Combined coiled tubing dredging tool and dredging system

Abstract

The utility model provides a combined type continuous oil pipe dredging tool and dredging system, which comprises a first-size continuous oil pipe, a quick connector and a second-size continuous oil pipe which are connected in sequence, and the quick connector comprises an upper connector and a lower connector. The upper connector is located at the upper end of the quick connector and used for being connected with a first-size coiled tubing, the lower connector is located at the lower end of the quick connector and used for being connected with a second-size coiled tubing, the first-size coiled tubing is used between a tubing hanger and a packer section, and the second-size coiled tubing is used for connecting a packer to an artificial well bottom section. The pipe diameter of the first-size coiled tubing is larger than that of the second-size coiled tubing. The first-size coiled tubing assembly and the second-size coiled tubing assembly are combined and designed through the quick connector, the problem that the size of a well completion tubular column is limited is solved, and the single well yield can be effectively recovered.

Description

Technical Field

[0001] The utility model belongs to the technical field of wellbore plugging removal, and particularly relates to a combined coiled tubing dredging tool and a dredging system. Background Technique

[0002] With the continuous deepening of natural gas exploitation, the problems faced by gas wells are becoming increasingly complex and diverse. Among them, frequent sand production has become one of the important factors affecting the normal production of gas wells. When the sand production of a gas well is serious, it will cause the wellbore to be blocked, thereby affecting the normal exploitation of natural gas. In severe cases, it may even force the gas well to shut down and stop production. This not only causes waste of resources, but also brings great challenges to the stable and increased production of oilfields.

[0003] To address this problem, the currently commonly used solution is to use coiled tubing dredging operations for sand washing and plugging removal. Coiled tubing dredging operations have the advantages of flexible operation and strong adaptability, and can effectively flush the sand in the wellbore to the ground, thereby restoring the production of a single well. However, in actual operation, due to the limitation of the completion string size in some gas wells, it is difficult to implement coiled tubing dredging operations. For example, the inner diameter of the packer in some wells is only 48.5 mm, and although the commonly used 1.75-inch (44.5 mm) coiled tubing can pass through, the unilateral clearance is only 2 mm, which makes the risk of getting stuck extremely high during the operation. Once the coiled tubing gets stuck in the wellbore, it will not only lead to the failure of the operation, but also may damage the wellbore, increasing the difficulty and cost of subsequent treatment. Therefore, for such small-size string wells, the traditional coiled tubing dredging operation plan is not feasible.

[0004] Therefore, it is necessary to study new wellbore plugging removal technologies for small-size string wells to restore the productivity of blocked wells. Content of the Utility Model

[0005] In order to solve the problems existing in the prior art, the utility model provides a combined coiled tubing dredging tool and a dredging system. By combining the first-size and second-size coiled tubing assemblies through a quick-connect joint, the problem of limited completion string size is solved, and the production of a single well can be effectively restored.

[0006] To achieve the above purpose, the utility model provides the following technical solution: A combined coiled tubing dredging tool includes a first-size coiled tubing, a quick-connect joint, and a second-size coiled tubing connected in sequence. The quick-connect joint includes an upper joint and a lower joint. The upper joint is located at the upper end of the quick-connect joint and is used to connect with the first-size coiled tubing. The lower joint is located at the lower end of the quick-connect joint and is used to connect with the second-size coiled tubing. The first-size coiled tubing is used between the tubing hanger and the packer section, and the second-size coiled tubing is used from the packer to the artificial bottom hole section. The diameter of the first-size coiled tubing is larger than that of the second-size coiled tubing.

[0007] Further, the first-size coiled tubing is 1.75-inch to 2-inch coiled tubing.

[0008] Further, the second-size coiled tubing is 1-inch to 1.5-inch coiled tubing.

[0009] Further, the packer is a 5-inch permanent packer.

[0010] Further, the length of the first-size coiled tubing is equal to the length from the tubing hanger to the packer plus 500 m to 1000 m.

[0011] Further, the length of the second-size coiled tubing is equal to the length from the packer to the artificial bottom hole plus 100 m to 300 m.

[0012] Further, both the upper joint and the lower joint are recessed joints, and at least two O-ring seals are provided on the upper part of the recessed joint.

[0013] The utility model provides a dredging system, including a wellhead device, a coiled tubing system, and a dredging tool string connected in sequence. Among them, the above-mentioned combined coiled tubing dredging tool is adopted in the coiled tubing system. The coiled tubing system and the dredging tool string are placed in the wellbore. The coiled tubing system is used to transport the working fluid in the working fluid system to the dredging tool string part.

