A method for layer-by-layer tieback of an offshore wellhead casing

Abstract

The application discloses a kind of marine wellhead casing layer-by-layer tie-in method, comprising the following steps, cutting water conductor, annulus plugging device is lowered, and annulus pressure is isolated;Remove wellhead device;Layered finishing casing, remove internal inflatable annulus plugging device;Lift the trestle;Using outer tie-in mode, tie-in oil layer casing, and carry out internal pressure test;Outer tie-in cylinder ties out technical casing, and carries out external pressure test;Using welding method, tie-in water conductor, and carry out external pressure test;Each layer casing head installation, and pressure test;Install blowout preventer;Complete wellhead tie-in.The application is aimed at the situation that water conductor, surface casing or technical casing is damaged after blowout of marine platform production well, after emergency rescue link ends, in the initial stage of platform resumption, layer-by-layer tie-in operation is carried out on wellhead casing, overall method is simple, strong feasibility, short construction period, can cope with a variety of complex situations.

Description

Technical Field

[0001] This invention belongs to the field of offshore oil well workover technology, and in particular relates to a method for reconnecting offshore wellhead casing layer by layer. Background Technology

[0002] In the development of offshore oil fields, slot resources have irreplaceable scarcity and importance. Generally, one slot corresponds to one riser, forming a drilling fluid circulation channel. At the same time, it serves as the load-bearing structure of the offshore wellhead. The riser contains the surface casing and technical casing, and is used for extraction using single-tube single-well or single-tube double-well technology.

[0003] In reality, although wellhead casing damage is relatively rare in offshore oil fields, when a well blowout occurs, oil or gas from the formation flows into the wellbore and is ejected to the surface uncontrollably, resulting in a blowout. Blowouts are often accompanied by the ejection of toxic gases, and the powerful impact can easily damage wellhead equipment.

[0004] Due to limitations in platform area, deck height, and tools used, there are currently no technical solutions for offshore wellhead reconstruction. Therefore, new solutions need to be sought for wellhead repair work. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a method for reconnecting the casing layer by layer in offshore wellheads, so as to solve the problem of wellhead casing reconnection and repair technology caused by well blowouts or other reasons on offshore platforms.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for layer-by-layer reconnection of marine wellhead casing, comprising the following steps:

[0007] S1. Cut the water-proof conduit and insert the annular sealing device to seal the annular pressure;

[0008] S2. Remove wellhead equipment;

[0009] S3. Trim the casing in layers and remove the annular sealing device;

[0010] S4. Erect elevated scaffolding;

[0011] S5. Reconnect the oil layer casing using an external reconnection method and conduct an internal pressure test;

[0012] S6. Use external return sleeve technology for the bushing and perform external pressure testing;

[0013] S7. Reconnect the water-proof conduit by welding and conduct an external pressure test;

[0014] S8. Install the sleeve heads of each layer and perform pressure testing;

[0015] S9. Install the blowout preventer;

[0016] S10. Complete wellhead reconnection.

[0017] Furthermore, in S1, after well control, observe for 30 minutes to confirm that there is no overflow or gas leakage, and detect that there is no harmful gas leakage in the wellbore. After controlling the pressure in the well, cut the riser.

[0018] Furthermore, in S1, the annular sealing device is an internal expansion type, which temporarily seals the annulus between the oil pipe and the casing.

[0019] Furthermore, in step S2, after the well is sealed using the annular sealing device in conjunction with the safety valve on the production tubing, the wellhead is dismantled.

[0020] Furthermore, step S3 includes the following steps:

[0021] S31. Clean the cement ring between the 9-5 / 8″ sleeve and the 13-3 / 8″ sleeve down to 1m below the 9-5 / 8″ sleeve;

[0022] S32. Cut and grind 13-3 / 8″ and 9-5 / 8″ sleeves in sequence, and grind out the chamfer.

[0023] S33. Remove the annular sealing device.

[0024] Furthermore, S5 includes the following steps:

[0025] S51. Connect the 9-5 / 8″ oil layer casing to the return pipe string and install the combined return pipe string connection.

[0026] S52. Secure the 9-5 / 8″ repair pipe test tool to the outer wall of the 9-5 / 8″ sleeve repair fitting.

