Separation structure and separation method

Abstract

The invention relates to a separation structure and a separation method, and relates to the technical field of multi-phase separation equipment. The separation structure comprises a liquid inlet pipe, a plurality of separation pipes and a plurality of transition pipes, the plurality of separation pipes are positioned above the liquid inlet pipe and are arranged at intervals along the axial direction of the liquid inlet pipe; the transition pipes are arranged at intervals in the axial direction of the liquid inlet pipe and correspond to the separation pipes one to one, one ends of the transition pipes communicate with the corresponding separation pipes, the other ends of the transition pipes communicate with the liquid inlet pipe, and the plane where the separation pipes are located is parallel to the liquid inlet pipe; the water phase outlet pipe is positioned at one end, close to the liquid inlet pipe, of the corresponding separation pipe; the inlet end of the water phase outlet pipe is communicated with the bottom of the corresponding liquid inlet pipe; the mixed-phase outlet pipes are arranged in the corresponding water-phase outlet pipes; and the inlet ends of the mixed-phase outlet pipes are communicated with the separation pipes and are positioned at the upper parts of the separation pipes. According to the technical scheme, the problems that an existing underwater separator is too large in size and too heavy can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of multiphase separation equipment, and in particular to a separation structure and a separation method. Background Art

[0002] With the rapid development of marine engineering technology and equipment, the exploration and development of marine oil and gas resources has extended from shallow waters to deep seas. In the process of marine oil and gas development advancing into the deep sea, the hydrostatic pressure gradually increases, making it more difficult to lift the oil and gas mixture produced from the wellhead. In addition, the wellhead output liquid is a multiphase mixture containing oil, natural gas, water, sediment, carbon dioxide and other associated gases. Direct transportation is prone to produce riser slug flow and hydrates, which increases the difficulty of lifting. Therefore, an underwater separator is usually set up at the wellhead to directly separate the oil, gas, water and solid phases of the output liquid. The separated oil phase, gas phase, etc. are transported to the offshore floating production system or the central offshore platform respectively, and the water phase is reinjected and the solid phase impurities are directly filtered underwater. However, the existing underwater separators are usually horizontal structures with many underwater accessories and low volume utilization, resulting in the separator being too large and too heavy. Summary of the Invention

[0003] The embodiments of the present invention provide a separation structure and a separation method, which can solve the problems of existing underwater separators being too large in size and too heavy in weight.

[0004] In a first aspect, an embodiment of the present invention provides a separation structure, including:

[0005] Liquid inlet pipe;

[0006] A plurality of separation tubes are located above the liquid inlet tube, the plurality of separation tubes are spaced apart along the axial direction of the liquid inlet tube, and the plane where the plurality of separation tubes are located is parallel to the liquid inlet tube;

[0007] a plurality of transition tubes, the plurality of transition tubes being arranged at intervals along the axial direction of the liquid inlet tube and corresponding one-to-one to the plurality of separation tubes, the transition tubes being located between the liquid inlet tube and the separation tubes, one end of the transition tube being connected to the corresponding separation tube, and the other end being connected to the liquid inlet tube, and the plane on which the plurality of separation tubes are located being parallel to the liquid inlet tube;

[0008] a plurality of water phase outlet pipes, corresponding one to one with the plurality of separation pipes, the water phase outlet pipes being located at one end of the corresponding separation pipe close to the liquid inlet pipe, and the inlet ends of the water phase outlet pipes being connected to the bottoms of the corresponding liquid inlet pipes; and

[0009] A plurality of mixed-phase outlet pipes respectively correspond to the plurality of water-phase outlet pipes. The mixed-phase outlet pipes are arranged in the corresponding water-phase outlet pipes. The inlet ends of the mixed-phase outlet pipes are connected to the separation pipes and are located at the upper part of the separation pipes.

[0010] In one embodiment, the transition duct comprises:

[0011] a horizontal pipe section, wherein the axial direction of the horizontal pipe section is perpendicular to the axial direction of the liquid inlet pipe;

[0012] a vertical pipe section, one end of which is connected to the liquid inlet pipe and the other end of which is connected to the horizontal pipe section, wherein the axial direction of the vertical pipe section is perpendicular to the axial directions of the horizontal pipe section and the liquid inlet pipe section; and

[0013] a connecting pipe section, one end of which is connected to the separation pipe and the other end of which is connected to the horizontal pipe section, wherein the connecting pipe section includes an arc-shaped conveying section;

[0014] Wherein, the inner diameter of the horizontal pipe section is not greater than the inner diameter of the liquid inlet pipe.

[0015] In one embodiment, the inner diameter of the horizontal pipe section is 0.15 m, and the length of the horizontal pipe section is 20-50 m.

[0016] In one embodiment, the separator tube comprises:

[0017] A main pipe section, wherein the axial direction of the main pipe is parallel to the axial direction of the horizontal pipe section;

[0018] a buffer pipe section, one end of which is connected to the main pipe section and the other end of which is connected to the connecting pipe section; and

[0019] A sealing head is provided on one end of the main pipe section away from the buffer pipe section;

[0020] The inner diameter of the buffer tube segment gradually increases along the axial direction of the buffer tube segment, and the inner diameter of one end of the buffer tube segment close to the connecting tube segment is smaller than the inner diameter of one end of the buffer tube segment close to the main tube segment.

[0021] In one embodiment, the inner diameter of the main pipe section is 0.46-0.76 m, and the length of the main pipe section is 20-50 m.

[0022] In one embodiment, the water phase outlet pipe comprises:

[0023] a first aqueous phase outlet pipe column, one end of which is connected to the bottom of the separation pipe, wherein the axial direction of the first aqueous phase outlet pipe column is perpendicular to the axial directions of the separation pipe and the liquid inlet pipe; and

[0024] One end of the second water phase outlet pipe string is connected to the first water phase outlet pipe string, and the axial direction of the second water phase outlet pipe string is perpendicular to the axial direction of the first water phase outlet pipe string.

[0025] In one embodiment, the mixed phase outlet pipe comprises:

[0026] a first mixed-phase outlet pipe string, which passes through the first aqueous-phase outlet pipe string, wherein the axial direction of the first mixed-phase outlet pipe string is parallel to the axial direction of the first aqueous-phase outlet pipe string; and

[0027] One end of the second mixed-phase outlet pipe string is connected to the first mixed-phase outlet pipe string, and the axial direction of the second mixed-phase outlet pipe string is perpendicular to the axial direction of the first mixed-phase outlet pipe string.

