System for recovering vented natural gas of drainage and production oil-gas well

Abstract

The invention belongs to the technical field of oilfield exploitation, and provides a system for recovering emptying natural gas of a discharge and exploitation oil and gas well, comprising: a compressor, the compressor comprises a screw compressor and a reciprocating compressor, the screw compressor and the reciprocating compressor are connected in series, and the screw compressor is located at the air inlet front end; the separator is connected between the compressor and the wellhead connecting pipe, and the separator is connected with the waste oil tank. According to the invention, a widely applicable skid-mounted system is provided, a general single equipment and control mode is changed, and multiple types of equipment combinations, load regulation and backflow control are adopted. And wide-range change of natural gas in different periods of the drainage wellhead is adapted. Rapid and continuous recovery of scattered natural gas becomes possible, emission of the natural gas is reduced to the maximum extent, and the natural environment is effectively protected. The system is designed in a prying mode, is manufactured in a factory mode, and has the advantages of being compact in structure, easy to transport and move and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield exploitation, and in particular relates to a system for recovering natural gas discharged from oil and gas wells. Background Art

[0002] Oil and gas wells produce a certain amount of natural gas during the process of exploitation, oil testing, and drainage. The amount and stability of the gas vary greatly. Generally, it is treated by directly venting it to the outside or burning it with a flare, which causes waste of resources and environmental pollution.

[0003] In order to solve the problem of energy waste and environmental pollution caused by venting natural gas during oil and gas wellhead production, a natural gas recovery system is currently used to recover the vented natural gas. The existing natural gas recovery system at the oil and gas wellhead is an integrated skid-mounted equipment consisting of a separation and metering skid, a compressor skid, and a dehydration and dehydrogenation skid. It is widely used for natural gas recovery during oil and gas well production, oil testing, and drainage. In order to adapt to a variety of gas volume ranges, PetroChina Tarim Oilfield has adopted a 2×10 4 m 3 / d, 3×10 4 m 3 / d, 5×10 4 m 3 / d, multiple skids are matched at three levels to achieve the purpose of adjusting production capacity. (Natural Gas and Petroleum, 2012, No. 5, P23, Li Xunji et al.) During the gas testing and production test of natural gas exploration and evaluation wells, a large amount of natural gas was vented by the Natural Gas Branch of Daqing Oilfield. The gas venting volume of each well varied greatly, ranging from 3 to 20×10 4 m 3 / d range, the operating flexibility of the recovery equipment is limited. The Natural Gas Branch Company designed a gas extraction valve group skid that meets the above conditions. When the venting pipeline pressure is higher than 0.5MPa, the regulating valve opens to release part of the gas volume to the recovery flare for ignition. When the venting pipeline pressure is lower than 0.5MPa, the regulating valve closes to recover as much venting air as possible. (Petroleum and Petrochemical Energy Conservation, 2016, No. 11, P48.49, Zhang Dandi and Li Yue). In order to adapt to a variety of gas volume ranges, the existing oil and gas wellhead natural gas recovery system is designed to be matched with multiple skids. Different grades of skid-mounted equipment are used for different wellheads. Different grades of skid-mounted equipment must be replaced at different times for the same wellhead, which reduces work efficiency and interrupts continuous production at the wellhead. Secondly, each grade of skid-mounted equipment cannot fully recover all the natural gas beyond the range. If the skid-mounted equipment is replaced or added, the transportation and hoisting costs will increase. Summary of the invention

[0004] The object of the present invention is to provide a system for recovering natural gas from venting oil and gas wells, aiming to solve the technical problem of poor adaptability of skid-mounted equipment for recovering natural gas in the prior art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A system for recovering natural gas from venting an oil and gas well, comprising a wellhead connecting pipe, a dirty oil tank, a dehydration skid, a natural gas pipeline and a tank truck pipeline, and the system also includes:

[0007] A compressor, the compressor comprising a screw compressor and a reciprocating compressor, the screw compressor and the reciprocating compressor are connected in series, and the screw compressor is located at the front end of the air intake;

[0008] A separator is connected between the compressor and the wellhead connecting pipe, and the separator is connected to the dirty oil tank.

