Underground multi-stage series-parallel multiphase cyclone separation device for offshore oilfield high-yield liquid oil well

Abstract

This invention relates to a multi-stage series-parallel multiphase cyclone separator for high-yield oil wells in offshore oilfields. It comprises: an oil-water separation and production structure, and a downhole drive and reinjection structure. The oil-water separation and production structure includes an upper centrifugal pump unit and a multi-stage oil-water separation device. The downhole drive and reinjection structure includes an oil-driving motor assembly and a lower centrifugal pump unit. The oil-water separation and production structure, through the multi-stage series-parallel cyclone separator, processes and separates oil, water, and sand mixtures at high volumes. Simultaneously, multiple parallel flow channels gather the oil phase separated by all the cyclones and discharge it into the upper centrifugal pump unit, where it is pumped out to the surface. The separated sand phase is stored in a settling chamber, and the water phase is reinjected underground. This invention is suitable for high-volume processing conditions in offshore oilfields, enabling multi-stage separation of the three phases (oil, water, and sand).

Description

Technical Field

[0001] This invention relates to a device capable of efficiently processing and separating large-volume oil-water mixtures on offshore platforms and achieving efficient separation of three-phase media (oil, water, and sand) in confined downhole spaces under high-volume processing conditions. Specifically, it relates to a multi-stage series-parallel multiphase cyclone separator for high-yield oil wells in offshore oil fields. Background Technology

[0002] With the increased intensity of oilfield exploitation, high water cut is a common problem in oilfields. As offshore oilfields are further developed, especially as they enter the mid-to-late stages of production, increasing processing capacity and large-volume oil extraction has become a major measure for stabilizing and increasing production. This results in a large amount of production water being lifted to the surface, causing bottlenecks in the water treatment capacity of offshore platforms and the fluid transport capacity of subsea pipelines, increasing the pressure on platform wastewater treatment and environmental protection. Simultaneously, the mixed fluids in wells generally contain small amounts of sand phase, which, over time, causes wear and tear on various equipment in the oil production system, reducing equipment lifespan.

[0003] To address the increasing volume of wastewater from oil wells, engineers have proposed several solutions. Patent document 1 (CN202011619048.2) utilizes two electric submersible pumps to lift the oil and water separated by a hydrocyclone in the downhole tubing. Although separation is completed downhole before lifting, this solution requires two electric submersible pumps with motors for each oil-water separator, resulting in a large space requirement. Furthermore, the separation efficiency of a single hydrocyclone is limited, limiting its processing capacity and failing to meet the demands of large-volume water treatment and transportation. Patent document 2 (CN202010206669.1) employs a lifting and reinjection system to raise the separated liquid to the surface or reinject it underground, but this method is costly and not conducive to energy conservation, environmental protection, or widespread application. Additionally, the hydrocyclone used in this invention is a conventional hydrocyclone with low separation efficiency. Secondly, directly exposing the motor to the liquid phase increases the risk of equipment corrosion, while ignoring the damage to equipment life caused by the accumulation of sand phase in the system during long-term operation. Summary of the Invention

[0004] The purpose of this invention is to provide a downhole multi-stage series-parallel multiphase cyclone separator for high-yield oil wells in offshore oil fields. This downhole multi-stage series-parallel multiphase cyclone separator is used to solve the problems of low crude oil separation efficiency and small processing capacity in existing offshore oil fields.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: This multi-stage series-parallel multiphase cyclone separator for high-yield offshore oil wells includes an oil-water separation and production structure and a downhole drive and reinjection structure. The oil-water separation and production structure is set above the downhole drive and reinjection structure. The oil-water separation and production structure includes an upper centrifugal pump group and a multi-stage oil-water separation device. The downhole drive and reinjection structure includes a drive motor assembly and a lower centrifugal pump group. While the drive motor assembly drives the lower centrifugal pump group to rotate, it also drives the upper centrifugal pump group to rotate through a transmission shaft passing through the multi-stage oil-water separation device. The multi-stage oil-water separation device uses multiple hydrocyclones connected in parallel and multiple stages of separation connected in series. Each stage of the oil-water separation device has a staged feed pipe, a staged combined sleeve, and a staged hydrocyclone group. The unit consists of parallel hydrocyclones. Each stage feed pipe is fitted onto the drive shaft. The annular space between each stage feed pipe and the drive shaft serves as the liquid inlet channel. Adjacent stage feed pipes are connected by a guide channel. Each stage feed pipe has multiple outlets arranged in a ring. The liquid inlet channel communicates with each hydrocyclone through the outlets of each stage feed pipe and multiple tangential inlets corresponding to the outer shell of each hydrocyclone. The hydrocyclone units connected in series at each stage are connected in parallel with respect to the liquid inlet channel. The stage combination sleeves are connected in sequence to form an assembled shell. An overflow channel and an underflow channel are provided inside the assembled shell. The overflow holes of each hydrocyclone communicate with the overflow channel, and the underflow ports of each hydrocyclone communicate with the underflow channel. The upper end of the overflow channel is connected to the upper centrifugal pump unit, and the lower end of the underflow channel is connected to the lower centrifugal pump unit. The guide bearing is provided with a drive shaft hole, and the bearing cavity is centrally located around the drive shaft hole. The drive shaft passes through the drive shaft hole, and the bearing is fitted inside the bearing cavity on the outside of the drive shaft. The upper and lower cavities of the guide channel are connected through a vertical cavity. The upper cavity, vertical cavity, and lower cavity are integrally connected to form a horizontal U-shaped groove. The bearing cavity is located in the U-shaped groove. The guide channel is connected to the liquid inlet channel through the upper retaining groove at the top of the upper cavity and the lower retaining groove at the bottom of the lower cavity. The guide bearing is also provided with a fan-shaped channel, which is located on the groove opening side of the U-shaped groove formed by the guide channel.

