Oil extraction system adopting dry type Christmas tree in underwater closed caisson and well drilling and completion method

Abstract

The invention relates to the technical field of Christmas trees, and discloses an oil production system adopting a dry-type Christmas tree in an underwater closed caisson and a drilling and completion method.The Christmas tree system comprises the caisson, the dry-type Christmas tree and a lifting short section, an opening is formed in the bottom of the caisson, the dry-type Christmas tree is installed in the caisson, the dry-type Christmas tree is provided with a main channel, and the lifting short section is connected with the caisson. One end of the lifting short section is connected with the top of the dry type Christmas tree, the other end of the lifting short section extends out of the caisson and is provided with a first connecting part, a blanking plug is arranged in the lifting short section, a waterproof sleeve with one end connected with the dry type Christmas tree is arranged at the bottom of the dry type Christmas tree, and the other end of the waterproof sleeve is connected with the opening side; a first connector is further arranged at the bottom of the dry-type Christmas tree, located in the waterproof sleeve and communicated with the main channel, the dry-type Christmas tree is provided with an oil outlet pipe, the oil outlet pipe extends out of the caisson, and the circumferential face of the oil outlet pipe is connected with the caisson in a sealed mode. According to the invention, the dry-type Christmas tree can perform well drilling and completion operation on the seabed, so that the cost of equipment is saved to a great extent.

Description

Technical Field

[0001] The present invention relates to the technical field of Christmas trees, and more particularly to an oil production system and a drilling and completion method using a dry Christmas tree in an underwater sealed caisson. Background Art

[0002] The conventional method for developing deepwater offshore oil and gas fields is to use subsea wellheads and Christmas trees for drilling, completion, and production operations. During the drilling and completion process, a semi-submersible drilling platform or drillship is used. A subsea blowout preventer is used to establish a wellhead on the seabed to complete the drilling and completion operations. Subsea Christmas trees are then installed for production. Conventional subsea Christmas trees cost millions of US dollars and are completely imported. Dry Christmas trees, however, are readily available in China for only a few hundred thousand RMB. The price of subsea wellheads and Christmas trees is tens or even hundreds of times higher than that of dry ones. However, dry wellheads and Christmas trees are currently unsuitable for subsea operations and production due to limitations such as sealing and remote control. Summary of the Invention

[0003] The present invention aims to overcome the problem in the prior art that dry Christmas trees cannot be used for underwater oil production operations. It provides an oil production system and drilling and completion method using a dry Christmas tree in an underwater sealed caisson, thereby converting the underwater Christmas tree into a dry Christmas tree and significantly saving equipment costs.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: Provided is an oil production system using a dry Christmas tree in an underwater sealed caisson, comprising a caisson, a dry Christmas tree, and a riser sub. The caisson has an opening at its bottom adapted for use with a high-pressure wellhead. The dry Christmas tree is installed in the caisson. The dry Christmas tree has a main passage. One end of the riser sub is connected to the top of the dry Christmas tree and communicates with the main passage. The other end of the riser sub extends out of the caisson and has a first connection portion for connection to an underwater blowout preventer. The circumference of the riser sub is sealed with the caisson. A plug is provided inside the riser sub. A water-blocking sleeve having one end connected thereto is provided at the bottom of the dry Christmas tree, the other end of the water-blocking sleeve being connected to the opening. A first connector for connection to a high-pressure wellhead is also provided at the bottom of the dry Christmas tree. The first connector is located within the riser sub and communicates with the main passage. The dry Christmas tree has an oil flow pipe, which extends out of the caisson and has a circumference sealed with the caisson.