[0014] Further, the wellhead device includes a blowout preventer box, a first-size blowout preventer, a second-size blowout preventer, and a Christmas tree. Among them, the Christmas tree is located at the wellhead, the blowout preventer box is installed above the Christmas tree, and both the first-size blowout preventer and the second-size blowout preventer are installed between the Christmas tree and the blowout preventer box.

[0015] Further, the coiled tubing system includes an injector head, a coiled tubing truck, and the above-mentioned combined coiled tubing dredging tool. Among them, the coiled tubing truck is connected to the injector head through a surface manifold. The injector head is installed above the wellhead and is connected to the wellhead through a blowout preventer.

[0016] Compared with the prior art, the utility model has at least the following beneficial effects:

[0017] The utility model provides a combined coiled tubing dredging tool. By designing the first and second coiled tubing components and cooperating with quick-connect joints, the problem of limited completion string size is effectively solved, enabling efficient dredging operations in smaller-sized wellbores.

[0018] The quick-connect joint of the utility model adopts a coiled tubing recessed joint and is equipped with an O-ring seal to ensure the sealing performance and reliability of the connection, avoiding leakage or detachment under harsh conditions such as high pressure and high temperature.

[0019] The combined coiled tubing dredging tool provided by the present utility model can select appropriate tubing sizes for different sections of the wellbore through the combined design of the first-size coiled tubing and the second-size coiled tubing, thereby optimizing the dredging effect and improving the operation efficiency.

[0020] The dredging system provided by the present utility model includes wellhead equipment, a coiled tubing system, a dredging tool string, and a working fluid system. Each part works together to form a complete dredging operation system, improving the safety and efficiency of the operation. By using the combined coiled tubing dredging tool of the present utility model in the coiled tubing system, effective dredging operations can be achieved, blockages in the wellbore can be removed, and the production of a single well can be restored or increased, providing strong support for the stable and increased production of the oilfield.

[0021] In summary, the combined coiled tubing dredging tool and dredging system provided by the present utility model can effectively solve the problem that small-sized pipe strings cannot perform conventional coiled tubing dredging operations, can quickly restore the productivity of wells with blocked wellbores, and add technical reserves to the field of wellbore plug removal. Description of the Drawings

[0022] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure of the present utility model in any way. At the same time, the shapes and proportions of the various parts in the drawings are only schematic and are used to assist in the understanding of the present utility model, rather than specifically defining the shapes and proportions of the various parts of the present utility model. Those skilled in the art can, under the teaching of the present utility model, select various possible shapes and proportional dimensions according to specific circumstances to implement the present utility model.

[0023] Figure 1 It is a schematic diagram of the dredging operation of the combined coiled tubing dredging tool.

[0024] Figure 2 It is a schematic diagram of a 1.75-inch coiled tubing inside a 5-inch packer (inner diameter 48.5 mm).

[0025] Figure 3 It is a schematic diagram of a 1.5-inch coiled tubing inside a 5-inch packer (inner diameter 48.5 mm).

[0026] Figure 4 It is a schematic diagram of a quick-connect joint.

[0027] Figure 5 It is a schematic diagram of the wellbore structure of an oil and gas well with a 5-inch packer (inner diameter 48.5 mm).

[0028] In the attached drawings: 1. Injection head; 2. Blowout preventer box; 3. 1.75-inch blowout preventer; 4. Drilling floor; 5. 1.5-inch blowout preventer; 6. Blowout preventer pipe; 7. Christmas tree; 8. Coiled tubing truck; 9. Tubing; 10. Coiled tubing; 11. Packer; 12. Quick coupling; 121. Upper joint; 122. Connecting sleeve; 123. Block; 124. Lower joint; 125. First sealing ring; 126. Second sealing ring; 127. Third sealing ring; 128. Screw; 13. Artificial bottom hole; 14. Tubing hanger. Detailed implementation mode

[0029] The present utility model will be further described below in conjunction with the attached drawings and the detailed implementation mode.