[0028] In one embodiment, the separation structure further comprises:

[0029] a multiphase pump connected to the outlet end of the mixed-phase outlet pipe; and

[0030] A water injection pump is connected to the outlet end of the water phase outlet pipe.

[0031] In a second aspect, an embodiment of the present invention provides a separation method, which is applied to the separation structure described above, comprising:

[0032] Injecting a mixed liquid into the transition pipe through the liquid inlet pipe, and performing steady flow of the mixed liquid through the transition pipe, wherein the mixed liquid includes an oil phase, a gas phase, and a water phase;

[0033] The mixed liquid after steady flow is input into the separation tube, and the mixed liquid undergoes gas-liquid separation and oil-water separation in the separation tube, so that the gas phase is located at the top of the separation tube and the oil phase is located between the gas phase and the water phase;

[0034] The gas phase and the oil phase are discharged through the mixed phase outlet pipe, and the water phase is discharged through the water phase outlet pipe; wherein the inlet end of the mixed phase outlet pipe is located at the upper part of the separation tube, and the inlet end of the water phase outlet pipe is located at the bottom of the separation tube.

[0035] In one embodiment, it further includes:

[0036] monitoring the liquid level of the aqueous phase in the separation tube, and accelerating the discharge of the aqueous phase in the separation tube by a water injection pump if the liquid level is greater than a first liquid level threshold;

[0037] If the liquid level is lower than the second liquid level threshold, the water phase in the separation tube is discharged at a reduced speed by the water injection pump.

[0038] Compared with the prior art, the advantages of the embodiments of the present invention are:

[0039] (1) Due to the different densities of the various phases in the mixed liquid, when the mixed liquid flows in the separation tube, the oil phase, gas phase, and water phase of the mixed liquid are separated under the action of gravity and gathered at different heights of the separation tube. The gas phase gathers at the top of the separation tube, the oil phase gathers at the upper part of the separation tube, and the water phase gathers at the bottom of the separation tube. The gas phase and the oil phase enter the mixed phase outlet pipe, and the water phase enters the water phase outlet pipe, thereby achieving multi-phase separation and separate discharge;

[0040] (2) By arranging a plurality of separation tubes and transition tubes in parallel in the axial direction of the liquid inlet pipe, the installation space of the separation structure is reduced, making the separation structure more compact; by arranging the mixed-phase outlet pipe in the water-phase outlet pipe, not only is it possible to separate different phases of matter through different pipes, but also the volume of the separation structure is saved; at the same time, the oil phase and the gas phase are mixed and transported through the mixed-phase outlet pipe. Compared with the separator in the prior art that uses different pipes to separate the oil phase and the gas phase, the present invention reduces the accessories of the separator and further reduces the volume and weight of the separator;

[0041] (3) In addition, by setting up multiple transition pipes and multiple separation pipes, the mixed liquid is divided into multiple streams of small flow liquids and separated simultaneously, which greatly improves the separation efficiency and separation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Hereinafter, the present invention will be described in more detail based on embodiments with reference to the accompanying drawings.

[0043] Figure 1 is a front view of a separation structure provided by one embodiment of the present invention;

[0044] Figure 2 yes Figure 1 A schematic diagram of the structure of the transition tube and the separation tube provided in the embodiment;

[0045] Figure 3 yes Figure 1 A cross-sectional view of the aqueous phase outlet pipe and the mixed phase outlet provided in the embodiment;

[0046] Figure 4 is a flow chart of a separation method provided by another embodiment of the present invention;

[0047] Figure 5 is a graph showing the relationship between oil content in water and residence time provided by another embodiment of the present invention;

[0048] Figure 6 A diagram showing the relationship between the water content in oil and the water content in the main pipe section is provided in another embodiment of the present invention;

[0049] Figure 7A graph showing the relationship between the water content in oil and the oil content in the main pipe section is provided in another embodiment of the present invention;

[0050] Figure 8 This is a relationship diagram of the inlet water content, the water content in the oil in the mixed-phase outlet pipe, and the oil flow rate provided by another embodiment of the present invention.

[0051] Reference numerals:

[0052] 10. Liquid inlet pipe;

[0053] 20, separation pipe; 210, main pipe section; 220, buffer pipe section; 230, head;

[0054] 30, transition pipe; 310, horizontal pipe section; 320, riser section; 330, connecting pipe section;

[0055] 40, water phase outlet pipe; 410, first water phase outlet pipe string; 4101, main straight pipe section; 4102, secondary straight pipe section; 4103, contraction pipe section; 420, second water phase outlet pipe string;

[0056] 50. Miscible phase outlet pipe; 510. First miscible phase outlet pipe string; 520. Second miscible phase outlet pipe string. DETAILED DESCRIPTION

[0057] The present invention will be further described below with reference to the accompanying drawings.

[0058] With the rapid development of marine engineering technology and equipment, the exploration and development of marine oil and gas resources has extended from shallow waters to deep seas. In the process of marine oil and gas development advancing into the deep sea, the hydrostatic pressure gradually increases, making it more difficult to lift the oil and gas mixture produced from the wellhead. In addition, the wellhead output liquid is a multiphase mixture containing oil, natural gas, water, sediment, carbon dioxide and other associated gases. Direct transportation is prone to produce riser slug flow and hydrates, which increases the difficulty of lifting. Therefore, an underwater separator is usually set up at the wellhead to directly separate the oil, gas, water and solid phases of the output liquid. The separated oil phase, gas phase, etc. are transported to the offshore floating production system or the central offshore platform respectively, and the water phase is reinjected and the solid phase impurities are directly filtered underwater. However, the existing underwater separators are usually horizontal structures with many underwater accessories and low volume utilization, resulting in the separator being too large and too heavy.

[0059] Example 1

[0060] like Figure 1-Figure 3 As shown, in order to solve the above technical problems, an embodiment of the present invention provides a separation structure, including a liquid inlet pipe 10, a plurality of separation pipes 20, a plurality of transition pipes 30, a plurality of water phase outlet pipes 40 and a plurality of mixed phase outlet pipes 50;

[0061] The plurality of separation tubes 20 are located above the liquid inlet tube 10. The plurality of separation tubes 20 are spaced apart along the axial direction of the liquid inlet tube 10. The plane where the plurality of separation tubes 20 are located is parallel to the liquid inlet tube 10.

