A system and method for pre-water distribution and water injection processing of an offshore wellhead platform

Abstract

The invention provides an offshore wellhead platform pre-water separation and water injection treatment system, comprising a gas-liquid separator, a pre-water separator, a microbubble generator, an air flotation tank and a self-circulation filter; the inlet of the gas-liquid separator is communicated with an incoming flow pipeline of the offshore wellhead platform, the liquid phase outlet of the gas-liquid separator is connected with the inlet of the pre-water separator through a pipeline, the water phase outlet of the pre-water separator is communicated with the water phase inlet of the air flotation tank through a microbubble generator, the water phase outlet of the air flotation tank is communicated with the water phase inlet of the self-circulation filter through a pipeline, and the water phase outlet of the self-circulation filter is communicated with an external water phase pipeline; the oil phase outlet of the pre-water separator, the oil phase outlet of the air flotation tank and the oil phase outlet of the self-circulation filter are respectively communicated with an external oil phase pipeline through pipelines; the gas phase outlet of the gas-liquid separator is communicated with an external gas phase pipeline through a pipeline, and the gas phase inlet of the microbubble generator and the gas phase inlet of the air flotation tank are respectively communicated with an external gas phase pipeline through pipelines.

Description

Technical Field

[0001] The invention relates to the technical field of multiphase separation of produced fluid from offshore oil fields, and in particular to a system and method for pre-water separation and water injection processing on an offshore wellhead platform. Background Art

[0002] At present, offshore oil and gas fields widely adopt the development model of central processing platform (CEP) plus unmanned wellhead platform (WHP), especially in the implementation and rolling development stage of adjustment development projects. Unmanned wellhead platform is unmanned during normal production. Remote control can be realized on the central processing platform. Personnel only need to board the offshore oil and gas production wellhead platform for regular inspection. Wellhead platform often has functions such as wellhead support, single well metering, produced liquid external transmission, water injection, etc., and can carry well repair module for well repair operation. As most of the main oil and gas fields at home and abroad enter the high water content or ultra-high water content development period, if the pre-water separation can be carried out on the wellhead platform and the separated sewage can be treated to meet the standards and then injected on site, it can directly avoid the round-trip transportation between high water content produced liquid, treated produced water and central processing platform, and avoid the problem that the water quality of the wellhead platform injection water deteriorates in the short term and cannot be treated due to the cleaning of the submarine pipeline, thereby greatly reducing the cost of oil field development. Of course, considering the area, construction cost, operation management and maintenance, the pre-water separation and water injection treatment process adopted by the wellhead platform is required to have the characteristics of short process, compact and efficient unit equipment, etc. In particular, with the application of unmanned fixed jacket platforms and offshore movable jack-up wellhead platforms in the development of marginal oil fields, higher requirements are placed on the reliability and efficiency of the wellhead platform pre-water distribution and water injection treatment processes.

[0003] Under the urgent need to implement "on-site water distribution, on-site treatment, and on-site reinjection" for oil well produced fluids on offshore wellhead platforms and onshore remote fault block oil fields, some new technologies and processes have emerged accordingly. For example, Chinese patent number CN105569629A discloses an on-site water distribution and water treatment device for oil field produced water. The main body consists of a bracket, a tank body, a hydrocyclone, an ejector, and a sewage return pump. The device integrates the functions of pre-water distribution and sewage treatment. The internal highly integrates four separation technologies such as cyclone, flotation, coalescence, and pressure sedimentation. The outlet sewage can be directly reinjected into the formation. It has the advantages of compact structure, small footprint, and high treatment efficiency. However, this technology concentrates multiple technologies into one tank body, and has the disadvantages of poor adaptability to working conditions and weak anti-fluctuation ability. At the same time, the device does not have the ability to remove suspended solids (SS), and there is a risk of formation blockage when it is directly reinjected into the formation.

[0004] Chinese patent number CN108979616A discloses a water separation system and water separation treatment method for wellhead produced materials. The main process includes a columnar cyclone separator, a high-efficiency horizontal separator, a hydrocyclone, a flotation tank, a gas filter, a gas injector and a nano-scale micro-bubble maker connected in sequence. The process features the use of advanced columnar cyclone separators and horizontal high-efficiency separators, and then through a hydrocyclone and compact flotation, part of the water in the crude oil is removed, and the gas-liquid two phases are roughly separated, so that the water content in the wellhead produced materials is greatly reduced. However, this process also does not consider the removal of suspended solids (SS) in sewage. At the same time, the nano-scale micro-bubbles produced by the nano-scale micro-bubble maker are not suitable for flotation oil removal processes due to their own difficulty in floating.

