An oil-gas-water three-phase automatic metering device and method

Abstract

The present invention discloses an automatic metering device and method for oil-gas-water three-phase, which relates to the field of metering and includes a liquid inlet pipe, a pump body, a degassing assembly, a water inlet assembly, a first liquid storage pipe, a second liquid storage pipe, a weighing assembly and a control unit. One ends of the liquid inlet pipe, the degassing assembly, the first liquid storage pipe and the second liquid storage pipe are respectively connected to four valve ports of a first switching valve. One ends of the water inlet assembly, the pump body, the other end of the first liquid storage pipe and the other end of the second liquid storage pipe are respectively connected to four valve ports of a second switching valve. The other ends of the degassing assembly, the water inlet assembly and the pump body are all communicated with the weighing assembly. The pump body, the degassing assembly and the weighing assembly are all communicatively connected to the control unit. The device of the present invention does not need to separate the oil and water two-phase fluids in the fluid to be measured, can perform single-phase fluid metering of the emulsion, and through the design of the liquid storage pipeline and the switching valve, the forward drainage and the reverse liquid discharge can be carried out simultaneously, realizing continuous and real-time metering.

Description

Technical Field

[0001] The present invention relates to the technical field of metrology, and particularly to an automatic metering device and method for oil, gas and water three phases. Background Art

[0002] In the oil and gas industry, indoor core displacement simulation experiments are often carried out to study the flow law of oil and gas in reservoirs, so as to provide a scientific basis for accurately grasping the production dynamics of oil and gas wells, formulating development plans and potential tapping measures. In such displacement experiments, the produced fluid is often a fluid to be measured mixed with oil, gas and water three phases. In order to study the seepage law of multiphase fluid in the core, it is necessary to measure the production of each phase fluid in real time at the outlet end. In the experiment, there often appear phenomena such as the volume of one of the phase fluids is tiny, or the three phases interact to form an emulsion, resulting in difficult separation, which puts forward higher requirements for the accurate metering of the three-phase fluid.

[0003] At present, the oil, gas and water three-phase metering device usually needs to separate the three phases first by using the density difference in a metering pipe with a larger diameter, and then measure them respectively. This type of device generally requires manual assistance for metering, has a low degree of automation, and is greatly affected by the diameter of the metering pipe, the separation speed and the flow speed of the fluid to be measured, and the metering accuracy is low. For the oil, gas and water fluids to be measured with difficult separation, there is currently no effective means to accurately measure them separately. Summary of the Invention

[0004] The purpose of the present invention is to provide an automatic metering device and method for oil, gas and water three phases to solve the problems existing in the above-mentioned prior art, so that the volume measurement of oil, gas and water does not require oil-water separation and has high metering accuracy.

[0005] To achieve the above purpose, the present invention provides the following scheme:

[0006] The present invention provides an automatic metering device for oil, gas and water three phases, including a liquid inlet pipe, a pump body, a degassing component, a water inlet component, a first liquid storage pipe, a second liquid storage pipe, a weighing component and a control unit. One end of the liquid inlet pipe, the degassing component, the first liquid storage pipe and one end of the second liquid storage pipe are respectively connected to four valve ports of a first switching valve. One end of the water inlet component, one end of the pump body, the other end of the first liquid storage pipe and the other end of the second liquid storage pipe are respectively connected to four valve ports of a second switching valve. The other ends of the degassing component, the water inlet component and the pump body are all communicated with the weighing component. The pump body, the degassing component and the weighing component are all in communication connection with the control unit.

[0007] Preferably, the first switching valve can switch the connection between the liquid inlet pipe and the first liquid storage pipe to the connection between the liquid inlet pipe and the second liquid storage pipe, and at the same time switch the connection between the degassing assembly and the second liquid storage pipe to the connection between the degassing assembly and the first liquid storage pipe; the second switching valve can switch the connection between the first liquid storage pipe and the water inlet assembly to the connection between the first liquid storage pipe and the pump body, and at the same time switch the connection between the second liquid storage pipe and the pump body to the connection between the second liquid storage pipe and the water inlet assembly.