[0005] In the technical solution of the present application, the entire oil production system is lowered to the seabed, an opening is set on the outer periphery of the conduit at the high-pressure wellhead, and a first connector is used to connect to the high-pressure wellhead and achieve a seal, so that the high-pressure wellhead is connected to the main channel; the deepwater drilling rig lowers the interconnected underwater blowout preventer and watertight pipe, and the underwater blowout preventer is connected to the first connection part of the rising short section to establish a seal and circulation channel in the well, and then the plug in the rising short section is removed; the lower wellbore is continued to be drilled and completion operations are carried out until the oil pipe hanger and production tubing are lowered, so that the oil pipe hanger is sealed in the dry oil production tree and sealed with the oil production tree body; the plug is re-lowered to seal the rising short section, and the underwater blowout preventer and isolation pipe are moved to wait for production. In the technical solution of the present application, the dry oil production tree can be drilled and completed on the seabed by using the caisson, rising short section, plug and first connector, which greatly saves the cost of equipment.

[0006] Furthermore, the first connector is hydraulically controlled or pneumatically controlled, and the first connector is connected to the high-pressure wellhead under the action of an underwater robot.

[0007] Furthermore, the underwater blowout preventer is provided with a second connector at one end connected to the rising nipple, and the other end of the underwater blowout preventer is connected to a riser.

[0008] Furthermore, the second connector is hydraulically controlled or pneumatically controlled, and the second connector is connected to the first connection portion under the action of the underwater robot.

[0009] Furthermore, a water pump is installed in the caisson, the water pump is connected to a power supply, the water outlet of the water pump is connected to a water outlet pipe, the water outlet pipe extends out of the caisson, and the circumference of the water outlet pipe is sealed with the caisson.

[0010] Furthermore, a sealing ring is provided at the opening of the caisson.

[0011] Furthermore, the connection type between the first connector and the high-pressure wellhead is H4 type.

[0012] Furthermore, the connection type between the first connection part and the underwater blowout preventer is H4 type.

[0013] Another aspect of the present invention provides a drilling and completion method using a dry Christmas tree in an underwater sealed caisson, using the above-mentioned oil production system, the drilling and completion method comprising: S1: Using a deepwater drilling rig to lower a guide tube, continue drilling a wellbore in the guide tube, lower a casing and a high-pressure wellhead into the wellbore, place the high-pressure wellhead on top of the guide tube, and cement the well; S2: The production main valve and the annulus main valve of the dry oil tree are closed, the oil production system is lowered so that the opening is sleeved on the outer periphery of the guide tube, and the first connector is connected to the high-pressure wellhead by an underwater robot and sealed; S3: After the subsea production system is installed, the riser and subsea blowout preventer are lowered, the subsea blowout preventer is docked with the first connection of the riser sub, the plug in the riser sub is removed using a slickline, and drilling and completion operations are continued; S4: After the drilling and completion operation is completed, the production tubing string and tubing hanger are lowered using the drill pipe and the lowering tool to seal the tubing hanger with the dry Christmas tree. Then, a plug is lowered into the riser sub using a wireline operation. S5: After verifying the sealing of the plug, remove the connection between the first connection part and the underwater blowout preventer, and pull out the riser and the underwater blowout preventer.

[0014] Furthermore, after step S5, the method further includes the following steps: opening the production main valve and the annulus main valve of the dry Christmas tree, while the XOV valve of the dry Christmas tree remains in a closed state, to carry out production.

[0015] Compared with the prior art, the present invention has the following advantages: in the present invention, the use of a caisson, a rising nipple, a plug, and a first connector enables a dry-type Christmas tree to be drilled and completed on the seabed, thereby greatly saving equipment costs; it also eliminates the sealing inspection process during the installation of the underwater Christmas tree, thereby improving operational efficiency, reducing operational costs, and alleviating the many risks associated with pressure testing operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of an oil production system using a dry-type Christmas tree in an underwater sealed caisson according to the present invention; Figure 2 The present invention is a flow chart of a well drilling and completion method using a dry Christmas tree in an underwater sealed caisson.

