A method for controlling a blowout in a marine well by drilling a riser.

Abstract

This invention discloses a method for controlling a blowout in a marine well by drilling through the riser. The method includes the following steps: establishing a working face using scaffolding; pre-positioning the crane vessel, workboat, and guard vessel before the operation; placing the casing drilling equipment, high-pressure pump, fire-fighting equipment, and protective gear on the workboat or wellhead area before drilling; selecting the drilling location and number of holes; pre-installing the riser backplate before drilling the outer riser; drilling the riser, technical casing, and production casing sequentially, confirming the safety of each annulus layer; upon discovering an overflow during drilling, quickly tightening the backplate; and implementing well control operations using heavy brine, barite slurry, or non-dispersible cement slurry. This invention addresses blowout situations in drilling or production wells on offshore platforms. It allows for close deployment of all aspects during emergency rescue, rapid sealing of the outer riser, and connection of the well control manifold to the internal wellbore. This enables successful well control and sealing operations in each annulus layer. The method is highly operable, has a short construction period, and requires minimal investment.

Description

Technical Field

[0001] This invention belongs to the field of offshore oil drilling well control technology, and in particular relates to a method for controlling well blowouts in offshore wells by drilling through the riser. Background Technology

[0002] The in-depth development of energy resources is a key issue in the current stage of energy technology development. In the development of offshore oil and gas resources, offshore drilling can effectively ensure the intensity of development. However, drilling operations are affected by the complex marine environment; if a blowout occurs, it will not only endanger the safety of workers but also cause a catastrophic disaster to the marine environment.

[0003] In reality, uncontrolled blowouts in offshore drilling are rare. Conventional blowout handling primarily involves drilling rescue wells and wellhead reconstruction techniques. Rescue well technology requires connecting the affected wellbore with the rescue wellbore before well control operations can be implemented. However, connecting the wellbore often requires inserting a strong magnetic guide tool into the affected well, a highly complex operation, and the technology is not yet mature in China. In onshore oilfields, after a blowout and fire, rescue teams are often organized to use wellhead reconstruction techniques. This involves disassembling and reassembling the flange of the old wellhead and reinstalling the blowout preventer to control the blowout and fire. However, wellhead reconstruction requires the use of large, long-arm lifting equipment. Offshore platforms, due to factors such as area, deck height, and obstacle avoidance, cannot use such large lifting equipment, making conventional wellhead reconstruction techniques impractical. Therefore, new solutions are needed for emergency response to uncontrolled offshore blowouts. Summary of the Invention

[0004] The problem to be solved by this invention is to provide an emergency rescue technology for well blowouts on offshore platforms, especially a method for drilling and controlling wells in the riser during well blowouts, in order to solve the problem of well blowouts on offshore platforms during drilling or production wells.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for controlling a blowout in a marine well by drilling a riser, comprising the following steps:

[0006] S1: Preparations before drilling operations;

[0007] S2: Select the location and number of openings according to the type of well shaft;

[0008] S3: Pre-install the back plate of the riser pipe on the outer wall of the riser pipe;

[0009] S4: Conduct hole drilling operations and confirm the safety of each annular space layer by layer;

[0010] S5: When an overflow is detected in the annulus, adjust the backplate, connect the cementing line, and carry out well control operations.

[0011] Furthermore, S1 includes the following steps:

[0012] S11: Erect scaffolding and establish a working surface;

[0013] S12: The crane vessel, work vessel, and guard vessel shall be positioned in accordance with the platform structure, slot area location, and construction schedule;

[0014] S13: Before drilling operations, place all large equipment, tools and fire protection equipment involved in the operation in the wellhead area or on the work boat;

[0015] S14: Connect all pipelines and conduct trial operation of the equipment, and install the sleeve opening power end equipment.