[0005] Chinese patent number CN212024989U discloses an oilfield produced fluid pre-water separation device and water injection device. The device mainly includes an elevation-type oil-water separator, a settling tank, a filter tank and a water injection tank connected in sequence. The produced fluid is separated into oil and water twice by the elevation-type oil-water separator and the settling tank, and the separated sewage is further filtered and optimized in the filter tank. However, this process has no gas-liquid separation function, and conventional gravity equipment such as settling tanks and filter tanks are difficult to apply to offshore platform oil well produced fluid treatment conditions. U.S. Patent US5965029 discloses a system and method for treating oil and gas well produced fluid. The main body is composed of a buffer tank, a centrifugal separator, a medium filter and an activated carbon adsorption component connected in sequence. It is particularly suitable for removing pollutants in acidic produced fluids from oil and gas wells, but has the disadvantages of long residence time, easy clogging and high operating cost. It cannot meet the treatment requirements of produced fluids in the high water content period.

[0006] Ramsey James White and others from Saudi Aramco National Oil Company proposed an inline water separator to deal with the problem of high water content produced fluid in mature oil fields at the 2022 Annual Meeting of the Society of Petroleum Engineers (SPE), and discussed it in detail from the aspects of investment cost and technical advantages. This technology is essentially a pre-water separation process to reduce the load of downstream equipment for crude oil processing. The inline water separator can have a variety of process combinations, but it is basically composed of a variety of compact separators connected in series to form a skid, and in a field test, it can achieve a separation efficiency of 70%-80%, and the oil content of the effluent water is reduced to 35ppm, which does not meet the oil content standard requirements for reinjection water.

[0007] PHJ Verbeek of Shell and A. Al-Moosani of Petroleum Development Oman proposed a modular tubular separation technology (ILS technology) for oilfield produced fluid reinjection treatment. The main body consists of a tubular degasser, a tubular oil-water separator, a spare compact separation tank and a hydrocyclone, which are used for gas-liquid separation, pre-water separation and sewage purification respectively. Compared with traditional separators, the obvious advantages of ILS technology include: it refers to pipeline design specifications and does not belong to the category of pressure vessels, it occupies a small area, has a compact space, is light in weight, and has low maintenance costs. At the same time, it can be reassembled and moved for operation due to the advantages of the "containerized" skid design. Although ILS technology has shown excellent separation performance in a field test of a light oil field in northern Oman and helped the oil field to improve its recovery rate, its operating range needs to be further improved and cannot meet the treatment needs of produced fluids in the high water content period.

[0008] Therefore, the existing pre-water separation and water injection treatment equipment has low integration, complex process flow, low oil-water separation efficiency, and the treated wastewater contains a large amount of suspended solids and oil phase, which does not meet the reinjection standards and cannot meet the treatment needs of produced fluids in the high water content period.

[0009] In view of this, the present invention is specially introduced. Summary of the invention

[0010] The purpose of the present invention is to provide an offshore wellhead platform pre-water distribution and water injection treatment system and method to solve the technical problems existing in the prior art, such as low integration of the current pre-water distribution and water injection treatment devices, complex process flow, low oil-water separation efficiency, and substandard quality of treated sewage. The preferred technical solutions among the many technical solutions provided by the present invention can produce many technical effects as described below.

[0011] To achieve the above object, the present invention provides the following technical solutions:

[0012] The present invention provides an offshore wellhead platform pre-water separation and water injection treatment system, comprising a gas-liquid separator, a pre-water separator, a microbubble generator, an air flotation tank and a self-circulating filter;

[0013] The inlet of the gas-liquid separator is connected to the incoming flow pipeline of the offshore wellhead platform, the liquid phase outlet of the gas-liquid separator is connected to the inlet of the pre-water separator through a pipeline, the water phase outlet of the pre-water separator is connected to the water phase inlet of the air flotation tank through the microbubble generator, the water phase outlet of the air flotation tank is connected to the water phase inlet of the self-circulation filter through a pipeline, and the phase outlet of the self-circulation filter is connected to the external water phase pipeline;

[0014] The oil phase outlet of the pre-water separator, the oil phase outlet of the air flotation tank and the oil phase outlet of the self-circulation filter are connected to the external oil phase pipeline through pipelines respectively;

[0015] The gas phase outlet of the gas-liquid separator is communicated with the external gas phase pipeline through a pipeline, and the gas phase inlet of the microbubble generator and the gas phase inlet of the air flotation tank are communicated with the external gas phase pipeline through pipelines respectively.

[0016] Preferably, the gas-liquid separator is arranged horizontally, and a primary swirl element and a secondary swirl element are arranged in sequence along the water flow direction in the cavity of the gas-liquid separator;

[0017] The top of the gas-liquid separator is provided with a primary gas phase outlet and a secondary gas phase outlet, and the primary gas phase outlet and the secondary gas phase outlet are both connected to the external gas phase pipeline through a gas phase discharge pipeline;

[0018] The bottom of the gas-liquid separator is provided with a primary liquid phase outlet and a secondary liquid phase outlet, and the primary liquid phase outlet and the secondary liquid phase outlet are both connected to the pre-water separator through a liquid phase discharge pipeline.