[0006] In the above scheme, the grading hydrocyclone assembly is installed inside the grading combination sleeve. The grading combination sleeve consists of a separating upper outer shell threadedly connected to a separating lower outer shell. The grading hydrocyclone assembly includes four hydrocyclones connected in parallel, a fixed combination plate, a guide bearing, a sand guide cover, and a sand settling chamber. The fixed combination plate consists of an upper fixed plate and a lower fixed plate, which are threadedly connected to the separating upper outer shell. The upper fixed plate has a drive shaft hole and four overflow pipe fixing holes evenly arranged outside the drive shaft hole. The lower fixed plate has a drive shaft hole and four hydrocyclone fixing holes evenly arranged outside the drive shaft hole. Each hydrocyclone fixing hole has a groove on its wall. A spherical fixing is provided on the outer wall of each hydrocyclone. One hydrocyclone is installed at each hydrocyclone fixing hole. The hydrocyclone is fixed to the lower fixing plate by the spherical fixing and the groove. The overflow pipe of the hydrocyclone is fixed through the overflow pipe fixing hole. There is an annular space between the upper fixing plate and the upper shell of the separator. The annular space is connected to the overflow channel inside the upper shell of the separator. The flow guide bearing is set below the hydrocyclone. Below the flow guide bearing is the sand guide cover and there is an annular space between the two. The annular space is connected to the bottom flow channel inside the lower shell of the separator. The lower end of the sand guide cover is threaded to the sand settling chamber. The annular space between the flow guide bearing and the sand guide cover is connected to the sand settling chamber through the sand discharge hole of the sand guide cover.

[0007] The hydrocyclone in the above scheme includes a hydrocyclone shell, a flow-guiding oil filter cone, a variable pitch spiral flow channel, and an inverted cone. The inverted cone is centrally located below the variable pitch spiral flow channel. The upper end of the variable pitch spiral flow channel is threadedly connected to the flow-guiding oil filter cone. The variable pitch spiral flow channel and the flow-guiding oil filter cone have interconnected overflow holes. The upper end of the overflow hole is an overflow pipe. The lower end of the flow-guiding oil filter cone is uniformly provided with filter holes. The pitch of the upper part of the variable pitch spiral flow channel is greater than the pitch of the lower part.

[0008] The above scheme has three stages of hydrocyclone separators: a primary hydrocyclone separator, a secondary hydrocyclone separator, and a tertiary hydrocyclone separator. The upper end of the primary hydrocyclone separator is threaded to an inlet bridge channel. Multiple liquid inlets are provided on the outer wall of the inlet bridge channel. A drive shaft passes through the drive shaft hole of the inlet bridge channel and connects to a centrifugal pump. The upper end of the primary feed pipe is inserted into a slot in the inlet bridge channel. An outlet is provided at the slot. The inlet and outlet communicate with each other, and the outlet communicates with the primary feed pipe. A bent overflow channel is also provided inside the inlet bridge channel, and the upper end of the overflow channel is connected to the centrifugal pump.

[0009] In the above scheme, the lower end of the separation shell of the three-stage cyclone separator group is connected to the upper end of the confluence connection by a thread, and the upper end of the lower bridge channel is placed at the lower end of the confluence connection and connected to the drive motor assembly.

[0010] In the above scheme, Tesla valves are installed at the overflow channels corresponding to the first-stage cyclone separator group, the second-stage cyclone separator group, and the third-stage cyclone separator group, respectively; Tesla valves are also installed at the underflow channels corresponding to the first-stage cyclone separator group, the second-stage cyclone separator group, and the third-stage cyclone separator group, respectively.

[0011] The above scheme includes two overflow channels and four underflow channels.

[0012] In the above scheme, when each stage of the hydrocyclone group is working, the oil-water mixture containing a small amount of sand phase enters the primary feed pipe, secondary feed pipe, and tertiary feed pipe through the inlet, respectively. It then enters the interior of each hydrocyclone through the tangential inlet on the hydrocyclone shell. The swirling field formed by the tangential inlet causes some of the lighter oil phase in the oil-water mixture to converge towards the center. As the guide oil filter cone moves downwards, some of the oil phase enters the interior of the guide oil filter cone through the filter holes. The remaining oil-water mixture is pressurized and the swirling field is enhanced by the variable pitch spiral flow channel, causing the remaining oil phase to be separated a second time. It enters the variable pitch spiral flow channel through the overflow hole and flows upwards together with the oil phase entering the guide oil filter cone, exiting from the overflow outlet into the annulus above the fixed assembly plate. The oil phase separated by each stage of the hydrocyclone group converges at the overflow outlet. In the overflow channel, the oil phase is lifted upwards stage by stage in the overflow channel, drawn into the upper centrifugal pump unit, discharged through the upper oil pipe coupling, and finally produced to the surface. After separation, the water phase and a small amount of sand phase are discharged from the hydrocyclone through the bottom outlet on the inverted cone, and then enter the annular cavity between the sand guide cover and the flow channel through the fan-shaped channel on the flow channel. The sand phase and part of the water phase fall into the primary sand settling cavity, the secondary sand settling cavity and the tertiary sand settling cavity through the sand discharge hole, respectively, and settle up. The water phase converges to the bottom flow channel. All the water phase merges downwards along the bottom flow channel stage by stage, and enters the interior of the confluence connection through the bottom flow channel on the confluence connection. Finally, all the water phase enters the annular cavity inside the lower bridge-type channel from the confluence channel, and then enters the downhole drive and reinjection structure from multiple drainage channels distributed circumferentially at its lower end. Beneficial effects

[0013] 1. This invention proposes a three-phase separation process device for oil-water-sand in high-volume oilfield operations. By connecting multiple hydrocyclones in series, each separation stage operates independently. The number of separation stages can be autonomously adjusted according to the required throughput, significantly increasing the device's processing capacity and applicability. Furthermore, this process device is suitable for a single motor to simultaneously drive two pump sets via a drive shaft, reducing the space occupied by the device and improving its versatility.

[0014] 2. The innovative oil-water separator structure proposed in this invention, applied to the separation of oil, water, and sand phases, can achieve secondary enhanced oil-water separation through a variable pitch spiral flow channel, thereby improving the oil-water separation efficiency. At the same time, the small amount of sand phase in the mixture can be separated, deposited, and stored separately, preventing the sand phase from accumulating in various process equipment over a long period of time and causing wear, which is beneficial to improving the equipment life.

[0015] 3. The separation structure proposed in this invention features two overflow channels for the separated oil phase and four underflow channels for the separated water phase. The overflow and underflow channels are arranged parallel to each other and do not interfere with each other. Ultimately, all the overflow channels converge and are pumped to the surface, while the underflow channels converge and are reinjected underground. This addresses transportation issues under high-volume processing conditions and ensures stable transportation during operation.