[0062] Multiple transition tubes 30 are arranged at intervals along the axial direction of the liquid inlet pipe 10 and correspond one-to-one to the multiple separation tubes 20. The transition tubes 30 are located between the liquid inlet pipe 10 and the separation tubes 20. One end of the transition tube 30 is connected to the corresponding separation tube 20, and the other end is connected to the liquid inlet pipe 10. The plane on which the multiple separation tubes 20 are located is parallel to the liquid inlet pipe 10.

[0063] The plurality of water phase outlet pipes 40 correspond one to one with the plurality of separation pipes 20 , respectively. The water phase outlet pipe 40 is located at one end of the corresponding separation pipe 20 close to the liquid inlet pipe 10 , and the inlet end of the water phase outlet pipe 40 is connected to the bottom of the corresponding liquid inlet pipe 10 ; and

[0064] The multiple mixed phase outlet pipes 50 correspond to the multiple water phase outlet pipes 40 one by one, and the mixed phase outlet pipes 50 are arranged in the corresponding water phase outlet pipes 40. The inlet end of the mixed phase outlet pipe 50 is connected to the separation pipe 20 and is located at the upper part of the separation pipe 20.

[0065] As can be seen from the above, due to the different densities of the various phases in the mixed liquid, when the mixed liquid flows in the separation tube 20, the oil phase, gas phase, and water phase of the mixed liquid are separated under the action of gravity based on the density difference and are respectively gathered at different heights of the separation tube 20. The gas phase is gathered at the top of the separation tube 20, the oil phase is gathered at the upper part of the separation tube 20, and the water phase is gathered at the bottom of the separation tube 20. The gas phase and the oil phase enter the mixed phase outlet pipe 50, and the water phase enters the water phase outlet pipe 40, thereby achieving multi-phase separation and being discharged separately.

[0066] By arranging multiple separation tubes 20 and transition tubes 30 side by side in the axial direction of the liquid inlet pipe 10, the installation space of the separation structure is reduced, making the separation structure more compact; by arranging the mixed-phase outlet pipe 50 in the water-phase outlet pipe 40, not only is it possible to separately transport different phase substances through different pipes, but the volume of the separation structure is also saved; at the same time, the oil phase and the gas phase are mixed and transported through the mixed-phase outlet pipe 50. Compared with the separator in the prior art that uses different pipes to separately transport the oil phase and the gas phase, the present invention reduces the accessories of the separator and further reduces the volume and weight of the separator.

[0067] In addition, by providing a plurality of transition pipes 30 and a plurality of separation pipes 20, the mixed liquid is divided into a plurality of small flow liquids and separated simultaneously, and the separation efficiency and separation effect are greatly improved.

[0068] It should be noted that the separation structure separates the mixed liquid, wherein the mixed liquid includes an oil phase, a gas phase and an aqueous phase; the mixed liquid includes but is not limited to oil-containing produced water from an oil field or industrial wastewater.

[0069] It should also be noted that the multiple separation tubes 20 work independently and do not interfere with each other, which is convenient for maintenance and installation. The structure of multiple separation tubes 20 connected in parallel is convenient for users to assemble according to actual needs, which greatly improves versatility and practicality. The multiple separation tubes 20 are arranged at equal intervals along the axial direction of the liquid inlet pipe 10. The number of separation tubes 20 can be set as needed, and this application does not impose specific restrictions. For example, Figure 1 As shown, the number of separation tubes 20 is 4-8.

[0070] It should also be noted that if Figure 1 As shown, the axial direction of the liquid inlet pipe 10 is parallel to the Y direction.

[0071] Example 2

[0072] like Figure 1-Figure 3 As shown, the separation structure includes a liquid inlet pipe 10, multiple separation pipes 20, multiple transition pipes 30, multiple water phase outlet pipes 40 and multiple mixed phase outlet pipes 50;

[0073] The plurality of separation tubes 20 are located above the liquid inlet tube 10. The plurality of separation tubes 20 are spaced apart along the axial direction of the liquid inlet tube 10. The plane where the plurality of separation tubes 20 are located is parallel to the liquid inlet tube 10.

[0074] Multiple transition tubes 30 are arranged at intervals along the axial direction of the liquid inlet pipe 10 and correspond one-to-one to the multiple separation tubes 20. The transition tubes 30 are located between the liquid inlet pipe 10 and the separation tubes 20. One end of the transition tube 30 is connected to the corresponding separation tube 20, and the other end is connected to the liquid inlet pipe 10. The plane on which the multiple separation tubes 20 are located is parallel to the liquid inlet pipe 10.

[0075] The plurality of water phase outlet pipes 40 correspond one to one with the plurality of separation pipes 20 , respectively. The water phase outlet pipe 40 is located at one end of the corresponding separation pipe 20 close to the liquid inlet pipe 10 , and the inlet end of the water phase outlet pipe 40 is connected to the bottom of the corresponding liquid inlet pipe 10 ; and

[0076] The multiple mixed phase outlet pipes 50 correspond to the multiple water phase outlet pipes 40 one by one, and the mixed phase outlet pipes 50 are arranged in the corresponding water phase outlet pipes 40. The inlet end of the mixed phase outlet pipe 50 is connected to the separation pipe 20 and is located at the upper part of the separation pipe 20.

[0077] As can be seen from the above, due to the different densities of the various phases in the mixed liquid, when the mixed liquid flows in the separation tube 20, the oil phase, gas phase, and water phase of the mixed liquid are separated under the action of gravity based on the density difference and are respectively gathered at different heights of the separation tube 20. The gas phase is gathered at the top of the separation tube 20, the oil phase is gathered at the upper part of the separation tube 20, and the water phase is gathered at the bottom of the separation tube 20. The gas phase and the oil phase enter the mixed phase outlet pipe 50, and the water phase enters the water phase outlet pipe 40, thereby achieving multi-phase separation and being discharged separately.

[0078] By arranging multiple separation tubes 20 and transition tubes 30 side by side in the axial direction of the liquid inlet pipe 10, the installation space of the separation structure is reduced, making the separation structure more compact; by arranging the mixed-phase outlet pipe 50 in the water-phase outlet pipe 40, not only is it possible to separately transport different phase substances through different pipes, but the volume of the separation structure is also saved; at the same time, the oil phase and the gas phase are mixed and transported through the mixed-phase outlet pipe 50. Compared with the separator in the prior art that uses different pipes to separately transport the oil phase and the gas phase, the present invention reduces the accessories of the separator and further reduces the volume and weight of the separator.