[0019] Preferably, the oil phase outlet of the pre-water separator is located at the top and is connected to the external oil phase pipeline through the first oil discharge pipeline, and the water phase outlet of the pre-water separator is located at the bottom and is connected to the microbubble generator through the first drainage pipeline;

[0020] The cavity of the pre-water separator is divided by a partition to form an oil phase collection area, a liquid inlet area and a water collection area which are arranged in sequence from top to bottom. The cavity of the pre-water separator is provided with swirl tubes which are evenly distributed in parallel. Static swirling blades are provided in the swirl tubes. The inlet of the swirl tubes is connected to the liquid inlet area, the oil phase outlet of the swirl tubes is connected to the oil phase collection area, and the water phase outlet of the swirl tubes is connected to the water collection area.

[0021] Preferably, the microbubble generator comprises a jet dissolved air pipeline group and a dissolved air releaser, the jet dissolved air pipeline group comprises a venturi pipeline, a dissolved air straight pipeline and a dissolved air water outlet pipeline, the gas phase inlet of the venturi pipeline is connected to the external gas phase pipeline through the first gas injection pipeline, the water phase inlet of the venturi pipeline is connected to the outlet of the water collection area through the first drainage pipeline, and the water phase outlet of the venturi pipeline is connected to the inlet of the dissolved air straight pipeline;

[0022] The dissolved air straight pipe is provided with a dissolved air inner part, the dissolved air inner part is a hollow truncated cone structure which is narrow at the top and wide at the bottom, and the outer diameter of the upper end of the dissolved air inner part is 1 / 2 to 2 / 3 of the inner diameter of the dissolved air straight pipe;

[0023] The dissolved air outlet pipe is arranged at the lower part of the dissolved air straight pipe and is connected with the air flotation tank through a second drainage pipe. The dissolved air releaser is arranged on the second drainage pipe.

[0024] Preferably, the flotation tank is arranged vertically, the water inlet pipe of the flotation tank is connected to the second drainage pipe, the oil phase outlet of the flotation tank is located at the top and is connected to the external oil phase pipe through the second oil drainage pipe, and the water phase outlet of the flotation tank is located at the bottom and is connected to the self-circulation filter through the third drainage pipe;

[0025] The flotation tank is provided with a perforated plate, a lifting pipe and an aeration assembly. The cavity of the flotation tank is divided by the perforated plate to form a primary separation zone and a secondary separation zone arranged in sequence from top to bottom. The primary separation zone is provided with a first frustum-shaped inclined plate arranged along its axial direction; the secondary separation zone is provided with a second frustum-shaped inclined plate arranged along its axial direction;

[0026] The lifting pipeline passes through the perforated plate and is respectively connected with the primary separation zone and the secondary separation zone. An aeration component is arranged below the lifting pipeline, and the aeration component is connected with the external gas phase pipeline through the second gas injection pipeline.

[0027] Preferably, the water phase inlet of the self-circulation filter is located at the top and is connected to the third drainage pipe, and the water phase outlet of the self-circulation filter is located on the side wall and is connected to the external water phase pipe.

[0028] Preferably, the self-circulating filter comprises a walnut shell filter, and the sewage outlet of the walnut shell filter is connected to the external oil phase pipeline through a backwash sewage pipeline.

[0029] A method for pre-water distribution and water injection processing of an offshore wellhead platform comprises the following steps:

[0030] S1: The produced liquid from the offshore wellhead platform enters the gas-liquid separator through the incoming flow pipeline for gas-liquid separation. The gas phase enters the external gas phase pipeline, and the liquid phase enters the pre-water separator;

[0031] S2: The pre-water separator separates the liquid phase into oil and water. The oil phase enters the external oil phase pipeline, and the water phase enters the microbubble generator;

[0032] S3: The micro-bubble generator dissolves gas in the water phase to form bubbles, and the generated micro-bubbles enter the air flotation tank together, and the gas phase is injected through the external gas phase pipeline;

[0033] S4: The flotation tank performs flotation separation on the water phase, the oil phase enters the external oil phase pipeline, the gas phase enters the external gas phase pipeline, and the water phase enters the self-circulating filter;

[0034] S5: The self-circulating filter filters the water phase, and the water phase enters the external water phase pipeline, and the oil phase enters the external oil phase pipeline.

[0035] The preferred technical solution of the present invention can at least produce the following technical effects:

[0036] The present invention effectively avoids the technical problems existing in the prior art that the current pre-water separation and water injection treatment device has low integration, complex process flow, low oil-water separation efficiency, and the quality of the treated sewage does not meet the standards. The present invention provides an offshore wellhead platform pre-water separation and water injection treatment system, including a gas-liquid separator, a pre-water separator, a microbubble generator, an air flotation tank, and a self-circulating filter; the inlet of the gas-liquid separator is connected to the incoming flow pipeline of the offshore wellhead platform, the liquid phase outlet of the gas-liquid separator is connected to the inlet of the pre-water separator through a pipeline, the water phase outlet of the pre-water separator is connected to the water phase inlet of the air flotation tank through a microbubble generator, the water phase outlet of the air flotation tank is connected to the water phase inlet of the self-circulating filter through a pipeline, and the phase outlet of the self-circulating filter is connected to the external water phase pipeline; the oil phase outlet of the pre-water separator, the oil phase outlet of the air flotation tank, and the oil phase outlet of the self-circulating filter are respectively connected to the external oil phase pipeline through pipelines; the gas phase outlet of the gas-liquid separator is connected to the external gas phase pipeline through a pipeline, and the gas phase inlet of the microbubble generator and the gas phase inlet of the air flotation tank are respectively connected to the external gas phase pipeline through pipelines. The present invention achieves preliminary gas-liquid separation through the synergistic effect of a gas-liquid separator, a pre-water separator, a microbubble generator, an air flotation tank and a self-circulating filter. The produced liquid enters the gas-liquid separator through an incoming flow pipeline, and then the separated liquid phase enters the pre-water separator for oil-water separation. The water phase outlet of the pre-water separator is connected to the microbubble generator, which generates tiny bubbles, driving the water phase to carry the bubbles into the air flotation tank, and the sewage is separated by air flotation. Finally, the water treated by the air flotation tank enters the self-circulating filter, and reaches the reinjection standard through circulating filtration. The oil phase outlet of the pre-water separator, the oil phase outlet of the air flotation tank and the oil phase outlet of the self-circulating filter are respectively connected to the external oil phase pipeline through pipelines to achieve oil phase recycling. The gas phase outlet of the gas-liquid separator, the gas phase outlet of the microbubble generator and the gas phase outlet of the air flotation tank are respectively connected to the external gas phase pipeline through pipelines to achieve gas recycling. The present invention has a highly integrated system, a simple and reliable process flow, improves the gas-liquid separation efficiency and the oil-water separation efficiency, and completes the oil well produced fluid from pre-water separation to wastewater reinjection in one stop. It is particularly suitable for the treatment of produced fluid in the high water content period of offshore oil fields, and can be directly promoted and applied to onshore oil fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a structural schematic diagram of a pre-water distribution and water injection processing system for an offshore wellhead platform provided by the present invention;

[0039] Figure 2 It is a structural schematic diagram of a micro-bubble generator of an offshore wellhead platform pre-water distribution and water injection treatment system provided by the present invention;

[0040] Figure 3 The present invention is a schematic structural diagram of a two-stage air flotation tank of an offshore wellhead platform pre-water distribution and water injection treatment system.

[0041] In the figure:

[0042] 1. Gas-liquid separator; 101. Primary swirl element; 102. Secondary swirl element; 103. Primary gas phase outlet; 104. Secondary gas phase outlet; 105. Primary liquid phase outlet; 106. Secondary liquid phase outlet;

[0043] 2. Pre-water separator; 201. Oil phase collection area; 202. Liquid inlet area; 203. Water collection area; 204. Cyclone tube; 205. First baffle; 206. Second baffle; 3. Microbubble generator; 301. Venturi pipe; 302. Dissolved air straight pipe; 303. Dissolved air internals; 304. Dissolved air outlet pipe; 305. Dissolved air releaser; 4. Air flotation tank; 401. Primary separation area; 4011. First cone-shaped inclined plate; 402. Secondary separation area; 4021. Second cone-shaped inclined plate; 40 3. Perforated plate; 404. Lifting pipe; 405. Aeration assembly; 406. Water inlet pipe; 5. Self-circulating filter; 6. Inflow pipe; 7. External water phase pipe; 8. External oil phase pipe; 9. External gas phase pipe; 10. Gas phase discharge pipe; 11. Liquid phase discharge pipe; 12. First drain pipe; 13. Second drain pipe; 14. Third drain pipe; 15. First oil discharge pipe; 16. Second oil discharge pipe; 17. Backwash sewage pipe; 18. First gas injection pipe; 19. Second gas injection pipe. DETAILED DESCRIPTION

[0044] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0045] like Figure 1-3 As shown, the present invention provides an offshore wellhead platform pre-water separation and water injection treatment system, including a gas-liquid separator 1, a pre-water separator 2, a microbubble generator 3, an air flotation tank 4 and a self-circulating filter 5.

[0046] The inlet of the gas-liquid separator 1 is connected to the incoming flow pipeline 6 of the offshore wellhead platform, the liquid phase outlet of the gas-liquid separator 1 is connected to the inlet of the pre-water separator 2 through a pipeline, the water phase outlet of the pre-water separator 2 is connected to the water phase inlet of the flotation tank 4 through the microbubble generator 3, the water phase outlet of the flotation tank 4 is connected to the water phase inlet of the self-circulation filter 5 through a pipeline, and the outgoing phase inlet of the self-circulation filter 5 is connected to the external water phase pipeline 7.

[0047] The oil phase outlet of the pre-water separator 2, the oil phase outlet of the flotation tank 4 and the oil phase outlet of the self-circulation filter 5 are connected to the external oil phase pipeline 8 through pipelines respectively.