[0008] Preferably, both the first switching valve and the second switching valve are planar four-way switching valves, and the planar four-way switching valve can be communicatively connected to the control unit.

[0009] Preferably, the degassing system includes a sealed container, a waterproof breathable pipe, a vacuum pump and a vacuum pressure gauge. The waterproof breathable pipe penetrates through both ends of the sealed container. One end of the waterproof breathable pipe is connected to the first switching valve, and the other end is communicated with the weighing assembly through a third liquid storage pipe. The vacuum pump and the vacuum pressure gauge are hermetically connected to the sealed container, and the vacuum pump and the vacuum pressure gauge can be communicatively connected to the control unit.

[0010] Preferably, micropores are evenly distributed on the pipe wall of the waterproof breathable pipe, and the size of the micropores is larger than the size of gas molecules and smaller than the size of liquid molecules.

[0011] Preferably, the water inlet assembly includes a water inlet pipe and an open water storage device. The lower end of the water storage device is connected to the water inlet pipe. The water inlet pipe is communicated with the upper end of the weighing assembly. The water inlet pipe is communicated with the second switching valve through a tee. A valve is arranged on the water inlet pipe, and the valve is located below the tee. The valve is an electromagnetic valve and can be communicatively connected to the control unit.

[0012] Preferably, the weighing assembly includes an electronic scale and an open liquid storage device. The liquid storage device is placed on the electronic scale, and the electronic scale can be communicatively connected to the control unit.

[0013] Preferably, the end of the pipeline connecting the pump body to the communicating liquid storage device and the end of the pipeline connecting the degassing assembly to the communicating liquid storage device are located at the bottom of the liquid storage device.

[0014] The present invention also discloses an automatic metering method for oil-gas-water three-phase, based on the above-mentioned automatic metering device for oil-gas-water three-phase, including the following steps:

[0015] Step 1, experimental preparation

[0016] Fill the liquid reservoir with enough water. Use a peristaltic pump to fill all pipelines with water. The control unit records the initial detected weight of the electronic scale as G0. Switch the first switching valve and the second switching valve to the pipeline flow state of forward drainage of the first liquid storage pipe. The valve below the water inlet pipe is in the open state. Turn on the vacuum pump, and keep the closed container of the degassing system under vacuum pressure throughout the experiment process;

[0017] Step 2, Forward drainage

[0018] The fluid to be measured enters the first liquid storage pipe through the liquid inlet pipe for forward drainage. At time interval t, the control unit records the detected weight G1 of the electronic scale. Then the single - time forward drainage weight increment is ΔG1 = G1 - G0;

[0019] Step 3, Combination of forward drainage and reverse liquid drainage

[0020] Switch the first switching valve and the second switching valve to the pipeline flow state of forward drainage of the second liquid storage pipe. The valve is closed. The fluid to be measured enters the second liquid storage pipe for forward drainage, and the drained water is collected in the water storage device. At the same time, the pump body is used to inject water into the first liquid storage pipe for reverse liquid drainage. The fluid to be measured is gradually displaced into the waterproof breather pipe of the degassing system. Then the gas phase components in the fluid to be measured are removed due to vacuum pumping, and only the oil - water fluid remains. When the drainage volume of the peristaltic pump is greater than the volume of the fluid to be measured but less than the volume of the third liquid storage pipe connected to the degassing system, at this time the fluid to be measured completely enters the degassing system to complete degassing but does not enter the liquid reservoir. The control unit records the stable detected weight G2 of the electronic scale at this time. The reduced weight of the water in the liquid reservoir at this time is ΔG2 = G1 - G2, and the reduced water volume is the volume of the gas in the fluid to be measured. Continue to displace the first liquid storage pipe so that the fluid to be measured is completely discharged from the liquid storage pipe into the liquid reservoir. The peristaltic pump stops. The control unit records the stable detected weight G3 of the electronic scale at this time. Let ΔG3 = G3 - G0. ΔG3 is the total mass of the oil and water in this section of the fluid to be measured. After G3 is measured, open the valve, and the water in the water storage device flows into the liquid reservoir under the action of gravity, and at the same time the water for subsequent forward displacement continuously flows into the liquid reservoir and is weighed;