[0079] In addition, by providing a plurality of transition pipes 30 and a plurality of separation pipes 20, the mixed liquid is divided into a plurality of small flow liquids and separated simultaneously, and the separation efficiency and separation effect are greatly improved.

[0080] It should be noted that the separation structure separates the mixed liquid, wherein the mixed liquid includes an oil phase, a gas phase and an aqueous phase; the mixed liquid includes but is not limited to oil-containing produced water from an oil field or industrial wastewater.

[0081] It should also be noted that the multiple separation tubes 20 work independently and do not interfere with each other, which is convenient for maintenance and installation. The structure of multiple separation tubes 20 connected in parallel is convenient for users to assemble according to actual needs, which greatly improves versatility and practicality. The multiple separation tubes 20 are arranged at equal intervals along the axial direction of the liquid inlet pipe 10. The number of separation tubes 20 can be set as needed, and this application does not impose specific restrictions. For example, Figure 1 As shown, the number of separation tubes 20 is 4-8.

[0082] It should also be noted that if Figure 1 As shown, the axial direction of the liquid inlet pipe 10 is parallel to the Y direction.

[0083] like Figure 2As shown, in some embodiments, the transition pipe 30 includes a horizontal pipe section 310, a vertical pipe section 320 and a connecting pipe section 330; the axial direction of the horizontal pipe section 310 is perpendicular to the axial direction of the liquid inlet pipe 10; one end of the vertical pipe section 320 is connected to the liquid inlet pipe 10 and the other end is connected to the horizontal pipe section 310, and the axial direction of the vertical pipe section 320 is perpendicular to the axial directions of the horizontal pipe section 310 and the liquid inlet pipe 10; one end of the connecting pipe section 330 is connected to the separation pipe 20 and the other end is connected to the horizontal pipe section 310, and the connecting pipe section 330 includes an arc-shaped conveying section; wherein, the inner diameter of the horizontal pipe section 310 is not greater than the inner diameter of the liquid inlet pipe 10.

[0084] The horizontal pipe section 310, vertical pipe section 320, and connecting pipe section 330 provide a structural foundation for connecting the transition pipe 30 with the liquid inlet pipe 10 and the separation pipe 20, transporting the mixed liquid from the liquid inlet pipe 10 to the separation pipe 20. The small inner diameter of the horizontal pipe section 310 adjusts the flow of the mixed liquid, increases the flow rate, and makes the flow of the mixed liquid more uniform and stable, reducing the possibility of slugging flow, thereby effectively preventing the formation of hydrates. Furthermore, the absence of internal components within the transition pipe 30 not only reduces the weight of the separation structure, but also ensures long-term trouble-free operation and reduces the burden of subsequent maintenance.

[0085] It should be noted that if Figure 1 As shown, the axial direction of the horizontal pipe section 310 is parallel to the X direction, and the axial direction of the vertical pipe section 320 is parallel to the Z direction.

[0086] It should also be noted that the horizontal pipe section 310 is located directly below the separation tube 20 to improve space utilization and further reduce the volume of the separation structure; the connecting pipe section 330 is U-shaped; and the connection between the horizontal pipe section 310 and the vertical pipe section 320 is a circular arc transition. Furthermore, the inner diameters of the horizontal pipe section 310, the connecting pipe section 330, and the vertical pipe section 320 are equal, and the inner diameter of the horizontal pipe section 310 is smaller than the inner diameter of the liquid inlet pipe 10.

[0087] It should also be noted that slug flow is a special gas-liquid two-phase vertical pipe flow pattern. Due to the interphase nature of the gas and liquid phases, it can cause dramatic fluctuations in the liquid holdup and pressure in the pipeline, making mixed oil and gas pipelines operating under this flow pattern inevitably subject to pulse stress shocks. Furthermore, slug flow significantly affects both the gas and liquid phases. Both the gas and liquid phases significantly influence the pressure gradient, and at high flow rates, liquid may be entrained in bubbles. By providing a horizontal pipe segment 310, the inner diameter of the horizontal pipe segment 310 is reduced, and the flow rate is increased, effectively suppressing slug flow.

[0088] In some embodiments, the inner diameter of the horizontal pipe section 310 is 0.15 m, and the length of the horizontal pipe section 310 is 20-50 m.

[0089] By limiting the inner diameter of the horizontal pipe section 310, the flow of the mixed liquid is made more stable, ensuring that slugging can be eliminated. This avoids the situation where the inner diameter of the horizontal pipe section 310 is too large, which does not significantly increase the flow rate, resulting in the continued existence of slugging and causing damage to the separation structure. This also avoids the situation where the inner diameter of the horizontal pipe section 310 is too small, resulting in low separation efficiency of the mixed liquid. By limiting the length of the horizontal pipe section 310, a sufficiently long flow path and time are reserved for the mixed liquid to stabilize the flow state and eliminate slugging. This avoids the situation where the length of the horizontal pipe section 310 is too large, resulting in low separation efficiency of the mixed liquid. This also avoids the situation where the length of the horizontal pipe section 310 is too small, resulting in the mixed liquid not having a sufficient flow path and time to eliminate slugging, resulting in the continued existence of slugging and causing damage to the separation structure.

[0090] It should be noted that the length of the horizontal pipe section 310 is equal to the length of the main pipe section 210 .

[0091] like Figure 2 As shown, in some embodiments, the separation tube 20 includes a main pipe section 210, a buffer pipe section 220 and a head 230; the axial direction of the main pipe is parallel to the axial direction of the horizontal pipe section 310; one end of the buffer pipe section 220 is connected to the main pipe section 210 and the other end is connected to the connecting pipe section 330; the head 230 is arranged on the end of the main pipe section 210 away from the buffer pipe section 220; wherein, the inner diameter of the buffer pipe section 220 gradually increases along the axial direction of the buffer pipe section 220, and the inner diameter of the end of the buffer pipe section 220 close to the connecting pipe section 330 is smaller than the inner diameter of the end of the buffer pipe section 220 close to the main pipe section 210.