[0009] As a preferred embodiment of the above technical solution, the separator includes a low-pressure separator and a high-pressure separator 2, the air inlet end of the screw compressor is connected to the low-pressure separator, the low-pressure separator is connected to the wellhead connecting pipe, the low-pressure separator is connected to the dirty oil tank, the air inlet end of the screw compressor is installed with a slide valve, the output part of the screw compressor is installed with a frequency conversion controller, the air outlet end of the screw compressor is connected to an air cooler, the air outlet end of the air cooler is connected to the high-pressure separator 2, and the air outlet end of the air cooler is also connected to a reflux pipeline. The end of the return pipe is connected to the air inlet of the screw compressor, the high-pressure separator 2 is connected to the dirty oil tank, the air outlet of the high-pressure separator 2 is connected to the reciprocating compressor, another frequency conversion controller is installed on the output part of the reciprocating compressor, the air outlet of the reciprocating compressor is connected to another air cooler, the air outlet of the air cooler is connected to a buffer tank, the air outlet of the air cooler is also connected to another return pipe, the end of the return pipe is connected to the air inlet of the reciprocating compressor, and the air outlet of the buffer tank is connected to a dehydration skid.

[0010] As a preferred embodiment of the above technical solution, the separator also includes a high-pressure separator 1, and the natural gas enters the separator through the wellhead connecting pipe, wherein the natural gas with a pressure less than or equal to 3MPa enters the low-pressure separator, and the natural gas with a pressure greater than or equal to 3MPa enters the high-pressure separator 1, wherein the natural gas with a pressure equal to 3MPa enters the low-pressure separator and is pressurized by the screw compressor without entering the reciprocating compressor but directly enters the natural gas pipeline, and the natural gas with a pressure equal to 25MPa passes neither the screw compressor nor the reciprocating compressor but directly enters the dehydration skid.

[0011] As a preferred embodiment of the above technical solution, an air inlet pipe is connected to the periphery of the separator, a sealing door is installed on the surface of the separator, an exhaust pipe is connected through the top of the separator, an oil drain cylinder, a filter screen and an aeration pipe are installed in the inner cavity of the separator from top to bottom, the oil drain cylinder passes through the bottom of the separator, the filter screen is located outside the oil drain cylinder, and an auxiliary mechanism is installed on the filter screen.

[0012] As a preferred embodiment of the above technical solution, the auxiliary mechanism includes:

[0013] A rotating rod, the exhaust pipe is rotatably mounted with the rotating rod, and an impeller is fixed to the periphery of the rotating rod;

[0014] A circular ring, a fixing plate is fixed at the bottom of the rotating rod, a plurality of connecting plates are arranged at the bottom of the fixing plate, a circular ring is arranged at the bottom of the plurality of connecting plates, the circular ring is located outside the oil drain cylinder, and the outer surface of the circular ring is in contact with the inner side of the filter screen;

[0015] Upper cleaning brush and lower cleaning brush, a plurality of upper cleaning brushes and a plurality of lower cleaning brushes are arranged on the outer side of the circular ring, a plurality of upper cleaning brushes are located above the filter net, and a plurality of lower cleaning brushes are located below the filter net.

[0016] As a preferred embodiment of the above technical solution, baffles are provided on opposite sides of two adjacent upper cleaning brushes.

[0017] As a preferred embodiment of the above technical solution, the oil drain cylinder includes an inner cylinder and an outer cylinder, a plurality of partitions are arranged between the inner cylinder and the outer cylinder, a discharge chamber is formed between two adjacent partitions, a plurality of through holes are opened on the periphery of the oil drain cylinder, the positions of the plurality of through holes coincide with those of the plurality of partitions, and a sealing cover is arranged on the top of the outer cylinder.

[0018] As a preferred embodiment of the above technical solution, a plurality of oil inlet pipes penetrate the periphery of the oil drain cylinder, and the oil inlet pipes are arranged to be inclined downward from the outside of the oil drain cylinder to the inside of the oil drain cylinder. The inner side of the connecting plate is an inclined surface and is inclined toward the rotation direction of the rotating rod.