[0016] 4. This invention achieves highly efficient separation of oil, water, and sand three-phase media. The multi-stage separation structure is connected in series and operates in parallel, with multiple flow paths that do not interfere with each other. It also features a layout where a single motor drives two pumps via a transmission shaft. This allows the process unit to flexibly handle high-volume oilfield operations and confined downhole environments, further expanding its applicability and improving the economics of oilfield extraction.

[0017] 5. The present invention relates to a structural design for a system in which one motor drives two pumps. Under the environmental conditions and requirements of confined downhole space and high-volume oilfield operations, the innovative hydrocyclone design helps to achieve efficient separation of oil, water, and sand three-phase media in each stage of the separation structure. At the same time, the multiple overflow channels and underflow channels are arranged in parallel and do not interfere with each other, ensuring the stability of transportation under high-volume conditions. This invention enables the efficient separation of oil, water, and sand three-phase media in confined downhole space and high-volume oilfield operations.

[0018] 6. The oil-water separation and production structure of this invention utilizes a multi-stage series-connected cyclone separator to process and separate oil-water-sand mixtures in large volumes. Simultaneously, multiple parallel flow channels gather the oil phase separated by all the cyclones together and discharge it into the upper centrifugal pump group. Together, they are pumped into the upper tubing coupling and produced to the surface. The separated sand phase is stored in the sedimentation chamber, while the water phase is finally gathered together and discharged into the downhole drive and reinjection structure. The downhole drive and reinjection structure pumps the separated and gathered water phase together into the lower tubing coupling through the lower centrifugal pump group and reinjects it underground. Furthermore, through the drive shaft running through the center of the entire device, one motor can drive two pump groups to work. This is suitable for large-scale processing conditions in offshore oilfields, enabling the processing of large volumes of oil-water-sand mixtures in a limited space and completing multi-stage separation of the three phases of oil, water, and sand. Attached Figure Description

[0019] Figure 1 (a) is an overall appearance view of the present invention; Figure 1 (b) is a cross-sectional view of the present invention.

[0020] Figure 2 (a) is an external view of the separation and extraction structure; Figure 2 (b) is a cross-sectional view of the separated and extracted structure.

[0021] Figure 3 An exploded view is created for the oil-water separation and production structure.

[0022] Figure 4 (a) is an external view of the primary oil-water separator; Figure 4 (b) is a cross-sectional view of the primary oil-water separator.

[0023] Figure 5 (a) is a structural view of the combined plate and hydrocyclone; Figure 5 (b) is a cross-sectional view of the combined plate and hydrocyclone structure.

[0024] Figure 6 (a) is an external view of the two-stage oil-water separator; Figure 6 (b) is a cross-sectional view of the two-stage oil-water separator.

[0025] Figure 7 (a) is an external view of the three-stage oil-water separator; Figure 7 (b) is a cross-sectional view of the three-stage oil-water separation unit.

[0026] Figure 8 This is an exploded view of the assembled shell.

[0027] Figure 9 (a) is an external view of the drive and reinjection structure; Figure 9 (b) is a cross-sectional view of the drive and back-injection structure.

[0028] In the diagram: 101-Inlet bridge channel, 1011-Liquid inlet, 1012-Liquid outlet, 1013-Overflow channel, 102-Drive shaft, 103-First-stage feed pipe, 1031-First-stage annular discharge port, 104-Fixed assembly plate, 1041-Hydrocyclone fixing hole, 1042-Groove, 1043-Overflow pipe fixing hole, 105-First-stage separator upper shell, 1051-Upper-stage overflow channel, 106-Hydrocyclone shell, 1061-Tangential inlet, 1062-Overflow hole. 1063-Spherical fixed part, 107-Drainage filter cone, 1071-Filter hole, 1072-Overflow outlet, 108-Variable pitch spiral flow channel, 1081-Overflow inlet, 109-Inverted cone, 1091-Underflow port, 110-Lower casing of primary separator, 1101-Next stage overflow channel, 1102-Next stage underflow channel, 111-Guide bearing, 1111-Guide channel, 1114-Fan-shaped channel, 112-Sand guide cover, 1121-Sand discharge hole, 113-Secondary separator Upper outer shell, 1131 - Primary settling chamber, 1132 - Upper secondary overflow channel, 1133 - Upper secondary underflow channel, 114 - Secondary separator lower outer shell, 1142 - Lower secondary overflow channel, 1143 - Lower secondary underflow channel, 115 - Secondary feed pipe, 1151 - Secondary annular discharge port, 116 - Tertiary feed pipe, 1161 - Tertiary annular discharge port, 117 - Tesla valve, 118 - Tertiary separator upper outer shell, 1181 - Secondary settling chamber, 1182 - Upper tertiary overflow channel 1183 - Upper tertiary underflow channel, 119 - Lower outer shell of tertiary separation, 1191 - Lower tertiary underflow channel, 120 - Merging connection, 1201 - Underflow channel, 1202 - Merging channel, 1203 - Tertiary sedimentation chamber, 121 - Lower bridge-type channel, 1211 - Internal annular cavity, 1212 - Drainage channel, 122 - Upper centrifugal pump unit, 123 - Upper oil pipe coupling, 201 - Lower outer shell, 202 - Drive motor assembly, 203 - Lower centrifugal pump unit, 204 - Lower oil pipe coupling. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings: See Figures 1-9This multi-stage series-parallel multiphase hydrocyclone separator for high-yield offshore oil wells includes an oil-water separation and production structure, and a downhole drive and reinjection structure. The oil-water separation and production structure is located above the downhole drive and reinjection structure. The oil-water separation and production structure includes an upper centrifugal pump unit and a multi-stage oil-water separator. The downhole drive and reinjection structure includes a drive motor assembly and a lower centrifugal pump unit. The drive motor assembly drives the lower centrifugal pump unit to rotate while simultaneously driving the upper centrifugal pump unit to rotate via a transmission shaft passing through the multi-stage oil-water separator. The multi-stage oil-water separator uses multiple hydrocyclones connected in parallel and multiple stages of separation connected in series. Each stage of the oil-water separator has a staged feed pipe, a staged combined sleeve, and a staged hydrocyclone assembly. The staged hydrocyclone assembly consists of parallel hydrocyclones... The device consists of several stages, each with its own feed pipe fitted around the drive shaft. The annular space between the feed pipe and the drive shaft serves as the liquid inlet channel. Adjacent feed pipes are connected via a guide channel. Each feed pipe has multiple outlets arranged in a ring. The liquid inlet channel communicates with each hydrocyclone through the outlets of the feed pipes and multiple tangential inlets corresponding to the outer shell of each hydrocyclone. The hydrocyclone assemblies connected in series at each stage are connected in parallel with respect to the liquid inlet channel. The stage combination sleeves are connected in sequence to form an assembled shell. An overflow channel and an underflow channel are provided inside the assembled shell. The overflow port of each hydrocyclone communicates with the overflow channel, and the underflow port of each hydrocyclone communicates with the underflow channel. The upper end of the overflow channel is connected to an upper centrifugal pump assembly, and the lower end of the underflow channel is connected to a lower centrifugal pump assembly.

