A high gas-containing deepwater underwater oil-gas-water-sand separation system and method

Abstract

The present application relates to a kind of high gas deepwater underwater oil-gas-water-sand separation system and method, the system includes: bifurcation pipeline, underwater separator and output pipeline, bifurcation pipeline is provided with one feed inlet, one gas outlet and one solid-liquid mixture outlet;Underwater separator includes a horizontal tank, horizontal tank is sequentially provided with separation chamber, oil buffer chamber and gas buffer chamber from left to right in it;Output pipeline includes water and sand outlet connector, liquid oil outlet connector and oil-gas mixed transport pipe.The present application relates to a kind of high gas deepwater underwater oil-gas-water-sand separation system and method, can separate the oil, gas, water, sand four-phase in deep sea oil and gas, suitable for underwater oil and gas field, both can meet the demand of production, and reduce the space occupied, meet the requirement of simple manufacturing process, have good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of produced fluid separation equipment for deep-sea oil and gas fields, specifically to a deep-water subsea oil, gas, water, and sand separation system and method with high gas content. Background Technology

[0002] The ocean, especially the deep sea, contains abundant oil and gas resources, but underwater extraction is difficult. If the produced fluid is transported to a surface platform for separation, a large amount of energy is consumed for pumping unrelated aqueous phases, resulting in oversized surface equipment, high energy consumption, and reduced production efficiency. In-situ separation of produced fluid underwater is a necessary measure.

[0003] Produced fluid separation generally relies on principles such as gravity separation, centrifugal separation, and chemical demulsification. Deep-sea separation is constrained by strict space and weight requirements, leading to significant limitations in separation system design. Chinese utility model patent application CN211987214U, entitled "A High-Efficiency Oil-Water Separator," discloses a tank with a heater for oil-water separation; Chinese utility model patent application CN111996031A, entitled "A Three-Phase Oil-Water Separator," discloses a three-phase oil-water separator with high and low weirs. However, in actual production, these devices suffer from drawbacks such as large size and complex control, and their effectiveness in handling large volumes of produced fluid is unsatisfactory. Large-scale separation equipment is also difficult to deploy in subsea separation applications. In summary, current separation equipment faces bottlenecks in platform-based processing facilities, and challenges in improving oil recovery, saving energy, and enhancing overall recovery efficiency. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a high-gas-content deep-water subsea oil-gas-water-sand separation system and method, which separates the aqueous phase from the produced fluid and reinjects it in situ. The separated oil and gas are then transported to the platform under wellhead pressure, solving the bottleneck problem of the platform's upper processing facilities, improving the recovery rate, saving energy consumption, and increasing the recovery rate.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention discloses a high-gas-content deep-water subsea oil-gas-water-sand separation system, comprising:

[0007] The branched pipeline is equipped with a feed inlet, a solid-liquid mixture outlet, and a gas outlet.

[0008] An underwater separator includes a horizontal tank containing, from left to right, a separation chamber, an oil buffer chamber, and a gas buffer chamber. The gas outlet is located at the top of the separation chamber. The solid-liquid mixture outlet extends to the bottom of the separation chamber. The oil buffer chamber has a water-sand outlet. The bottom, side walls, and top of the gas buffer chamber are respectively provided with a liquid-oil outlet, an oil-gas mixture outlet, and a pure gas outlet.

[0009] The output pipeline includes a water-sand outlet connector, a liquid oil outlet connector, an oil-gas mixture outlet connector, and a pure gas outlet connector. The water-sand outlet connector is installed on the water-sand outlet, the liquid oil outlet connector is installed on the liquid oil outlet, the oil-gas mixture outlet connector is installed on the oil-gas mixture outlet, and the pure gas outlet connector is installed on the pure gas outlet. The oil-gas mixture outlet connector and the pure gas outlet connector are connected by a tee to form an oil-gas mixture transmission pipeline.

[0010] Furthermore, the branched pipeline includes a horizontal liquid collecting pipe, an inclined gas collecting pipe, and several vertical branch pipes. One end of the horizontal liquid collecting pipe is set as the feed inlet, and the other end is set as the solid-liquid mixture outlet. The discharge end of the inclined gas collecting pipe is set as the gas outlet. The horizontal liquid collecting pipe and the inclined gas collecting pipe are connected sequentially from low to high by several vertical branch pipes, and one end of each vertical branch pipe is vertically set on the horizontal liquid collecting pipe, and the other end converges on the inclined gas collecting pipe.