[0019] As a preferred embodiment of the above technical solution, a liquid level sensor is installed on the inner wall of the separator, and the liquid level sensor is on the same horizontal plane as the top of the oil drain barrel. A drain pipe is installed on the separator, and the drain pipe is located between the aeration pipe and the filter screen. A solenoid valve is installed on the drain pipe, and the liquid level sensor and the solenoid valve are evenly connected to an external control unit.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention provides a widely applicable skid-mounted system, which changes the general single equipment and control mode, adopts a combination of various types of equipment, and adds load regulation and reflux control. It adapts to the large-scale changes of natural gas at the wellhead at different times. It makes it possible to quickly and continuously recover scattered natural gas, minimizes the emission of natural gas, and effectively protects the natural environment. The system is skid-mounted and factory-made, with the advantages of compact structure, easy transportation and relocation;

[0022] 2. In the present invention, a method is designed to adapt to 2×104 m 3 / d, 3×10 4 m 3 / d, 5×10 4 m 3 / d three-level system, changing the multi-skid matching, adapting to different periods at the same wellhead, without the need for multi-skid deployment. The combination of screw compressor and reciprocating compressor, combined with load regulation, frequency conversion control and reflux control, adapts to the wide variation of natural gas pressure and realizes the full recovery of vented natural gas during the trial production;

[0023] 3. In the present invention, two integral skids are designed, which can be stacked on site, convenient for transportation, and save space. They can also be disassembled for use, saving investment.

[0024] 4. In the present invention, bubbles are generated by aeration through the aeration pipe, and the bubbles will slowly rise. During the rising process, the bubbles will contact the dirty oil on the surface of the impurities. Since the dirty oil has a certain surface activity and viscosity, the bubbles may be adsorbed on the surface of the dirty oil, thereby slowly carrying the dirty oil away from the bottom of the water, and slowly separating the dirty oil from the impurities; at the same time, the presence of bubbles increases the average density in the water, so that the buoyancy of the impurities with originally larger density increases, so that the impurities slowly float up, and in the process of floating up, the bubbles are adsorbed on the surface of the dirty oil, so that the dirty oil is slowly separated from the impurities, and the separated impurities slowly sink; in addition, the bubbles will cause the flow and disturbance of water, and the disturbance of the water flow helps to break the adhesion between the dirty oil and the impurities, so that the dirty oil is more easily driven by the bubbles to float up, thereby improving the efficiency of separating the dirty oil from the impurities; this separation method of dirty oil and impurities is not easy to affect the purity of natural gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the overall process flow chart of the present invention;

[0026] Figure 2 This is the compressor process flow chart;

[0027] Figure 3 It is a schematic diagram of the separator structure;

[0028] Figure 4 Schematic diagram of the internal structure of the separator;

[0029] Figure 5 Schematic diagram of the internal structure of the exhaust pipe;

[0030] Figure 6 This is a schematic diagram of some structures after disassembly;

[0031] Figure 7 It is a schematic diagram of the auxiliary mechanism structure;

[0032] Figure 8Schematic diagram of the oil drain cylinder structure.

[0033] In the figure:

[0034] 1. Wellhead connecting pipe; 2. Separator; 2a. Low-pressure separator; 2b. High-pressure separator 1; 2c. High-pressure separator 2; 21. Inlet pipe; 22. Sealing door; 3. Sewage oil tank; 4. Compressor; 41. Screw compressor; 411. Sliding valve; 42. Reciprocating compressor; 5. Dehydration skid; 6. Natural gas pipeline; 7. Tank truck pipeline; 8. Air cooler; 9. Buffer tank; 10. Frequency converter; 11. Reflux pipeline; 12. Exhaust Air pipe; 13. Aeration pipe; 14. Filter screen; 15. Oil drain cylinder; 151. Discharge chamber; 152. Partition plate; 153. Through hole; 154. Oil inlet pipe; 155. Sealing cover; 16. Auxiliary mechanism; 161. Rotating rod; 162. Impeller; 163. Fixing plate; 164. Connecting plate; 165. Ring; 166. Upper cleaning brush; 167. Lower cleaning brush; 168. Baffle; 17. Drain pipe; 18. Liquid level sensor. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0037] like Figure 1 and Figure 2 As shown, a system for recovering natural gas from venting an oil and gas well comprises a wellhead connecting pipe 1, a waste oil tank 3, a dehydration skid 5, a natural gas pipeline 6 and a tank truck pipeline 7, and the system also comprises:

[0038] Compressor 4, compressor 4 includes a screw compressor 41 and a reciprocating compressor 42, the screw compressor 41 and the reciprocating compressor 42 are connected in series, and the screw compressor 41 is located at the front end of the air intake;

[0039] The separator 2 is connected between the compressor 4 and the wellhead connecting pipe 1, and the separator 2 is connected to the waste oil tank 3.