[0021] Step 4, Calculation of the volumes of oil, gas, and water by the forward - reverse displacement weighing method

[0022] The calculation principle of the control unit is as follows: By draining the piston of the fluid to be measured forward and weighing the drained water, the volume of the fluid to be measured in this section entering the liquid storage pipe can be calculated; By injecting water backward to drive the fluid to be measured into the degassing system, degassing is completed and the original volume occupied by gas is filled with water. By measuring the reduced weight of water, the gas volume in the fluid to be measured can be calculated. By discharging all the degassed oil-water fluid and weighing it, the mass of the oil-water fluid can be obtained. Then, combined with the density of the single-phase fluid in the fluid to be measured, the volumes of the three-phase fluids in the fluid to be measured can be calculated respectively;

[0023] The specific calculation method is as follows: Assume that at a time interval of t, the volumes of oil, gas, and water in the fluid to be measured entering a certain liquid storage pipe are V0, V g , V w respectively. Given that the densities of oil and water are ρ o , ρ w respectively, the mass of the water discharged during the forward drainage stage of this section of the fluid to be measured is ΔG1 = G1 - G0. Therefore, we get

[0024] ΔG1 = (V o + V g + V w )ρ w (1)

[0025] After degassing the fluid to be measured, ΔG2 = G1 - G2. At this time, the reduced volume of water in the liquid storage device is the gas volume in the fluid to be measured, that is, we get

[0026]

[0027] When all the degassed oil-water fluid is driven out and weighed, the increased weight ΔG3 = G3 - G0 in the liquid storage device relative to the initial G0 at this time, then the true weight of the oil-water fluid can be obtained as

[0028] ΔG3 = V o ρ o + V w ρ w (3)

[0029] By jointly solving equations (1), (2), and (3), the volumes of oil, gas, and water V0, V g , V w produced in the experiment during the time interval t can be calculated.

[0030] Preferably, the time interval t is any duration such that the total volume of single - stage forward drainage is less than the total volume of the first liquid storage tube; after all the oil - water fluid to be measured is expelled from the third liquid storage tube connected to the degassing system, the directions of the first switching valve and the second switching valve are simultaneously switched, enabling the degassing and metering of the fluid to be measured entering the first liquid storage tube and the second liquid storage tube respectively. By switching the first switching valve and the second switching valve to form two parallel storage pipelines for the fluid to be measured, forward drainage and reverse liquid discharge can be carried out simultaneously, realizing continuous real - time metering of the fluid to be measured until the end of the experiment.

[0031] The present invention has achieved the following technical effects compared with the prior art:

[0032] The device of the present invention does not require the separation of the oil - water two - phase fluid in the fluid to be measured, can perform single - phase fluid metering of the emulsion, and through the design of the liquid storage pipeline and the switching valve, forward drainage and reverse liquid discharge can be carried out simultaneously, realizing continuous real - time metering. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is a schematic structural diagram of a state of the oil - gas - water three - phase automatic metering device of the present invention;

[0035] Figure 2 It is a schematic structural diagram of another state of the oil - gas - water three - phase automatic metering device of the present invention;

[0036] Wherein: 1 - liquid inlet pipe, 2 - first switching valve, 3 - second switching valve, 31 - first liquid storage tube, 32 - second liquid storage tube, 33 - third liquid storage tube, 4 - degassing system, 41 - sealed container, 42 - waterproof breathable pipe, 43 - vacuum pump, 44 - vacuum pressure gauge, 5 - pump body, 6 - valve, 7 - water storage device, 8 - liquid storage device, 9 - electronic scale, 10 - control unit, 11 - water inlet pipe, 100 - oil - gas - water three - phase automatic metering device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0038] The object of the present invention is to provide an automatic metering device and method for oil, gas and water phases to solve the problems existing in the prior art, so that the volume measurement of oil, gas and water does not require oil-water separation and has high metering accuracy.