[0011] Furthermore, the lowest of the several vertical branch pipes is vertically positioned at the junction of the feed inlet and the horizontal liquid collection pipe.

[0012] Furthermore, the air outlet is connected to the inclined air collection pipe via a bend.

[0013] Furthermore, a disc-shaped buffer is provided in the separation chamber, which is located directly below the outlet of the inclined gas collecting pipe; the solid-liquid mixture outlet of the horizontal liquid collecting pipe extends to the bottom of the separation chamber.

[0014] Furthermore, a solid-liquid separator is provided between the separation chamber and the oil buffer chamber to separate them, and a gap is reserved between the solid-liquid separator and the bottom surface of the horizontal tank to form a water phase guide gap, allowing the water phase to flow from the bottom while hindering the flow of sand solids; an upper gas-liquid separator is provided at the top and a lower gas-liquid separator is provided at the bottom between the oil buffer chamber and the gas buffer chamber, and the upper and lower gas-liquid separators are staggered to separate the oil buffer chamber and the gas buffer chamber.

[0015] Furthermore, the height of the solid-liquid separator is 1 / 3 of the height of the internal space of the horizontal tank.

[0016] Furthermore, the oil buffer chamber is equipped with a differential pressure gas-liquid interface measuring instrument and a capacitor oil-water interface measuring instrument, which are arranged one in front of the other in the rear space between the solid-liquid separator and the lower gas-liquid separator.

[0017] Furthermore, it also includes a control system, which comprises a controller, a water-sand output control device, an oil output control device, and an oil-gas mixture output control device. The water-sand output control device includes a water-sand outlet electric regulating valve, a water injection pump, and a water flow meter. The water-sand outlet electric regulating valve, the water injection pump, and the water flow meter are sequentially arranged on the water-sand outlet pipe from front to back according to the fluid flow direction. The oil output control device includes an oil outlet electric regulating valve, an oil pump, and an oil flow meter. The oil outlet electric regulating valve, the oil pump, and the oil flow meter are sequentially arranged on the water-sand outlet pipe from front to back according to the fluid flow direction. The components are arranged sequentially from front to back on the oil outlet pipe; the oil-gas mixture output control device includes an oil-gas mixture electric regulating valve and a mixture pump, which are arranged sequentially from front to back on the oil-gas mixture pipe according to the fluid flow direction; the water-sand outlet electric regulating valve, the water injection pump, the water flow meter, the oil outlet electric regulating valve, the oil pump, the oil flow meter, the oil-gas mixture electric regulating valve, the mixture pump, the differential pressure gas-liquid interface measuring instrument, and the capacitive oil-water interface measuring instrument are respectively connected to the controller via wires.

[0018] This invention also discloses a method for separating oil, gas, water, and sand in deep water with high gas content, employing the aforementioned deep water oil, gas, water, and sand separation system with high gas content, comprising:

[0019] Step 1: In deep-sea oil and gas fields, a mixture of oil, gas, water, and sand in the high-gas-content produced fluid flows in from the inlet. At the branching pipeline, the gas phase separates, forming a mixture of oil, water, and sand solids / liquids, a gas phase mixture, and the liquid droplets it carries.

[0020] The oil-water-sand solid-liquid mixture moves along the horizontal liquid collection pipe and enters the separation chamber directly through the solid-liquid mixture outlet.

[0021] The gas-phase mixture and the droplets it carries are divided into two parts after passing through the inclined gas collecting pipe from the vertical branch pipe. Some of the droplets carried by the gas-phase mixture collide with the pipe walls of the vertical branch pipe and the inclined gas collecting pipe and gather together. They fall into the horizontal liquid collecting pipe through the vertical branch pipe and enter the horizontal tank along with the oil-water-sand solid-liquid mixture. The gas-phase mixture with some droplets removed and the remaining droplets it carries flow from the gas outlet into the disc-shaped buffer inside the horizontal tank of the underwater separator.

[0022] Step 2: In the separation chamber, the gas mixture and the remaining liquid droplets it carries are sprayed onto the disc-shaped buffer, pass through the oil buffer chamber, cross the upper gas-liquid separator and enter the gas buffer chamber, and diffuse into the upper space of the horizontal tank. Part of the gas mixture and some of the liquid droplets it carries flow out from the pure gas outlet, thereby achieving further separation of the gas phase and the solid-liquid mixture.