[0040] In one case of this embodiment, the boosting range of the screw compressor 41 is 0.5 MPa-3 MPa, and the boosting range of the reciprocating compressor 42 is 3 MPa-25 MPa.

[0041] In actual application of this embodiment, natural gas from the wellhead enters the skid-mounted system, and first passes through the separator 2 for pre-separation to separate some free dirty oil and sewage in the natural gas. The preliminarily treated natural gas enters the compressor 4 for pressurization. In order to adapt to the pressure range of 0.5-25MPa, the screw compressor 41 and the reciprocating compressor 42 are connected in series, which breaks through the range of 1.0MPa of the lower limit of the intake pressure of the reciprocating compressor 42. At the same time, the two equipments complement each other, meet the requirements of 25MPa tank truck, expand the adaptability range of the skid-mounted equipment to the wellhead pressure, save energy consumption, and make the adaptability of this system stronger;

[0042] The reciprocating compressor 42 is suitable for high compression ratio applications, with a maximum compression ratio of 20:1; the reciprocating compressor 42 is designed with a variable number of compressor cylinders to suit various wellhead parameters.

[0043] Further, the separator 2 includes a low-pressure separator 2a and a high-pressure separator 2c, the air inlet end of the screw compressor 41 is connected to the low-pressure separator 2a, the low-pressure separator 2a is connected to the wellhead connecting pipe 1, the low-pressure separator 2a is connected to the dirty oil tank 3, the air inlet end of the screw compressor 41 is installed with a slide valve 411, the output part of the screw compressor 41 is installed with a frequency conversion controller 10, the air outlet end of the screw compressor 41 is connected to the air cooler 8, the air outlet end of the air cooler 8 is connected to the high-pressure separator 2c, and the air outlet end of the air cooler 8 is also connected to the return pipe 11, the return pipe 11 is connected to the return pipe 12, and the return pipe 12 is connected to the return pipe 13. The end of the pipeline 11 is connected to the air inlet end of the screw compressor 41, the high-pressure separator 2c is connected to the dirty oil tank 3, the air outlet end of the high-pressure separator 2c is connected to the reciprocating compressor 42, another frequency conversion controller 10 is installed on the output part of the reciprocating compressor 42, the air outlet end of the reciprocating compressor 42 is connected to another air cooler 8, the air outlet end of the air cooler 8 is connected to the buffer tank 9, the air outlet end of the air cooler 8 is also connected to another return pipe 11, the end of the return pipe 11 is connected to the air inlet end of the reciprocating compressor 42, and the air outlet end of the buffer tank 9 is connected to the dehydration skid 5.

[0044] In actual application, in terms of the control of the screw compressor 41, the opening of the slide valve 411 is automatically adjusted by the intake pressure to adapt to the load change, the speed of the screw compressor 41 is adjusted by the frequency conversion controller 10, the compressor processing capacity is adjusted in time, and the low gas volume range requirements are met by adjusting the slide valve 411 and the frequency conversion controller 10. Even in the case of low gas volume (natural gas interruption), the operation can be met and the large-scale gas volume change at the wellhead can be adapted; in terms of the control of the reciprocating compressor 42, the return pipe 11 is used to stabilize the intake pressure through the gas replenishment process under low flow conditions, expand the operating range, and save energy. The speed of the reciprocating compressor 42 is adjusted by the frequency conversion controller 10 to adjust the compressor processing capacity in time, and the gas volume change at the wellhead at different periods is adapted by adjusting the return pipe 11 and the frequency conversion controller 10. At the same time, the reciprocating compressor 42 is designed with multiple compression cylinders and two pressure level intake systems are designed to meet the conditions of simultaneous production of high and low pressure wells at different wellheads on a platform.

[0045] Designing two air inlet points, high and low pressure, can meet the simultaneous production of multiple wells on a platform. It can also achieve pressure changes at different times on a single inlet before entering different systems, thereby improving production efficiency and saving energy.