[0039] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0040] As Figures 1 to 2 shown: This embodiment provides an automatic metering device 100 for oil, gas and water phases, including a liquid inlet pipe 1, a pump body 5, a degassing component, a water inlet component, a first liquid storage pipe 31, a second liquid storage pipe 32, a weighing component and a control unit 10. One end of the liquid inlet pipe 1, the degassing component, the first liquid storage pipe 31 and one end of the second liquid storage pipe 32 are respectively connected to four valve ports of the first switching valve 2, and one end of the water inlet component, one end of the pump body 5, the other end of the first liquid storage pipe 31 and the other end of the second liquid storage pipe 32 are respectively connected to four valve ports of the second switching valve 3. The other ends of the degassing component, the water inlet component and the pump body 5 are all communicated with the weighing component, and the pump body 5, the degassing component and the weighing component are all communicatively connected to the control unit 10.

[0041] The first switching valve 2 can switch the connection between the liquid inlet pipe 1 and the first liquid storage pipe 31 to the connection between the liquid inlet pipe 1 and the second liquid storage pipe 32, and at the same time switch the connection between the degassing component and the second liquid storage pipe 32 to the connection between the degassing component and the first liquid storage pipe 31; the second switching valve 3 can switch the connection between the first liquid storage pipe 31 and the water inlet component to the connection between the first liquid storage pipe 31 and the pump body 5, and at the same time switch the connection between the second liquid storage pipe 32 and the pump body 5 to the connection between the second liquid storage pipe 32 and the water inlet component. The first switching valve 2 and the second switching valve 3 are both planar four-way switching valves, both including four valve ports A, B, C, and D, and can realize the switching from the state of AC and BD being connected to each other to the state of AB and CD being connected to each other. The planar four-way switching valve can be communicatively connected to the control unit 10 to realize automatic control and calculation.

[0042] The degassing system 4 includes a sealed container 41, a waterproof breathable pipe 42, a vacuum pump 43 and a vacuum pressure gauge 44. The waterproof breathable pipe 42 penetrates through both ends of the sealed container 41 and is sealed and connected. One end of the waterproof breathable pipe 42 is connected to the first switching valve 2, and the other end is communicated with the weighing assembly through the third liquid storage pipe 33. The vacuum pump 43 and the vacuum pressure gauge 44 are sealed and connected to the sealed container 41, and the vacuum pump 43 and the vacuum pressure gauge 44 can be communicatively connected to the control unit 10. The waterproof breathable pipe 42 is located in the middle of the sealed container 41. The negative pressure atmosphere created by the vacuum pump 43 can separate the gas and enter the sealed container 41. The pipe wall of the waterproof breathable pipe 42 is evenly distributed with micropores. The size of the micropores is larger than the size of gas molecules and smaller than the size of liquid molecules. Gas can freely pass through the pipe wall of the waterproof breathable pipe 42, but liquid cannot. The waterproof breathable pipe 42 can be an expanded polytetrafluoroethylene pipe (ePTFE pipe). Among them, the first liquid storage pipe 31, the second liquid storage pipe 32 and the third liquid storage pipe 33 are preferably smooth on the pipe wall and the pipe diameter should not be too large. Generally, stainless steel or glass pipelines with an inner diameter of 3 mm - 6 mm are preferably selected, which is more convenient for the piston displacement of the mixed fluid and water in the pipeline.

