Offshore oil well abandonment operations system and method

Abstract

This disclosure provides a system and method for abandoning offshore oil wells. The system includes: an abandonment well operating point (BOP) suitable for installation on the wellhead of a well to be abandoned; a grease-filled blowout preventer (BOP) lowered to the BOP via a wire rope for abandonment operations. The BOP includes: a pipe body; a pressure control head located at the upper part of the pipe body, wherein the wire rope passes through the pressure control head, which is suitable for maintaining a dynamic seal during the wire rope's raising and lowering processes; and a wire rope tool kit slidably disposed within the pipe body and connected to the wire rope. The tool kit allows for the selection of matching tools according to operational requirements. During the abandonment process, the grease-filled BOP and the BOP work together to control the wellbore pressure. This system eliminates the need for a riser, lowering the grease-filled BOP via a wire rope across open water for abandonment operations of production wells, instead of using drill pipe and risers on large drilling vessels, resulting in lower costs and higher efficiency.

Description

Technical Field

[0001] This disclosure relates to the field of offshore oil well abandonment operation technology, and in particular to a riserless system and method for offshore oil well abandonment operation using an offshore support vessel. Background Technology

[0002] Well abandonment refers to the process of abandoning a production well, injection well, or exploration well for safety reasons when it is no longer in use, ensuring its sealing and preventing future environmental harm. This involves permanently sealing the casing and plugging system downhole by installing a bridge plug and applying cement, then recovering the production tubing and Christmas tree onto a ship at sea.

[0003] The main challenges in well abandonment and production string recovery are maintaining a sufficient pressure safety barrier during operations, effectively controlling the volume of fluid in the wellbore, and having the capability for pipe handling and safe operation. These challenges can be addressed with the invention of the grease-injected blowout preventer (BOP). Using the grease-injected BOP in well abandonment operations allows for comprehensive control of wellbore pressure, enabling riserless well abandonment.

[0004] According to international and regional regulations, as well as the responsibilities of well owners, offshore oil and gas wells must be abandoned when they reach the end of their production life. Therefore, abandoning offshore oil and gas wells will be a major issue in the future.

[0005] In today's deepwater oil and gas well abandonment market, using conventional methods and equipment such as large, expensive floating drilling rigs or workover rigs for well abandonment operations is economically unsustainable. This necessitates the use of more cost-effective and environmentally friendly methods and equipment.

[0006] With many offshore oil fields nearing the end of their production life, thousands of offshore oil and gas wells need to be abandoned, and there is a great deal of work to be done in the area of ​​offshore oil and gas well abandonment. In addition to those offshore oil wells that need to be abandoned, tens of thousands of older oil exploration wells are temporarily abandoned because they are planned to be reopened in the future. Some wells are abandoned due to economic factors (the cost of conventional permanent abandonment is too high).

[0007] Currently, the production string of a vertical wellhead is vertically supported by the wellhead, allowing for the initial retrieval of the vertical wellhead. In contrast, the production string and tubing of a horizontal wellhead are vertically supported internally by the wellhead itself, necessitating the retrieval of the production string before the horizontal wellhead, complicating well abandonment procedures. However, the horizontal wellhead is now the most commonly used due to its advantages over the vertical wellhead, although its well abandonment procedure is more cumbersome and costly. Summary of the Invention

[0008] To address the aforementioned technical problems, this disclosure provides an offshore oil well abandonment operation system and method that enables more efficient and safer abandonment operations on vertical and horizontal well production trees. It eliminates the need for risers and allows the abandonment operation to be carried out using only an offshore support vessel equipped with a riserless abandonment system.

[0009] According to one aspect of the inventive concept of this disclosure, an offshore oil well abandonment operation system is provided, comprising:

[0010] Wire rope;

[0011] Abandoned well BOP is suitable for installation on the well tree of wells to be abandoned.

[0012] A grease injection blowout preventer (BOP) is lowered to the abandoned well (BOP) via a wire rope for well abandonment operations. The grease injection BOP includes:

[0013] tube body;

[0014] A pressure control head is disposed at the upper part of the pipe body, wherein the wire rope passes through the pressure control head, and the pressure control head is adapted to maintain a dynamic seal during the raising and lowering of the wire rope in the well;

[0015] A wire rope tool bag is slidably disposed inside the tube, and the wire rope tool bag is connected to the wire rope. The wire rope tool bag can select matching tools according to the operation requirements.

[0016] During the well abandonment process, the grease injection blowout preventer and the well abandonment BOP work together to control the wellbore pressure.

[0017] According to some embodiments of this disclosure, the offshore oil well abandonment operation system further includes:

[0018] The oil pipe hanger connecting sleeve has its upper end connected to the lower end of the pipe body, and its lower end is provided with an oil pipe hanger sealing head, which is suitable for docking with the oil pipe hanger.

[0019] According to some embodiments of this disclosure, the offshore oil well abandonment operation system further includes:

[0020] Open water pipeline hoisting equipment includes a ship hoisting tool string, ROV shut-off valve, and ROV cement hose bracket;

[0021] The connecting rod is connected at one end to the open water pipeline hoisting tool;

[0022] A tubing hanger lowering tool is connected to the other end of the connecting rod; the tubing hanger lowering tool is suitable for locking the tubing hanger; and

[0023] The tubing hanger release module is located above the well fluid level control unit. The tubing hanger release module is used to release the locking of the tubing hanger so that the production tubing string can be freely suspended, thereby facilitating its lifting and retrieval.

[0024] According to some embodiments of this disclosure, the offshore oil well abandonment operation system further includes:

[0025] In an emergency, the BOP manifold is disconnected and connected to the abandoned well BOP via the high circulation pipeline, medium circulation pipeline, and low circulation pipeline to form three circulation loops;

[0026] A well abandonment circulation hose, one end of which is connected to the emergency disconnect module, and the other end connected to the vessel; and

[0027] The blowout preventer control umbilical cable is clamped at the top to the steel wire of the emergency disconnect tension system, connected at the bottom to the emergency disconnect module, and connected to the ship at the other end.

[0028] According to some embodiments of this disclosure, the offshore oil well abandonment operation system further includes:

[0029] Well fluid level control unit, including:

[0030] The well fluid level sensor is located below the well fluid level control unit.