[0027] S53. Use a manual hydraulic pump to test the joint seal at 7MPa through the test hole of the test tool. If the pressure does not drop after 15 minutes, it is considered qualified.

[0028] Furthermore, step S6 includes the following steps:

[0029] S61. Connect the 13-3 / 8″ technical sleeve to the return pipe, and lower the connection of the return pipe.

[0030] S62. Secure the 13-3 / 8″ repair pipe test tool to the outer wall of the 13-3 / 8″ sleeve;

[0031] S63. Use a manual hydraulic pump to test the seal of the connector at 3.5 MPa through the test hole of the test tool. If the pressure does not drop after 15 minutes, it is considered qualified.

[0032] Furthermore, if the sealing pressure test of the connector fails, the connector is removed and replaced with a new connector, and the connector repair operation is repeated. If the pressure test is successful, the pressure test device is removed.

[0033] Furthermore, S7 includes the following steps:

[0034] S71. Weld two lifting lugs to the outside of the newly made 20″ water-tight pipe, make a 45° chamfer at the bottom, assemble it with the cut end of the original pipe, and weld the circumferential weld of the new and old pipe bodies.

[0035] S72. Use a manual hydraulic pump to test the seal of the connector at 7MPa through the test hole of the test tool. If the pressure does not drop after 15 minutes, it is considered qualified.

[0036] Furthermore, S8 includes the following steps:

[0037] S81, cut and grind the 20″ water-tight conduit, install the 20″ water-tight conduit head, lock the clamps, injection mold, and pressure test;

[0038] S82, 13-3 / 8″ sleeve and 20″ catheter tip annular mounting slip hanger;

[0039] S83, cut and grind 13-3 / 8″ sleeve; install 13-3 / 8″ and 9-5 / 8″ sleeve heads, injection mold, and pressure test;

[0040] S84, 9-5 / 8″ and 13-3 / 8″ casing head annular mounting slip hangers;

[0041] S85, cut and grind 9-5 / 8″ sleeve, install oil pipe head, injection mold, and pressure test.

[0042] The advantages and positive effects of this invention are:

[0043] This invention provides a method for repairing and reconnecting damaged wellhead casing at offshore sites, characterized by low operational difficulty and cost. By inserting an internally expanding annulus plugging device between the casing and tubing, and in conjunction with a safety valve on the production tubing string, temporary sealing of the oil and gas well can be achieved, ensuring a safe working environment. The casing reconnection device used has a simple structure and a straightforward reconnection process. The reconnection structure itself includes a sealing mechanism, allowing for sealing performance testing in conjunction with a pressure testing device. This layer-by-layer reconnection method for offshore wellhead casing is technically reliable, enabling the restoration of production in offshore oil wells and enhancing the value of damaged wells. Attached Figure Description

[0044] Figure 1 This is an overall flowchart of an embodiment of the present invention. Detailed Implementation

[0045] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0046] The following further describes the embodiments of the present invention in conjunction with the accompanying drawings:

[0047] As Figure 1 shown, a method for layer-by-layer back connection of an offshore wellhead casing includes the following steps.

[0048] S1. Kill the well, control the pressure in the well, then cut the riser, and lower an internal expansion type annulus plugging device to seal the annulus pressure. Specifically, observe the pressure value on the pressure gauge at the top of the wellhead cap, determine the density of the kill fluid according to the pressure value, remove the pressure gauge, connect the kill line, and squeeze the kill fluid into the wellbore to kill the well. After killing the well, open the pressure relief valve, observe for 30 minutes, and confirm that there is no overflow or bubbles in the wellbore as qualified. At the same time, monitor whether there is any harmful gas overflow at the wellhead. After controlling the pressure in the well, according to the determined cutting height, that is, 0.5 m above the cable deck, use a beveling machine to cut the 20" riser and make a flat end face. If the cement sheath between the 20" riser and the 13-3 / 8" casing is too high and does not meet the back connection condition of the 13-3 / 8" casing adapter, use a high-pressure water gun or an extended pneumatic pick to clean the cement in the annulus of the casing, and clean to a depth of 1.5 m below the cutting point to meet the requirement of back connecting the 13-3 / 8" casing. Clean the cement and other impurities on the outer wall of the 3-1 / 2" tubing, clean the rust and impurities on the inner wall of the end face of the 9-5 / 8" casing, and lower an internal expansion type annulus plugging device to temporarily plug the annulus between the tubing and the 9-5 / 8" casing and the 3-1 / 2" tubing.