[0092] By setting up the buffer pipe section 220 with an expanded diameter, the flow rate of the mixed liquid is adjusted to reduce the flow rate of the mixed liquid and prevent the mixed liquid from impacting the main pipe section 210. By setting up the main pipe section 210 to provide a structural basis for the separation of the mixed liquid, the mixed liquid undergoes gas phase separation and oil-water separation in the flow direction. When it flows to the head 230, the gas phase, oil phase, and water phase are separated and respectively gathered at different heights of the separation pipe 20. The structure is simple and the separation effect is good. In addition, no internal components are set in the separation pipe 20, which not only reduces the weight of the separation structure, but also ensures long-term trouble-free operation and reduces the burden of subsequent maintenance.

[0093] It should be noted that the separation tube 20 is a high-strength steel separation tube 20 with a strong bearing capacity and can be used in deep water environments below 1,500 meters.

[0094] It should also be noted that the head 230 is a hemispherical head 230; the inner diameter of the end of the buffer pipe section 220 connected to the connecting pipe section 330 is D1, and the inner diameter of the connecting pipe section 330 is D2, wherein D1=D2.

[0095] In some embodiments, the inner diameter of the main pipe section 210 is 0.46-0.76 m, and the length of the main pipe section 210 is 20-50 meters.

[0096] By limiting the inner diameter and length of the main pipe section 210, a large aspect ratio design of the main pipe section 210 is achieved. The small inner diameter of the main pipe section 210 greatly reduces the demand for wall thickness, and at the same time, the droplets of each phase can more easily reach the interface, thereby further improving the separation performance. The large length of the main body not only expands the phase boundary interface, but also extends the residence time of the mixed liquid, thereby further improving the separation efficiency and separation effect.

[0097] like Figure 3 As shown, in some embodiments, the water phase outlet pipe 40 includes a first water phase outlet pipe column 410 and a second water phase outlet pipe column 420; one end of the first water phase outlet pipe column 410 is connected to the bottom of the separation pipe 20, and the axial direction of the first water phase outlet pipe column 410 is perpendicular to the axial direction of the separation pipe 20 and the liquid inlet pipe 10; one end of the second water phase outlet pipe column 420 is connected to the first water phase outlet pipe column 410, and the axial direction of the second water phase outlet pipe column 420 is perpendicular to the axial direction of the first water phase outlet pipe column 410.

[0098] By setting up a second water phase outlet pipe column 420 and a first water phase outlet pipe column 410 perpendicular to each other, the flow direction of the fluid can be changed, and the density difference can be used to separate the oil phase and gas phase flowing into the water phase outlet pipe 40, thereby preventing the oil phase and gas phase from flowing out of the second water phase outlet pipe column 420 along with the water phase.

[0099] like Figure 3 As shown, exemplarily, in some embodiments, the first water phase outlet pipe string 410 includes a main straight pipe section 4101, a reduced pipe section 4103 and a secondary straight pipe section 4102, and the two ends of the reduced pipe section 4103 are respectively connected to the main straight pipe section 4101 and the secondary straight pipe section 4102, the end of the main straight pipe section 4101 away from the reduced pipe section 4103 is connected to the bottom of the separation tube 20, and the end of the secondary straight pipe section 4102 away from the reduced pipe section 4103 is blocked; the inner diameter of the reduced pipe section 4103 gradually decreases along the axial direction of the reduced pipe section 4103, and the inner diameter of the end of the reduced pipe section 4103 close to the main straight pipe section 4101 is larger than the inner diameter of the end of the reduced pipe section 4103 close to the secondary straight pipe section 4102; wherein, the second water phase outlet pipe string 420 is connected to the secondary straight pipe section 4102.

[0100] It should be noted that the inner diameter of the end of the reduced pipe section 4103 close to the main straight pipe section 4101 is D3, the inner diameter of the end of the reduced pipe section 4103 close to the secondary straight pipe section 4102 is D4, the inner diameter of the main straight pipe section 4101 is also D3, and the inner diameter of the secondary straight pipe section 4102 is also D4.

[0101] It should also be noted that the inner diameter of the second water phase outlet pipe column 420 is smaller than the inner diameter of the secondary straight pipe section 4102.

[0102] By providing a main straight pipe section 4101 with a relatively large inner diameter and a secondary straight pipe section 4102 with a relatively small inner diameter, and connecting them through a reduced pipe section 4103 , the water phase can be effectively caused to gather in the second water phase outlet pipe column 420 .

[0103] like Figure 3 As shown, in some embodiments, the mixed-phase outlet pipe 50 includes a first mixed-phase outlet pipe string 510 and a second mixed-phase outlet pipe string 520; the first mixed-phase outlet pipe string 510 is inserted into the first water-phase outlet pipe string 410, and the axial direction of the first mixed-phase outlet pipe string 510 is parallel to the axial direction of the first water-phase outlet pipe string 410; one end of the second mixed-phase outlet pipe string 520 is connected to the first mixed-phase outlet pipe string 510, and the axial direction of the second mixed-phase outlet pipe string 520 is perpendicular to the axial direction of the first mixed-phase outlet pipe string 510.

[0104] By arranging the first mixed-phase outlet pipe string 150 and the second mixed-phase outlet pipe string 520 perpendicular to each other, the fluid in the mixed-phase outlet pipe 50 can adapt to the flow direction of the horizontal pipeline laid flat on the seabed, thereby playing a diversion role.

[0105] It should be noted that the gas phase separated in the main pipe section 210 gathers at the top of the main pipe section 210, and the oil phase gathers at the upper part of the main pipe section 210. The gas phase and the oil phase flow in through the first mixed-phase outlet column 510, mix, and then flow out from the second mixed-phase outlet column 520.

[0106] It should also be noted that if Figure 3 As shown, the second mixed-phase outlet column 520 is located below the second aqueous-phase outlet column 420 .

[0107] In some embodiments, the separation structure further includes a multiphase pump and a water injection pump; the multiphase pump is connected to the outlet end of the mixed phase outlet pipe 50; and the water injection pump is connected to the outlet end of the water phase outlet pipe 40.

[0108] Multiphase separation is carried out on the seabed through a separation structure. The water phase is injected back into the reservoir by a water injection pump, and the oil phase and gas phase are mixed and pressurized and lifted by a multiphase pump. This eliminates the need to transport large amounts of water from deepwater mature oilfield production, eliminates the bottleneck of existing upper settings, and reduces the water treatment equipment required for the upper platform. It can also supplement reservoir pressure, reduce wellhead back pressure, improve recovery rate, and accelerate oilfield production. At the same time, it can eliminate slug flow generated during transportation and effectively avoid the formation of hydrates.