[0023] Another portion of the liquid droplets carried by the gas phase mixture splashes onto the wall of the horizontal tank and the upper gas-liquid separator plate, and drips onto the bottom surface of the horizontal tank, where they mix with the solid-liquid mixture that enters the horizontal tank from the horizontal liquid collection pipe, forming a second solid-liquid mixture.

[0024] The second solid-liquid mixture is kept in the separation chamber for oil-water separation. The sand is blocked by the solid-liquid separator, which increases the residence time. The water at the bottom layer enters the oil buffer chamber through the water phase guide slit at the bottom of the solid-liquid separator, and the oil at the top layer crosses the solid-liquid separator and enters the oil buffer chamber, thereby achieving the separation of sand from water and oil.

[0025] Step 3: In the oil buffer chamber, the oil enters the tail of the horizontal tank through the lower gas-liquid separator, while the water remains in the oil buffer chamber, achieving further separation of the incompletely separated oil and water.

[0026] The oil and the gas phase mixture that permeates the upper space of the horizontal tank form an oil-gas mixture, which flows out from the oil-gas mixture outlet pipe and merges with the gas phase flowing out from the pure gas outlet pipe, and flows into the oil-gas mixing pipeline. The oil-gas mixture is then transported out by the mixing pump.

[0027] Step 4: The sand solids settle to the bottom of the horizontal tank and flow with the water during drainage, finally flowing out from the water-sand outlet pipe.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] This invention discloses a high-gas-content deep-water subsea oil, gas, water, and sand separation system and method. The separation system includes a branched pipeline at the front end for gas-liquid pre-separation, forming a two-stage separation system with the subsea separator. This increases separation efficiency, enabling more efficient separation of produced fluids. The branched pipeline reduces the residence time required for separation by the subsea separator, significantly reducing its size and saving space. The system's smaller size allows for reduced wall thickness compared to larger equipment in the high-pressure environment of the deep sea, saving materials and reducing manufacturing difficulties. The oil phase can be discharged along with the gas through a mixing pipeline. The system uses fewer valves and pumps for control, making operation convenient. This invention discloses a high-gas-content deep-water subsea oil, gas, water, and sand separation system and method that can meet the requirements of high-gas-content multiphase separation and satisfy the needs of deep-sea oil and gas development. Attached Figure Description

[0030] Figure 1This is a schematic diagram of the structure of the high gas content deep-water subsea oil, gas, water and sand separation system provided in Embodiment 1 of the present invention.

[0031] Explanation of reference numerals in the attached diagram: 1-Branching pipeline, 10-Horizontal liquid collection pipe, 11-Inlet, 12-Solid-liquid mixture outlet, 13-Gas outlet, 14-Inclined gas collection pipe, 15-Vertical branch pipe;

[0032] 2-Underwater separator; 20-Horizontal tank; 21-Separation chamber; 210-Disc buffer; 22-Oil buffer chamber; 220-Water sand outlet; 23-Gas buffer chamber; 231-Liquid oil outlet; 232-Oil-gas mixture outlet; 233-Pure gas outlet; 24-Solid-liquid separator; 25-Upper gas-liquid separator; 26-Lower gas-liquid separator; 27-Differential pressure gas-liquid interface measuring instrument; 28-Capacitive oil-water interface measuring instrument.

[0033] 3-Output pipeline, 31-Water sand outlet pipe, 32-Liquid oil outlet pipe, 33-Oil-gas mixture outlet pipe, 34-Pure gas outlet pipe, 35-Oil-gas mixture transmission pipeline;

[0034] 41-Water and sand output control device; 411-Water and sand outlet electric regulating valve; 412-Water injection pump; 413-Water flow meter;

[0035] 42-Oil output control device, 421-Oil outlet electric regulating valve, 422-Oil circuit pump, 423-Oil circuit flow meter;

[0036] 43-Oil-gas mixture output control device; 431-Oil-gas mixture electric regulating valve; 432-Mixed pump. Detailed Implementation

[0037] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0038] In the description of this invention, it should be understood that the terms "front", "rear", "front end", "rear end", "rear part", "tail part", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0039] To address the bottlenecks in platform-based processing facilities, improve oil recovery, and save energy, this invention targets the four phases of oil, gas, water, and sand in deep-sea oil and gas. A two-stage separation system is constructed by branched pipelines and a subsea separator, which gradually separates the four phases of oil, gas, water, and sand within the subsea separator. This system can separate the four phases of oil, gas, water, and sand in deep-sea oil and gas, increasing separation efficiency and making the separation of produced fluids more efficient.