[0049] S2. Remove the wellhead device. Specifically, the internal expansion type annulus plugging device cooperates with the safety valve on the production string to seal the oil well, and remove the wellhead devices such as the Christmas tree, tubing head, and casing head.

[0050] S3. Trim the casing in layers, chamfer the inner and outer sides of the casing, and remove the internal expansion type annulus plugging device. Specifically, use a high-pressure water gun to wash the annulus of the casing and clean the cement in the annulus. Clean the cement ring between the 9-5 / 8" casing and the 13-3 / 8" casing to 1 m below the 9-5 / 8" casing to meet the construction conditions for the back connection of the adapter. Use a beveller to cut the top end of the 13-3 / 8" casing at 0.6 m above the cable deck and make a 45° chamfer; clean the rust and impurities on the outer walls of the end faces of the 9-5 / 8" and 13-3 / 8" casings to meet the back connection standard of the casing adapter; open the pressure relief port of the internal expansion type annulus plugging device of the 9-5 / 8" casing, confirm that there is no overflow and gas overflow in the wellbore, and remove the internal expansion type annulus plugging device of the 9-5 / 8" casing; use a beveller to make a chamfer at the top end of the 9-5 / 8" casing.

[0051] S4. Build a high scaffold to meet the operation requirements of personnel.

[0052] S5. Adopt the external back connection method, use the back connection cylinder to back connect the production casing, and conduct internal pressure testing through the pressure testing device. Specifically, connect the simulated back connection pipe string, combination: 1.2 m of 9-5 / 8" casing simulated adapter + reducer sub + 6-1 / 2" drill collar, and place it on the drill floor. Connect the back connection pipe string, combination: 1.2 m of 9-5 / 8" casing adapter + 9 m of matching casing + reducer sub + 5" drill pipe plug + 6-1 / 2" drill collar. Lower the simulated adapter, slowly feed the pipe string. When it reaches 1-2 m from the end face of the casing to be back connected, slowly lower it, and扶正 the adapter into the casing on the deck surface. Continue to lower the pipe string, apply a pressure of 5T - 6T, record parameters such as the change in hook load and depth, confirm the success of the simulated back connection, and ensure that the casing meets the back connection conditions. Lower the connected adapter pipe string, evenly apply butter at the slip position of the adapter and the outer wall of the 9-5 / 8〞 casing. Lower the back connection pipe string and confirm the position of the adapter according to the simulated back connection depth. Lift the pipe string by 10T to confirm that the slips firmly grip the casing and confirm the success of the back connection. Clamp the 9-5 / 8" back connection pipe string pressure testing tool on the outer walls of the 9-5 / 8" casing adapter and the 13-3 / 8" casing respectively. Use a manual hydraulic pump to conduct a pressure test of 7 MPa on the seal of the adapter through the pressure test hole of the pressure testing tool, and keep the pressure stable for 15 min without dropping to be qualified. If the pressure test is unqualified, withdraw the adapter and replace it with a new one, and re-conduct the back connection operation. If the pressure test is qualified, remove the pressure testing device. Lift the back connection pipe string by 10T to make the �-5 / 8" casing remain centered in the 13-3 / 8" casing, and wedge a centralizer into the annulus. According to the cement return height in the annulus between the 9-5 / 8" and 13-3 / 8" casings, pour cement into the B annulus until the amount of cement slurry reaches the bottom position of the adapter. Uncouple the drill collar and the drill pipe plug, and pull out the drill pipe.