[0109] It should be noted that the separation structure also includes a liquid level meter and a variable speed drive; a liquid level meter is provided in each separation tube 20, which is used to monitor the liquid level height of the aqueous phase in the separation tube 20; the variable speed drive is electrically connected to the water injection pump, and the variable speed drive controls the operation of the water injection pump according to the liquid level height of the aqueous phase, thereby controlling the flow rate of the aqueous phase.

[0110] It should also be noted that the air pressure in the separation structure can be controlled and regulated by the multiphase pump.

[0111] It should also be noted that the separation structure also includes post-processing equipment connected to the water injection pump. The post-processing equipment is used to perform a second-stage separation and filtration on the aqueous phase to separate suspended particles, oil phase, etc. from the aqueous phase. In addition, the post-processing equipment includes but is not limited to water purification equipment. The specific structure and operating principle of the post-processing equipment are prior art and will not be further described in this application.

[0112] After the first stage of separation in the separation structure, the separated aqueous phase still contains a certain amount of dispersed contaminants, such as suspended particles and oil droplets. Therefore, if the separated aqueous phase is directly injected into the reservoir, the suspended particles and oil droplets will be deposited in the porous medium, resulting in a decrease in injection capacity and formation damage, thereby significantly reducing permeability and causing a decrease in production. Therefore, the performance of the separator is usually characterized by the oil content in water (OiW) or total oil and grease (TOG) in the aqueous phase outlet pipe 40 and the water content (WC) in the mixed phase outlet pipe 50. Among them, the separation indicators of the separation structure provided by the present invention are:

[0113] The maximum TOG is 2000 ppm, and the maximum water content in the oil flow is 15%. Therefore, it can be seen that the separation structure provided by the present invention has a good separation effect.

[0114] In order to ensure the separation effect of the separation structure and realize gravity separation, it is also necessary to maintain the stratified flow pattern within the separation structure. Therefore, the oil apparent flow velocity Vso is less than 10 cm / s, and the water apparent flow velocity Vsw is less than 10 cm / s. For fluids with high gas volume fraction, when the apparent flow velocities of each liquid are between 2-20 cm / s, the flow is in stratified flow.

[0115] In order to ensure the separation effect of the separation structure and realize gravity separation, it is necessary to ensure the phase separation residence time in the separation tube 20, and design the length and inner diameter of the separation tube 20 according to the phase separation residence time and flow rate, etc.; among them, when the oil API is greater than 35° and the relative density is greater than 0.85, the residence time in the separation tube 20 is 3-5 minutes; when the separation temperature is greater than 37°C, the residence time is 5-10 minutes; when the separation temperature is 27-37°C, the residence time is 10-20 minutes; when the separation temperature is 15-27°C, the residence time is 20-30 minutes.

[0116] In addition, the phase separation residence time can also be determined based on the droplet cutoff diameter. The droplet cutoff diameter is based on the cutoff diameter corresponding to the smallest droplet that is completely removed from the continuous phase. According to Stokes' law, in order to ensure a good separation effect, the oil droplet cutoff diameter is 150 microns. Of course, the oil droplet cutoff diameter can also be other values based on the specific design data of different separation structures.

[0117] Example 3

[0118] like Figure 4 As shown, an embodiment of the present invention further provides a separation method, which is applied to the separation structure described in any embodiment of the present invention, comprising:

[0119] S101: injecting a mixed liquid into the transition pipe 30 through the liquid inlet pipe 10, and performing steady flow of the mixed liquid through the transition pipe 30, wherein the mixed liquid includes an oil phase, a gas phase, and a water phase;

[0120] S102: Inputting the mixed liquid after steady flow into the separation tube 20, and causing the mixed liquid to undergo gas-liquid separation and oil-water separation in the separation tube 20, so that the gas phase is located at the top of the separation tube 20, and the oil phase is located between the gas phase and the water phase;

[0121] S103: The gas phase and the oil phase are discharged through the mixed phase outlet pipe 50, and the water phase is discharged through the water phase outlet pipe 40; wherein, the inlet end of the mixed phase outlet pipe 50 is located at the upper part of the separation tube 20, and the inlet end of the water phase outlet pipe 40 is located at the bottom of the separation tube 20.

[0122] In some embodiments, the separation method further comprises:

[0123] monitoring the liquid level of the aqueous phase in the separation tube 20, and if the liquid level is greater than a first liquid level threshold, accelerating the discharge of the aqueous phase in the separation tube 20 by a water injection pump;

[0124] If the liquid level is lower than the second liquid level threshold, the water phase in the separation tube 20 is discharged at a reduced speed by the water injection pump.

[0125] By monitoring the liquid level of the aqueous phase, we can prevent the liquid level of the aqueous phase from being too high or too low, which will affect the separation effect and cause the gas phase, oil phase and aqueous phase to be discharged from the same outlet pipe and unable to be discharged separately.

[0126] It should be noted that the first liquid level threshold is located below the inlet end of the mixed phase outlet pipe 50, and the second liquid level threshold is located above the inlet end of the water phase outlet pipe 40. The first liquid level threshold is greater than the second liquid level threshold. The specific value is set according to actual needs and is not limited in this application.

[0127] It should also be noted that the liquid level of the aqueous phase is monitored by a liquid level meter, and the specific structure and working principle of the liquid level meter are both existing technologies and are not limited in this application.

[0128] In some embodiments, the separation method further comprises:

[0129] monitoring the air pressure in the separation tube 20, and if the air pressure is greater than a first pressure threshold, accelerating the discharge of the gas phase and / or oil phase in the separation tube 20 by a multiphase pump;

[0130] If the gas pressure is less than the second pressure threshold, the water phase in the separation tube 20 is discharged at a reduced speed by the multiphase pump.

[0131] By monitoring the air pressure in the separation tube 20, the air pressure is prevented from being too high or too low, thereby ensuring the normal progress of the separation work and protecting the separation structure.

[0132] It should be noted that the specific values of the first pressure threshold and the second pressure threshold are set according to actual needs, and this application does not impose any restrictions, and the first pressure threshold is greater than the second pressure threshold.