[0017] In the attached figure: 1. caisson; 2. dry Christmas tree; 3. rising nipple; 4. underwater blowout preventer; 5. plug; 6. first connector; 7. high-pressure wellhead; 8. guide tube; 9. riser sleeve; 10. production main valve; 11. annulus main valve; 12. riser; 14. production tubing string; 15. tubing hanger; 16. XOV valve. DETAILED DESCRIPTION

[0018] The present invention is further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only and are schematic, not actual, representations. They should not be construed as limiting this patent. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted from the drawings.

[0019] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0020] Example 1 like Figure 1 As shown, an oil production system using a dry Christmas tree in an underwater sealed caisson includes a caisson 1, a dry Christmas tree 2, and a rising sub 3. The bottom of the caisson 1 is provided with an opening adapted to a high-pressure wellhead 7. The dry Christmas tree 2 is installed in the caisson 1. The dry Christmas tree 2 has a main channel. One end of the rising sub 3 is connected to the top of the dry Christmas tree 2 and communicates with the main channel. The other end of the rising sub 3 extends out of the caisson 1 and has a first connection portion for connecting to an underwater blowout preventer 4. The rising sub 3 The circumference of the dry Christmas tree 2 is sealed and connected to the caisson 1. A plug 5 is provided inside the lifting short section 3. The bottom of the dry Christmas tree 2 is provided with a water-blocking sleeve 9 with one end connected thereto. The other end of the water-blocking sleeve 9 is connected to the opening side. The bottom of the dry Christmas tree 2 is also provided with a first connector 6 for connecting to the high-pressure wellhead 7. The first connector 6 is located in the water-blocking sleeve 9 and is connected to the main channel. The dry Christmas tree 2 has an oil outlet pipe, which extends out of the caisson 1 and the circumference of the oil outlet pipe is sealed and connected to the caisson 1.

[0021] In this embodiment, the oil production system is lowered to the seabed as a whole, and the opening is set on the outer periphery of the conduit 8 at the high-pressure wellhead 7. The first connector 6 is used to connect with the high-pressure wellhead 7 and seal it so that the high-pressure wellhead 7 is connected to the main channel; the deep-water drilling rig lowers the interconnected underwater blowout preventer 4 and the watertight pipe 12, and the underwater blowout preventer 4 is connected to the first connection part of the rising short section 3 to establish a seal and circulation channel in the well, and then the plug 5 in the rising short section 3 is removed; the lower wellbore is continued to be drilled, and completion operations are carried out until the oil pipe hanger 15 and the production tubing string 14 are lowered, so that the oil pipe hanger 15 is sealed in the dry oil production tree 2 and sealed with the oil production tree body; the plug 5 is lowered again to seal the rising short section 3, and the underwater blowout preventer 4 and the isolation pipe are moved to wait for production. Since the bottom of the dry oil production tree 2 is provided with a waterproof sleeve 9 with one end connected to it, and the other end of the waterproof sleeve 9 is connected to the opening side, during the process of lowering seawater into the caisson 1, the seawater enters the waterproof sleeve 9 through the opening at the bottom of the caisson 1, and then enters the main channel through the first connector 6 provided in the waterproof sleeve 9, thereby preventing seawater from entering the caisson 1.

[0022] It should be noted that in this embodiment, the dry Christmas tree 2 can be a horizontal Christmas tree. The first connector 6 and the high-pressure wellhead 7 have the same connection type. The first connector 6 is a subsea wellhead connector. When connected to the high-pressure wellhead 7, the high-pressure wellhead 7 can communicate with the main channel. Subsea wellhead connectors are conventional technology, and therefore the specific structure of the subsea wellhead connector is not described in detail in this embodiment. The structure of the subsea wellhead connector can refer to the structure of the subsea wellhead connector disclosed in Publication No. "CN107013176 A," but is not limited to the structure disclosed in Publication No. "CN107013176 A." It should also be noted that the riser sub 3 can be integrated with the main channel of the dry Christmas tree 2 or connected to the top of the dry Christmas tree 2 via a flange. A mounting hole is provided on the caisson 1 , the lifting short circuit is passed through the mounting hole, and the lifting short section 3 is sealedly connected to the caisson 1 by welding, so that a part of the lifting short section 3 is located inside the caisson 1 and a part of the lifting short section 3 extends out of the caisson 1 .