[0043] The water inlet assembly includes a water inlet pipe 11 and an open water storage device 7. The lower end of the water storage device 7 is connected to the water inlet pipe 11. The water inlet pipe 11 is communicated with the upper end of the weighing assembly. The water inlet pipe 11 is communicated with the second switching valve 3 through a tee. A valve 6 is arranged on the water inlet pipe 11. The valve 6 is preferably an electromagnetic valve. The valve 6 is located below the tee, and the valve 6 can be communicatively connected to the control unit 10. The weighing assembly includes an electronic scale 9 and an open liquid storage device 8. The liquid storage device 8 is placed on the electronic scale 9, and the electronic scale 9 can be communicatively connected to the control unit 10. The end of the pipeline communicating with the liquid storage device 8 where the pump body 5 is located and the end of the pipeline communicating with the liquid storage device 8 where the degassing assembly is located are at the bottom of the liquid storage device 8, ensuring that both ends are always below the water surface, which is convenient for the water absorption and reflux of the third liquid storage pipe 33 and the pump body 5.

[0044] In this embodiment, the liquid storage device 8 used is a beaker, the water storage device 7 used is a liquid storage cup, the control unit 10 is a computer, the pump body 5 is a peristaltic pump, and the valve 6, the electronic scale 9, the peristaltic pump, the vacuum pressure gauge 44 and the vacuum pump 43 are all communicatively connected to the computer for automatic reading and control. The structure of this embodiment is simple, with high measurement accuracy and high automation. It can realize the automatic measurement of oil, gas and water without oil-water separation, solving the disadvantages of insufficient measurement accuracy in the current technology and being unable to be applied to the measurement of emulsions.

[0045] Embodiment 2

[0046] This embodiment discloses a method for automatically measuring oil, gas and water phases. Based on the oil, gas and water three-phase automatic metering device 100 in Embodiment 1, it specifically includes the following steps:

[0047] Step 1, Experimental preparation

[0048] The liquid storage device 8 (beaker) is filled with enough water. The peristaltic pump is used to fill all pipelines with water. The control unit 10 records the initial detected weight of the electronic scale 9 as G0. The first switching valve 2 and the second switching valve 3 are switched to the pipeline flow state of the first liquid storage pipe 31 for forward drainage. As Figure 1 shown in the figure, the valve 6 below the water inlet pipe 11 is in the open state. The vacuum pump 43 is turned on, and the closed container 41 of the degassing system 4 maintains a vacuum pressure and a negative pressure throughout the experiment for easy degassing.

[0049] Step 2, forward drainage

[0050] The fluid to be measured enters the first liquid storage pipe 31 through the liquid inlet pipe 1 for forward drainage. At time interval t, the control unit 10 records the detected weight G1 of the electronic scale 9. Then the weight increment of a single forward drainage is ΔG1 = G1 - G0; the time interval t can be arbitrarily selected, but it is necessary to ensure that the total volume of the water discharged each time (ΔG1 / ρ w ) is less than the total volume of the first liquid storage pipe 31.

[0051] Step 3, combination of forward drainage and reverse liquid drainage

[0052] The first switching valve 2 and the second switching valve 3 are switched to the pipeline flow state of the second liquid storage pipe 32 for forward drainage. As Figure 2 shown in the figure, the valve 6 is closed. The fluid to be measured enters the second liquid storage pipe 32 for forward drainage, and the discharged water is collected in the water storage device 7; at the same time, the pump body 5 is used to inject water into the first liquid storage pipe 31 for reverse liquid drainage. The fluid to be measured is gradually displaced into the waterproof breathable pipe 42 of the degassing system 4. Then the gas-phase components in the fluid to be measured are removed by vacuum pumping, and only the oil-water fluid remains. When the drainage volume of the peristaltic pump is greater than the volume of the fluid to be measured (ΔG1 / ρ w)When it is less than the volume of the third liquid storage pipe 33 connected to the degassing system 4, or when the length of the waterproof breathing pipe 42 and the pipe of the degassing system 4 is increased so that the fluid to be measured entering at one time can be completely located within the waterproof breathing pipe 42 for static exhaust, at this time, the fluid to be measured completely enters the degassing system 4 to complete degassing, but does not enter the liquid storage device 8. The control unit 10 records the stable detection weight G2 of the electronic scale 9 at this time. At this time, the reduced weight of the water in the liquid storage device 8 is ΔG2 = G1 - G2, and the reduced volume of water is the volume of gas in the fluid to be measured; continue to displace the first liquid storage pipe 31 so that the fluid to be measured is completely discharged from the liquid storage pipe and enters the liquid storage device 8, the peristaltic pump stops, and the control unit 10 records the stable detection weight G3 of the electronic scale 9 at this time. Let ΔG3 = G3 - G0, and ΔG3 is the total mass of oil and water in this section of the fluid to be measured. After G3 is measured, open the valve 6, and the water in the water storage device 7 flows into the liquid storage device 8 completely under the action of gravity, and at the same time, the water for subsequent forward displacement continues to flow into the liquid storage device 8 to be weighed; at this time, the control unit 10 records the detection weight of the electronic scale 9 as the new G0', which can be used for the next measurement.