[0048] The gas phase outlet of the gas-liquid separator 1 is connected to the external gas phase pipeline 9 through a pipeline, and the gas phase inlet of the microbubble generator 3 and the gas phase inlet of the air flotation tank 4 are connected to the external gas phase pipeline 9 through pipelines respectively.

[0049] The present invention uses the synergistic effect of the gas-liquid separator 1, the pre-water separator 2, the microbubble generator 3, the flotation tank 4 and the self-circulation filter 5, and the produced liquid enters the gas-liquid separator 1 through the incoming flow pipe 6 to achieve preliminary separation of gas and liquid. Then, the separated liquid phase enters the pre-water separator 2 for oil-water separation. The water phase outlet of the pre-water separator 2 is connected to the microbubble generator 3, which generates tiny bubbles, drives the water phase to carry the bubbles into the flotation tank 4, and the sewage is separated by flotation. Finally, the water treated by the flotation tank 4 enters the self-circulation filter 5 and reaches the re-injection standard through circulation filtration. The oil phase outlet of the pre-water separator 2, the oil phase outlet of the flotation tank 4 and the oil phase outlet of the self-circulation filter 5 are respectively connected to the external oil phase pipeline 8 through pipelines to achieve the recovery of the oil phase. The gas phase outlet of the gas-liquid separator 1, the gas phase outlet of the microbubble generator 3 and the gas phase outlet of the flotation tank 4 are respectively connected to the external gas phase pipeline 9 through pipelines to achieve gas recovery. The present invention has a highly integrated system, a simple and reliable process flow, improves the gas-liquid separation efficiency and the oil-water separation efficiency, and completes the oil well produced fluid from pre-water separation to wastewater reinjection in one stop. It is particularly suitable for the treatment of produced fluid in the high water content period of offshore oil fields, and can be directly promoted and applied to onshore oil fields.

[0050] As an optional embodiment, the gas-liquid separator 1 preferably adopts a horizontally arranged tubular two-stage gas-liquid separator. The cavity of the gas-liquid separator 1 is provided with a primary swirl element 101 and a secondary swirl element 102 which are sequentially arranged along the water flow direction.

[0051] A primary gas phase outlet 103 and a secondary gas phase outlet 104 are provided at the top of the gas-liquid separator 1 , and both the primary gas phase outlet 103 and the secondary gas phase outlet 104 are connected to the external gas phase pipeline 9 through the gas phase discharge pipeline 10 .

[0052] A primary liquid phase outlet 105 and a secondary liquid phase outlet 106 are provided at the bottom of the gas-liquid separator 1 . Both the primary liquid phase outlet 105 and the secondary liquid phase outlet 106 are connected to the pre-water separator 2 through a liquid phase discharge pipe 11 .

[0053] The produced liquid from the wellhead platform enters the gas-liquid separator 1 for gas-liquid separation, passes through the first-level swirling element 101 for first-level cyclone degassing, and the liquid phase is discharged to the pre-water separator 2 through the first-level liquid phase outlet 105 on the side wall, and the gas phase and the remaining liquid phase continue to flow to the second-level swirling element 102 for second-level cyclone deliquidation, and the gas phase is discharged to the external gas phase pipeline 9 through the first-level gas phase outlet 103 at the tail end of the second-level swirling element 102, and the liquid phase is further precipitated and separated by gravity to separate the remaining gas and liquid phases, and the separated gas phase is discharged to the external gas phase pipeline 9 through the second-level gas phase outlet 104, and the liquid phase is discharged to the pre-water separator 2 through the second-level liquid phase outlet 106.

[0054] The gas-liquid separator 1 provided by the present invention can realize gas-liquid separation in a single tube. The gas phase is discharged from the primary gas phase outlet 103 and the secondary gas phase outlet 104, and enters the external gas phase pipeline 9 through the gas phase discharge pipeline 10 respectively. The liquid phase is discharged from the primary liquid phase outlet 105 and the secondary liquid phase outlet 106, and enters the pre-water separator 2 through the liquid phase discharge pipeline 11 respectively, which can be applied to a wide range of gas-containing produced liquid working conditions and has strong anti-fluctuation performance.

[0055] As an optional embodiment, the oil phase outlet of the pre-water separator 2 is located at the top and is connected to the external oil phase pipeline 8 through the first oil discharge pipe 15, and the water phase outlet of the pre-water separator 2 is located at the bottom and is connected to the microbubble generator 3 through the first drain pipe 12.

[0056] The cavity of the pre-water separator 2 is divided by a first partition 205 and a second partition 206 to form an oil phase collection area 201, a liquid inlet area 202 and a water collection area 203 arranged in sequence from top to bottom. The cavity of the pre-water separator 2 is provided with swirl tubes 204 arranged in parallel and evenly distributed. Static swirling blades are provided in the swirl tubes 204. The inlet of the swirl tubes 204 is connected to the liquid inlet area 202, the oil phase outlet of the swirl tubes 204 is connected to the oil phase collection area 201, and the water phase outlet of the swirl tubes 204 is connected to the water collection area 203.