[0016] Furthermore, in S11, due to the influence of tides, the scaffolding is laid at a depth of 3m above the water surface, and the working surface is created at a depth of 6m below the cable walkway. The scaffolding has a load-bearing capacity of more than 500kg and includes a bottom working surface and a top protective layer.

[0017] Furthermore, in S13, the large equipment involved in the operation is placed on the work vessel. The large equipment involved in the operation includes a casing drilling equipment power source, a fire-fighting engine, and a high-pressure pump. The work tools and fire protection tools are placed in the wellhead area. The work tools and fire protection tools include casing drilling tool holders, various pipelines, auxiliary tools, fire-fighting and protective tools. The wellhead area is also equipped with gas monitoring equipment, wind vanes, mobile lighting, fire pipeline monitoring equipment, fire pipeline protection equipment, and fire pipeline tools.

[0018] Furthermore, in S2, when performing a blowout control operation on a single-tube dual-well, one observation hole and two working holes are opened on the riser; when performing a blowout control operation on a single-tube single-well, one observation hole and one working hole are opened on the riser.

[0019] Furthermore, in S2, the opening height is located between 0.8m and 1.7m above the working surface. When opening the hole, the observation hole is opened first, and then the working hole is opened.

[0020] Furthermore, in S3, after the casing drilling machine drills through annulus A, annulus B, and annulus C, the back plate of the riser quickly seals the outer riser.

[0021] Furthermore, in S4, the workers and equipment are all positioned upwind. After drilling through the riser and surface casing into the B annulus, drilling is stopped and the cutter is withdrawn for inspection. Once the safety of the B annulus is confirmed, drilling operations are then carried out in the C annulus.

[0022] Furthermore, S5 includes the following steps:

[0023] S51: Inject weighted brine into the annulus of the casing and tubing through the opening to balance the pressure inside the well;

[0024] S52: The specific gravity of the heavy brine is 1.3. If the oil spill shows a decreasing trend, continue pumping. If there is no decreasing trend, increase the specific gravity of the heavy brine up to 1.5 until the overflow pressure in the well is stable.

[0025] S53: After stabilization, barite slurry is pumped in and naturally settles to form a bridge plug to seal the blockage and ensure that the oil and gas do not rise.

[0026] S54: If the barite plug cannot control the overflow, inject cement to form a solid seal.

[0027] Furthermore, when there is no cement in the C ring, first fill the C ring with cement and seal it, then drill through the internal A ring.

[0028] The advantages and positive effects of this invention are:

[0029] Compared to rescue well technology, this invention requires the insertion of a strong magnetic guide tool into the accident well to connect the accident wellbore and the rescue wellbore. This method is less technically challenging, has a shorter construction period, and requires less investment. Compared to wellhead reconstruction technology commonly used in onshore oilfields, this method utilizes the old wellhead, disassembling and reassembling the flange, and reinstalling the blowout preventer. It requires less platform deck space, smaller equipment size, lower threat level, and is highly operable. The pre-installed riser backplate allows for rapid sealing of the outer riser after the casing drilling rig drills through the A, B, and C annexes, connecting the kill manifold to the internal wellbore, achieving both well control and flow control. The equipment is lightweight, has good sealing performance, and is easy to install. In actual handling of a single-tube dual-well blowout and fire accident in the Bohai Oilfield, the riser drilling and kill technology successfully completed the kill and sealing operations of the A, B, and C annexes, demonstrating excellent results and providing technical support for emergency rescue of blowouts after drilling and completion on offshore platforms. The emergency rescue technology for overall well blowout is not complicated, and it can effectively control the blowout and reduce the handling cost. Attached Figure Description

[0030] Figure 1 This is an overall flowchart of an embodiment of the present invention. Detailed Implementation

[0031] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0033] like Figure 1 As shown, a method for controlling a blowout in a marine well by drilling a riser includes the following steps.

[0034] S1: Preparations before drilling operations. Specifically, S1 includes the following steps.