[0053] Step Four, Calculation of the Volumes of Oil, Gas, and Water by the Forward and Reverse Displacement Weighing Method

[0054] The calculation principle of the control unit 10 is that by the piston-type drainage of the fluid to be measured in the forward direction and weighing the discharged water, the volume of this section of the fluid to be measured entering the liquid storage pipe can be calculated; by reverse water injection, the fluid to be measured is driven into the degassing system 4 to complete degassing and fill the volume originally occupied by gas with water. By measuring the reduced weight of water, the volume of gas phase in the fluid to be measured can be calculated. By discharging all the oil-water fluid after degassing and weighing it, the mass of the oil-water fluid can be obtained. Combining with the density of the single-phase fluid in the fluid to be measured, the volumes of the three-phase fluids in the fluid to be measured can be calculated respectively.

[0055] The specific calculation method is as follows: Assume that at a time interval of t, the volumes of oil, gas, and water in the fluid to be measured entering a certain liquid storage pipe are V0, V g 、V w , respectively. Given that the densities of oil and water are ρ o 、ρ w , respectively. The mass of the water discharged during the forward water drainage stage of this section of the fluid to be measured is ΔG1 = G1 - G0. Therefore, we get

[0056] ΔG1 = (V o +V g +V w )ρ w (1)

[0057] After the fluid to be measured is degassed, ΔG2 = G1 - G2. At this time, the reduced volume of water in the liquid storage device 8 is the volume of gas in the fluid to be measured, that is, we get

[0058]

[0059] When the oil-water fluid is completely displaced and weighed after degassing, at this time, the increased weight ΔG3 = G3 - G0 in the liquid storage device 8 relative to the initial G0, then the true weight of the oil-water fluid can be obtained as

[0060] ΔG3 = V o ρ o +V w ρ w (3)

[0061] By jointly solving the formulas (1), (2), and (3), the volumes V0, V g , V w .

[0062] Among them, the time interval t is any duration that makes the total volume of single forward drainage less than the total volume of the first liquid storage tube 31, then the total flow rate v of the fluid to be measured can also be calculated 总 =(V0 + V g +V w ) / t, and the flow rates of oil, gas, and water respectively are v0 = V0 / t, v g =V g / t, v w =V w / t; when all the oil-water fluid to be measured is displaced from the third liquid storage tube 33 connected to the degassing system 4 after degassing, at the same time, switch the directions of the first switching valve 2 and the second switching valve 3, and the fluid to be measured entering the first liquid storage tube 31 and the second liquid storage tube 32 can be degassed and metered respectively. By switching the first switching valve 2 and the second switching valve 3 to form two parallel storage pipelines for the fluid to be measured, the forward drainage and the reverse liquid drainage can be carried out simultaneously, realizing the continuous real-time metering of the fluid to be measured until the end of the experiment.

[0063] The metering method in this embodiment does not require separating the oil and water two-phase fluids in the mixed liquid. Therefore, the volumes of water and oil in the emulsion can be measured. Through the design of the two pipelines by the plane four-way switching valve, the forward drainage and the reverse liquid drainage can be carried out simultaneously, realizing the continuous real-time metering of the single-phase fluid.