[0046] Furthermore, the separator 2 also includes a high-pressure separator 2b, and the natural gas enters the separator 2 through the wellhead connecting pipe 1, wherein the natural gas with a pressure less than or equal to 3MPa enters the low-pressure separator 2a, and the natural gas with a pressure greater than or equal to 3MPa enters the high-pressure separator 2b, wherein the natural gas with a pressure equal to 3MPa enters the low-pressure separator 2a, and after being pressurized by the screw compressor 41, it does not enter the reciprocating compressor 42 but directly enters the natural gas pipeline 6, and the natural gas with a pressure equal to 25MPa neither passes through the screw compressor 41 nor the reciprocating compressor 42, but directly enters the dehydration skid 5.

[0047] In actual application, this embodiment is designed with two gas inlet points, high and low pressure, and a process in which natural gas with a pressure equal to 3.0 MPa directly enters the natural gas pipeline 6 and natural gas with a pressure equal to 25.0 MPa directly enters the dehydration skid 5 or tank truck pipeline 7. Formation energy is used to directly charge compressed natural gas or pipelines, saving energy consumption.

[0048] like Figure 3-Figure 8 As shown, the outer periphery of the separator 2 is connected with an air inlet pipe 21, the surface of the separator 2 is installed with a sealing door 22, the top of the separator 2 is penetrated with an exhaust pipe 12, the inner cavity of the separator 2 is sequentially installed with an oil drain cylinder 15, a filter screen 14 and an aeration pipe 13 from top to bottom, the oil drain cylinder 15 penetrates the bottom of the separator 2, the filter screen 14 is located outside the oil drain cylinder 15, and the filter screen 14 is installed with an auxiliary mechanism 16.

[0049] It should be noted that natural gas contains not only dirty oil and sewage, but also a small amount of gravel impurities. When separating dirty oil and sewage, dirty oil, sewage and impurities will be located in the separator 2 after separation. Dirty oil is easily attached to the surface of impurities, and these impurities will sink to the bottom of the water. Dirty oil attached to the surface of impurities cannot be separated and discharged. If the impurities are directly discharged together with the dirty oil attached to the surface, it will cause environmental pollution and reduce the amount of dirty oil collected. At present, the impurities are generally separated from the dirty oil by heating. By heating water, the impurities in the water are heated, so that the dirty oil attached to the impurities is separated from the impurities, thereby achieving the effect of separating impurities from the dirty oil. However, water vapor will be generated when heating water, and the generated water vapor may be discharged with the natural gas, which reduces the purity of the natural gas.

[0050] In actual application of this embodiment, a portion of water is injected into the separator 2 in advance to prevent the dirty oil from floating due to low water content in the natural gas, and at the same time, a portion of the pressurized natural gas is passed into the aeration pipe 13; when the natural gas is separated, the natural gas enters the separator 2 through the air inlet pipe 21. Due to the effect of centrifugal force, the dirty oil, sewage and impurities in the natural gas fall to the bottom of the inner cavity of the separator 2 due to gravity, and the natural gas is discharged through the exhaust pipe 12. The dirty oil slowly floats on the water surface, while the impurities sink to the bottom of the water. Aeration through the aeration pipe 13 generates bubbles in the water, which slowly rise. During the rising process, the bubbles will contact the dirty oil on the surface of the impurities. Since the dirty oil has a certain surface activity and viscosity, the bubbles may be adsorbed on the dirt. The oil surface is gradually taken away from the bottom of the water, and the oil is gradually separated from the impurities; at the same time, the presence of bubbles increases the average density of the water, which increases the buoyancy of the impurities with a larger density, causing the impurities to slowly float up. During the floating process, the bubbles are adsorbed on the surface of the oil, so that the oil is gradually separated from the impurities, and the separated impurities slowly sink; in addition, the bubbles will cause the flow and disturbance of the water, and the disturbance of the water flow will help to break the adhesion between the oil and the impurities, making the oil more easily floated by the bubbles, thereby improving the efficiency of separating the oil from the impurities; the bubbles burst when they rise to the water surface, and the natural gas in the bubbles is discharged through the exhaust pipe 12; this separation method of oil and impurities is not easy to affect the purity of the natural gas;

[0051] The pressurized natural gas is passed into the separator 2 through the aeration pipe 13, and the natural gas can be separated again, thereby improving the purity of the natural gas finally output.