[0030] The oil-water separation and extraction structure includes an inlet bridge channel 101, a drive shaft 102, a primary feed pipe 103, a fixed assembly plate 104, a primary separation upper shell 105, a hydrocyclone shell 106, a flow-guiding filter cone 107, a variable pitch spiral flow channel 108, an inverted cone 109, a primary separation lower shell 110, a flow guide bearing 111, a sand guide cover 112, a secondary separation upper shell 113, a secondary separation lower shell 114, a secondary feed pipe 115, a tertiary feed pipe 116, a Tesla valve 117, and a third-stage valve. The system comprises a primary separator upper housing 118, a tertiary separator lower housing 119, a manifold connection 120, a lower bridge-type channel 121, an upper centrifugal pump unit 122, and an upper oil pipe coupling 123. The upper end of the inlet bridge-type channel 101 is threadedly connected to the lower end of the upper centrifugal pump unit 122, and the upper end of the upper centrifugal pump unit 122 is threadedly connected to the upper oil pipe coupling. The lower end of the inlet bridge-type channel 101 is threadedly connected to the upper end of the primary separator upper housing 105. The internal threads of the primary separator upper housing 105 are connected to a fixed assembly plate 104. The upper end of the variable pitch spiral flow channel 108 is threadedly connected to the lower end of the guide oil filter cone 107 and then placed inside the hydrocyclone housing 106. The upper end of the guide oil filter cone 107 passes through the overflow hole 1062 at the center of the upper end of the hydrocyclone housing 106 and is inserted into the overflow pipe fixing hole 1043 on the fixed assembly plate 104. The lower end of the hydrocyclone housing 106 is threaded to the inverted cone 109, while the spherical fixing 1063 on its surface enters vertically from the lower end of the groove 1042 opened in the fixing assembly plate 104, and then rotates and snaps into place along the groove. The primary feed pipe 103 passes through the fixing assembly plate 104, with its upper end connected to the lower center groove of the inlet bridge channel 101, and its lower end connected to the upper groove of the guide bearing 111 inside the primary separation lower housing 110.The lower end of the primary separation upper outer shell 105 is threadedly connected to the upper end of the primary separation lower outer shell 110; the lower end of the primary separation lower outer shell 110 is threadedly connected to the secondary separation upper outer shell 113, and the guide bearing 111 is placed inside it from above. The position of the guide bearing 111 is restricted by the annular boss structure on the inner wall of the primary separation lower outer shell 110; the upper end of the secondary separation upper outer shell 113 has a primary sand settling chamber 1131 threadedly connected to the sand guide cover 112, and the lower end is threadedly connected to the secondary separation lower outer shell 114. Inside, like the primary separation upper outer shell 105, a fixed assembly plate 104 and various hydrocyclone components are placed. The secondary feed pipe 115 also passes through the fixed assembly plate 104, with its upper end connected to the lower slot of the guide bearing 111 inside the primary separation lower outer shell 110, and its lower end connected to the upper slot of the guide bearing 111 inside the secondary separation lower outer shell 114; the secondary separation lower outer shell 115... The guide bearing 111 is placed inside the lower housing 110 of the first-stage separation in the same manner. The lower end of the lower housing 114 of the second-stage separation is threaded to the upper end of the upper housing 118 of the third-stage separation via threads. At the same time, its lower end can also be connected to the upper housing 113 of the second-stage separation. The lower end of the upper housing 113 of the second-stage separation is then threaded to the lower housing 114 of the second-stage separation. The same parts are arranged inside, so that multi-stage connections can be formed as needed. The upper housing 118 of the third-stage separation is arranged with the fixed combination plate 104 and the various components of the hydrocyclone in the same manner. The upper end of the third-stage feed pipe 116 is connected to the lower slot of the guide bearing 111 inside the lower housing 114 of the second-stage separation. The lower end of the upper housing 118 of the third-stage separation is threaded to the upper end of the lower housing 119 of the third-stage separation. The lower end of the lower housing 119 of the third-stage separation is threaded to the upper end of the confluence connection 120.

[0031] The inlet bridge channel 101 has six circumferentially distributed liquid inlets 1011, a central liquid outlet 1012, and two overflow channels 1013 inside; the primary feed pipe 103 is a hollow structure with a primary annular discharge port 1031 on its surface; the fixed assembly plate 104 consists of two threaded fixing plates, the lower fixing plate has four hydrocyclone fixing holes 1041 and grooves 1042, and the upper fixing plate has four overflow pipe fixing holes 1043; the primary separator upper shell 105 is a hollow structure with two upper-stage overflow channels 1051 inside; the hydrocyclone... The outer casing 106 has a tangential inlet 1061, an overflow hole 106, and a spherical fixing 1063; the guide oil filter cone 107 is a hollow structure with an oil filter hole 1071 and an overflow outlet 1072; the variable pitch spiral flow channel 108 is a hollow structure with an overflow inlet 1081; the inverted cone 109 has a bottom flow outlet 1091; the first-stage separator lower casing 110 is a hollow structure with two next-stage overflow channels 1101 and four next-stage bottom flow channels 1102 inside; the guide bearing 111 has a bearing inside and a guide channel 111 bypassing the bearing. The system has two slots, an upper slot and a lower slot, and a fan-shaped channel 1114; the sand guide cover 112 has a sand discharge hole 1121 and a bearing hole 1122; the secondary separation upper shell 113 has a primary sand settling chamber 1131, two upper secondary overflow channels 1132, and four upper secondary underflow channels 1133; the secondary separation lower shell 114 is a hollow structure with two lower secondary overflow channels 1142 and four lower secondary underflow channels 1143; the secondary feed pipe 115 is a hollow structure with a secondary annular discharge port 1151 on its surface; the tertiary feed... Pipe 116 has a three-stage annular discharge port 1161; the three-stage separation upper shell 118 has a two-stage sedimentation chamber 1181, two upper three-stage overflow channels 1182, and four upper three-stage underflow channels 1183; the three-stage separation lower shell 119 is a hollow structure with four lower three-stage underflow channels 1191; the confluence connection 120 has four underflow channels 1201, a confluence channel 1202, and a three-stage sedimentation chamber 1203; the lower bridge channel 121 has a bearing inside and an internal annular cavity 1211, with multiple drainage channels 1212 distributed circumferentially at its lower end. The upper end of the lower bridge channel 121 is placed at the lower end of the confluence connection 120 and connected to the drive motor assembly 202. Tesla valves 117 are placed in the overflow and underflow channels at each stage to prevent backflow. The drive shaft 102 passes through the oil-water separation and extraction structure and is connected to the pump and motor through corresponding shaft connection devices. After connection, it starts working.