[0064] In this specification, specific examples are used to elaborate the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An automatic measurement method for oil-gas-water three-phase, based on an automatic measurement device for oil-gas-water three-phase, characterized in that: The oil-gas-water three-phase automatic metering device includes a liquid inlet pipe, a pump body, a degassing assembly, a water inlet assembly, a first liquid storage pipe, a second liquid storage pipe, a weighing assembly and a control unit. One end of the liquid inlet pipe, the degassing assembly, the first liquid storage pipe and one end of the second liquid storage pipe are respectively connected to four valve ports of a first switching valve. One end of the water inlet assembly, one end of the pump body, the other end of the first liquid storage pipe and the other end of the second liquid storage pipe are respectively connected to four valve ports of a second switching valve. The other ends of the degassing assembly, the water inlet assembly and the pump body are all communicated with the weighing assembly. The pump body, the degassing assembly and the weighing assembly are all in communication connection with the control unit. The degassing assembly includes a sealed container, a waterproof breather pipe, a vacuum pump and a vacuum pressure gauge. The waterproof breather pipe penetrates through both ends of the sealed container. One end of the waterproof breather pipe is connected to the first switching valve, and the other end is communicated with the weighing assembly through a third liquid storage pipe. The water inlet assembly includes a water inlet pipe and an open water storage device. The lower end of the water storage device is connected to the water inlet pipe. The water inlet pipe is communicated with the upper end of the weighing assembly. The water inlet pipe is communicated with the second switching valve through a tee. A valve is arranged on the water inlet pipe and is located below the tee. The weighing assembly includes an electronic scale and an open liquid storage device. It includes the following steps: Step 1, experiment preparation Fill the liquid storage device with enough water. Use the pump body to fill all pipelines with water. The control unit records the initial detected weight of the electronic scale as G0. The first switching valve and the second switching valve are switched to the pipeline flow state of the first liquid storage pipe discharging water forward. The valve below the water inlet pipe is in the open state. Turn on the vacuum pump, and keep the sealed container of the degassing assembly under vacuum pressure throughout the experiment. Step 2, forward drainage The fluid to be measured enters the first liquid storage pipe through the liquid inlet pipe for forward drainage, and the time interval is When, the control unit records the detected weight G1 of the electronic scale, and the weight increment of a single forward drainage is ; Step 3, combination of forward drainage and reverse liquid drainage The first switching valve and the second switching valve are switched to the pipeline flow state of the second liquid storage pipe for forward drainage, the valve is closed, and the fluid to be measured enters the second liquid storage pipe for forward drainage, and the drained water is collected in the water storage device; at the same time, the pump body injects water into the first liquid storage pipe for reverse drainage, and the fluid to be measured is gradually displaced into the waterproof breathable pipe of the degassing assembly. Then, the gas-phase components in the fluid to be measured are removed by vacuum pumping, and only the oil-water fluid remains. When the drainage volume of the pump body is greater than the volume of the fluid to be measured but less than the volume of the third liquid storage pipe connected to the degassing assembly, at this time, the fluid to be measured completely enters the degassing assembly to complete degassing but does not enter the liquid storage device. The control unit records the stable detection weight G2 of the electronic scale at this time. At this time, the weight of the water reduced in the liquid storage device is , and the reduced water volume is the volume of the gas in the fluid to be measured; continue to displace the first liquid storage pipe so that the fluid to be measured is completely discharged from the liquid storage pipe and enters the liquid storage device, the pump body stops, and the control unit records the stable detection weight G3 of the electronic scale at this time. Let , which is the total mass of the oil and water in this section of the fluid to be measured. After G3 is measured, the valve is opened, and the water in the water storage device flows into the liquid storage device completely under the action of gravity. At the same time, the water for subsequent forward displacement continues to flow into the liquid storage device and is weighed; Step 4, calculation of the volumes of oil, gas and water by the forward and reverse displacement weighing method The calculation principle of the control unit is that by the forward piston-type drainage of the fluid to be measured and weighing the discharged water, the volume of this section of the fluid to be measured entering the liquid storage pipe can be calculated. By reverse water injection, the fluid to be measured is driven into the degassing assembly to complete degassing and fill the volume originally occupied by gas with water. By measuring the reduced weight of the water, the gas phase volume in the fluid to be measured can be calculated. By discharging all the degassed oil-water fluid and weighing it, the mass of the oil-water fluid can be obtained. Then, combined with the density of the single-phase fluid in the fluid to be measured, the volumes of the three-phase fluids in the fluid to be measured can be calculated respectively.