[0052] Furthermore, the auxiliary mechanism 16 includes:

[0053] A rotating rod 161 is rotatably mounted in the exhaust pipe 12, and an impeller 162 is fixed to the outer periphery of the rotating rod 161;

[0054] A ring 165, a fixing plate 163 is fixed at the bottom of the rotating rod 161, a plurality of connecting plates 164 are arranged at the bottom of the fixing plate 163, a ring 165 is arranged at the bottom of the plurality of connecting plates 164, the ring 165 is located at the outside of the oil drain cylinder 15, and the outer surface of the ring 165 is in contact with the inner side of the filter screen 14;

[0055] Upper cleaning brush 166 and lower cleaning brush 167 , a plurality of upper cleaning brushes 166 and a plurality of lower cleaning brushes 167 are arranged on the outer side of the ring 165 , the plurality of upper cleaning brushes 166 are located above the filter screen 14 , and the plurality of lower cleaning brushes 167 are located below the filter screen 14 .

[0056] Furthermore, a baffle 168 is provided on the opposite side of two adjacent upper cleaning brushes 166 .

[0057] It should be noted that when bubbles float up, they will drive impurities upward. After moving upward, the impurities can easily come into contact with the dirty oil floating on the water surface, causing the dirty oil to adhere to the surface of the impurities.

[0058] In actual application of this embodiment, when natural gas is discharged from the exhaust pipe 12, the flowing natural gas drives the impeller 162 to rotate, thereby rotating the rotating rod 161, and the rotating rod 161 rotates the ring 165 through the fixing plate 163 and the plurality of connecting plates 164, thereby rotating the plurality of upper cleaning brushes 166 around the rotating rod 161. The upper cleaning brush 166 will hit the floating impurities when rotating, and the impurities can promote the separation of the dirty oil attached to the surface of the impurities from the impurities after being hit. The impact of the impurities and the separation of the dirty oil can effectively prevent the impurities from continuing to move upward, and prevent the dirty oil from attaching to the surface of the impurities again; at the same time, when the upper cleaning brush 166 rotates, the baffles 168 on both sides of the upper cleaning brush 166 will block the impurities, further preventing the impurities from continuing to move upward, and further preventing the dirty oil from attaching to the surface of the impurities again;

[0059] During the rotation of the upper cleaning brush 166 , the upper cleaning brush 166 will clean the surface of the impurities, thereby accelerating the separation of the dirty oil and the impurities;

[0060] During the process of cleaning impurities with the upper cleaning brush 166, the impurities may clog the filter 14. At this time, the bottom of the filter 14 is cleaned by the lower cleaning brush 167 to effectively prevent the impurities from being clogged on the filter 14. At the same time, the lower cleaning brush 167 can also clean the surface of the impurities to further accelerate the separation of the dirty oil and impurities.

[0061] Furthermore, the oil drain cylinder 15 includes an inner cylinder and an outer cylinder, a plurality of partitions 152 are arranged between the inner cylinder and the outer cylinder, a discharge chamber 151 is formed between two adjacent partitions 152, a plurality of through holes 153 are opened on the periphery of the oil drain cylinder 15, the positions of the plurality of through holes 153 and the plurality of partitions 152 coincide, and a sealing cover 155 is arranged on the top of the outer cylinder.

[0062] Furthermore, a plurality of oil inlet pipes 154 penetrate the outer periphery of the oil drain cylinder 15 . The oil inlet pipes 154 are arranged to be tilted downward from the outside of the oil drain cylinder 15 to the inside of the oil drain cylinder 15 . The inner side of the connecting plate 164 is an inclined surface and is tilted toward the rotation direction of the rotating rod 161 .