[0057] Furthermore, the pre-water separator 2 is arranged vertically, and the pre-water separator 2 includes a single-tube large-capacity static cyclone pre-water separator 2, which can ensure that the oil-water ratio and hydraulic conditions of the liquid inlet area 202 are stable and uniform to the greatest extent. At the same time, the processing capacity of a single cyclone tube 204 can reach 20m 3 / h or more, effectively avoiding the easy clogging problem of conventional hydrocyclones.

[0058] The two ends of the cyclone 204 are respectively mounted on the first baffle 205 and the second baffle 206. The cyclone 204 adopts a tangential liquid inlet method, so that when the liquid phase enters the cyclone 204, it can form a cyclone more quickly through the static swirling blades to achieve oil-water separation with good separation effect.

[0059] The separated oil phase is swirled into the oil collecting chamber and enters the external oil phase pipeline 8 through the first oil discharge pipe 15. The separated water phase enters the water collecting area 203 and is discharged to the micro bubble generator 3 through the first drain pipe 12.

[0060] As an optional implementation, Figure 2 As shown, the microbubble generator 3 includes a jet dissolved air pipeline group and a dissolved air releaser 305. The jet dissolved air pipeline group includes a venturi pipeline 301, a dissolved air straight pipeline 302 and a dissolved air water outlet pipeline 304. The gas phase inlet of the venturi pipeline 301 is connected to the external gas phase pipeline 9 through the first gas injection pipeline 18, the water phase inlet of the venturi pipeline 301 is connected to the outlet of the water collection area 203 through the first drainage pipe 12, and the water phase outlet of the venturi pipeline 301 is connected to the inlet of the dissolved air straight pipeline 302.

[0061] A dissolved air inner part 303 is fixedly arranged in the dissolved air straight pipe 302 . The dissolved air inner part 303 is a hollow truncated cone structure that is narrow at the top and wide at the bottom. The outer diameter of the upper end of the dissolved air inner part 303 is 1 / 2 to 2 / 3 of the inner diameter of the dissolved air straight pipe 302 .

[0062] The dissolved air outlet pipe 304 is arranged at the lower part of the dissolved air straight pipe 302 and is connected to the two-stage air flotation tank 4 through the second drainage pipe 13 . The dissolved air releaser 305 is arranged on the second drainage pipe 13 .

[0063] Furthermore, the gas injection amount of the Venturi pipe 301 is 5% to 10% of the water inlet flow rate of the Venturi pipe 301, and the average particle size of the bubbles is between 30 and 50 μm.

[0064] The dissolved gas releaser 305 may preferably be a ball valve, and the dissolved gas pressure can be adjusted by adjusting the opening of the ball valve to achieve the regulation of bubbles.

[0065] The gas phase inlet of the venturi pipe 301 is connected to the external gas phase pipeline 9 through the first gas injection pipeline 18, and the gas source is provided for the gas dissolving process through the external gas phase pipeline 9. The water phase treated by the pre-water separator 2 enters the venturi pipe 301 through the first drainage pipe 12. Due to the Venturi effect of the venturi pipe 301, the gas is integrated into the water phase, and then passes through the dissolved gas straight pipe 302 to make the gas better mixed with the water phase. When the water phase passes through the second drainage pipe 13, the dissolved gas releaser 305 causes the gas in the water phase to be released, forming a large number of fine bubbles, and the water phase entrains the bubbles and enters the two-stage flotation tank 4.

[0066] As an optional implementation, Figure 3 As shown, the flotation tank 4 preferably adopts a vertical single tank two-stage flotation tank. The water inlet pipe 406 of the flotation tank 4 is connected to the second drain pipe 13, the oil phase outlet of the flotation tank 4 is located at the top, and is connected to the external oil phase pipeline 8 through the second oil drain pipe 16, and the water phase outlet of the flotation tank 4 is located at the bottom, and is connected to the self-circulation filter 5 through the third drain pipe 14.

[0067] The flotation tank 4 is provided with a perforated plate 403, a lifting pipe 404 and an aeration assembly 405. The cavity of the flotation tank 4 is divided by the perforated plate 403 to form a primary separation zone 401 and a secondary separation zone 402 arranged in sequence from top to bottom. The primary separation zone 401 is provided with a first frustum-shaped inclined plate 4011 arranged along its axial direction. The secondary separation zone 402 is provided with a second frustum-shaped inclined plate 4021 arranged along its axial direction.

[0068] The lifting pipe 404 passes through the perforated plate 403 and is connected to the primary separation zone 401 and the secondary separation zone 402 respectively. An aeration component 405 is arranged below the lifting pipe 404. The aeration component 405 is connected to the external gas phase pipeline 9 through the second gas injection pipeline 19. The gas injection volume is 1 / 20~1 / 25 of the liquid phase flow rate.

[0069] Furthermore, the cavity of the flotation tank 4 is divided by a perforated plate 403 to form a primary separation zone 401 and a secondary separation zone 402 arranged from top to bottom to achieve flotation separation, and the hydraulic retention time is ≤3min to ensure the stability and reliability of the oil-water separation effect.