[0040] Example 1: A high-gas-content deep-water subsea oil-gas-water-sand separation system

[0041] Embodiment 1 of the present invention provides a deep-water subsea oil-gas-water-sand separation system with high gas content. Its structure will be described in detail below with reference to the accompanying drawings.

[0042] See Figure 1 The high-gas-content deep-water subsea oil, gas, water, and sand separation system includes a branching pipeline 1, a subsea separator 2, an output pipeline 3, and a control system.

[0043] The branched pipeline 1 is provided with a feed inlet 11, an air outlet 13, and a solid-liquid mixture outlet 12.

[0044] Specifically, the branch pipe 1 includes a horizontal liquid collecting pipe 10, several vertical branch pipes 15 and an inclined gas collecting pipe 14. One end of the horizontal liquid collecting pipe 10 is set as a feed inlet 11 and the other end is set as a solid-liquid mixture outlet 12. The discharge end of the inclined gas collecting pipe 14 is set as a gas outlet 13.

[0045] The horizontal liquid collecting pipe 10 and the inclined gas collecting pipe 14 are connected in sequence from low to high by several vertical branch pipes 15. Specifically, one end of each vertical branch pipe 15 is vertically installed on the horizontal liquid collecting pipe 10, and the other end is collected on the inclined gas collecting pipe 14.

[0046] More specifically, the lowest vertical branch pipe 15 among the several vertical branch pipes 15 is vertically arranged at the junction of the feed inlet 11 and the horizontal liquid collection pipe 10.

[0047] To facilitate the flow of gas from the outlet 13, the outlet 13 is connected to the inclined gas collecting pipe 14 by a bend.

[0048] Specifically, several vertical branch pipes 15 are arranged horizontally and evenly.

[0049] Specifically, the angle between the inclined gas collecting pipe 14 and the horizontal liquid collecting pipe 10 is 5~30°.

[0050] More specifically, the horizontal liquid collecting pipe 10, the vertical branch pipe 15, and the inclined gas collecting pipe 14 have a diameter of 150 mm and an angle of 15°.

[0051] The underwater separator 2 includes a horizontal tank 20, within which, from left to right, are arranged a separation chamber 21, an oil buffer chamber 22, and an air buffer chamber 23.

[0052] The air outlet 13 is located at the top of the separation chamber 21. Specifically, a disc-shaped buffer 210 is provided in the separation chamber 21. The disc-shaped buffer 210 is located directly below the air outlet 13 of the inclined gas collecting pipe 14 and is used to receive the oil-gas-water mixture flowing out from the air outlet 13 of the inclined gas collecting pipe 14.

[0053] The solid-liquid mixture outlet 12 extends to the bottom of the separation chamber 21. Specifically, the solid-liquid mixture outlet 12 of the horizontal collecting pipe 10 extends to the bottom of the separation chamber 21.

[0054] The oil buffer chamber 22 is provided with a water sand outlet 220, and the bottom, side wall and top plate of the gas buffer chamber 23 are respectively provided with a liquid oil outlet 231, an oil-gas mixture outlet 232 and a pure gas outlet 233.

[0055] Specifically, a solid-liquid separator 24 is provided between the separation chamber 21 and the oil buffer chamber 22 to separate the two. A gap is reserved between the solid-liquid separator 24 and the bottom surface of the horizontal tank 20 to form a water phase guide gap, so that the water phase can flow from the bottom and hinder the flow of sand solids, thereby realizing the separation of sand solids from oil and water.

[0056] An upper gas-liquid separator 25 is provided at the top and a lower gas-liquid separator 26 is provided at the bottom between the oil buffer chamber 22 and the gas buffer chamber 23. The upper gas-liquid separator 25 and the lower gas-liquid separator 26 are staggered to separate the oil buffer chamber 22 and the gas buffer chamber 23.

[0057] To reduce the mixing and emulsification of oil and water, the height of the solid-liquid separator 24 is 1 / 3 of the height of the internal space of the horizontal tank 20.

[0058] More specifically, the solid-liquid separator 24 is fixed to the inner wall of the horizontal tank 20, the lower gas-liquid separator 26 is fixed to the inner wall and bottom of the horizontal tank 20, and the upper gas-liquid separator 25 is fixed to the inner wall and top of the horizontal tank 20.

[0059] To monitor the gas-liquid interface, a differential pressure gas-liquid interface measuring instrument 27 is installed in the oil buffer chamber 22.