[0063] In actual application of this embodiment, the dirty oil is attached to the water surface, part of the dirty oil is located in the inner cylinder, and part of the dirty oil is located outside the outer cylinder. When the water surface is higher than the highest point of the oil discharge cylinder 15, the dirty oil floating on the water surface will enter the discharge chamber 151 and be discharged, and finally enter the dirty oil tank 3; when the water level drops, the dirty oil that has not been discharged will move downward, and the dirty oil will slowly enter the inner cylinder from the oil inlet pipe 154. Since the area of ​​the dirty oil in the inner cylinder is small, the dirty oil in the inner cylinder is easier to enter the discharge chamber 151 and be discharged, so that the discharge efficiency of the dirty oil can be improved;

[0064] When the rotating rod 161 rotates, the connecting plates 164 rotate around the rotating rod 161. Since the inner side of the connecting plates 164 is an inclined surface, the connecting plates 164 stir the water to flow in the opposite direction toward the oil inlet pipe 154, so that the dirty oil attached to the water surface can enter the oil inlet pipe 154 more easily, further improving the discharge efficiency of the dirty oil.

[0065] Furthermore, a liquid level sensor 18 is installed on the inner wall of the separator 2, and the liquid level sensor 18 is on the same horizontal plane as the top of the oil drain tube 15. A drain pipe 17 is installed on the separator 2, and the drain pipe 17 is located between the aeration pipe 13 and the filter screen 14. A solenoid valve is installed on the drain pipe 17, and the liquid level sensor 18 and the solenoid valve are evenly connected to an external control unit.

[0066] It should be noted that if the water level in the separator 2 keeps rising, the water in the separator 2 will be connected with the waste oil and discharged into the waste oil tank 3, thereby causing the waste oil to contain water, thereby increasing the subsequent processing cost of the waste oil.

[0067] In one case of this embodiment, the external control unit may be a computer terminal, which transmits a signal to the external control unit through the liquid level sensor 18, and the external control unit controls the switch of the solenoid valve according to the signal.

[0068] In actual application of this embodiment, when the water level in the separator 2 reaches the liquid level sensor 18, the liquid level sensor 18 transmits a signal to the external control unit, and the external control unit controls the solenoid valve to open, so that the water in the separator 2 is discharged. The opening time of the solenoid valve is specified within a range to avoid excessive discharge of water in the separator 2, resulting in the inability to discharge the dirty oil for a long time. When the opening time of the solenoid valve has passed, the solenoid valve is closed, and the water level continues to rise, so that the dirty oil can be discharged; this effectively avoids the increase in the subsequent processing cost of the dirty oil due to the water and the dirty oil.

[0069] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A system for recovering natural gas from venting an oil and gas well, comprising a wellhead connecting pipe (1), a waste oil tank (3), a dehydration skid (5), a natural gas pipeline (6) and a tank truck pipeline (7), characterized in that: The system further comprises: A compressor (4), the compressor (4) comprising a screw compressor (41) and a reciprocating compressor (42), the screw compressor (41) and the reciprocating compressor (42) being connected in series, and the screw compressor (41) being located at the front end of the air intake; A separator (2) is connected between the compressor (4) and the wellhead connecting pipe (1), and the separator (2) is connected to the waste oil tank (3).

2. The system for recovering natural gas from venting oil and gas wells according to claim 1, characterized in that: The separator (2) comprises a low-pressure separator (2a) and a high-pressure separator (2c); the air inlet end of the screw compressor (41) is connected to the low-pressure separator (2a); the low-pressure separator (2a) is connected to a wellhead connecting pipe (1); the low-pressure separator (2a) is connected to a waste oil tank (3); a sliding valve (411) is installed at the air inlet end of the screw compressor (41); a frequency conversion controller (10) is installed on the output element of the screw compressor (41); the air outlet end of the screw compressor (41) is connected to an air cooler (8); the air outlet end of the air cooler (8) is connected to the high-pressure separator (2c); the air outlet end of the air cooler (8) is also connected to a return pipe (11); the return pipe (11) is connected to the return pipe (12); The end of the pipeline (11) is connected to the air inlet of the screw compressor (41), the high-pressure separator 2 (2c) is connected to the waste oil tank (3), the air outlet of the high-pressure separator 2 (2c) is connected to the reciprocating compressor (42), another variable frequency controller (10) is installed on the output part of the reciprocating compressor (42), the air outlet of the reciprocating compressor (42) is connected to another air cooler (8), the air outlet of the air cooler (8) is connected to a buffer tank (9), the air outlet of the air cooler (8) is also connected to another return pipeline (11), the end of the return pipeline (11) is connected to the air inlet of the reciprocating compressor (42), and the air outlet of the buffer tank (9) is connected to a dehydration skid (5).

