b and the water 3.3c are layered in the multiphase fluid separation device 3.2 due to their different densities.

[0045] like Figure 4 As shown, the multiphase fluid separation device 3.2 is a hollow cylinder made of stainless steel 316L, with an inner diameter of d and an outer diameter of D. There is a pad at each end, and the pad diameter is D. d, thickness is T, the total height of the separation device is H, the top of the device is provided with a 1 / 8 inch internal threaded opening, and the upper and lower sides are also provided with 1 / 8 inch internal threaded openings. The top of the multiphase fluid separation device 3.2 is connected to the second end pad 2.3b in the core clamping subsystem 2 through a stainless steel pipe 1.5; the upper left end and the upper right end are respectively connected to the second three-way 1.6b and the fourth valve 1.7e in the fluid injection and circulation control subsystem 1 through a stainless steel pipe 1.5; the lower left end and the lower right end are respectively connected to the differential pressure gauge 3.1 and the back pressure valve 3.4 in the multiphase fluid separation subsystem 3 through a stainless steel pipe 1.5.

[0046] The data acquisition subsystem 4 includes a computer 4.1, a USB data line 4.2, an acquisition card 4.3, a first cable 4.4a, a second cable 4.4b, a third cable 4.4c, and a fourth cable 4.4d; the connection relationship is: the acquisition card 4.3 is connected to the computer 4.1 through the USB data line 4.2; the acquisition card 4.3 is respectively connected to one end of the first cable 4.4a, the second cable 4.4b, the third cable 4.4c, and the fourth cable 4.4d, and the other ends of the first cable 4.4a, the second cable 4.4b, the third cable 4.4c, and the fourth cable 4.4d are respectively connected to the first pressure sensor 1.9a, the second sensor 1.9b in the fluid injection and circulation control subsystem 1, the core clamping subsystem pressure sensor 2.8 in the core clamping subsystem 2, and the differential pressure gauge 3.1 in the multiphase fluid separation subsystem 3.

[0047] The temperature control subsystem includes a constant temperature water tank 5.1 and an external circulating water pipe 5.2; the fluid collection subsystem 6 includes a fluid collection subsystem tee 6.1, a fluid collection subsystem first valve 6.2a, a fluid collection subsystem second valve 6.2b, a first fluid collection container 6.3a, and a second fluid collection container 6.3b. The specific structural connection relationship of each component is as follows: the external circulating water pipe 5.2 connects the constant temperature water tank 5.1 with the first metering pump 1.4a and the second metering pump 1.4b in the fluid injection and circulation control subsystem 1; one end of the fluid collection subsystem tee 6.1 is connected to the back pressure valve 3.4 in the multiphase fluid separation subsystem 3; the other two ends are respectively connected to the fluid collection subsystem first valve 6.2a and the fluid collection subsystem second valve 6.2b; the fluid collection subsystem first valve 6.2a is connected to the first fluid collection container 6.3a; the fluid collection subsystem second valve 6.2b is connected to the second fluid collection container 6.3b.

[0048] Through the above experimental system design, supercritical carbon dioxide oil recovery experiments under different experimental conditions (different confining pressures, pore pressures, and temperatures) can be carried out to provide guidance for actual engineering practice. During the experiment, through clever design, that is, the mutual cooperation of stainless steel pipes and valves, the recycling of displacement fluids during the experiment was realized, which saved the experimental cost to a certain extent and met the policy requirements of low carbon and environmental protection. In addition, during the process of fluid separation and collection, a differential pressure gauge is used to monitor the changes in the liquid level in the separation device in real time. Due to the differences in the density of different fluids, the differential pressure gauge reading decreases at different rates over time during the fluid collection process. Through this feature, the time point when the separation of water and oil is completed can be accurately judged, and the volume of oil and water displaced can be calculated, thereby improving the separation efficiency of multiphase fluids. In general, the experimental system has a simple principle, clear structure, reasonable design, and powerful functions, and can meet the experimental requirements of displacement and separation under different experimental conditions.

[0049] The method for separating and collecting multiphase fluids in the supercritical carbon dioxide circulation oil recovery process using the present invention is as follows:

[0050] 1. Make a device according to the present invention.

[0051] 2. Prepare the test sample 2.5 saturated with oil and water, and wrap it with plastic wrap to prevent the oil and water from evaporating.

[0052] 3. Neatly stack the first end gasket 2.3a, the first porous gasket 2.4a, the sample 2.5, the second porous gasket 2.4b, and the second end gasket 2.3b together, and tightly wrap and seal them with the sealing material 2.6 to isolate the sample 2.5 from the confining pressure liquid 2.2.