[0023] The first connector 6 is hydraulically or pneumatically controlled, and the underwater robot connects the first connector 6 to the high-pressure wellhead 7. In this embodiment, the first connector 6 is hydraulically or pneumatically controlled for locking and unlocking. The underwater robot inserts a pressure tool (hot spur) into the pressure port to lock the first connector 6 and the high-pressure wellhead 7; the underwater robot removes the pressure tool (hot spur) from the pressure port to unlock the first connector 6 and the high-pressure wellhead 7.

[0024] In addition, the underwater blowout preventer 4 is provided with a second connector at one end connected to the riser sub 3. The other end of the underwater blowout preventer 4 is connected to the riser 12. In this embodiment, the second connector has the same connection type as the first connector and is also a subsea wellhead connector. Subsea wellhead connectors are conventional technology, so the specific structure of the subsea wellhead connector is not detailed in this embodiment. The structure of the subsea wellhead connector can refer to the structure of the subsea wellhead connector disclosed in Publication No. "CN107013176 A," but is not limited to the structure disclosed in that publication. It should be noted that the subsea blowout preventer 4 and the riser 12 can be connected using a flange and bolts.

[0025] The second connector is hydraulically or pneumatically controlled, and the underwater robot connects the second connector to the first connection portion. In this embodiment, the second connector is hydraulically or pneumatically controlled for locking and unlocking. By inserting a pressure tool (hot spur) into the pressure port via the underwater robot, the second connector is locked to the first connection portion of the lifting sub 3; by removing the pressure tool (hot spur) from the pressure port via the underwater robot, the second connector is unlocked from the first connection portion of the lifting sub 3.

[0026] In addition, a water pump is installed in the caisson 1, and the water pump is connected to a power source. The water outlet of the water pump is connected to a water outlet pipe, which extends out of the caisson 1, and the circumference of the water outlet pipe is sealed with the caisson 1. In this embodiment, as the caisson 1 is lowered to the seabed, some water will enter the interior of the caisson 1 through the opening at the bottom of the caisson 1. After the first connector 6 is connected to the high-pressure wellhead 7, one end of the water outlet pipe is connected to the water outlet of the water pump through the water pump provided in the caisson 1, and the other end of the water outlet pipe is provided outside the caisson 1. The water in the caisson 1 can be discharged from the caisson 1 by the action of the water pump. It should also be noted that the power source located in the caisson 1 is a waterproof power source, and the outer periphery of the power source is coated with a material that is resistant to seawater erosion and waterproof. Under the erosion of seawater, the power source will not be damaged.

[0027] A sealing ring is also provided at the opening of the caisson 1. It should be noted that after the Christmas tree system is lowered, when the opening is fitted over the outer circumference of the conduit 8, the sealing ring maintains sealed contact with the outer circumference of the conduit 8, thereby preventing seawater from entering the interior of the caisson 1 and ensuring the airtightness of the interior of the caisson 1.

[0028] Furthermore, the connection between the first connector 6 and the high-pressure wellhead 7 is of the H4 type. In this embodiment, the H4 type joint uses a threaded extrusion and sealing ring sealing method, of which the H-type 24° cone seal is the most commonly used type. This design effectively prevents leakage and ensures a tight connection between the first connector 6 and the high-pressure wellhead 7.

[0029] The connection between the first connection portion and the underwater blowout preventer 4 is an H4 type. In this embodiment, the H4 type joint uses a threaded extrusion and sealing ring sealing method, of which the H-type 24° cone seal is the most commonly used type. This design can effectively prevent leakage and ensure the airtightness of the connection between the first connection portion and the underwater blowout preventer 4.