[0060] In order to monitor the oil-water interface, a capacitive oil-water interface measuring instrument 28 is installed in the oil buffer chamber 22.

[0061] Specifically, the differential pressure gas-liquid interface measuring instrument 27 and the capacitive oil-water interface measuring instrument 28 are existing technologies, and are set one after the other in the rear space between the solid-liquid separator 24 and the lower gas-liquid separator 26. The differential pressure gas-liquid interface measuring instrument 27 obtains the gas-liquid interface by solving the equation by monitoring the pressure values ​​of pressure sensors at different heights, and the capacitive oil-water interface measuring instrument 28 obtains the oil-water interface by monitoring the dielectric constant at different heights, thereby formulating a control scheme.

[0062] In this invention, "front" refers to the feed inlet 11, and "rear" refers to the output pipe 3, such as... Figure 1 As shown.

[0063] The lower gas-liquid separator 26 is located at the rear end of the upper gas-liquid separator 25, maintaining a horizontal spacing of 0.5m. The lower gas-liquid separator 26 and the upper gas-liquid separator 25 are located at approximately 1 / 4 of the rear part of the horizontal tank body 20.

[0064] To ensure that the gas moves backward without being blocked by the liquid phase, a certain gap is maintained between the lower gas-liquid separator 26 and the upper gas-liquid separator 25 at their respective heights.

[0065] Continue to refer to Figure 1 The output pipeline includes a water-sand outlet pipe 31, a liquid oil outlet pipe 32, an oil-gas mixture outlet pipe 33, a pure gas outlet pipe 34, and an oil-gas mixture transport pipe 35.

[0066] Water and sand outlet pipe 31 is installed on water and sand outlet 220;

[0067] The liquid oil outlet pipe 32 is vertically installed on the liquid oil outlet 231;

[0068] The oil-gas mixture outlet pipe 33 is horizontally installed on the oil-gas mixture outlet 232, and the pure gas outlet pipe 34 is installed on the pure gas outlet 233. The oil-gas mixture outlet pipe 33 and the pure gas outlet pipe 34 are connected by a tee to form an oil-gas mixture transmission pipe 35.

[0069] Specifically, the water-sand outlet pipe 31 is located before the lower gas-liquid separator 26 and is fixed to the bottom of the horizontal tank 20;

[0070] The liquid oil outlet pipe 32 is located after the lower gas-liquid separator 26 and is fixed to the bottom of the horizontal tank 20;

[0071] The oil-gas mixture outlet pipe 33 is installed on the side wall at the rear of the horizontal tank 20;

[0072] The pure gas outlet pipe 34 is located at the top of the horizontal tank 20;

[0073] The discharge end of the oil-gas mixture outlet pipe 33 is connected to the pure gas outlet pipe 34 through a bend, forming an oil-gas mixture transport pipe 35.

[0074] The control system includes a controller, a water and sand output control device 41, an oil output control device 42, and an oil-gas mixture output control device 43.

[0075] The water and sand output control device 41 includes a water and sand outlet electric regulating valve 411, a water injection pump 412 and a water flow meter 413. The water and sand outlet electric regulating valve 411, water injection pump 412 and water flow meter 413 are arranged sequentially from front to back on the water and sand outlet pipe 31 according to the fluid flow direction.

[0076] The oil output control device 42 includes an oil outlet electric regulating valve 421, an oil circuit pump 422, and an oil circuit flow meter 423. The oil outlet electric regulating valve 421, the oil circuit pump 422, and the oil circuit flow meter 423 are arranged sequentially from front to back on the liquid oil outlet pipe 32 according to the fluid flow direction.

[0077] The oil-gas mixture output control device 43 includes an oil-gas mixture electric regulating valve 431 and a mixture pump 432, which are arranged sequentially from front to back on the oil-gas mixture pipeline 35 according to the fluid flow direction.

[0078] The water-sand outlet electric regulating valve 411, water injection pump 412, water flow meter 413, oil outlet electric regulating valve 421, oil pump 422, oil flow meter 423, oil-gas mixed transport electric regulating valve 431, mixed transport pump 432, differential pressure gas-liquid interface measuring instrument 27, and capacitive oil-water interface measuring instrument 28 are respectively connected to the controller via wires.

[0079] When the produced fluid flow rate is 30m 3 When the gas-liquid ratio is 1000~5000:1, this high-gas-content deep-water subsea oil-gas-water-sand separation system is as follows: Figure 1 As shown.