[0035] S11: Erect scaffolding and establish a working surface. Specifically, due to tidal influences, scaffolding will be laid at a height of 3 meters above the water surface, and a working surface will be created at a height of 6 meters below the cable walkway. The scaffolding will be a two-layer structure with a clearance height greater than 3 meters. The bottom layer will be the working surface, and the top layer will be a protective layer. The protective layer will have steel plates and will be covered with fire-resistant materials, providing protection against impacts, fire, oil, and leaks. Oil collection and diversion channels will be installed on the riser pipe to isolate oil flowing from the riser pipe walls. All scaffolding will have a load-bearing capacity greater than 500 kg. The wellhead will be painted pink as the working area, and the green area will be used for personnel escape.

[0036] S12: The crane vessel, workboat, and guard vessel shall be positioned according to the platform structure, slot area location, and construction schedule. Specifically, when the workboat enters the site, the crane vessel must weigh anchor and retrieve its mooring lines, or loosen its anchor lines to the seabed. The workboat is equipped with DP2 dynamic positioning, with a positioning accuracy of 2m-3m in winds below Force 6, and a distance of 5m from the platform's working point. Operations shall be suspended and the vessel moved away from the platform if the wind force exceeds Force 6. If the wind force reaches Force 7 or above, the vessel must evacuate to seek shelter. Therefore, all connecting cables between the equipment on deck and the on-site work point are equipped with emergency release devices.

[0037] S13: Before drilling operations, all large equipment, tools, and fire protection equipment involved in the operation shall be placed in the wellhead area or on the work vessel. Specifically, the large equipment involved in the operation shall be placed on the work vessel, including power sources for casing drilling equipment, fire engines, high-pressure pumps, and other large equipment. The tools and fire protection equipment shall be placed in the wellhead area, including casing drilling tool holders, various pipelines, auxiliary tools, fire protection, and protective equipment. Gas monitoring equipment, wind vanes, mobile lighting, fire pipelines, and other monitoring and protection equipment and tools shall be appropriately deployed in the wellhead area.

[0038] S14: Connect all pipelines and conduct trial runs of the equipment, and install the sleeve-drilled power end equipment. Specifically, secure and pressure test the pipelines, secure small equipment such as the exhaust fan, and conduct trial runs of all equipment to ensure normal operation. Connect the high-pressure water cleaning equipment and use a high-pressure water gun to clean the grease trap from the water-cooled pipe. Install the sleeve-drilled power end equipment. Before the operation, hold a technical briefing and risk analysis meeting to inform all operators of the relevant risks and countermeasures, clarify personnel responsibilities, understand the work content, identify key operation nodes, familiarize themselves with escape routes, and confirm that communication is uninterrupted.

[0039] S2: Select the location and number of openings. Specifically, select appropriate opening locations and numbers based on the scaffolding height, platform structure, and wellbore type. Opening locations can be chosen between 0.8m and 1.7m above the bottom of the scaffolding, between the sea surface and the bottom deck. However, avoid openings near the 13-3 / 8" and 9-5 / 8" casing couplings inside the riser. Considering the need for two layers of scaffolding, and taking into account tidal effects, the bottom working plane should be at least 3m above sea level, and the top working plane should have approximately 3m of clearance. For blowout control operations in a single-well, double-tube system, ideally, three openings should be made on the riser: one observation hole to observe the location of the two 13-3 / 8" wells inside the 36" riser and the integrity of the C-annulus wellbore; and two working holes connected to the two emergency wells for well control operations and balancing formation pressure. A single-well, single-tube system can have one observation hole and one working hole.

[0040] S3: Pre-install the riser backplate on the outer wall of the riser. Specifically, install the casing drilling equipment, and before drilling the outer riser, pre-install the specially developed riser backplate on the outer wall of the riser using bolts. The specially developed riser backplate consists of a bandage, a fastening system, and a sealing pipeline connection device. It enables the casing drilling machine to quickly seal the outer riser after drilling through the A, B, and C annulus, connecting the kill manifold to the internal wellbore, thus achieving both kill and throttling effects.