[0053] S6. The outer tieback string connects the production casing, and external pressure testing is carried out through the pressure testing device. Specifically, connect the simulated tieback pipe string assembly: 13-3 / 8" simulated casing adapter + reducer sub + 6-1 / 2" drill collar. After connection, place it on the drill floor. Connect the tieback pipe string assembly: 1.78 m of 13-3 / 8" casing adapter + 11 m of matching casing + reducer sub + 5" drill pipe plug + 6-1 / 2" drill collar. Lower the simulated adapter, slowly feed the pipe string. When it reaches 1-2 meters from the end face of the casing to be tied back, slowly rotate it clockwise to introduce the bottom tieback casing into the adapter. Slowly lower the pipe string, record parameters such as the change in hook load and depth position, and confirm the successful simulated tieback and that the casing meets the tieback conditions. Apply butter evenly on the slip position of the adapter and the outer wall of the 13-3 / 8" casing. Lower the connected adapter pipe string. Lower the tieback pipe string and confirm the adapter is in place according to the simulated tieback depth. Lift the pipe string by 10 T overpull to confirm the slips grip the casing firmly and the tieback is successful. Clamp the 13-3 / 8" tieback pipe string pressure testing tool on the outer wall of the 13-3 / 8" casing adapter and the outer wall of the 20" casing respectively. Use a manual hydraulic pump to conduct pressure testing on the adapter seal at 3.5 MPa through the pressure testing hole of the pressure testing tool. If the pressure remains stable for 15 minutes without dropping, it is qualified. If the pressure testing is unqualified, withdraw the adapter, replace it with a new one, and re-perform the tieback operation. If the pressure testing is qualified, remove the pressure testing device. Lift the tieback pipe string by 10 T overpull to keep the 13-3 / 8" casing centered in the 20" casing, and wedge a wooden centralizer into the annulus. According to the cement return height in the annulus between the 13-3 / 8" and 20" casings, pour cement into Annulus C until the cement slurry reaches the bottom position of the adapter. Uncouple the drill collar and drill pipe plug threads and pull out the drill pipe.

[0054] S7. The riser is tiebacked by welding, and external pressure testing is carried out through the pressure testing device. Specifically, weld two lifting lugs on the outside of the newly fabricated 20" riser pipe, and chamfer the bottom at 45°. Lift the 20" riser pipe to be welded from the drill floor deck to the installation position. Align and tack weld it with the cut end of the original pipe. Weld the circumferential welds of the new and old pipe bodies. Assemble each set of 3 split collars to the circumferential weld position, requiring the center of the collar height to be at the circumferential weld. If the gap between the collar and the pipe body is large, use a knife handle and wedge to assist in reducing the gap. After assembly, perform fillet weld and seam weld construction on the collar. Assemble each set of 4 wellhead support plates evenly to the original pipe below the collar. Weld the bottom of the support plate to the wedge on the winch deck, and weld the vertical surface of the support plate to the original riser pipe. Use a manual hydraulic pump to conduct pressure testing on the adapter seal at 7 MPa through the pressure testing hole of the pressure testing tool. If the pressure remains stable for 15 minutes without dropping, it is qualified.

[0055] S8. Install and pressure test the casing heads at each layer. Specifically, cut and grind the 20″ watertight conduit. Install the 20″ watertight conduit head, tighten the slips, injection mold, and pressure test. Install the slip hanger around the 13-3 / 8″ casing and the 20″ conduit head. Cut and grind the 13-3 / 8″ casing. Install the 13-3 / 8″ and 9-5 / 8″ casing heads, injection mold, and pressure test. Install the slip hanger around the 9-5 / 8″ casing and the 13-3 / 8″ casing head. Cut and grind the 9-5 / 8″ casing, install the tubing head, injection mold, and pressure test.

[0056] S9. Install the blowout preventer.

[0057] S10. Complete wellhead reconnection.

[0058] In summary, this invention provides a method for repairing and reconnecting damaged wellhead casing in offshore environments that is both easy to implement and cost-effective. By inserting an internally expanding annulus plugging device between the casing and tubing, and using a safety valve on the production tubing string, temporary sealing of the oil and gas well can be achieved, creating a safe working environment. The casing reconnection device used has a simple structure and a straightforward reconnection process. The reconnection structure itself includes a sealing mechanism, allowing for sealing performance testing with a pressure testing device. This layer-by-layer reconnection method for offshore wellhead casing is technically reliable, enabling the restoration of production in offshore oil wells and enhancing the value of damaged wells.