[0053] 4. Connect the first cross-piece 1.8a in the fluid injection and circulation control subsystem 1 to the first end pad 2.3a in the core clamping subsystem 2 through the stainless steel pipe 1.5; connect the second end pad 2.3b of the core clamping subsystem 2 to the multiphase fluid separation device 3.2 in the multiphase fluid separation subsystem 3;

[0054] 5. Inject confining pressure liquid 2.2 into the pressure chamber 2.1 through the confining pressure pump 2.9. When the pressure of the confining pressure liquid in the pressure chamber 2.1 reaches the pressure required for the experiment (determined by the pressure sensor reading), stop injecting and maintain the pressure stable.

[0055] 6. Open the valve of the gas cylinder 1.1, fill the first metering pump 1.4a with carbon dioxide, and adjust the pressure of the first metering pump 1.4a and the temperature of the constant temperature water tank 5.1 to make the carbon dioxide in a supercritical state.

[0056] 7. Set the first metering pump 1.4a and the second metering pump 1.4b to constant pressure mode respectively, open the first valve 1.7a and the fourth valve 1.7e in the fluid injection and circulation control subsystem 1, close the second valve 1.7b and the third valve 1.7c, and the first metering pump 1.4a injects fluid into the sample 2.5 at a pressure slightly higher than that of the second metering pump 1.4b, and the supercritical carbon dioxide flooding experiment can be carried out.

[0057] 8. When the fluid volume in the first metering pump 1.4a is insufficient, close the first valve 1.7a and the fourth valve 1.7e in the fluid injection and circulation control subsystem 1, and readjust the pressure of the first metering pump 1.4a and the second metering pump 1.4b. After the pressure stabilizes, open the second valve 1.7b and the third valve 1.7c to achieve the circulation displacement of supercritical carbon dioxide.

[0058] 9. When the reading of the differential pressure gauge 3.1 in the multiphase fluid separation subsystem 3 does not change, the displacement is considered complete. Open the first valve 6.2a of the fluid collection subsystem 6 in the fluid collection subsystem, adjust the pressure of the back pressure valve 3.4 in the multiphase fluid separation subsystem 3, and make the water 3.3c in the multiphase fluid separation device 3.2 flow into the first fluid collection container 6.3a in the fluid collection subsystem 6. Observe the reading change of the differential pressure gauge 3.1 in the multiphase fluid separation subsystem 3. When the slope of the differential pressure gauge 3.1 decreases sharply ( Figure 5 ), close the first valve 6.2a of the fluid collection subsystem 6, open the second valve 6.2b of the fluid collection subsystem 6, and allow the oil 3.3b in the multiphase fluid separation device 3.2 to flow into the second fluid collection container 6.2b in the fluid collection subsystem 6. When the reading of the differential pressure gauge 3.1 drops to zero, indicating that the phase separation of the oil 3.3b and the water 3.3c is completed, close the second valve 6.2b of the fluid collection subsystem 6. At this point, the displacement and fluid collection work is completed.