[0030] Example 2 like Figure 2 As shown, a drilling and completion method using a dry oil tree in an underwater sealed caisson is applied to the oil production system in the above embodiment 1. The drilling and completion method includes: S1: Use a deepwater drilling rig to lower the guide tube 8, continue drilling the wellbore in the guide tube 8, lower the casing and the high-pressure wellhead 7 into the wellbore, place the high-pressure wellhead 7 on the top of the guide tube 8 and cement the well.

[0031] In step S1, the deepwater drilling rig is a semi-submersible drilling platform or a deepwater drilling ship. The deepwater drilling rig jets into a 30-inch guide tube 8, and then continues to drill a 17-1 / 2-inch wellbore. A 13-3 / 8-inch casing and a high-pressure wellhead 7 are run into the wellbore so that the high-pressure wellhead 7 is seated on the top of the guide tube 8, and then cementing operations are performed.

[0032] S2: The production main valve 10 and the annulus main valve 11 of the dry oil tree 2 are closed, and the oil production system is lowered so that the opening is sleeved on the outer periphery of the guide tube 8. The first connector 6 is connected to the high-pressure wellhead 7 by an underwater robot and sealed.

[0033] In step S2, the plug 5 of the lifting sub 3 has a sealing effect, preventing seawater from entering the caisson 1 through the lifting sub 3 during the lowering of the oil production system. After the opening is sleeved on the outer periphery of the guide tube 8, the first connector 6 faces the high-pressure wellhead 7. The drill pipe and underwater robot are used to connect the first connector 6 to the high-pressure wellhead 7 and seal it.

[0034] S3: After the underwater oil production system is installed, the riser 12 and the underwater blowout preventer 4 are lowered, and the underwater blowout preventer 4 is docked with the first connection part of the lifting short section 3. The plug 5 in the lifting short section 3 is removed by wire operation, and the drilling and completion operation is continued.

[0035] In this embodiment, after connecting the subsea BOP 4 to the first connection of the riser sub 3, the plug 5 is removed, allowing the riser 12, subsea BOP 4, riser sub 3, the main channel of the dry tree 2, the channel of the first connector 6, the high-pressure wellhead 7, and the casing to communicate, facilitating subsequent drilling and completion operations. Specifically, drilling of the lower wellbore is continued, another corresponding casing is run, and completion operations are performed.

[0036] S4: After the drilling and completion operation is completed, the production tubing string 14 and the tubing hanger 15 are lowered using the drill pipe and the lowering tool to seal the tubing hanger 15 with the dry oil production tree 2. Then, the plug 5 is lowered into the lifting short section 3 using a steel wire operation.

[0037] In step S4, the production string 14 is connected to the tubing hanger 15, and the production string 14 is located below the tubing hanger 15. The tubing hanger 15 is provided with a positioning and sealing device, which can cooperate with the dry oil tree 2 to achieve sealing.

[0038] S5: After verifying that the plug 5 is sealed, the connection between the first connection part and the underwater blowout preventer 4 is removed, and the riser 12 and the underwater blowout preventer 4 are pulled out.

[0039] Example 3 The difference between Example 3 and Example 2 is that, in this embodiment, after step S5, the following steps are further included: opening the production main valve 10 and the annulus main valve 11 of the dry Christmas tree 2, while the XOV valve 16 of the dry Christmas tree 2 remains in the closed state, and production is carried out.

[0040] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. An oil production system using a dry-type Christmas tree in an underwater sealed caisson, characterized in that: The invention comprises a caisson (1), a dry oil tree (2) and a rising short section (3), wherein the bottom of the caisson (1) is provided with an opening adapted to a high-pressure wellhead (7), the dry oil tree (2) is installed in the caisson (1), the dry oil tree (2) has a main channel, one end of the rising short section (3) is connected to the top of the dry oil tree (2) and communicates with the main channel, the other end of the rising short section (3) extends out of the caisson (1) and has a first connection portion for connecting to an underwater blowout preventer (4), and the circumference of the rising short section (3) is sealed and connected to the caisson (1). The interior of the lifting short section (3) is provided with a plug (5), the bottom of the dry oil tree (2) is provided with a water-blocking sleeve (9) with one end connected thereto, the other end of the water-blocking sleeve (9) is connected to the opening side, and the bottom of the dry oil tree (2) is also provided with a first connector (6) for connecting to a high-pressure wellhead (7), the first connector (6) is located in the water-blocking sleeve (9) and is connected to the main channel, the dry oil tree (2) has an oil outlet pipe, the oil outlet pipe extends out of the caisson (1) and the peripheral surface of the oil outlet pipe is sealed and connected to the caisson (1).