[0059] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for layer-by-layer reconnection of marine wellhead casing, characterized in that: Includes the following steps, S1. Use a beveling machine to cut the water-stop pipe and insert the annular sealing device to seal the annular pressure. S2. Remove wellhead equipment; S3. Trim the casing in layers and remove the annular sealing device. S3 includes the following steps: S31. Clean the cement ring between the 9-5 / 8″ sleeve and the 13-3 / 8″ sleeve down to 1m below the 9-5 / 8″ sleeve; S32. Cut and grind 13-3 / 8″ and 9-5 / 8″ sleeves in sequence, and grind out the chamfer. S33. Remove the annular sealing device; S4. Erect elevated scaffolding; S5. Reconnect the oil layer casing using an external reconnection method and conduct an internal pressure test. S5 includes the following steps: S51. Connect the 9-5 / 8″ oil layer casing to the return pipe string and install the combined return pipe string connection. S52. Secure the 9-5 / 8″ repair pipe test tool to the outer wall of the 9-5 / 8″ sleeve repair fitting. S53. Use a manual hydraulic pump to test the joint seal at 7MPa through the test hole of the test tool. If the pressure does not drop after 15 minutes, it is considered qualified. S6. The sleeve is reconnected using an external return sleeve technology, and an external pressure test is performed. S6 includes the following steps: S61. Connect the 13-3 / 8″ technical sleeve to the return pipe, and lower the connection of the return pipe. S62. Secure the 13-3 / 8″ repair pipe test tool to the outer wall of the 13-3 / 8″ sleeve; S63. Use a manual hydraulic pump to test the joint seal at 3.5 MPa through the test hole of the test tool. If the pressure does not drop after 15 minutes, it is considered qualified. S7. Reconnect the water-proof conduit by welding and conduct an external pressure test; S8. Install the sleeve heads of each layer and perform pressure testing; S9. Install the blowout preventer; S10. Complete wellhead reconnection.

2. The method for layer-by-layer reconnection of marine wellhead casing according to claim 1, characterized in that: In S1, after well control, observe for 30 minutes to confirm that there is no overflow or gas leakage, and detect that there is no harmful gas leakage in the wellbore. After controlling the pressure in the well, cut the riser.

3. A method for layer-by-layer reconnection of marine wellhead casing according to claim 1 or 2, characterized in that: In S1, the annular sealing device is an internal expansion type, which temporarily seals the annulus between the oil pipe and the casing.

4. A method for layer-by-layer reconnection of marine wellhead casing according to claim 1 or 2, characterized in that: In step S2, after the well is sealed using the annular sealing device in conjunction with the safety valve on the production tubing, the wellhead is dismantled.

5. A method for layer-by-layer reconnection of marine wellhead casing according to claim 1 or 2, characterized in that: If the sealing pressure test of the connector fails, remove the connector, replace it with a new one, and repeat the connection operation. If the pressure test passes, remove the pressure testing device.

6. A method for layer-by-layer reconnection of marine wellhead casing according to claim 1 or 2, characterized in that: S7 includes the following steps: S71. Weld two lifting lugs to the outside of the newly made 20″ water-proof conduit, make a 45° chamfer at the bottom, assemble it with the cut end of the original pipe, and weld the circumferential weld of the new and old pipe bodies. S72. Use a manual hydraulic pump to test the seal of the connector at 7MPa through the test hole of the test tool. If the pressure does not drop after 15 minutes, it is considered qualified.

7. The method for layer-by-layer reconnection of marine wellhead casing according to claim 6, characterized in that: S8 includes the following steps: S81, cut and grind the 20″ water-tight conduit, install the 20″ water-tight conduit head, lock the clamps, injection mold, and pressure test; S82, 13-3 / 8″ sleeve and 20″ water-proof conduit head annular installation of slip hanger; S83, cut and grind 13-3 / 8″ sleeve; install 13-3 / 8″ and 9-5 / 8″ sleeve heads, injection mold, and pressure test; S84, 9-5 / 8″ and 13-3 / 8″ casing head annular mounting slip hangers; S85, cut and grind 9-5 / 8″ sleeve, install oil pipe head, injection mold, and pressure test.

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