[0080] The separated oil and gas resources are transported to the offshore platform under formation pressure. The separated water and sand phases are reinjected into the formation to replenish the pressure, increase the recovery of offshore oil and gas fields, reduce the space occupied by subsea separation equipment and simplify control.

[0081] Example 2: A method for separating oil, gas, water, and sand in deep-water environments with high gas content.

[0082] Embodiment 2 of the present invention provides a method for deep-water subsea oil, gas, water, and sand separation with high gas content, using the deep-water subsea oil, gas, water, and sand separation system with high gas content provided in Embodiment 1. The method includes the following steps:

[0083] Step 1: The mixture of oil, gas, water, and sand in the high-gas-content produced fluid of the deep-sea oil and gas field flows in through the feed inlet 11, and the gas phase is separated through the branch pipe 1, forming an oil-water-sand solid-liquid mixture and a gas phase mixture, along with the liquid droplets it carries.

[0084] The oil-water-sand solid-liquid mixture moves along the horizontal liquid collection pipe 10 and directly enters the separation chamber 21 through the solid-liquid mixture outlet 12;

[0085] The gas-phase mixture and the droplets it carries are divided into two parts after passing through the inclined gas collecting pipe 14 from the vertical branch pipe 15. Some of the droplets carried by the gas-phase mixture collide with the pipe walls of the vertical branch pipe 15 and the inclined gas collecting pipe 14 and gather together. They fall into the horizontal liquid collecting pipe 10 through the vertical branch pipe 15 and enter the horizontal tank 20 together with the oil-water-sand solid-liquid mixture. The gas-phase mixture with some droplets removed and the remaining droplets it carries flow from the gas outlet 13 into the disc-shaped buffer 210 inside the horizontal tank 20 of the underwater separator 2.

[0086] Step 2: In the separation chamber 21, the gas phase mixture and the remaining liquid droplets it carries are sprayed onto the disc-shaped buffer 210, pass through the oil buffer chamber 22, cross the upper gas-liquid separator 25 and enter the gas buffer chamber 23, and diffuse into the upper space of the horizontal tank 20. Some of the gas mixture and some of the liquid droplets it carries flow out from the pure gas outlet 233, thereby achieving further separation of the gas phase and the solid-liquid mixture.

[0087] Another portion of the liquid droplets carried by the gas phase mixture splashes onto the wall of the horizontal tank 20 and the upper gas-liquid separator 25, and drips onto the bottom surface of the horizontal tank 20, where they mix with the solid-liquid mixture that enters the horizontal tank 20 from the horizontal liquid collection pipe 10 to form a second solid-liquid mixture.

[0088] The second solid-liquid mixture is held in the separation chamber 21 for oil-water separation. The sand is blocked by the solid-liquid separator 24, increasing the residence time. The water at the bottom layer enters the oil buffer chamber 22 through the water phase guide slit at the bottom of the solid-liquid separator 24, and the oil at the top layer crosses the solid-liquid separator 24 and enters the oil buffer chamber 22, thereby achieving the separation of sand from water and oil.

[0089] Step 3: In the oil buffer chamber 22, the oil enters the tail of the horizontal tank 20 through the lower gas-liquid separator 26, while the water remains in the oil buffer chamber 22, thus achieving further separation of the incompletely separated oil and water.

[0090] The oil and the gas phase mixture that permeates the upper space of the horizontal tank 20 form an oil-gas mixture, which flows out from the oil-gas mixture outlet pipe 33 and merges with the gas phase flowing out from the pure gas outlet pipe 34, and flows into the oil-gas mixing pipe 35. The oil-gas mixture is then transported out by the mixing pump 432.

[0091] Step 4: The sand solids settle to the bottom of the horizontal tank 20, and flow with the water during drainage, finally flowing out from the water-sand outlet pipe 31.

[0092] In step two, the capacitive oil-water interface measuring instrument 28 obtains the oil-water interface by monitoring the dielectric constant at different heights; based on the monitoring results of the capacitive oil-water interface measuring instrument 28, the controller stops the electric regulating valve 411 at the water-sand outlet and the water injection pump 412 when the oil-water interface is too low, and opens the electric regulating valve 411 at the water-sand outlet and the water injection pump 412 when the oil-water interface is too high.