[0032] The separation structure employs multiple hydrocyclones connected in parallel and multi-stage separation in series, allowing for adjustment of the separation structure as needed. Simultaneously, there are two overflow channels: the upper-level overflow channel 1051, the upper-second-level overflow channel 1132, the upper-third-level overflow channel 1182, and the first-level overflow channel 1013. There are four underflow channels: the lower-level underflow channel 1102, the lower-second-level underflow channel 1143, the lower-third-level underflow channel 1191, and the underflow channel 1021. Multiple separation devices operate simultaneously, and multiple flow channels share the same transport capacity to meet the demands of high-volume operation.

[0033] During operation, an oil-water mixture containing a small amount of sand phase enters the device through inlet 1011, and then flows sequentially from outlet 1012 into the primary feed pipe 103, the guide channel 1111 inside the guide bearing 111, the secondary feed pipe 115, the guide channel 1111 inside the next guide bearing 111, and the tertiary feed pipe 116. The mixture then passes through the primary annular outlet 1031, the secondary annular outlet 1151, and the tertiary annular outlet 1161, entering the annular region between the combined plate 104 and the primary separator upper shell 105, the secondary separator upper shell 113, and the tertiary separator upper shell 118. It then enters the hydrocyclone through the tangential inlet 1061 on the hydrocyclone shell 106. The swirling flow field formed by 1061 causes some of the lighter oil phase in the mixture to converge towards the center. As the guide oil filter cone 107 moves downward, some of the oil phase enters the interior of the guide oil filter cone 107 through the filter holes 1071. The remaining mixture is pressurized and the swirling flow field is enhanced by the variable pitch spiral flow channel 108, causing the remaining oil phase to be separated a second time and enter the interior of the variable pitch spiral flow channel 108 from the overflow inlet 1081. Then, together with the oil phase that entered the guide oil filter cone 107, it is discharged from the overflow outlet 1072 into the annular area above the fixed combination plate 104, and enters the upper-level overflow channel 1051, the upper-second-level overflow channel 1132, and the upper-third-level overflow channel 1182 respectively. All the oil phase flows along the upper-third-level overflow channel 118. 2. The oil phase from the lower secondary overflow channel 1142 merges with the oil phase from the upper secondary overflow channel 1132, and then merges with the oil phase from the upper primary overflow channel 1051 along the lower primary overflow channel 1101. Finally, all the oil phase is drawn from the overflow channel 1013 into the upper centrifugal pump unit 122, and then discharged through the upper oil pipe coupling 123 to the surface. After separation, the water phase and a small amount of sand phase are discharged from the hydrocyclone through the bottom outlet 1091 on the inverted cone 109, and then enter the annular cavity between the sand guide cover 112 and the guide channel 111 through the fan-shaped channel 1114 on the guide channel 111. The sand phase and part of the water phase fall into the primary sand settling chamber 1131, the secondary sand settling chamber 118, and the tertiary sand settling chamber 1203 through the sand discharge hole 1121. The sediment settles inside, and when the subsequent equipment is removed, the internal sediment can be drained. The water phase enters the next-level underflow channel 110, the next-level underflow channel 1143, and the next-level underflow channel 1191 respectively. All the water phases merge along the next-level underflow channel 1102, the next-level underflow channel 1133 and the next-level underflow channel 1143, and then along the next-level underflow channel 1183 and the next-level underflow channel 1191, and enter the inside of the confluence connection 120 through the upper underflow channel 1201. Finally, all the water phases enter the internal annular cavity 1211 of the bridge channel 121 from the confluence channel 1202, and then enter the downhole drive and reinjection structure from the multiple drainage channels 1212 distributed around its lower end.

[0034] The downhole drive and reinjection structure includes: a lower housing 201, a drive motor assembly 202, a lower centrifugal pump assembly 203, and a lower tubing coupling 204; the upper end of the lower housing 201 is threadedly connected to the lower end of the manifold 120, and the lower end is threadedly connected to the lower centrifugal pump assembly 203; the drive motor assembly 202 is placed inside the lower housing 201; the upper end of the drive motor assembly 202 is connected to the lower end of the bridge channel 121, and the central internal coupling is connected to the drive shaft 102; the lower end of the lower centrifugal pump assembly 203 is threadedly connected to the lower tubing coupling 204.

[0035] During operation, the drive motor assembly 202 drives the lower centrifugal pump unit 203 to rotate, and at the same time the transmission shaft 102 rotates, thereby driving the upper centrifugal pump unit 122 to work. The water phase that is separated from the oil-water separation and produced structure enters the annular area between the lower outer shell 201 and the drive motor assembly 202 through the drainage channel 1212 on the bridge channel 121. Finally, it is drawn into the lower centrifugal pump unit 203, discharged from the lower oil pipe coupling 204, and finally reinjected into the ground.