[0031] An ROV bracket for the suction / injection hose is installed above the well fluid level sensor;

[0032] The well fluid level control pump is connected to the well fluid level control unit via a well fluid level control hose.

[0033] The well fluid level control pump is a bidirectional pump. When the tubing string is lowered, the well fluid is pumped out from the well fluid level control unit, and when the tubing string is retrieved, the well fluid is pumped back into the well to maintain the well fluid level.

[0034] According to another aspect of the inventive concept of this disclosure, a method for abandoning offshore oil wells is also provided, employing the offshore oil well abandonment system as described above, the method comprising the following operations:

[0035] S1: The tubing plug is recovered using the grease-injected blowout preventer, tubing hanger connecting sleeve, wire rope tool kit, and abandoned well BOP;

[0036] S2: Well control, and use grease injection blowout preventer, wire rope tool kit and abandoned well BOP for plugging operations;

[0037] S3: Unlock and recover the tubing hang and production tubing string using the tubing hang lowering tool, open water tubing hang lifting tool, and tubing hang release module; and

[0038] S4: Unlock the wellhead via hydraulic control of the umbilical cable, and recover the wellhead and abandoned well operating point (BOP) using the well abandonment hoisting tool.

[0039] According to some embodiments of this disclosure, operation S1 includes sub-operations:

[0040] S101: Assemble the grease injection blowout preventer and the oil pipe hanging connection sleeve, wherein the wire rope passes through the pressure control head and is connected to the wire rope tool bag;

[0041] S102: The grease injection blowout preventer and the tubing hanger connecting sleeve are lowered into the abandoned well BOP by the wire rope until the tubing hanger sealing head at the lower end of the tubing hanger connecting sleeve is locked with the tubing hanger.

[0042] S103: Close the lower gate of the abandoned well BOP, and then close the upper gate of the abandoned well BOP using a low shutdown operation pressure, wherein the grease injection blowout preventer pipe can slide relative to the upper gate;

[0043] S104: Release the lock between the grease injection blowout preventer and the oil pipe connecting sleeve, lift the grease injection blowout preventer until the interface sleeve is mechanically locked below the upper gate blowout preventer, and close the upper gate using high closing operation pressure, wherein a seal is formed between the upper gate and the grease injection blowout preventer;

[0044] S105: Lower the wire rope tool bag into the oil pipe hanging connection sleeve, position and lock it on the oil pipe hanging plug, unlock the oil pipe hanging plug, and lift the wire rope tool bag into the grease injection anti-blowout pipe.

[0045] S106: Close the annular blowout preventer (BOP) of the abandoned well, open the upper gate valve, raise the grease injection BOP until its lower end exceeds the blind flange BOP, and close the blind flange BOP; and

[0046] S107: Activate the annular blowout preventer, lift the grease injection blowout preventer pipe through the open water area, and complete the retrieval of the oil pipe with the plug.

[0047] According to some embodiments of this disclosure, the tubing plug includes an upper tubing plug and a lower tubing plug. The upper tubing plug is first retrieved through operations S101 to S107, and the lower tubing plug is retrieved through operations S102 to S107.

[0048] According to some embodiments of this disclosure, operation S2 includes sub-operations:

[0049] S201: Volume control of well fluid, including injecting or pumping well fluid into the well;

[0050] S202: Pump in kill fluid, which enters the production tubing from below the lower gate and finally enters the reservoir; and

[0051] S203: Seal the wellbore.

[0052] According to some embodiments of this disclosure, operation S3 further includes sub-operations:

[0053] S301: Assemble the tubing lowering tool and the open water tubing lifting tool;

[0054] S302: Lower the tubing hanger into the abandoned well BOP, and position and lock the lower end of the tubing hanger onto the well; and

[0055] S303: Release the lock between the tubing hanger and the wellhead, and complete the recovery operation of the tubing hanger and production tubing string using the open water tubing hanger lifting tool.

[0056] According to some embodiments of this disclosure, operation S4 includes sub-operations:

[0057] S401: Connect the hydraulic control umbilical cable to the abandoned well BOP to release the lock between the wellhead and the wellhead;

[0058] S402: Lock the abandoned well BOP and the abandoned well lifting tool and lift them up to complete the recovery of the wellhead and abandoned well BOP.

[0059] According to the offshore oil well abandonment operation system and method of this disclosure, the offshore support vessel deploys a workover derrick and a deep-water crane, and uses wire ropes to raise and lower the grease injection blowout preventer, and operates different wire rope operation tools in the production well to complete the abandonment operation. Attached Figure Description

[0060] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0061] Figure 1 This is a schematic diagram of the structure of an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure;

[0062] Figure 2 This is a schematic diagram of another working stage of an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure;

[0063] Figure 3 This is a schematic diagram of the structure of the grease injection blowout preventer and tubing hanger connecting sleeve of an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure;

[0064] Figure 4This is a schematic diagram of the structure of an open water tubing hoisting tool for an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure;

[0065] Figure 5 This is an exploded structural diagram of the well abandonment operation system (BOP) and upper connection assembly of an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure.

[0066] Figure 6 yes Figure 5 The diagram shows the assembly structure of the abandoned well BOP and its upper connecting components;

[0067] Figure 7 This is a schematic diagram of the structure of the grease injection blowout preventer and tubing hanger connecting sleeve for recovering the upper tubing hanger plug in an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure.

[0068] Figures 8-12 yes Figure 7 The diagram shows the structure of the abandoned well BOP, grease injection blowout preventer, and tubing hanger during each stage of the recovery process.

[0069] Figures 13-15 This is a schematic diagram of the various stages of the recovery tubing hanger and production tubing string of an offshore oil well abandonment operation system according to exemplary embodiments of the present disclosure; and

[0070] Figure 16 This is a schematic diagram of the production tree and BOP recovery process of an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure.