2. The oil production system using a dry type Christmas tree in an underwater closed caisson according to claim 1, characterized in that: The first connector (6) is hydraulically controlled or pneumatically controlled, and the first connector (6) is connected to the high-pressure wellhead (7) under the action of an underwater robot.

3. The oil production system using a dry type Christmas tree in an underwater closed caisson according to claim 1, characterized in that: The underwater blowout preventer (4) is provided with a second connector at one end connected to the lifting short section (3), and the other end of the underwater blowout preventer (4) is connected to a watertight pipe (12).

4. The oil production system using a dry type Christmas tree in an underwater closed caisson according to claim 3, characterized in that: The second connector is hydraulically controlled or pneumatically controlled, and the second connector is connected to the first connection portion under the action of the underwater robot.

5. The oil production system using a dry type Christmas tree in an underwater sealed caisson according to claim 1, characterized in that: A water pump is installed in the caisson (1), the water pump is connected to a power source, a water outlet end of the water pump is connected to a water outlet pipe, the water outlet pipe extends out of the caisson (1), and the peripheral surface of the water outlet pipe is sealed with the caisson.

6. The oil production system using a dry type Christmas tree in an underwater sealed caisson according to claim 1, characterized in that: A sealing ring is also provided at the opening of the caisson (1).

7. The oil production system using a dry type Christmas tree in an underwater sealed caisson according to claim 1, characterized in that: The connection type between the first connector (6) and the high-pressure wellhead (7) is both H4 type.

8. The oil production system using a dry type Christmas tree in an underwater sealed caisson according to claim 1, characterized in that: The connection type between the first connection part and the underwater blowout preventer (4) is H4 type.

9. A drilling and completion method using a dry Christmas tree in an underwater sealed caisson, characterized in that: Applying the oil production system according to any one of claims 1 to 8, the drilling and completion method comprises: S1: Using a deepwater drilling rig to lower a guide tube (8), continue drilling a wellbore in the guide tube (8), lower a casing and a high-pressure wellhead (7) into the wellbore, place the high-pressure wellhead on top of the guide tube, and cement the well; S2: The production main valve (10) and the annulus main valve (11) of the dry oil tree (2) are placed in a closed state, the oil production system is lowered so that the opening is sleeved on the outer periphery of the guide tube (8), and the first connector (6) is docked with the high-pressure wellhead (7) by using an underwater robot and sealed; S3: After the underwater production system is installed, the riser (12) and the underwater blowout preventer (4) are lowered, the underwater blowout preventer (4) is docked with the first connection portion of the riser sub (3), the plug (5) in the riser sub (3) is removed by wireline operation, and the drilling and completion operation is continued; S4: After the drilling and completion operation is completed, the production tubing string (14) and the tubing hanger (15) are lowered using the drill pipe and the lowering tool, so that the tubing hanger (15) and the dry oil tree (2) are sealed, and then the plug (5) is lowered into the lifting short section (3) using a steel wire operation; S5: After verifying that the plug (5) is sealed, the connection between the first connection part and the underwater blowout preventer (4) is disassembled, and the riser (12) and the underwater blowout preventer (4) are removed.

10. The method for drilling and completing a well using a dry Christmas tree in an underwater sealed caisson according to claim 9, wherein: After step S5, the following steps are also included: opening the production main valve (10) and the annulus main valve (11) of the dry oil tree (2), while the XOV valve (16) of the dry oil tree (2) remains in a closed state, and production is carried out.

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