2. The automatic metering method for oil-gas-water three-phase according to claim 1, characterized in that: The first switching valve can switch the connection between the liquid inlet pipe and the first liquid storage pipe to the connection between the liquid inlet pipe and the second liquid storage pipe, and at the same time switch the connection between the degassing assembly and the second liquid storage pipe to the connection between the degassing assembly and the first liquid storage pipe. The second switching valve can switch the connection between the first liquid storage pipe and the water inlet assembly to the connection between the first liquid storage pipe and the pump body, and at the same time switch the connection between the second liquid storage pipe and the pump body to the connection between the second liquid storage pipe and the water inlet assembly.

3. The automatic measurement method for oil-gas-water three-phase according to claim 1, wherein: Both the first switching valve and the second switching valve are planar four-way switching valves, and the planar four-way switching valve can be communicatively connected to the control unit.

4. The automatic metering method for oil-gas-water three-phase according to claim 1, characterized in that: The vacuum pump and the vacuum pressure gauge are hermetically connected to the closed container, and the vacuum pump and the vacuum pressure gauge can be communicatively connected to the control unit.

5. The automatic measurement method for oil-gas-water three-phase according to claim 4, characterized in that: Micropores are evenly distributed on the tube wall of the waterproof breathable tube, and the size of the micropores is larger than the size of gas molecules and smaller than the size of liquid molecules.

6. The automatic metering method for oil-gas-water three-phase according to claim 1, wherein: The valve is a solenoid valve and can be communicatively connected to the control unit.

7. The automatic metering method for oil-gas-water three-phase according to claim 1, characterized in that: The liquid storage tank is placed on the electronic scale, and the electronic scale can be communicatively connected to the control unit.

8. The automatic metering method for oil-gas-water three-phase according to claim 7, characterized in that: The end of the pipeline connecting the pump body and the liquid storage tank and the end of the pipeline connecting the degassing assembly and the liquid storage tank are located at the bottom of the liquid storage tank.

9. The automatic oil-gas-water three-phase metering method according to claim 1, wherein: In step four, volume calculation of oil, gas, and water by the forward and reverse displacement weighing method The specific calculation method is as follows: Assume that at a time interval of t, the volumes of oil, gas, and water in the fluid to be measured entering a certain liquid storage pipe are V0, V g , V w respectively. Given that the densities of oil and water are , respectively, the mass of water discharged from the fluid to be measured during the forward drainage stage in this section is , so we get （1） After degassing the fluid to be measured, , the reduced volume of water in the reservoir at this time is the volume of gas in the fluid to be measured, thus obtaining （2） When all the oil-water fluid is driven out and weighed after degassing, the weight increase in the liquid reservoir relative to the initial G0 at this time , then the true weight of the oil-water fluid can be obtained as （3） By jointly solving equations (1), (2), and (3), the time interval can be calculated. The volumes V0, V of oil, gas, and water produced in the experiment within g , V w .

10. The automatic metering method for oil-gas-water three-phase according to claim 9, characterized in that: The time interval is any duration such that the total volume of a single forward drainage is less than the total volume of the first liquid storage tube; After all the oil-water fluid to be measured is displaced from the third liquid storage pipe connected to the degassing assembly after degassing, the directions of the first switching valve and the second switching valve are switched simultaneously, and the fluid to be measured entering the first liquid storage pipe and the second liquid storage pipe can be degassed and measured respectively. Two parallel storage pipelines for the fluid to be measured are switched out through the first switching valve and the second switching valve, so that forward drainage and reverse liquid discharge can be carried out simultaneously, realizing continuous real-time metering of the fluid to be measured until the end of the experiment.

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