[0071] The meanings of the reference numerals in the above figures are as follows:

[0072] 1-Sea surface; 2-Offshore support vessel; 3-Deepwater crane; 4-Workover derrick; 5-Moon pool; 6-Emergency disconnect tension system; 7-Abandoned well system control cable; 8-BOP circulation hose parking module; 9-BOP volume control system well fluid injection / extraction hose parking module; 10-Abandoned well circulation high-pressure hose; 11-Volume control power control cable; 12-Abandoned well BOP; 13-Emergency disconnect module; 14-Well fluid level control pump; 15-Well fluid injection / extraction hose; 16-Well fluid level control hose; 17-Tree of production; 18-Tubing hanger release module; 19-BOP control cable; 20-Emergency disconnect 21-Broken short section; 22-Tubing hanger connecting sleeve; 23-Grease injection blowout preventer; 24-Wire rope; 25-Wire rope tool kit; 26-Grease reservoir; 27-Interface sleeve mechanical lock; 28-Tubing hanger plugger retrieval tool; 29-Tubing hanger sealing head; 30-Tubing hanger positioning module; 31-BOP gate sealing surface; 32-Grease injection blowout preventer locking support seat; 33-Open water tubing hanger lifting tool; 34-Oil 35-Tubing hanger; 36-Production tubing string; 37-ROV shut-off valve; 38-Marine crane lifting tool string; 39-ROV cement hose bracket; 40-Well fluid level control unit; 41-ROV bracket for suction / injection hose; 42-BOP annular blowout preventer; 43-Blind flange blowout preventer; 44-Upper gate; 45-Lower gate; 46-BOP connector; 47-Tubing hanger interface sleeve locating pin; 48-Downhole Circulation module; 49-Emergency disconnect BOP manifold; 50-Lower circulation line; 51-Middle circulation line; 52-High circulation line; 53-Climbing cylinder; 54-Climbing positioning pin; 55-Underwater camera; 56-Well fluid / seawater connection surface; 57-Well fluid level sensor; 58-Tubing hanger plug; 59-Tubing hanger lower plug; 60-Wellhead; 61-Seabed; 62-BOP lifting tool; 63-Hydraulic control umbilical cable. Detailed Implementation

[0073] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0074] However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of embodiments of this disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure.

[0075] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0076] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0077] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0078] To address the aforementioned technical problems, embodiments of this disclosure provide a low-cost and safe system for abandoning offshore oil and gas wells using a floating offshore support vessel. This system eliminates the need for a riser, using wire ropes instead of drill pipes to cross open water from the offshore support vessel for abandoning production wells. The main components of this new system include a grease-filled blowout preventer with a pressure control head, an abandonment BOP (Blow-Out Preventer) with a well fluid level control unit, a tubing hanger activation module, a tubing hanger connection sleeve, a wire rope toolkit, a well fluid level control pump, and an abandonment circulation high-pressure hose.

[0079] In this embodiment, the key feature is the introduction of a grease-filled blowout preventer (BOP) deployed on a wire rope. This BOP connects to a tubing hanger sleeve, which is locked onto the tubing hanger. In abandoned well BOPs or other conventional subsea BOPs, the BOP gate is closed and sealed. A wire rope tool kit, sealed within the grease-filled BOP, serves to connect and operate various wire rope tools within the production well. Furthermore, the BOP remains closed and sealed throughout the entire abandoned well operation in a pressurized production well.

[0080] The main challenges in well abandonment and production string recovery are maintaining a sufficient pressure safety barrier during operations, effectively controlling the volume of fluid in the wellbore, and having the capability for pipe handling and safe operation. These challenges can be addressed with the invention of the grease-injected blowout preventer (BOP). In well abandonment operations, the grease-injected BOP allows for comprehensive control of wellbore pressure, enabling riserless well abandonment.

[0081] The embodiments disclosed herein provide a low-cost and safe system for abandoning offshore oil and gas wells using a floating offshore support vessel. This system eliminates the need for a riser, using wirelines on the support vessel instead of drill pipes to cross open water for abandoning production wells. The main components of this new system include an abandonment BOP with a well fluid level control unit, a tubing hanger activation module, a tubing hanger connector, a grease blowout preventer with a pressure control head, a wireline tool kit, a well fluid level control pump, and an abandonment circulation high-pressure hose.

[0082] Figure 1 This is a schematic diagram of the structure of an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure; Figure 2 This is a schematic diagram of another working stage of an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure; Figure 3 This is a schematic diagram of the structure of the grease injection blowout preventer and tubing hanger of an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure.

[0083] According to one aspect of the inventive concept of this disclosure, an offshore oil well abandonment operation system is provided, such as... Figures 1 to 3 As shown, the system includes a well abandonment plug (BOP) 12, a grease-filled blowout preventer (BOP) 22, and a wire rope tool kit 24. The BOP 12 is suitable for installation on the wellhead tree 17 of a well to be abandoned. The grease-filled BOP 22 is lowered to the BOP 12 via a wire rope 23 for well abandonment operations. The grease-filled BOP 22 includes a pipe body and a pressure control head 25. The pressure control head 25 is located at the upper part of the pipe body, through which the wire rope 23 passes. The pressure control head 25 is used to maintain a dynamic seal during the raising and lowering of the wire rope 23. The wire rope tool kit 24 is slidably installed within the pipe body and connected to the wire rope 23. The tool kit 24 allows for the selection of matching tools according to operational requirements. During well abandonment, the grease-filled BOP 22 and the BOP 12 work together to control the wellbore pressure.

[0084] According to some embodiments of this disclosure, the offshore oil well abandonment operation system also includes a tubing hanger connecting sleeve 21, the upper end of which is connected to the lower end of the pipe body, and the lower end is provided with a tubing hanger sealing head 29, which is suitable for docking with the tubing hanger 35.