[0036] The present invention is described in more detail below: This type of multi-stage series-parallel multiphase cyclone separator for high-yield offshore oil wells, such as... Figure 1 As shown, the device is placed vertically inside the downhole pipeline. During operation, the sand-containing oil-water mixture enters the device through the inlet 1011. After being separated by various separation devices, the oil phase collected in the overflow channels is drawn by the upper centrifugal pump unit 122 and discharged into the upper tubing coupling 123, and then lifted to the surface. The separated water phase is drawn by the lower centrifugal pump unit 203 through the underflow channels and finally into the lower tubing coupling 204, and then reinjected into the downhole. Note that the device has a drive shaft 102 running through it from top to bottom. Therefore, the pump structure connected at both ends of the device can be connected and operate simultaneously via the drive shaft 102, making it suitable for a system where one motor drives two pumps. Separation and extraction structures, such as Figure 2As shown, the drive shaft 102 drives the upper and lower centrifugal pump sets 122 to rotate. The mixture entering through the inlet 1011 flows sequentially into each stage of the feed pipe from the outlet 1012, and then enters the separation section from the annular outlets of each stage of the feed pipe, as shown in the figure, with the first-stage feed pipe 103 and the first-stage annular outlet 1031. After separation by each stage of the separation device, the oil phase merges with the oil phase in the upper third-stage overflow channel 1182, the lower second-stage overflow channel 1142, and the upper second-stage overflow channel 1132, and then merges with the oil phase in the lower first-stage overflow channel 1101 and the upper first-stage overflow channel 1051. Finally, all the oil phases are drawn out from the overflow channel 1013 by the upper centrifugal pump set 122 and discharged into the upper oil pipe coupling 123. The discharge device is then lifted to the ground. A Tesla valve 117 is placed in the flow channel to stabilize the flow rate and prevent backflow. It is worth noting that the figure shows a two-stage separation structure installed in a cycle, and the number of stages installed in the cycle can be freely adjusted according to the needs during operation.

[0037] like Figure 3 and Figure 4 As shown, an oil-water mixture containing a small amount of sand phase enters the device through inlet 1011, then flows into the primary feed pipe 103 from outlet 1012. Subsequently, the mixture enters the annular region between the combined plate 104 and the primary separator upper shell 105 through the primary annular outlet 1031. It then enters the hydrocyclone through the tangential inlet 1061 on the hydrocyclone shell 106. After hydrocyclone separation, the light oil phase is discharged from overflow outlet 1072 into the annular region above the combined plate 104 and enters the upper overflow channel 1051, where it merges with the oil phase separated by the secondary and tertiary separation structures flowing in from the lower overflow channel 1101. Finally, all the oil phases are drawn together from overflow channel 1013 into the upper centrifugal pump group 122. After separation, the aqueous phase and a small amount of sand phase are discharged from the hydrocyclone through the underflow port 1091 on the inverted cone 109. They then pass through the fan-shaped channel 1114 on the guide bearing 111 and enter the annular cavity between the sand guide cover 112 and the guide bearing 111. The sand phase and part of the aqueous phase fall into the primary sedimentation chamber 1131 through the sand discharge hole 1121 and settle. The sediment can be drained when the device is removed later. The aqueous phase enters the next-stage underflow channel 1102 and then flows into the upper secondary underflow channel 1133 in the secondary separation structure. Tesla valves 117 are placed in each flow channel to stabilize the flow rate and prevent backflow. The mixture in the primary feed pipe 103 flows through the guide channel 1111 inside the guide bearing 111 into the secondary feed pipe 115 in the secondary separation structure. The external view and sectional view of the fixed assembly plate and hydrocyclone structure are shown below. Figure 5As shown, the upper end of the variable pitch spiral flow channel 108 is threadedly connected to the lower end of the oil-draining cone 107 and then placed inside the hydrocyclone housing 106. The upper end of the oil-draining cone 107 passes through the overflow hole 1062 at the center of the upper end of the hydrocyclone housing 106 and is inserted into the overflow pipe fixing hole 1043 on the fixing assembly plate 104. The lower end of the hydrocyclone housing 106 is threadedly connected to the inverted cone 109, and at the same time, the spherical fixing 1063 on its surface enters vertically from the lower end of the groove 1042 opened in the fixing assembly plate 104, and then rotates and clamps together along the groove. The mixture enters the hydrocyclone through the tangential inlet 1061 on the hydrocyclone shell 106. The swirling field formed by the tangential inlet 1061 causes some of the light oil phase in the mixture to converge towards the center. As the guide oil filter cone 107 moves downward, some of the oil phase enters the guide oil filter cone 107 through the filter holes 1071. The remaining mixture is pressurized and the swirling field is enhanced by the variable pitch spiral channel 108, which causes the remaining oil phase to be separated and enter the variable pitch spiral channel 108 through the overflow inlet 1081. Then, together with the oil phase that entered the guide oil filter cone 107, it is discharged from the overflow outlet 1072 into the annular area above the combined plate 104. After separation, the water phase and a small amount of sand phase are discharged from the hydrocyclone through the bottom outlet 1091 on the inverted cone 109. The inverted cone 109 plays a role in improving oil-water separation.

[0038] The appearance and cross-sectional view of the secondary separation structure are as follows: Figure 6As shown in (a) and (b), the mixture flowing from the primary separation structure into the secondary feed pipe 115 enters the annular region between the combined plate 104 and the upper shell 113 of the secondary separation through the secondary annular outlet 1151. It then enters the hydrocyclone through the tangential inlet 1061 on the hydrocyclone shell 106. After hydrocyclone separation, the light oil phase is discharged from the overflow outlet 1072 into the annular region above the combined plate 104 and enters the upper secondary overflow channel 1132. There, it merges with the oil phase separated by the tertiary separation structure flowing into the lower secondary overflow channel 1142 and flows into the next primary overflow channel 1101. After separation, the aqueous phase and a small amount of sand phase are discharged from the hydrocyclone through the underflow port 1091 on the inverted cone 109. Then, they enter the annular cavity between the sand guide cover 112 and the guide bearing 111 through the fan-shaped channel 1114 on the guide bearing 111. The sand phase and part of the aqueous phase fall into the secondary sedimentation chamber 1181 through the sand discharge hole 1121 and settle. When the device is removed later, the sediment inside can be emptied. The aqueous phase enters the lower secondary underflow channel 1143 and flows into the upper tertiary underflow channel 1183 in the tertiary separation structure together with the aqueous phase after primary separation. The Tesla valve 117 is placed in each flow channel to stabilize the flow rate and prevent backflow. The mixture in the secondary feed pipe 115 flows into the tertiary feed pipe 116 in the tertiary separation structure through the guide channel 1111 inside the second guide bearing 111. It is worth mentioning that, in addition to connecting to a tertiary separation structure, a secondary separation structure can also be connected to another secondary separation structure, thereby allowing for flexible adjustment of the number of separation structures according to the required range of mixed liquor processing volume.