[0093] In step three, the differential pressure gas-liquid interface measuring instrument 27 obtains the gas-liquid interface by solving the equation based on the pressure values ​​of pressure sensors at different heights; according to the monitoring results of the differential pressure gas-liquid interface measuring instrument 27, the controller opens the oil outlet electric regulating valve 421 and the oil circuit pump 422 when the gas-liquid interface reaches a certain height, and stops the oil outlet electric regulating valve 421 and the oil circuit pump 422 when the gas-liquid interface is lower than a certain height.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for deep-water subsea oil-gas-water-sand separation with high gas content, comprising a deep-water subsea oil-gas-water-sand separation system with high gas content, characterized in that, The high-gas-content deep-water subsea oil, gas, water, and sand separation system includes a branching pipeline (1), a subsea separator (2), an output pipeline (3), and a control system. The branched pipeline (1) is provided with a feed inlet (11), a solid-liquid mixture outlet (12), and a gas outlet (13). The branched pipeline (1) includes a horizontal liquid collection pipe (10), an inclined gas collection pipe (14), and several vertical branch pipes (15). One end of the horizontal liquid collection pipe (10) is set as the feed inlet (11), and the other end is set as the solid-liquid mixture outlet (12). The discharge end of the inclined gas collection pipe (14) is set as the gas outlet (13). The horizontal liquid collection pipe (10) and the inclined gas collection pipe (14) are connected from low to high through several vertical branch pipes (15). One end of each vertical branch pipe (15) is vertically set on the horizontal liquid collection pipe (10), and the other end is collected on the inclined gas collection pipe (14). The underwater separator (2) includes a horizontal tank (20), in which a separation chamber (21), an oil buffer chamber (22), and a gas buffer chamber (23) are arranged sequentially from left to right. The gas outlet (13) is located at the top of the separation chamber (21); the solid-liquid mixture outlet (12) extends to the bottom of the separation chamber (21); the oil buffer chamber (22) is provided with a water-sand outlet (220); and the bottom of the gas buffer chamber (23) is provided with a liquid-oil outlet (23). 1) The gas buffer chamber (23) has an oil-gas mixture outlet (232) on its side wall and a pure gas outlet (233) on its top; wherein, a disc-shaped buffer (210) is provided in the separation chamber (21), and the disc-shaped buffer (210) is located directly below the gas outlet (13) of the inclined gas collecting pipe (14); the solid-liquid mixture outlet (12) of the horizontal liquid collecting pipe (10) extends to the bottom of the separation chamber (21); the separation chamber A solid-liquid separator (24) is provided between (21) and the oil buffer chamber (22) to separate them. A gap is reserved between the solid-liquid separator (24) and the bottom surface of the horizontal tank (20) to form a water phase guide gap, so that the water phase can flow from the bottom and hinder the flow of sand solids. An upper gas-liquid separator (25) is provided at the upper part and a lower gas-liquid separator (26) is provided at the lower part between the oil buffer chamber (22) and the gas buffer chamber (23). 26) The oil buffer chamber (22) and the gas buffer chamber (23) are staggered to separate them; the height of the solid-liquid separator (24) is 1 / 3 of the height of the internal space of the horizontal tank (20); a differential pressure gas-liquid interface measuring instrument (27) and a capacitor oil-water interface measuring instrument (28) are installed in the oil buffer chamber (22), and the differential pressure gas-liquid interface measuring instrument (27) and the capacitor oil-water interface measuring instrument (28) are set one in front of the other in the rear space between the solid-liquid separator (24) and the lower gas-liquid separator (26); The output pipeline (3) includes a water-sand outlet pipe (31), a liquid oil outlet pipe (32), an oil-gas mixture outlet pipe (33), and a pure gas outlet pipe (34). The water-sand outlet pipe (31) is installed on the water-sand outlet (220), the liquid oil outlet pipe (32) is installed on the liquid oil outlet (231), the oil-gas mixture outlet pipe (33) is installed on the oil-gas mixture outlet (232), and the pure gas outlet pipe (34) is installed on the pure gas outlet (233). The oil-gas mixture outlet pipe (33) and the pure gas outlet pipe (34) are connected by a tee to form an oil-gas mixture transmission pipeline (35). The control system includes a controller, a water and sand output control device (41), an oil output control device (42), and an oil-gas mixture output control device (43). The water and sand output control device (41) includes a water and sand outlet electric regulating valve (411), a water injection pump (412), and a water flow meter (413). The water and sand outlet electric regulating valve (411), the water injection pump (412), and the water flow meter (413) are arranged sequentially from front to back on the water and sand outlet pipe (31) according to the fluid flow direction. The oil output control