[0041] S4: Conduct the drilling operation, confirming the safety of each annulus layer by layer. Specifically, confirm that security and communication equipment are in normal working order, observe the wind direction, and position personnel and equipment upwind. Three people should be assigned to the wellhead work area: one to operate the equipment and observe the drilling operation, one to be responsible for safety supervision, and one to be in a suitable position for overall command. Mark lines on the drill bit to determine the drilling depth. Use a casing drilling machine, feed the drill bit, and press the feed lever on the control panel to begin drilling. Observe changes in drill cuttings, drill bit sound, and drilling depth to comprehensively determine whether drilling has succeeded.

[0042] S5: When an annular overflow is detected, install the backplate, connect the cementing line, and implement well control operations. Specifically, after the cementing skid and manifold system are installed, switch operation and water flow function tests should be performed separately, followed by low-pressure and high-pressure tests at 2.1 MPa, with a pressure stabilization time of no less than 15 minutes. Pressure testing is required every time the pipeline is reinstalled. Due to the unclear wellhead and downhole conditions, the well control plan considers stabilizing formations with a maximum pressure coefficient of 1.2. The well control fluid is added at a specific gravity of 0.1. To ensure reservoir protection, heavy brine well control is preferred. To ensure stable oil and gas, after the heavy brine has controlled the wellbore pressure, barite well control fluid is injected to form a barite plug at the cable packer to stabilize the upward flow of oil and gas. If there is a lack of cement in the C annulus during well control operations, the C annulus can be filled with cement and sealed first, then the internal A annulus can be drilled through, effectively reducing mutual interference between annulus spaces. Staged drilling allows for successful penetration through the annulus of each casing layer and the establishment of circulation channels, facilitating well control and well kill. For optimal well kill results, a kill fluid density of 1.52 g / cm³ is recommended. 3 Potassium formate saline solution, 1.80 g / cm³ 3 Barite paste, 1.90 g / cm³ 3 Non-dispersible cement slurry. If there is no leakage, it is recommended to use brine + barite slurry alternately for well control. After the overflow is controlled, pump non-dispersible cement slurry for annular sealing. If leakage occurs during the pumping of brine or barite slurry, it is recommended to directly pump non-dispersible cement slurry for annular sealing.

[0043] In summary, this invention, when used in actual handling of a blowout and fire accident in a single-tube dual-well well in the Bohai Oilfield, can safely connect the A, B, and C annulus layer by layer, connect the kill manifold to the internal wellbore, quickly seal the outer riser, and successfully complete the kill and sealing operations of the A, B, and C annulus. It has demonstrated good performance and provides technical support for emergency rescue and relief of blowouts after drilling and completion on offshore platforms.

[0044] The advantages and positive effects of this invention are:

[0045] Compared to rescue well technology, this invention requires the insertion of a strong magnetic guide tool into the accident well to connect the accident wellbore and the rescue wellbore. This method is less technically challenging, has a shorter construction period, and requires less investment. Compared to wellhead reconstruction technology commonly used in onshore oilfields, this invention utilizes the old wellhead, disassembling and reassembling the flange, and reinstalling the blowout preventer. It requires less platform deck space, smaller equipment size, lower threat level, and is highly operable. The pre-installed riser backplate allows for rapid sealing of the outer riser after the casing drilling rig drills through the A, B, and C annexes, connecting the kill manifold to the internal wellbore, achieving both well control and flow control. The equipment is lightweight, provides good sealing, and is easy to install. In actual handling of a single-tube dual-well blowout and fire accident in the Bohai Oilfield, the riser drilling and kill technology successfully completed the kill and sealing operations of the A, B, and C annexes, demonstrating excellent performance and providing technical support for emergency rescue of blowouts after drilling and completion on offshore platforms. The emergency rescue technology for overall well blowout is not complicated, and it can effectively control the blowout and reduce the handling cost.