[0039] The external view and cross-sectional view of the three-stage separation structure are as follows: Figure 7As shown in (a) and (b), the mixture flowing from the secondary separation structure into the tertiary feed pipe 116 enters the annular region between the combined plate 104 and the upper shell 118 of the tertiary separation through the tertiary annular outlet 1161. It then enters the hydrocyclone through the tangential inlet 1061 on the hydrocyclone shell 106. After hydrocyclone separation, the light phase oil phase is discharged from the overflow outlet 1072 into the annular region above the combined plate 104, enters the upper tertiary overflow channel 1182, and then flows into the lower secondary overflow channel 1142. After separation, the aqueous phase and a small amount of sand phase are discharged from the hydrocyclone through the bottom flow port 1091 on the inverted cone 109 and enter the annular cavity above the sand guide cover 112. The sand phase and part of the aqueous phase fall into the third-stage sedimentation chamber 1203 through the sand discharge hole 1121 and settle. When the device is removed later, the internal sedimentation can be emptied at the same time. The aqueous phase enters the lower third-stage bottom flow channel 1191 and enters the inside of the confluence connection 120 through the bottom flow channel 1201 on the confluence connection 120 together with the aqueous phase after the first and second stage separation. The Tesla valve 117 is placed in each flow channel to stabilize the flow rate and prevent backflow. Finally, all the aqueous phase enters the internal annular cavity 1211 of the bridge channel 121 from the confluence channel 1202, and then enters the downhole drive and reinjection structure 2 from the multiple drainage channels 1212 distributed around its lower end. Figure 8 The diagram shows the overflow channel 1013 on the inlet bridge channel 101, the upper overflow channel 1051 on the upper shell 105 of the first-stage separator, the lower overflow channel 1101 and the lower underflow channel 1102 on the lower shell 110 of the first-stage separator, the upper second-stage overflow channel 1132 and the upper second-stage underflow channel 1133 on the upper shell 113 of the second-stage separator, the lower second-stage overflow channel 1142 and the lower second-stage underflow channel 1143 on the lower shell 114 of the second-stage separator, the upper third-stage overflow channel 1182 and the upper third-stage underflow channel 1183 on the upper shell 118 of the third-stage separator, the lower third-stage underflow channel 1191 on the lower shell 119 of the third-stage separator, and the underflow channel 1201 on the confluence connection 120 from different observation angles; the appearance and cross-sectional view of the drive and reinjection structure are shown below. Figure 9 As shown in (a) and (b), the drive motor assembly 202 drives the lower centrifugal pump group 203 to rotate. The water phase that is separated from the oil-water separation and produced structure 1 enters the annular area between the lower outer shell 201 and the drive motor assembly 202 through the drainage channel 1212 on the bridge channel 121. It is then sucked into the lower centrifugal pump group 203, discharged from the lower oil pipe coupling 204, and finally reinjected into the ground.

[0040] This invention addresses the challenges of high-volume oilfield operations and confined downhole spaces by providing a multi-stage separation unit that can be connected in series and operated in parallel. Each stage of the separator achieves efficient separation of oil, water, and sand phases. The overflow and underflow channels are arranged parallel to each other, ensuring stable transport during high-volume operations. The design is also suitable for a single motor driving two pumps, enhancing its applicability to confined downhole environments. The innovative hydrocyclone design improves oil-water separation efficiency, while the sand settling structure prevents sand from accumulating and causing wear on various process components, thus enhancing the overall economic efficiency of the unit.

Claims

1. A downhole multi-stage series-parallel multiphase cyclone separation device for high liquid rate offshore oilfield oil wells, characterized in that: This multi-stage series-parallel multiphase hydrocyclone separator for high-yield offshore oil wells includes an oil-water separation and production structure, and a downhole drive and reinjection structure. The oil-water separation and production structure is located above the downhole drive and reinjection structure. The oil-water separation and production structure includes an upper centrifugal pump unit and a multi-stage oil-water separation device. The downhole drive and reinjection structure includes a drive motor assembly and a lower centrifugal pump unit. The drive motor assembly drives the lower centrifugal pump unit to rotate while simultaneously driving the upper centrifugal pump unit to rotate via a transmission shaft passing through the multi-stage oil-water separation device. The multi-stage oil-water separation device uses multiple hydrocyclones connected in parallel and separated in series. Each stage of the oil-water separation device has a staged feed pipe, a staged combined sleeve, and a staged hydrocyclone assembly. The staged hydrocyclone assembly consists of parallel hydrocyclones. The assembly consists of several stages, each with its own feed pipe fitted around the drive shaft. The annular space between the feed pipe and the drive shaft serves as the liquid inlet channel. Adjacent feed pipes are connected via a flow guide channel. Each feed pipe has multiple outlets arranged in a ring. The liquid inlet channel communicates with each hydrocyclone through the outlets of each feed pipe and multiple tangential inlets corresponding to the outer shell of each hydrocyclone. The hydrocyclone assemblies connected in series at each stage are connected in parallel with respect to the liquid inlet channel. The stage combination sleeves are connected in sequence to form an assembled shell. An overflow channel and an underflow channel are provided inside the assembled shell. The overflow holes of each hydrocyclone communicate with the overflow channel, and the underflow ports of each hydrocyclone communicate with the underflow channel. The upper end of the overflow channel is connected to the upper centrifugal pump assembly, and the lower end of the underflow channel is connected to the lower centrifugal pump assembly. The flow guide bearing has a drive shaft hole, and the bearing cavity is centrally located around the drive shaft hole. The drive shaft passes through the drive shaft hole, and the bearing is fitted inside the bearing cavity on the outside of the drive shaft. The upper and lower cavities of the flow guide channel are connected through a vertical cavity. The upper cavity, vertical cavity, and lower cavity are integrally connected to form a horizontal U-shaped groove. The bearing cavity is located in the U-shaped groove. The flow guide channel is connected to the liquid inlet channel through the upper retaining groove at the top of the upper cavity and the lower retaining groove at the bottom of the lower cavity. The flow guide bearing also has a fan-shaped channel, which is located on the groove opening side of the U-shaped groove formed by the flow guide channel. The graded hydrocyclone assembly is housed within a graded combination sleeve, which consists of a separate upper outer shell threadedly connected to a separate lower outer shell. The graded hydrocyclone assembly includes four hydrocyclones connected in parallel, a fixed assembly plate, a guide bearing, a sand guide cover, and a sand settling chamber. The fixed assembly plate consists of an upper fixed plate and a lower fixed plate, which are threadedly connected to the separate upper outer shell. The upper fixed plate has a drive shaft hole and four overflow pipe fixing holes evenly arranged outside the drive shaft hole. The lower fixed plate has a drive shaft hole and four hydrocyclone fixing holes evenly arranged outside the drive shaft hole. Each hydrocyclone fixing hole has a groove on its wall. A spherical fixing is provided on the outer wall of the hydrocyclone, and one hydrocyclone is installed at each hydrocyclone fixing hole. The hydrocyclone is fixed to the lower fixing plate by the spherical fixing and the groove. The overflow pipe of the hydrocyclone is fixed through the overflow pipe fixing hole. There is an annular space between the upper fixing plate and the upper shell of the separator, and the annular space is connected to the overflow channel in the upper shell of the separator. The flow guide bearing is set below the hydrocyclone, and there is an annular space between the flow guide bearing and the sand guide cover. The annular space is connected to the bottom flow channel in the lower shell of the separator. The lower end of the sand guide cover is threaded to the sand settling chamber. The annular space between the flow guide bearing and the sand guide cover is connected to the sand settling chamber through the sand discharge hole of the sand guide cover.