[0133] It should also be noted that the air pressure value in the separation tube 20 can be monitored by a barometer. The specific structure and working principle of the barometer are all existing technologies and are not limited in this application.

[0134] The following is a detailed description of a more specific embodiment of the present application:

[0135] Example 4

[0136] When applied to the X1 oilfield at a water depth of 1,500 meters, the design is to produce 50,000 to 92,000 barrels of liquid per day from early to end of life, with a water content of 30% to 85% and a GVF of 75% to 10% (for light oil). The separation pressure is 60 bar and the separation temperature is 50°C. The oil viscosity is 4 cP and the density is 790 kg / m3. 3 .

[0137] To ensure the separation effect of the separation structure and realize gravity separation, the separation structure must maintain a stratified flow pattern, and the phase separation residence time must be no less than 3 minutes, and the slug volume must be 10m 3The separation structure includes eight separation tubes 20, the outer diameter of the separation tube 20 is 610 mm, the inner diameter is 553 mm, and the length is 50 m. The inner diameter of the liquid inlet pipe 10 is 157 mm, and the inner diameters of the vertical pipe section 320 and the horizontal pipe section 310 are both 157 mm.

[0138] Example 5

[0139] When applied to the X2 field in a water depth of 1,400 meters, it is designed to produce 49,000 to 92,000 barrels of liquid per day from early to end of life, with water contents ranging from 34% to 83% and a GOR of 110-200 Sm 3 The shut-in wellhead pressure is 250 bar, the fluid is typical light oil (32°API), the separation pressure is 60 bar, and the separation temperature is 50°C.

[0140] The separation structure includes eight separation tubes 20, each with an outer diameter of 610 mm, an inner diameter of 553 mm, and a length of 50 m. The horizontal pipe section 310 has an inner diameter of 153 mm and a length of 50 m. The residence time is 5 minutes for oil and 6 minutes for water. The separation diameter is 80 μm for water in oil, which is the cutoff diameter. The maximum water particle size allowed in the oil phase is 80 μm.

[0141] Example 5

[0142] According to the ratio of 2.8:1, a laboratory model of the separation structure was established as an example, wherein the separation structure includes four separation pipes 20, the main pipe section 210 has an inner diameter of 200 mm and a length of 18 meters, and the horizontal pipe section 310 has an inner diameter of 56 mm.

[0143] Model water and model oil are passed through two 10m 3 The special storage tank is injected into the separation structure through two centrifugal pumps as the oil phase and water phase in the mixed liquid. The flow rate of the water phase and the oil phase can reach 40m 3 / h. The injection flow rate was measured using a Coriolis mass flowmeter.

[0144] A high-resolution camera is installed on each separation tube 20 to measure the oil droplet size and oil concentration online. In addition, the separation tube 20 can be made of a transparent material to observe the separation situation.

[0145] Experimental operating conditions:

[0146] (1) Inlet pressure: 2.7-11 bara;

[0147] (2) Inlet temperature: 22.8-30.2°C;

[0148] (3) Liquid flow rate (water + oil): 20, 40, 50 and 60m 3 / h;

[0149] (4) Moisture content: 15%, 35%, 50%, 65% and 85%;

[0150] (5) Gas volume fraction: 0, 20%, 35% and 54%;

[0151] (6) Water / oil mixture viscosity: 1.2-16.3 cP;

[0152] (7) Air flow rate: 50m at maximum pressure 3 / h;

[0153] (8) Inlet shear rate: ΔP 0.03-2.63 bara / maximum velocity: 0.7-3.88 m / s;

[0154] (9) Water level setting points: 90, 100 and 110 mm;

[0155] (10) Water residence time: 2-20 min;

[0156] (11) Water apparent velocity: 1-10 cm / s;

[0157] The experimental fluids were tested under ambient pressure and temperature conditions using air as the gas phase, model water as the water phase, and model oil as the oil phase, where the model water was tap water. No chemicals were used, and an oil-soluble (red) dye was used to visualize the oil / water interface.

[0158] In addition, the model oils used in the experiment were selected based on viscosity criteria. The viscosity of model oil 2 is approximately 5 times that of model oil 1. The main characteristics of the model oils are as follows:

[0159] Model oil 1:

[0160] (1) CA (aromatic carbon) 5%, CN (cycloalkane carbon) 58%, CP (paraffin carbon) 37%

[0161] (2) Density @ 15°C: 863 kg / m 3 ;

[0162] (3) Viscosity @ 40°C: 2.93 cSt;

[0163] (4) Viscosity @ 22.7°C: 4.8 cP

[0164] (5) Maximum viscosity @ 40% water content: 9 cP @ 22.5 °C.

[0165] Model oil 2:

[0166] (1)CA 1%, CN 45%, CP 54%

[0167] (2) Density @ 15°C: 872 kg / m 3 ;

[0168] (3) Viscosity @ 40°C: 14 cSt;

[0169] (4) Viscosity @ 28.4°C: 22.8 cP;

[0170] (5) Maximum viscosity @ 10% water content: 23.4 cP @ 28.4 °C.

[0171] Example 5 Multiple experiments were conducted by changing the experimental operating conditions. For example, multiple experiments were conducted at different water contents, i.e., different water phase volume ratios, while keeping other parameters unchanged; multiple experiments were conducted at different gas volume fractions, i.e., different gas phase volume ratios, while keeping other parameters unchanged; and multiple experiments were conducted at different residence times while keeping other parameters unchanged. The influence of each factor on the separation performance of the separation structure was obtained. The experimental results are described in detail below:

[0172] (1) Influence of gas

[0173] Under the above-mentioned flow conditions of flow rate, water content, gas volume fraction, etc., the presence of gas improves the water separation efficiency and reduces the final oil content in water (i.e., the oil content in the water phase separated by the separation structure) because the effective floating of bubbles causes the oil droplet size to increase.

[0174] However, when the oil content in water is high, the presence of gas will deteriorate the water quality, and as the oil content in water increases, the quality of the separated water becomes worse. This result is caused by high fluid shear and high level fluctuations (wave or slug-like).

[0175] (2) Residence time

[0176] like Figure 5 As shown, it is shown that the oil content in water decreases with the increase of the residence time of the water phase, indicating that the separation structure requires sufficient time to obtain the equilibrium condition between oil and water.