[0070] The function of the first conical inclined plate 4011 is to strengthen the primary flotation separation effect of the primary separation zone 401 .

[0071] The water phase treated by the microbubble generator 3 enters the primary separation zone 401, and is guided by the first cone-shaped inclined plate 4011 to separate oil and water. The separated oil phase floats to the liquid surface, and the separated liquid phase enters the secondary separation zone 402 through the perforated plate 403. The aeration component 405 is connected to the external gas phase pipeline 9 through the second gas injection pipeline 19, and provides a gas source for the oil and gas separation process through the external gas phase pipeline 9. The gas source enters the secondary separation zone 402 through the aeration component 405, and promotes the oil-water separation in the secondary separation zone 402 through the gas lift effect. The separated oil phase floats to the liquid surface of the primary separation zone 401 through the lifting pipeline 404, and then is discharged to the external oil phase pipeline 8 through the second oil discharge pipe 16.

[0072] As an optional embodiment, the water phase inlet of the self-circulating filter 5 is located at the top and is connected to the third drainage pipe 14 , and the water phase outlet of the self-circulating filter 5 is located on the side wall and is connected to the external water phase pipeline 7 .

[0073] As an optional embodiment, the self-circulating filter 5 includes a walnut shell filter, the sewage outlet of the walnut shell filter is connected to the external oil phase pipeline 8 through the backwash sewage pipe 17, and the sewage outlet of the walnut shell filter is located above the water phase outlet of the walnut shell filter.

[0074] The sewage first enters the walnut shell filter, where the suspended solids and part of the oil phase are removed by the walnut shell filter material. The backwash sewage is discharged into the external oil phase pipeline 8 through the backwash sewage pipeline 17, and the treated sewage that meets the standards is connected to the oil well water injection system through the external water phase pipeline 7.

[0075] The walnut shell filter does not need a matching backwash water tank, making the overall equipment compact and easy to maintain. The walnut shell filter realizes the backwash regeneration of the walnut shell filter material inside the walnut shell filter through structures such as the central nozzle. The labyrinth flow channel structure inside the walnut shell filter causes a strong scrubbing effect between the walnut shell filter materials, so that the dirty oil and impurities are separated from the walnut shell filter material. The backwash sewage is discharged through the backwash sewage pipe 17, and the walnut shell filter material is retained in the tank for continued use.

[0076] The present invention provides a method for pre-water distribution and water injection processing of an offshore wellhead platform, comprising the following steps:

[0077] S1: The produced liquid from the offshore wellhead platform enters the gas-liquid separator 1 through the incoming flow pipeline 6 for gas-liquid separation, the gas phase enters the external gas phase pipeline 9, and the liquid phase enters the pre-water separator 2;

[0078] S2: The pre-water separator 2 separates the liquid phase into oil and water, the oil phase enters the external oil phase pipeline 8, and the water phase enters the microbubble generator 3;

[0079] S3: The micro-bubble generator 3 dissolves gas into bubbles in the gas-liquid phase, and the generated micro-bubbles enter the air flotation tank 4 together, and the gas phase comes from the external gas phase pipeline 9;

[0080] S4: The flotation tank 4 performs flotation separation on the water phase, the oil phase enters the external oil phase pipeline 8, the gas phase is injected through the external gas phase pipeline 9, and the water phase enters the self-circulation filter 5;

[0081] S5: The self-circulating filter 5 filters the water phase, and the water phase enters the external water phase pipeline 7, and the oil phase enters the external oil phase pipeline 8.