[0085] According to some embodiments of this disclosure, such as Figures 1 to 3 As shown, on the sea surface 1, an offshore support vessel 2 is used to carry out well abandonment operations. The offshore support vessel 2 has a workover derrick 4, a deepwater crane 3, and a moon pool 5. A small-sized abandoned well BOP12 is connected to the top of the production tree 17. Before the tubing hanger connector 21 enters the abandoned well BOP12, the tubing hanger connector 21 is connected to the grease-filled blowout preventer 22. The grease-filled blowout preventer 22 is lowered and raised using a wire rope 23 on the offshore support vessel 2. The tubing hanger connector 21 includes a tubing hanger sealing head 29, which is mated and sealed to the tubing hanger 35. The tubing hanger connector 21 also includes a tubing hanger positioning module 30, a BOP gate sealing surface 31, and a grease-filled blowout preventer locking support 32. The deepwater crane 3 is used to install and retrieve the abandoned well BOP12, tubing hanger 35, production string 36, horizontal production tree, and wellhead system 60. Meanwhile, the plugging operation was carried out by the wire rope tool kit 24 and the abandoned well high-pressure circulation hose 10. During the operation, the abandoned well BOP12 and the grease injection blowout preventer 22 were used for well control.

[0086] According to some embodiments of this disclosure, the grease preventer 22 includes an interface sleeve mechanical lock 27 that locks with the grease preventer locking support 32 and serves as the outer shell of the wire rope tool kit 24. The grease preventer 22 also includes a grease reservoir 26 and a pressure control head 25, which has a high-pressure sealing and wire rope emergency clamping function.

[0087] In this embodiment, a well repair derrick 4 and a deep-water crane 3 are deployed on the offshore support vessel. The grease injection blowout preventer 22 is raised and lowered by the wire rope 23. The wire rope tool kit 24 is sealed inside the grease injection blowout preventer 22. Different wire rope operation tools are operated in the production well to complete the well abandonment operation.

[0088] Figure 5 This is an exploded structural diagram of the well abandonment operation system (BOP) and upper connection assembly of an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure. Figure 6 yes Figure 5 The diagram shows the assembly structure of the abandoned well BOP and its upper connecting components.

[0089] According to some embodiments of this disclosure, such as Figure 5 and Figure 6 As shown, the hydraulically or electrically operated subsea BOP connector 46 is installed at the bottom of the abandoned well BOP 12 and locked to the Christmas tree 17. The lower part of the abandoned well BOP 12 includes the BOP well control and circulation system, the main components of which are the downhole circulation module 48, the upper gate valve 44, the lower gate valve 45, the blind flange blowout preventer 43, and the BOP annular blowout preventer 42. The main circulation lines are the high circulation line 52, the medium circulation line 51, and the lower circulation line 50, all of which are connected to the emergency disconnect BOP manifold module 49.

[0090] According to some embodiments of this disclosure, the grease-filled blowout preventer 22 connected to the wire rope 23 on the offshore support vessel 2 can be locked in the abandoned well (BOP) 12 to form a high-pressure seal. Subsequently, the same set of wire ropes 23 can be used to lower the wire rope toolkit 24 into the production tubing 36.

[0091] According to some embodiments of this disclosure, the grease injection anti-blowout pipe 22 is equipped with a wire rope holder and a pressure control head 25. Optionally, a smooth linear wire rope, an electric wire rope, a braided wire rope, or a lightweight composite wire rope can be used.

[0092] According to some embodiments of this disclosure, the grease injection blowout preventer 22 includes a pressure control head 25 that forms a high-pressure seal between the wire rope 23 and the grease injection blowout preventer 22. In the event of an emergency disconnection, the BOP shear blind flange 43 cuts the wire rope 23, and the overspeed triggering of the pressure control head 25 as the wire rope 23 falls automatically clamps the wire rope 23, preventing it from falling into the production tubing 36.

[0093] According to some embodiments of this disclosure, the grease preventer 22 serves as the outer shell of the wire rope tool bag 24. The grease preventer 22 also includes a grease reservoir 26 and a pressure control head 25, the grease reservoir 26 supplying grease to the pressure control head 25.

[0094] Figure 4 This is a schematic diagram of the structure of an open water tubing hoisting tool for an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure.

[0095] According to some embodiments of this disclosure, such as Figure 4 As shown, the offshore oil well abandonment operation system also includes an open water tubing hanger lifting tool 33, a connecting rod, a tubing hanger lowering tool 34, and a tubing hanger release module 18. The open water tubing hanger lifting tool 33 includes a ship lifting tool string, an ROV shut-off valve, and an ROV cement hose bracket. One end of the connecting rod is connected to the open water tubing hanger lifting tool 33. The tubing hanger lowering tool 34 is connected to the other end of the connecting rod and is used to lock the tubing hanger 35. The tubing hanger release module 18 is located above the well fluid level control unit and is used to release the locking of the tubing hanger 35, allowing the production tubing string to suspend freely, thus facilitating lifting and retrieval.

[0096] According to some embodiments of this disclosure, the tubing hanger release module 18 is used to unlock the tubing hanger 35 in the wellhead 17. Specifically, the tubing hanger release module 18 is used to unlock and lift the tubing hanger 35 inside the wellhead 17 until the tubing 35 is freely suspended inside the wellhead 17. The system includes a set of climbing hydraulic cylinders 53, climbing positioning pins 54, and an underwater camera 55.

[0097] According to some embodiments of this disclosure, an open-water tubing hanger lifting tool 33 is connected to a tubing hanger lowering tool 34 to retrieve the production tubing string 36 from the production well. The tubing hanger lifting tool 33 includes a marine crane lifting tool string 38, an ROV (remotely operated vehicle) shut-off valve 37, and an ROV cement hose bracket 39. The tubing hanger lowering tool 34 is locked onto the tubing hanger 35, and the production tubing string 36 is connected to the tubing hanger 35.

[0098] According to some embodiments of this disclosure, the offshore well abandonment operation system further includes an emergency disconnection BOP manifold 49, an emergency disconnection module 13, an abandonment circulation hose 10, and a blowout preventer control umbilical cable 19. The emergency disconnection BOP manifold 49 is connected to the abandoned well BOP via a high circulation line 52, a medium circulation line 51, and a low circulation line 50, forming three circulation loops; the abandoned well circulation hose 10 is connected at one end to the emergency disconnection module 13 and at the other end to the vessel; the blowout preventer control umbilical cable 19 is connected at one end to the emergency disconnection module 13 and at the other end to the vessel.