device (42) includes an oil outlet electric regulating valve (421), an oil pump (422), and an oil flow meter (423). The oil outlet electric regulating valve (421), the oil pump (422), and the oil flow meter (423) are arranged sequentially from front to back according to the fluid flow direction. The oil and gas mixture output control device (43) is arranged sequentially on the oil outlet pipe (32); the oil and gas mixture output control device (43) includes an oil and gas mixture electric regulating valve (431) and a mixture pump (432), which are arranged sequentially from front to back on the oil and gas mixture pipe (35) according to the fluid flow direction; the water sand outlet electric regulating valve (411), the water injection pump (412), the water flow meter (413), the oil outlet electric regulating valve (421), the oil pump (422), the oil flow meter (423), the oil and gas mixture electric regulating valve (431), the mixture pump (432), the differential pressure gas-liquid interface measuring instrument (27), and the capacitive oil-water interface measuring instrument (28) are respectively connected to the controller through wires; The deep-water subsea oil-gas-water-sand separation method with high gas content includes the following steps: Step 1: The mixture of oil, gas, water, and sand in the high-gas-content produced fluid of the deep-sea oil and gas field flows in from the feed inlet (11), and the gas phase is separated in the branch pipe (1), forming an oil-water-sand solid-liquid mixture and a gas phase mixture and the droplets it carries. The oil-water-sand solid-liquid mixture moves along the horizontal collection pipe (10) and enters the separation chamber (21) directly through the solid-liquid mixture outlet (12); The gas mixture and the droplets it carries are divided into two parts after passing through the inclined gas collecting pipe (14) from the vertical branch pipe (15). Some of the droplets carried by the gas mixture collide with the pipe walls of the vertical branch pipe (15) and the inclined gas collecting pipe (14) and gather together. They fall into the horizontal liquid collecting pipe (10) through the vertical branch pipe (15) and enter the horizontal tank (20) together with the oil-water-sand solid-liquid mixture. The gas mixture with some droplets removed and the remaining droplets it carries flow from the gas outlet (13) into the disc-shaped buffer (210) inside the horizontal tank (20) of the underwater separator (2). Step 2: In the separation chamber (21), the gas phase mixture and the remaining liquid droplets it carries are sprayed onto the disc-shaped buffer (210), pass through the oil buffer chamber (22), cross the upper gas-liquid separator (25) and enter the gas buffer chamber (23), and diffuse into the upper space of the horizontal tank (20). Part of the gas mixture and part of the liquid droplets it carries flow out from the pure gas outlet (233), thereby achieving further separation of the gas phase and the solid-liquid mixture. Another portion of the liquid droplets carried by the gas phase mixture splashes onto the wall of the horizontal tank (20) and the upper gas-liquid separator (25), and drips onto the bottom surface of the horizontal tank (20), where it mixes with the solid-liquid mixture that enters the horizontal tank (20) from the horizontal liquid collection pipe (10) to form a second solid-liquid mixture. The second solid-liquid mixture is kept in the separation chamber (21) for oil-water separation. The sand is blocked by the solid-liquid separator (24), increasing the residence time. The water at the bottom layer enters the oil buffer chamber (22) through the water phase guide slit at the bottom of the solid-liquid separator (24), and the oil at the top layer crosses the solid-liquid separator (24) and enters the oil buffer chamber (22), thereby realizing the separation of sand from water and oil. Step 3: In the oil buffer chamber (22), the oil enters the tail of the horizontal tank (20) through the lower gas-liquid separator (26), while the water remains in the oil buffer chamber (22), thus achieving further separation of the incompletely separated oil and water; The oil and the gas phase mixture that permeates the upper space of the horizontal tank (20) form an oil-gas mixture, which flows out from the oil-gas mixture outlet pipe (33) and merges with the gas phase flowing out from the pure gas outlet pipe (34) and flows into the oil-gas mixing pipe (35). The oil-gas mixture is then transported out by the mixing pump (432). Step 4: The sand solids settle to the bottom of the horizontal tank (20), and flow with the water during drainage, finally flowing out from the water-sand outlet pipe (31).

2. The method for separating oil, gas, water, and sand in deep-water environments with high gas content according to claim 1, characterized in that, The lowest vertical branch pipe (15) among the several vertical branch pipes (15) is vertically arranged at the junction of the feed inlet (11) and the horizontal liquid collection pipe (10).

3. The method for separating oil, gas, water, and sand in deep-water environments with high gas content according to claim 1, characterized in that, The air outlet (13) and the inclined air collection pipe (14) are connected by a bend.

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