[0177] (3) Water content in oil

[0178] Unlike the oil content in water, the water content in oil (i.e., the water content in the oil phase separated by the separation structure) is not only related to the oil flow rate and water residence time in the separation structure, but also to the geometric shape of the separation structure; in addition, the mixed phase outlet pipe 50 will also cause water loss.

[0179] like Figure 6 As shown, the increase of water content in the separation tube (water content greater than 50%) will lead to an increase in the water flow in the mixed phase outlet pipe 50, resulting in an increase in the water content in the oil;

[0180] like Figure 7 As shown, the reduction of oil content in the separation tube (oil content is less than 30%) will lead to a higher water content in the oil;

[0181] like Figure 8 As shown, the oil flow in the separation pipe is low (the oil flow is less than 10m 3 / h), which will cause the water content in the oil to increase.

[0182] While the present invention has been described with reference to preferred embodiments, various modifications may be made and equivalent components may be substituted without departing from the scope of the present invention. In particular, the various technical features described in the various embodiments may be combined in any manner, provided no structural conflicts exist. The present invention is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A separation structure, characterized in that: include: Liquid inlet pipe; A plurality of separation tubes are located above the liquid inlet tube, the plurality of separation tubes are spaced apart along the axial direction of the liquid inlet tube, and the plane where the plurality of separation tubes are located is parallel to the liquid inlet tube; a plurality of transition tubes, the plurality of transition tubes being arranged at intervals along the axial direction of the liquid inlet tube and corresponding one-to-one to the plurality of separation tubes, the transition tubes being located between the liquid inlet tube and the separation tubes, one end of the transition tube being connected to the corresponding separation tube, and the other end being connected to the liquid inlet tube, and the plane on which the plurality of separation tubes are located being parallel to the liquid inlet tube; A plurality of water phase outlet pipes, corresponding one to one with the plurality of separation pipes, the water phase outlet pipes being located at one end of the corresponding separation pipe close to the liquid inlet pipe, and the inlet ends of the water phase outlet pipes being connected to the bottoms of the corresponding liquid inlet pipes; as well as A plurality of mixed-phase outlet pipes respectively correspond to the plurality of water-phase outlet pipes. The mixed-phase outlet pipes are arranged in the corresponding water-phase outlet pipes. The inlet ends of the mixed-phase outlet pipes are connected to the separation pipes and are located at the upper part of the separation pipes.

2. The separation structure according to claim 1, characterized in that The transition duct comprises: a horizontal pipe section, wherein the axial direction of the horizontal pipe section is perpendicular to the axial direction of the liquid inlet pipe; a vertical pipe section, one end of which is connected to the liquid inlet pipe and the other end of which is connected to the horizontal pipe section, wherein the axial direction of the vertical pipe section is perpendicular to the axial directions of the horizontal pipe section and the liquid inlet pipe section; and a connecting pipe section, one end of which is connected to the separation pipe and the other end of which is connected to the horizontal pipe section, wherein the connecting pipe section includes an arc-shaped conveying section; Wherein, the inner diameter of the horizontal pipe section is not greater than the inner diameter of the liquid inlet pipe.

3. The separation structure according to claim 2, characterized in that The inner diameter of the horizontal pipe section is 0.15m, and the length of the horizontal pipe section is 20-50m.

4. The separation structure according to claim 2, characterized in that The separation tube comprises: A main pipe section, wherein the axial direction of the main pipe is parallel to the axial direction of the horizontal pipe section; a buffer pipe section, one end of which is connected to the main pipe section and the other end of which is connected to the connecting pipe section; and A sealing head is provided on one end of the main pipe section away from the buffer pipe section; The inner diameter of the buffer tube segment gradually increases along the axial direction of the buffer tube segment, and the inner diameter of one end of the buffer tube segment close to the connecting tube segment is smaller than the inner diameter of one end of the buffer tube segment close to the main tube segment.

5. The separation structure according to claim 4, characterized in that The inner diameter of the main pipe section is 0.46-0.76m, and the length of the main pipe section is 20-50m.

6. The separation structure according to any one of claims 1 to 5, characterized in that: The water phase outlet pipe comprises: a first aqueous phase outlet pipe column, one end of which is connected to the bottom of the separation pipe, wherein the axial direction of the first aqueous phase outlet pipe column is perpendicular to the axial directions of the separation pipe and the liquid inlet pipe; and One end of the second water phase outlet pipe string is connected to the first water phase outlet pipe string, and the axial direction of the second water phase outlet pipe string is perpendicular to the axial direction of the first water phase outlet pipe string.

7. The separation structure according to claim 6, characterized in that The mixed phase outlet pipe comprises: a first mixed-phase outlet pipe string, which passes through the first aqueous-phase outlet pipe string, wherein the axial direction of the first mixed-phase outlet pipe string is parallel to the axial direction of the first aqueous-phase outlet pipe string; and One end of the second mixed-phase outlet pipe string is connected to the first mixed-phase outlet pipe string, and the axial direction of the second mixed-phase outlet pipe string is perpendicular to the axial direction of the first mixed-phase outlet pipe string.

8. The separation structure according to any one of claims 1 to 5, characterized in that: The separation structure further comprises: a multiphase pump connected to the outlet end of the mixed-phase outlet pipe; and A water injection pump is connected to the outlet end of the water phase outlet pipe.

9. A separation method, applied to the separation structure according to any one of claims 1 to 8, characterized in that: include: Injecting a mixed liquid into the transition pipe through the liquid inlet pipe, and performing steady flow of the mixed liquid through the transition pipe, wherein the mixed liquid includes an oil phase, a gas phase, and a water phase; The mixed liquid after steady flow is input into the separation tube, and the mixed liquid undergoes gas-liquid separation and oil-water separation in the separation tube, so that the gas phase is located at the top of the separation tube and the oil phase is located between the gas phase and the water phase; The gas phase and the oil phase are discharged through the mixed phase outlet pipe, and the water phase is discharged through the water phase outlet pipe; wherein the inlet end of the mixed phase outlet pipe is located at the upper part of the separation tube, and the inlet end of the water phase outlet pipe is located at the bottom of the separation tube.

10. The separation method according to claim 9, characterized in that Also includes: monitoring the liquid level of the aqueous phase in the separation tube, and accelerating the discharge of the aqueous phase in the separation tube by a water injection pump if the liquid level is greater than a first liquid level threshold; If the liquid level is lower than the second liquid level threshold, the water phase in the separation tube is discharged at a reduced speed by the water injection pump.

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