[0046] 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 controlling a blowout-induced runaway well by drilling a riser, characterized in that: Includes the following steps, S1: Preparations before drilling operations; S2: Select the location and number of openings according to the type of well shaft; S3: The riser backplate is pre-installed on the outer wall of the riser. The casing drilling equipment is installed. Before drilling the outer riser, the riser backplate is pre-installed on the outer wall of the riser with bolts. The riser backplate consists of a bandage, a fastening system and a sealing pipeline connection device. It can quickly seal the outer riser after the casing drilling machine drills through the A annulus, B annulus and C annulus, and connect the kill manifold to the internal wellbore to achieve the kill and throttling effects. S4: Perform the drilling operation and confirm the safety of each annulus layer by layer. In S4, the operators and equipment are all arranged upwind. After drilling through the water-proof pipe and the surface casing to enter the B annulus, stop drilling and retract the tool to check and confirm that the B annulus is safe before proceeding with the drilling operation of the C annulus. S5: When an annular overflow is detected, adjust the backplate, connect the cementing line, and implement well control operations. S5 includes the following steps: S51: Inject weighted brine into the annulus of the casing and tubing through the opening to balance the pressure inside the well; S52: Increase the specific gravity of the brine to 1.

3. If the oil spill shows a decreasing trend, continue pumping. If there is no decreasing trend, increase the specific gravity of the brine up to 1.5 until the overflow pressure in the well stabilizes. S53: After stabilization, barite slurry is pumped in and naturally settles to form a bridge plug to seal the blockage and ensure that the oil and gas do not rise. S54: If the barite plug cannot control the overflow, inject cement to form a solid seal.

2. The method for controlling a blowout-induced runaway marine well by drilling a riser according to claim 1, characterized in that: S1 includes the following steps: S11: Erect scaffolding and establish a working surface; S12: The crane vessel, work vessel, and guard vessel shall be positioned in accordance with the platform structure, slot area location, and construction schedule; S13: Before drilling operations, place all large equipment, tools and fire protection equipment involved in the operation in the wellhead area or on the work boat; S14: Connect all pipelines and conduct trial operation of the equipment, and install the sleeve opening power end equipment.

3. The method for controlling a blowout-prone marine well by drilling a riser according to claim 2, characterized in that: In S11, due to the influence of tides, the scaffolding is laid at a depth of 3m above the water surface, and the working surface is created at a depth of 6m below the cable walkway. The scaffolding has a load-bearing capacity of more than 500kg and includes a bottom working surface and a top protective layer.

4. A method for controlling a blowout-induced runaway marine well by drilling a riser according to claim 2 or 3, characterized in that: In S13, the large equipment involved in the operation includes a casing drilling equipment power source, a fire-fighting power source, and a high-pressure pump; the working tools and fire protection tools include casing drilling tool holders, various pipelines, auxiliary tools, fire-fighting tools, and protective tools. The wellhead area is also equipped with gas monitoring equipment, wind vanes, mobile lighting, fire pipeline monitoring equipment, fire pipeline protection equipment, and fire pipeline tools.

5. A method for controlling a blowout-induced runaway marine well by drilling a riser according to any one of claims 1 to 3, characterized in that: In S2, when performing a blowout control operation on a single-tube double-well, one observation hole and two working holes are opened on the riser; when performing a blowout control operation on a single-tube single-well, one observation hole and one working hole are opened on the riser.

6. The method for controlling a blowout-induced runaway marine well by drilling a riser according to claim 5, characterized in that: In S2, the opening height is between 0.8m and 1.7m above the working surface. When opening the hole, the observation hole is opened first, and then the working hole is opened.

7. A method for controlling a blowout-induced runaway marine well by drilling a riser according to claim 1 or 2, characterized in that: When there is no cement in the C ring, first fill the C ring with cement and seal it, then drill through the internal A ring.

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