[0099] According to some embodiments of this disclosure, the offshore oil well abandonment operation system further includes a well fluid level control unit 40 and a well fluid level control pump 14. The well fluid level control unit 40 includes a well fluid level sensor 57 and an ROV bracket 41 for the suction / injection hose. The well fluid level sensor 57 is disposed below the well fluid level control unit 40; the ROV bracket 41 for the suction / injection hose is mounted above the well fluid level sensor 57. The well fluid level control pump 14 is connected to the well fluid level control unit 40 via a well fluid level control hose 16.

[0100] According to some embodiments of this disclosure, the abandoned well BOP12 is connected to the pressurized or unpressurized wellhead 17.

[0101] According to some embodiments of this disclosure, the well fluid level control unit 40 is configured with a well fluid level sensor 57 for monitoring the fluid level of the production well.

[0102] According to some embodiments of this disclosure, the well fluid level control pump 14 is connected to the well fluid level control unit 40 via a well fluid level control hose 16, which is equipped with an emergency disconnect break section 20.

[0103] The well fluid level control pump 14 is placed on the seabed 61. The well fluid level control pump 14 and the abandoned well BOP 12 are connected via a well fluid level control hose 16 equipped with an emergency disconnect break section 20. The well fluid level control pump 14 is connected to the offshore support vessel 2 via a control umbilical cable 11 and a well fluid injection / suction hose 15. The abandoned well high-pressure circulation hose 10 is vertically supported by the BOP circulation hose parking module 8. The abandoned well system control cable 7 and the BOP control cable 19 are fixed to the cables of the emergency disconnect tension system 6 and arranged together with the heave compensation device. The volume control power control cable 11 and the well fluid injection / suction hose 15 are vertically supported by the BOP volume control system well fluid injection / suction hose parking module 9 and placed in the moon pool 5. Both the abandoned well high-pressure circulation hose 10 and the BOP control cable 19 are connected to the emergency disconnect module 13.

[0104] According to some embodiments of this disclosure, when circulating fluid enters the wellbore, the well fluid level control unit 40 is used to adjust the height of the drilling fluid / seawater communication fluid level 56 to control the hydrostatic pressure in the well. The well fluid level control unit 40 includes a set of well fluid level sensors 57 and an ROV bracket 41 for a suction / injection hose. The ROV bracket 41 for the suction / injection hose is connected to the well fluid level control pump 14 on the seabed 61 via a well fluid level control hose 16 having an emergency disconnect break section 20.

[0105] According to some embodiments of this disclosure, the abandoned well (BOP) 12 is connected to the offshore support vessel 2 via an abandoned well circulation high-pressure hose 10, control umbilical cables 11 and 19, and a well fluid injection / extraction hose 15. The abandoned well circulation high-pressure hose 10 is vertically supported by a BOP circulation hose support module 8. The BOP control umbilical cable 19 is clamped onto the steel wire of the emergency disconnect tension system 6 of the emergency disconnect module 13 and is equipped with a heave compensation device. The volume control power control umbilical cable 11 and the well fluid injection / extraction hose 15 are vertically supported by a BOP volume control system well fluid injection / extraction hose parking module 9 and placed in the moon pool 5 of the offshore support vessel. The abandoned well circulation high-pressure hose 10, the BOP control umbilical cable 19, and the abandoned well control system umbilical cable 7 are all connected to the emergency disconnect module 13.

[0106] According to some embodiments of this disclosure, the well fluid level control pump 14 is a bidirectional pump, which adjusts the well fluid / seawater communication level 56 in the well fluid level control unit 40 by injecting or pumping in accordance with the well fluid level sensor 57 outputting the well fluid / seawater communication level 56 adjustment signal.

[0107] According to some embodiments of this disclosure, the pressurized well abandonment steps of the offshore oil well abandonment operation system include: recovering the tubing packer, recovering the downhole tools, washing the well, sealing the bottom of the well, sealing the perforated section above the well, sealing the casing short section, sealing the annulus, installing the surface plug, and performing pressure tests on all plugs to verify their integrity.

[0108] In this embodiment, the main challenges of well abandonment and production string recovery are maintaining a sufficient pressure safety barrier during operations, effectively controlling the volume of fluid in the wellbore, and having the capability for pipe handling and safe operation. These challenges can be addressed through the invention of the grease-injected blowout preventer (BOP). The use of the grease-injected BOP in well abandonment operations allows for comprehensive control of wellbore pressure, enabling riserless well abandonment.

[0109] To recover the production tubing string, first connect the tubing hook lowering tool to the tubing hook, then use the tubing hook release module to unlock the tubing hook, and finally use a deep-water crane to recover the tubing hook and production tubing string onto the ship. A pipe handling system will be installed on the deck of the offshore support vessel to unhook the recovered production tubing string and place it horizontally on the deck of the offshore support vessel.

[0110] According to another aspect of the inventive concept of this disclosure, a method for abandoning offshore oil wells is also provided, employing the offshore oil well abandonment system as described above, the method comprising operations S1 to S4.

[0111] According to some embodiments of this disclosure, operation S1 includes: retrieving the tubing plug using a grease-filled blowout preventer, a tubing hanger connector, a wire rope tool kit, and a well abandonment plug (BOP).

[0112] According to some embodiments of this disclosure, operation S2 includes: killing the well and performing plugging operations using a wireline toolkit, a grease-filled blowout preventer, and a boll stopper (BOP).

[0113] According to some embodiments of this disclosure, operation S3 includes: unlocking the tubing hanger and recovering the tubing hanger and production tubing string through the tubing hanger lowering tool, the open water tubing hanger lifting tool, and the tubing hanger release module.

[0114] According to some embodiments of this disclosure, operation S4 includes: unlocking the wellhead via hydraulic control of the umbilical cable and recovering the wellhead and abandoned wellhead (BOP) via a well abandonment lifting tool.

[0115] According to some embodiments of this disclosure, operation S1 further includes sub-operations S101 to S107.

[0116] According to some embodiments of this disclosure, sub-operation S101 includes assembling the grease injection blowout preventer and the oil pipe hanger, wherein a wire rope passes through a pressure control head and is connected to a wire rope tool kit.

[0117] According to some embodiments of this disclosure, sub-operation S102 includes: lowering the grease injection blowout preventer and tubing hanger connecting sleeve into the abandoned well (BOP) using a wire rope until the tubing hanger sealing head at the lower end of the tubing hanger connecting sleeve is locked with the tubing hanger.