2. The downhole multi-stage series-parallel multiphase cyclone separator for high-yield oil wells in offshore oilfields according to claim 1, characterized in that: The hydrocyclone includes a hydrocyclone shell, a flow-guiding oil filter cone, a variable pitch spiral channel, and an inverted cone. The inverted cone is centrally located below the variable pitch spiral channel. The upper end of the variable pitch spiral channel is threadedly connected to the flow-guiding oil filter cone. The variable pitch spiral channel and the flow-guiding oil filter cone have interconnected overflow holes. The lower end of the flow-guiding oil filter cone has uniformly arranged oil filter holes. The pitch of the upper part of the variable pitch spiral channel is greater than the pitch of the lower part.

3. The downhole multi-stage series-parallel hydrocyclone separator for high liquid loading offshore oil wells according to claim 2, characterized in that: The graded hydrocyclone group has three stages: a primary hydrocyclone separator group, a secondary hydrocyclone separator group, and a tertiary hydrocyclone separator group. The upper end of the upper shell of the primary hydrocyclone separator group is threaded to an inlet bridge channel. The outer wall of the inlet bridge channel is provided with multiple liquid inlets. The drive shaft passes through the drive shaft hole of the inlet bridge channel and is connected to the centrifugal pump group. The upper end of the primary feed pipe is inserted into the slot of the inlet bridge channel. The slot is provided with an outlet. The inlet and outlet communicate with each other. The outlet communicates with the primary feed pipe. A bent overflow channel is also provided in the inlet bridge channel. The upper end of the overflow channel is connected to the centrifugal pump group.

4. The downhole multi-stage, series-parallel, multiphase, hydrocyclone separation apparatus for high liquid loading offshore oil wells of claim 3, wherein: The lower end of the separation shell of the three-stage cyclone separator group is connected to the upper end of the confluence connection by a thread, and the upper end of the lower bridge channel is placed at the lower end of the confluence connection and connected to the drive motor assembly.

5. The downhole multi-stage, series-parallel, multiphase, hydrocyclone separation apparatus for high liquid loading offshore oil wells of claim 4, wherein, Tesla valves are installed at the locations of the first-stage, second-stage, and third-stage cyclone separator groups in the overflow channel; Tesla valves are also installed at the locations of the first-stage, second-stage, and third-stage cyclone separator groups in the underflow channel.

6. The downhole multi-stage, series-parallel, multiphase, hydrocyclone separation apparatus for high liquid loading offshore oil wells of claim 5, wherein, There are two overflow channels and four underflow channels.

7. The downhole multi-stage, series-parallel, multiphase, cyclonic separation apparatus for high fluid production offshore oilfield high fluid production oil wells of claim 6, wherein, When the hydrocyclone group at each stage is working, the oil-water mixture containing a small amount of sand phase enters the primary feed pipe, secondary feed pipe and tertiary feed pipe respectively through the inlet. It enters the interior of each hydrocyclone through the tangential inlet on the outer shell of each hydrocyclone. The swirling field formed by the tangential inlet causes some of the light oil phase in the oil-water mixture to converge towards the center. As the guide oil filter cone moves downward, some of the oil phase enters the interior of the guide oil filter cone through the filter hole. The remaining oil-water mixture is pressurized and the swirling field is enhanced by the variable pitch spiral flow channel, so that the remaining oil phase is separated a second time and enters the interior of the variable pitch spiral flow channel through the overflow hole. It then flows upward together with the oil phase that entered the guide oil filter cone and is discharged from the overflow outlet into the annulus above the fixed combination plate. The oil phase separated by each stage of the hydrocyclone group converges into the overflow channel. The oil phase is lifted upward in the overflow channel stage by stage and is sucked into the upper centrifugal pump group. It is then discharged through the upper oil pipe coupling and finally extracted to the ground. After separation, the aqueous phase and a small amount of sand phase are discharged from the hydrocyclone through the bottom outlet on the inverted cone. Then, they enter the annular cavity between the sand guide cover and the guide channel through the fan-shaped channel on the guide channel. The sand phase and part of the aqueous phase fall into the primary sand settling cavity, the secondary sand settling cavity and the tertiary sand settling cavity through the sand discharge holes and settle. The aqueous phase converges into the bottom channel. All the aqueous phases merge down the bottom channel step by step and enter the interior of the confluence connection through the bottom channel on the confluence connection. Finally, all the aqueous phases enter the annular cavity inside the lower bridge channel from the confluence channel, and then enter the downhole drive and reinjection structure from the multiple drainage channels distributed circumferentially at its lower end.

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