[0082] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0083] In the description of the present invention, it should be noted that, unless otherwise specified, the meaning of "plurality" is two or more; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0084] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0085] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "an example" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0086] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A pre-water distribution and water injection processing system for an offshore wellhead platform, It is characterized in that It includes gas-liquid separator, pre-water separator, micro-bubble generator, air flotation tank and self-circulating filter; The inlet of the gas-liquid separator is connected to the incoming flow pipeline of the offshore wellhead platform, the liquid phase outlet of the gas-liquid separator is connected to the inlet of the pre-water separator through a pipeline, the water phase outlet of the pre-water separator is connected to the water phase inlet of the air flotation tank through the microbubble generator, the water phase outlet of the air flotation tank is connected to the water phase inlet of the self-circulation filter through a pipeline, and the water phase outlet of the self-circulation filter is connected to the external water phase pipeline; The oil phase outlet of the pre-water separator, the oil phase outlet of the air flotation tank and the oil phase outlet of the self-circulation filter are respectively connected to the external oil phase pipeline through pipelines; The gas phase outlet of the gas-liquid separator is communicated with the external gas phase pipeline through a pipeline, and the gas phase inlet of the microbubble generator and the gas phase inlet of the air flotation tank are respectively communicated with the external gas phase pipeline through pipelines; the oil phase outlet of the pre-water separator is located at the top and is communicated with the external oil phase pipeline through the first oil discharge pipeline, and the water phase outlet of the pre-water separator is located at the bottom and is communicated with the microbubble generator through the first drainage pipeline; The cavity of the pre-water separator is divided by a partition to form an oil phase collection area, a liquid inlet area and a water collection area arranged in sequence from top to bottom. The cavity of the pre-water separator is provided with swirl tubes arranged in parallel and evenly distributed. Static swirl blades are provided in the swirl tubes. The inlet of the swirl tube is connected to the liquid inlet area, the oil phase outlet of the swirl tube is connected to the oil phase collection area, and the water phase outlet of the swirl tube is connected to the water collection area. The microbubble generator comprises a jet dissolved air pipeline group and a dissolved air releaser, the jet dissolved air pipeline group comprises a venturi pipeline, a dissolved air straight pipeline and a dissolved air water outlet pipeline, the gas phase inlet of the venturi pipeline is connected to the external gas phase pipeline through the first gas injection pipeline, the water phase inlet of the venturi pipeline is connected to the outlet of the water collection area through the first drainage pipeline, and the water phase outlet of the venturi pipeline is connected to the inlet of the dissolved air straight pipeline; The dissolved air straight pipe is provided with an air-dissolving inner part, which is a hollow truncated cone-shaped structure narrow at the top and wide at the bottom, and the outer diameter of the upper end of the dissolved air inner part is 1 / 2 to 2 / 3 of the inner diameter of the dissolved air straight pipe; The dissolved air outlet pipe is arranged at the lower part of the dissolved air straight pipe and is connected with the air flotation tank through a second drainage pipe. The dissolved air releaser is arranged on the second drainage pipe.

2. An offshore wellhead platform pre-water distribution and water injection processing system according to claim 1, It is characterized in that The gas-liquid separator is arranged horizontally, and a primary swirl element and a secondary swirl element are arranged in sequence along the water flow direction in the cavity of the gas-liquid separator; The top of the gas-liquid separator is provided with a primary gas phase outlet and a secondary gas phase outlet, and the primary gas phase outlet and the secondary gas phase outlet are both connected to the external gas phase pipeline through a gas phase discharge pipeline; The bottom of the gas-liquid separator is provided with a primary liquid phase outlet and a secondary liquid phase outlet, and the primary liquid phase outlet and the secondary liquid phase outlet are both connected to the pre-water separator through a liquid phase discharge pipeline.

3. The offshore wellhead platform pre-water distribution and water injection processing system according to claim 1, It is characterized in that The flotation tank is arranged vertically, the water inlet pipe of the flotation tank is connected to the second drainage pipe, the oil phase outlet of the flotation tank is located at the top and is connected to the external oil phase pipe through the second oil drainage pipe, and the water phase outlet of the flotation tank is located at the bottom and is connected to the self-circulation filter through the third drainage pipe; The flotation tank is provided with a perforated plate, a lifting pipe and an aeration assembly. The cavity of the flotation tank is divided by the perforated plate to form a primary separation zone and a secondary separation zone arranged in sequence from top to bottom. The primary separation zone is provided with a first frustum-shaped inclined plate arranged along its axial direction; the secondary separation zone is provided with a second frustum-shaped inclined plate arranged along its axial direction; The lifting pipeline passes through the perforated plate and is respectively connected with the primary separation zone and the secondary separation zone. An aeration component is arranged below the lifting pipeline, and the aeration component is connected with the external gas phase pipeline through the second gas injection pipeline.

4. The offshore wellhead platform pre-water distribution and water injection processing system according to claim 3, It is characterized in that The water phase inlet of the self-circulating filter is located at the top and is communicated with the third drainage pipe. The water phase outlet of the self-circulating filter is located on the side wall and is communicated with the external water phase pipeline.

5. The offshore wellhead platform pre-water distribution and water injection processing system according to claim 4, It is characterized in that The self-circulating filter comprises a walnut shell filter, and the sewage outlet of the walnut shell filter is connected with the external oil phase pipeline through a backwash sewage pipeline.

6. A method for treating a pre-water distribution and water injection treatment system for an offshore wellhead platform according to claim 1, It is characterized in that The steps include: S1: The produced liquid from the offshore wellhead platform enters the gas-liquid separator through the incoming flow pipeline for gas-liquid separation. The gas phase enters the external gas phase pipeline, and the liquid phase enters the pre-water separator; S2: The pre-water separator separates the liquid phase into oil and water. The oil phase enters the external oil phase pipeline, and the water phase enters the microbubble generator; S3: The micro-bubble generator dissolves gas and liquid into bubbles, and the generated micro-bubbles enter the flotation tank together, and the gas phase comes from the external gas phase pipeline; S4: The flotation tank performs flotation separation on the water phase, the oil phase enters the external oil phase pipeline, the gas phase is injected from the external gas phase pipeline, and the water phase enters the self-circulating filter; S5: The self-circulating filter filters the water phase, and the water phase enters the external water phase pipeline, and the oil phase enters the external oil phase pipeline.

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