[0118] According to some embodiments of this disclosure, sub-operation S103 includes: closing the lower gate of the abandoned well BOP, and then closing the upper gate of the abandoned well BOP using a low shutdown operation pressure, wherein the grease injection blowout preventer is slidable relative to the upper gate.

[0119] According to some embodiments of this disclosure, sub-operation S104 includes: releasing the lock between the grease injection blowout preventer and the oil pipe connecting sleeve, lifting the grease injection blowout preventer until the interface sleeve is mechanically locked below the upper gate blowout preventer, and closing the upper gate using a high closing operation pressure, wherein a seal is formed between the upper gate and the grease injection blowout preventer.

[0120] According to some embodiments of this disclosure, sub-operation S105 includes: lowering the wire rope tool kit into the tubing hanger connection sleeve, positioning and locking it on the tubing hanger plug and unlocking the tubing hanger plug, and lifting the wire rope tool kit into the grease injection blowout preventer.

[0121] According to some embodiments of this disclosure, sub-operation S106 includes: closing the annular blowout preventer of the abandoned well (BOP), opening the upper gate, raising the grease injection blowout preventer pipe until the lower end of the grease injection blowout preventer pipe extends above the blind flange blowout preventer, and closing the blind flange blowout preventer.

[0122] According to some embodiments of this disclosure, sub-operation S107 includes: opening the annular blowout preventer, lifting the grease injection blowout preventer pipe through open water, and completing the retrieval of the oil pipe with the plug attached.

[0123] According to some embodiments of this disclosure, the tubing plug includes an upper tubing plug and a lower tubing plug. The upper tubing plug is first retrieved through operations S101 to S107, and then the lower tubing plug is retrieved through operations S102 to S107.

[0124] According to some embodiments of this disclosure, operation S2 further includes sub-operations S201 to S203.

[0125] According to some embodiments of this disclosure, sub-operation S201 includes controlling the well fluid level, including injecting or pumping well fluid into the well.

[0126] According to some embodiments of this disclosure, sub-operation S202 includes: pumping kill fluid into the production tubing from below the lower gate and finally into the reservoir.

[0127] According to some embodiments of this disclosure, sub-operation S203 includes: plugging the wellbore.

[0128] According to some embodiments of this disclosure, operation S3 further includes sub-operations S301 to S303.

[0129] According to some embodiments of this disclosure, sub-operation S301 includes assembling the tubing lowering tool and the open water tubing lifting tool.

[0130] According to some embodiments of this disclosure, sub-operation S302 includes: lowering the tubing hanger into the abandoned well (BOP), positioning and locking the lower end of the tubing hanger.

[0131] According to some embodiments of this disclosure, sub-operation S303 includes: releasing the lock between the tubing hanger and the wellhead, and completing the recovery operation of the tubing hanger and production tubing string using an open water tubing hanger lifting tool.

[0132] According to some embodiments of this disclosure, operation S4 further includes sub-operations S401 to S401.

[0133] According to some embodiments of this disclosure, sub-operation S401 includes: connecting the hydraulic control umbilical cable to the abandoned wellhead (BOP) and releasing the lock between the wellhead and the wellhead.

[0134] According to some embodiments of this disclosure, sub-operation S402 includes: locking and lifting the abandoned well BOP and abandoned well lifting tool to complete the recovery of the wellhead and abandoned well BOP.

[0135] Figure 7 This is a schematic diagram of the structure of the grease injection blowout preventer and tubing hanger connecting sleeve for recovering the upper tubing hanger plug in an offshore oil well abandonment operation system according to an exemplary embodiment of the present disclosure. Figures 8-12 yes Figure 7 The diagram shows the structure of the abandoned well BOP, grease injection blowout preventer, and tubing hanger during each stage of the recovery process. Figures 13-15 This is a schematic diagram of the various stages of the recovery tubing hanger and production tubing string of an offshore oil well abandonment operation system according to exemplary embodiments of the present disclosure; Figure 16 This is a schematic diagram of the structure of the wellhead and BOP recovery process of an offshore oil well abandonment operation system according to exemplary embodiments of the present disclosure.

[0136] To more clearly describe the offshore oil well abandonment operation system and method according to the embodiments of this disclosure, the following description is based on specific embodiments and accompanying drawings. Figures 7-16 The working process will be further explained.

[0137] Example 1

[0138] The offshore oil well abandonment operation system disclosed in the above embodiments of this disclosure is installed on the tree 17, and the tree 17 is connected to the high-pressure wellhead 60.

[0139] Recycle the oil pipe plug.

[0140] like Figure 7 As shown, the tubing is lowered through the wellbore BOP12 via the connecting sleeve 21 and the grease-filled blowout preventer 22 with the wire rope tool kit 24, and the tubing is retrieved by attaching the plug 58. The wire rope tool kit 24 is attached to the wire rope 23, and is used to lower the tool kit 24 into or retrieve it from the wellbore BOP12. At the top of the grease-filled blowout preventer 22, the wire rope 23 passes through the pressure control head 25. The pressure control head 25 provides a pressure seal between the working wire rope 23 and the grease-filled blowout preventer 22.

[0141] like Figure 8 As shown, the tubing hanger connector 21 and the grease-filled blowout preventer 22 with the wire rope tool kit 24 are lowered through the abandoned well BOP12. The tubing hanger connector 21 is lowered until the tubing hanger positioning module 30 and the tubing hanger sealing head 29 are locked into the tubing hanger 35 (positioned using the tubing hanger interface sleeve positioning pin 47). At this time, the wire rope tool kit 24 is still inside the grease-filled blowout preventer 22. The lower gate BOP45 will close the BOP gate sealing surface 31 to prevent well pressure that may be generated when the tubing hanger is retrieved and the plugger 58 is applied.