3. The system for recovering natural gas from venting oil and gas wells according to claim 2, characterized in that: The separator (2) further comprises a high-pressure separator (2b), wherein natural gas enters the separator (2) through the wellhead connecting pipe (1), wherein natural gas with a pressure less than or equal to 3 MPa enters the low-pressure separator (2a), and natural gas with a pressure greater than or equal to 3 MPa enters the high-pressure separator (2b), wherein natural gas with a pressure equal to 3 MPa enters the low-pressure separator (2a), and after being pressurized by a screw compressor (41), does not enter the reciprocating compressor (42) but directly enters the natural gas pipeline (6), and natural gas with a pressure equal to 25 MPa does not pass through the screw compressor (41) or the reciprocating compressor (42), but directly enters the dehydration skid (5).

4. The system for recovering natural gas from venting oil and gas wells according to claim 3, characterized in that: The separator (2) is connected to an air inlet pipe (21) at its periphery, a sealing door (22) is installed on the surface of the separator (2), an exhaust pipe (12) is connected through the top of the separator (2), an oil drain cylinder (15), a filter screen (14) and an aeration pipe (13) are installed in sequence from top to bottom in the inner cavity of the separator (2), the oil drain cylinder (15) passes through the bottom of the separator (2), the filter screen (14) is located outside the oil drain cylinder (15), and an auxiliary mechanism (16) is installed on the filter screen (14).

5. The system for recovering natural gas from venting of oil and gas wells according to claim 4, characterized in that: The auxiliary mechanism (16) comprises: A rotating rod (161), the rotating rod (161) is rotatably mounted in the exhaust pipe (12), and an impeller (162) is fixed to the periphery of the rotating rod (161); A circular ring (165), a fixing plate (163) is fixed at the bottom of the rotating rod (161), a plurality of connecting plates (164) are arranged at the bottom of the fixing plate (163), a circular ring (165) is arranged at the bottom of the plurality of connecting plates (164), the circular ring (165) is located outside the oil drain cylinder (15), and the outer surface of the circular ring (165) is in contact with the inner side of the filter screen (14); An upper cleaning brush (166) and a lower cleaning brush (167); a plurality of upper cleaning brushes (166) and a plurality of lower cleaning brushes (167) are arranged on the outer side of the circular ring (165); the plurality of upper cleaning brushes (166) are located above the filter screen (14), and the plurality of lower cleaning brushes (167) are located below the filter screen (14).

6. The system for recovering natural gas from venting of oil and gas wells according to claim 5, characterized in that: A baffle (168) is provided on the opposite side of two adjacent upper cleaning brushes (166).

7. The system for recovering natural gas from venting oil and gas wells according to claim 5, characterized in that: The oil drain cylinder (15) comprises an inner cylinder and an outer cylinder, a plurality of partitions (152) are arranged between the inner cylinder and the outer cylinder, a discharge chamber (151) is formed between two adjacent partitions (152), a plurality of through holes (153) are opened on the periphery of the oil drain cylinder (15), the positions of the plurality of through holes (153) and the plurality of partitions (152) coincide, and a sealing cover (155) is arranged on the top of the outer cylinder.

8. The system for recovering natural gas from venting oil and gas wells according to claim 7, characterized in that: A plurality of oil inlet pipes (154) are passed through the outer periphery of the oil drain cylinder (15). The oil inlet pipes (154) are arranged to be inclined downward from the outside of the oil drain cylinder (15) toward the inside of the oil drain cylinder (15). The inner side of the connecting plate (164) is an inclined surface and is inclined toward the rotation direction of the rotating rod (161).

9. The system for recovering natural gas from venting oil and gas wells according to claim 4, characterized in that: A liquid level sensor (18) is installed on the inner wall of the separator (2), and the liquid level sensor (18) is on the same horizontal plane as the top of the oil drain cylinder (15). A drain pipe (17) is installed on the separator (2), and the drain pipe (17) is located between the aeration pipe (13) and the filter screen (14). A solenoid valve is installed on the drain pipe (17), and the liquid level sensor (18) and the solenoid valve are evenly connected to an external control unit.

Images