Claims

1. A method for separating and collecting multiphase fluids in a supercritical carbon dioxide circulation oil recovery process using a supercritical carbon dioxide circulation oil recovery experimental device based on multiphase fluid separation, characterized in that: The steps include: 1) manufacturing the device, which comprises a fluid injection and circulation control subsystem, a core clamping subsystem, a multiphase fluid separation subsystem, a data acquisition subsystem, and a temperature control subsystem; the stainless steel pipe in the fluid injection and circulation control subsystem is connected to the first end pad in the core clamping subsystem, the second end pad in the core clamping subsystem is connected to the multiphase fluid separation device in the multiphase fluid separation subsystem through the stainless steel pipe, and the multiphase fluid separation device is respectively connected to the second three-way and the fourth valve in the fluid injection and circulation control subsystem through the stainless steel pipe; the constant temperature water tank in the temperature control subsystem is connected to the first metering pump and the second metering pump in the fluid injection and circulation control subsystem through an external water pipe, and the first pressure sensor and the second pressure sensor in the fluid injection and circulation control subsystem, the core clamping subsystem pressure sensor in the core clamping subsystem, and the differential pressure gauge in the multiphase fluid separation subsystem are respectively connected to the acquisition card in the data acquisition subsystem through the first cable, the second cable, the third cable, and the fourth cable; 2) Prepare the test sample saturated with oil and water, and wrap it with plastic wrap to prevent the oil and water from evaporating; 3) neatly stacking the first end gasket, the first porous gasket, the sample, the second porous gasket, and the second end gasket together, and tightly wrapping and sealing them with a sealing material to isolate the sample from the confining pressure liquid; 4) Connecting the first cross-piece in the fluid injection and circulation control subsystem to the first end pad in the core clamping subsystem through a stainless steel pipe; connecting the second end pad in the core clamping subsystem to the multiphase fluid separation device in the multiphase fluid separation subsystem; 5) Injecting confining pressure liquid into the pressure chamber through the confining pressure pump. When the pressure of the confining pressure liquid in the pressure chamber reaches the pressure required for the experiment, the injection is stopped and the pressure is maintained stable; 6) Open the valve of the gas cylinder, fill the first metering pump with carbon dioxide, and adjust the pressure of the first metering pump and the temperature of the constant temperature water tank to make the carbon dioxide in a supercritical state; 7) The first metering pump and the second metering pump are respectively set to a constant pressure mode, the first valve and the fourth valve in the fluid injection and circulation control subsystem are opened, the second valve and the third valve are closed, and the first metering pump injects fluid into the sample at a pressure slightly higher than that of the second metering pump, and a supercritical carbon dioxide flooding experiment can be performed; 8) When the fluid volume in the first metering pump is insufficient, the first valve and the fourth valve in the fluid injection and circulation control subsystem are closed, and the pressure of the first metering pump and the second metering pump are readjusted. After the pressure is stable, the second valve and the third valve are opened to realize the circulation displacement of supercritical carbon dioxide; 9) When the differential pressure gauge reading in the multiphase fluid separation subsystem stops changing, the displacement is considered complete; Open the first valve of the fluid collection subsystem in the fluid collection subsystem, adjust the pressure of the back pressure valve in the multiphase fluid separation subsystem, and allow the water in the multiphase fluid separation device to flow into the first fluid collection container in the fluid collection subsystem; The differential pressure gauge reading in the multiphase fluid separation subsystem changes. When the downward slope of the differential pressure gauge reading changes suddenly, the first valve of the fluid collection subsystem in the fluid collection subsystem is closed, and the second valve of the fluid collection subsystem in the fluid collection subsystem is opened to allow the oil in the multiphase fluid separation device to flow into the second fluid collection container in the fluid collection subsystem. When the differential pressure gauge reading drops to zero, indicating that the separation of the oil and water phases is completed, the second valve of the fluid collection subsystem in the fluid collection subsystem is closed, and the displacement and fluid collection work are completed.

2. The method according to claim 1, characterized in that: The fluid injection and circulation control subsystem includes a gas cylinder, a pressure reducing valve, a first filter, a second filter, a first metering pump, a second metering pump, a stainless steel pipe, a first three-way, a second three-way, a first valve, a second valve, a third valve, a fourth valve, a first four-way, a second four-way, a first pressure sensor, a second pressure sensor, and a vacuum pump. The gas cylinder in the fluid injection and circulation control subsystem is connected to the pressure reducing valve, the pressure reducing valve is connected to the first filter, the first filter is connected to the first metering pump, the first fluid metering pump is connected to one end of the first three-way through the stainless steel pipe, and the other two ends of the first three-way are respectively connected to the first valve The first valve is connected to the third valve, the third valve is connected to one end of the second three-way valve, the other two ends of the second three-way valve are respectively connected to the differential pressure gauge and the multiphase fluid separation device in the multiphase fluid separation subsystem, the first valve is connected to one end of the first four-way valve; the other three ends of the first four-way valve are respectively connected to the second valve, the first pressure sensor, and the first end pad in the core clamping subsystem, the second valve is connected to one end of the second four-way valve, the other three ends of the second four-way valve are respectively connected to the fourth valve, the second pressure sensor, and the second metering pump, the fourth valve is connected to the multiphase fluid separation device in the multiphase fluid separation subsystem, and the second metering pump is connected to the second filter; The second filter is connected to the vacuum pump.

3. The method according to claim 1, characterized in that: The multiphase fluid separation subsystem includes a differential pressure gauge, a multiphase fluid separation device, and a back pressure valve. One end of the differential pressure gauge is connected to the lower left end of the multiphase fluid separation device, and the other end of the differential pressure gauge is connected to the second three-way connection in the fluid injection and circulation control subsystem; one end of the back pressure valve is connected to the lower right end of the multiphase fluid separation device, and the other end of the back pressure valve is connected to the three-way connection of the fluid collection subsystem in the fluid collection subsystem; the top of the multiphase fluid separation device is connected to the second end pad in the core clamping subsystem through a stainless steel pipe.

4. The method according to claim 3, characterized in that: The multiphase fluid separation device is a hollow cylinder with a pad at the upper and lower ends respectively, a 1 / 8inh internal threaded opening at the top thereof, and 1 / 8inh internal threaded openings on both sides of the upper and lower ends. The top of the multiphase fluid separation device is connected to the second end pad in the core clamping subsystem through a stainless steel pipe, and the upper left and upper right ends are respectively connected to the second three-way and fourth valve in the fluid injection and circulation control subsystem through stainless steel pipes; the lower left and lower right ends are respectively connected to the differential pressure gauge and back pressure valve in the multiphase fluid separation subsystem through stainless steel pipes.

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