[0142] like Figure 9 As shown, the upper gate 44 is closed near the grease-filled blowout preventer 22 using a low shut-off operating pressure, allowing the grease-filled blowout preventer 22 to slide upwards, unlocking the interface sleeve mechanical lock 27 from the grease-filled blowout preventer locking support 32. The grease-filled blowout preventer 22 is lifted until the interface sleeve mechanical lock 27 stops below the upper gate 44. Then, the upper gate 44 is closed using a high shut-off operating pressure. This creates a high-pressure seal between the grease-filled blowout preventer 22 and the abandoned well BOP12 below the upper gate 44. At this point, the pressure control head 25 of the grease-filled blowout preventer 22, the upper gate 44, and the lower gate 45 completely seal the well. Next, the wireline tool kit 24 is lowered into the tubing hanger connection sleeve 21, positioned and locked onto the tubing hanger plug 58, and then unlocked. The tubing hanger plug 58 is then safely retrieved. During this process, the sealed abandoned well BOP12 controls the pressure or leakage in the tubing hanger.

[0143] like Figure 10 As shown, the tubing cap plug 58 is retrieved from the abandoned well BOP12, which remains closed. After the tubing cap plug 58 is unlocked from the tubing hanger 35 and it is confirmed that there is no pressure leakage from the tubing cap packer, the wireline tool kit 24 with the tubing cap plug 58 is retrieved into the grease-filled blowout preventer 22. For safety, the BOP annular blowout preventer 42 is closed around the wireline 23, and the upper gate 44 is opened. Next, the grease-filled blowout preventer 22 is raised so that its lower end is above the BOP blind flange blowout preventer 43, and for safety, the blind flange blowout preventer 43 is closed.

[0144] The grease-injected blowout preventer 22 and the tubing hanger connector 21 are deployed together in the open water area. The tubing hanger connector 21 is positioned, locked, and sealed within the tubing hanger 35. The lower gate 45 at the bottom of the abandoned well BOP12 closes near the grease-injected blowout preventer 22, forming a pressure seal between the production string 36 and the open water area to control the whole-well pressure, facilitating the use of the wireline tool kit 24 within the production string.

[0145] like Figure 11 As shown, open the BOP annular blowout preventer 42, lift the grease injection blowout preventer pipe 22 through the open water recovery oil pipe and attach the plug 58 to the offshore support vessel.

[0146] like Figure 12 As shown, the grease-injected blowout preventer (BOP) 22 is inserted into the abandoned well BOP12 to retrieve the tubing hanger plug 59, following the procedure described above for retrieving the tubing hanger plug 58. When both tubing hanger plugs (upper tubing hanger 58 and lower tubing hanger 59) have been retrieved and the well is in the open state, the grease-injected BOP 22 is used to perform a permanent or temporary well abandonment operation on the production well. During well abandonment operations using various wireline tools, the abandoned well BOP and the grease-injected BOP 22 are used to seal the well.

[0147] like Figure 6 As shown, the abandoned well BOP12 is equipped with numerous circulation lines for well abandonment operations. Volume control is established using the well fluid / seawater interconnection level 56 in the well fluid level control unit 40, and well fluid is injected or pumped into the well fluid level control unit 40 using the well fluid level control pump 14. The downhole safety valves in the production tree 17 and production tubing 36 are opened, and kill fluid is pumped in using the high circulation line 52. The kill fluid enters the production tubing 36 from below the upper gate 44 and finally enters the reservoir. After kill, the pressure is controlled by the grease-injected blowout preventer 22, and the wireline tool kit 24 is deployed for plugging and other operations, such as: drilling tubing above the production packer; injecting kill fluid into the annulus; cementing into the reservoir; setting the mechanical bridge plug at the production packer location and pressure testing; cementing the plug above the production packer and pressure testing; cutting tubing above the cement plug; confirming 100% tubing cut; and cementing the top plug and pressure testing.

[0148] When the wire rope is pulled or sheared, the pressure control head 25 provides a high-pressure seal to the wire rope 23. In the event of an emergency disconnection, the wire rope clamp automatically clamps the pulled or sheared wire rope to prevent it from falling into the production tubing 36, and the lifting of the grease injection blowout preventer 22 can retrieve the pulled or sheared wire rope 23 onto the offshore support vessel 2.

[0149] Recycle tubing hangers and production tubing strings.

[0150] like Figure 13As shown, to recover the tubing hanger 35 and production string 36, the tubing hanger lowering tool 34 is first connected to the open water tubing hanger lifting tool 33, which is mounted on the ship crane lifting tool string 38. Next, the tubing hanger recovery system is lowered into the abandoned well (BOP), automatically positioned, and locked onto the tubing hanger 35. To unlock the tubing hanger 35 from the wellhead 17, a tubing hanger release module 18 is installed on top of the well fluid level control unit 40. The climbing positioning pin 54 is locked onto the tubing hanger lifting tool 33 rod in the seawater, and the tubing hanger 35 is unlocked from the wellhead 17.

[0151] like Figure 14 As shown, a deep-water crane is used to retrieve the tubing hanger 35 and production tubing string 36 to the offshore support vessel 2.

[0152] like Figure 15 As shown, the offshore support vessel 2 is a device for unhooking and horizontally placing the recovered production tubing 36. During the recovery of the production tubing, the well fluid level will decrease as the tubing is pulled out. The well fluid level control pump 14 is used to inject well fluid into the well fluid level control unit 40 to maintain a constant well fluid level and the required hydrostatic pressure.

[0153] Recover wellheads and abandoned well platelets (BOPs).

[0154] like Figure 16 As shown, the hydraulic control umbilical cable 63 is connected to the abandoned well BOP12, and the production tree 17 is unlocked from the wellhead 60; then the BOP lifting tool 62 is locked to the abandoned well BOP12, and the entire assembly is then lifted and retrieved onto the offshore support vessel 2.

[0155] The embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. It should be noted that implementations not illustrated or described in the drawings or the main text of the specification are forms known to those skilled in the art and have not been described in detail. Furthermore, the definitions of the various components described above are not limited to the specific structures, shapes, or methods mentioned in the embodiments, and those skilled in the art can easily modify or substitute them.

[0156] It should also be noted that, in the specific embodiments of this disclosure, unless otherwise stated otherwise, the numerical parameters in this specification and the appended claims are approximate values ​​and can be changed according to the desired characteristics obtained from the content of this disclosure. Specifically, all numbers used in the specification and claims to indicate dimensions, range conditions, etc., of the composition should be understood to be modified by the term "about" in all cases. Generally, this means that there may be variations of ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments.

[0157] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0158] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A system for abandoning offshore oil wells, characterized in that, include: Abandoned well BOP is suitable for installation on the well tree of wells to be abandoned. A grease injection blowout preventer (BOP) is lowered to the abandoned well (BOP) via a wire rope for well abandonment operations. The grease injection BOP includes: tube body; A pressure control head is disposed at the upper part of the pipe body, wherein the wire rope passes through the pressure control head, and the pressure control head is adapted to maintain a dynamic seal during the raising and lowering of the wire rope in the well; A wire rope tool bag is slidably disposed inside the tube, and the wire rope tool bag is connected to the wire rope. The wire rope tool bag can select matching tools according to the operation requirements. During the well abandonment process, the grease injection blowout preventer and the well abandonment BOP work together to control the wellbore pressure; Open water pipeline hoisting equipment includes a ship crane hoisting tool string, ROV shut-off valve, and ROV cement hose bracket; The connecting rod is connected at one end to the open water pipeline hoisting tool; A tubing hanger lowering tool is connected to the other end of the connecting rod; the tubing hanger lowering tool is suitable for locking the tubing hanger; and The tubing hanger release module is located above the well fluid level control unit. The tubing hanger release module is used to release the locking of the tubing hanger to the well tree, so that the production tubing string can be freely suspended.

2. The offshore oil well abandonment operation system according to claim 1, characterized in that, Also includes: The oil pipe hanger connecting sleeve has its upper end connected to the lower end of the pipe body, and its lower end is provided with an oil pipe hanger sealing head, which is suitable for docking with the oil pipe hanger.

3. The offshore oil well abandonment operation system according to claim 1, characterized in that, Also includes: In an emergency, the BOP manifold is disconnected and connected to the abandoned well BOP via the high circulation pipeline, medium circulation pipeline, and low circulation pipeline to form three circulation loops; The abandoned well circulation hose is connected at one end to the emergency disconnect module and at the other end to the boat; as well as The blowout preventer control umbilical cable is clamped at the top to the steel wire rope of the emergency disconnect tension system, and connected at the bottom to the emergency disconnect module.

4. The offshore oil well abandonment operation system according to claim 1, characterized in that, Also includes: Well fluid level control unit, including: The well fluid level sensor is located below the well fluid level control unit. An ROV bracket for the suction / injection hose is installed above the well fluid level sensor; The well fluid level control pump is connected to the well fluid level control unit via a well fluid level control hose; The well fluid level control pump is a bidirectional pump. When the tubing string is lowered, the well fluid is pumped out from the well fluid level control unit, and when the tubing string is retrieved, the well fluid is pumped back into the well to maintain the well fluid level.

5. A method for abandoning an offshore oil well, characterized in that, Using the offshore well abandonment operation system as described in any one of claims 2 to 4, the method includes the operation of: Operation S1: Retrieve the tubing plug using the grease-injected blowout preventer, tubing hanger connector, wire rope tool kit, and abandoned well BOP; Operation S2: Kill the well and use the grease blowout preventer, wire rope tool kit and abandoned well BOP for plugging operations; Operation S3: Unlock the tubing hanger and recover the tubing hanger and production tubing string using the tubing hanger lowering tool, open water tubing hanger lifting tool, and tubing hanger release module; as well as Operation S4: Unlock the wellhead via hydraulic control using the umbilical cable, and recover the wellhead and abandoned BOP using the well abandonment hoisting tool, including: S401: Connect the hydraulic control umbilical cable to the abandoned well BOP to release the lock between the wellhead and the wellhead; S402: Lock the abandoned well BOP and the abandoned well lifting tool and lift them up to complete the recovery of the wellhead and abandoned well BOP.

6. The method for abandoning offshore oil wells according to claim 5, characterized in that, Operation S1 includes sub-operations: S101: Assemble the grease injection blowout preventer and the oil pipe hanging connection sleeve, wherein the wire rope passes through the pressure control head and is connected to the wire rope tool bag; S102: The grease injection blowout preventer and the tubing hanger connecting sleeve are lowered into the abandoned well BOP by the wire rope until the tubing hanger sealing head at the lower end of the tubing hanger connecting sleeve is locked with the tubing hanger. S103: Close the lower gate of the abandoned well BOP, and then close the upper gate of the abandoned well BOP using a low shutdown operation pressure, wherein the grease injection blowout preventer pipe can slide relative to the upper gate; S104: Release the lock between the grease injection blowout preventer and the oil pipe connecting sleeve, lift the grease injection blowout preventer until the interface sleeve is mechanically locked below the upper gate blowout preventer, and close the upper gate using high closing operation pressure, wherein a seal is formed between the upper gate and the grease injection blowout preventer; S105: Lower the wire rope tool bag into the tubing hanger connecting sleeve, position and lock it on the tubing hanger plug, and unlock the tubing hanger plug. Then, lift the wire rope tool bag into the grease injection anti-blowout pipe. S106: Close the annular blowout preventer (BOP) of the abandoned well, open the upper gate valve, raise the grease injection BOP until its lower end exceeds the blind flange BOP, and close the blind flange BOP; and S107: Activate the annular blowout preventer, lift the grease injection blowout preventer pipe through the open water area, and complete the retrieval of the oil pipe plug.

7. The method for abandoning offshore oil wells according to claim 5, characterized in that, Operation S2 includes sub-operations: S201: Volume control of well fluid, including injecting or pumping well fluid into the well; S202: Pump in kill fluid, which enters the production tubing from below the lower gate and finally enters the reservoir; and S203: Seal the wellbore.

8. The method for abandoning offshore oil wells according to claim 5, characterized in that, Operation S3 includes sub-operations: S301: Assemble the tubing lowering tool and the open water tubing lifting tool; S302: Lower the tubing hanger into the abandoned well BOP, and position and lock the lower end of the tubing hanger onto the well; and S303: Release the lock between the tubing hanger and the wellhead, and complete the recovery operation of the tubing hanger and production tubing string using the open water tubing hanger lifting tool.

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