[0030] A combined coiled tubing dredging tool of the present utility model includes a coiled tubing 10. The coiled tubing 10 is successively a first-size coiled tubing, a quick coupling 12, a second-size coiled tubing, a connector, a motor head assembly, and a jet tool from top to bottom. Among them, the diameter of the first-size coiled tubing is larger than that of the second-size coiled tubing. The first-size coiled tubing is used between the tubing hanger 14 and the packer 11 section, and the second-size coiled tubing is used for the section from the packer 11 to the artificial bottom hole 13; both ends of the quick coupling 12 are pit joints. The principle of this pit joint is to use a special pit joint pressing tool to press the coiled tubing wall at the pit of the joint to realize the connection between the joint and the coiled tubing. This joint has good tensile and torsional resistance performance, and at the same time ensures that the outer diameter of the joint is the same as that of the coiled tubing.

[0031] Specifically, the quick coupling 12 includes an upper joint 121, a connecting sleeve 122, a block 123, a lower joint 124, a first sealing ring 125, a second sealing ring 126, and a third sealing ring 127. The upper joint 121 is located at the upper end of the quick coupling 12 and is used to connect with the 1.75-inch coiled tubing. The connecting sleeve 122 is located between the upper joint 121 and the lower joint 124 and plays a role in connection and support to ensure the overall stability and strength of the joint; the block 123 is located around or inside the connecting sleeve 122 and is used to realize the quick connection and locking function of the joint. The design of the block 123 allows the joint to be quickly fixed after being inserted into the coiled tubing and prevents accidental detachment; the lower joint 124 is located at the lower end of the quick coupling 12 and is connected with the 1.5-inch coiled tubing. The upper joint 121 and the lower joint 124 are connected through the connecting sleeve 122, the block 123, the screw 128, and the second sealing ring 126. The pit joint part of the upper joint 121 is provided with a first sealing ring 125, and the pit joint part of the lower joint 124 is provided with a third sealing ring 127. The setting of the sealing rings can ensure the sealing performance between the joint and the coiled tubing. They can effectively prevent fluid leakage and ensure the safety and efficiency of the operation.

[0032] The pressing tool of the pit joint uses a hand pump as hydraulic power. The pressing pressure of a single pit is 1500psi. When in use, insert the pit joint into the continuous tubing, align the pressing screw on the pressing tool with the pit on the joint, use the hand pump to press the hydraulic cylinder to the pressing screw, and the pressing screw presses the continuous tubing, deforming the continuous tubing and pressing it into the pit, thereby fixing the joint and the continuous tubing. There are 2 O-rings on the upper part of the pit joint to ensure the sealing of the joint and the continuous tubing. The tool string is connected through the pit to form a complete set of dredging equipment, which is used to spray high-pressure fluid in the continuous tubing dredging operation to clear wellbore blockages.

[0033] Preferably, the packer 11 is a 5-inch permanent packer. For the 5-inch permanent packer, the first size of the continuous tubing of the utility model can be selected from 1.75 inches to 2 inches, and the length is equal to the length from the tubing hanging to the packer plus 500m to 1000m; the second size of the continuous tubing can be selected from 1 inch to 1.5 inches, and the length is equal to the length from the packer 11 to the bottom of the artificial well 13 plus 100 to 300m.

[0034] Preferably, the combined coiled tubing dredging tool of the utility model adopts 1.75-inch coiled tubing, quick-connect joint 12, 1.5-inch coiled tubing, 1.5-inch connector, 1.5-inch motor head assembly, and 1.5-inch jet tool;

[0035] The utility model also provides a dredging system including wellhead equipment, a coiled tubing system, a dredging tool string, and a working fluid system, wherein:

[0036] The wellhead equipment includes a blowout preventer box 2, a 1.75-inch blowout preventer 3, a 1.5-inch blowout preventer 5 and a Christmas tree 7. The Christmas tree 7 is located at the wellhead and is the core component that connects the underground pipe string with the ground equipment, providing wellhead sealing and fluid control functions. The blowout preventer box 2 is installed above the Christmas tree 7 to prevent the fluid in the well from blowing out during the continuous tubing operation and to protect the safety of wellhead equipment and personnel. The 1.75-inch blowout preventer 3 and the 1.5-inch blowout preventer 5 are respectively used to control the wellhead pressure during the operation of continuous tubing of different sizes to ensure the safety of the operation. Both are installed between the Christmas tree 7 and the blowout preventer box 2 and connected by a flange. The blowout preventer 6 is connected below the blowout preventer to further guide and control the wellhead fluid during the continuous tubing operation.

[0037] The coiled tubing system includes an injection head 1, a coiled tubing vehicle 8 and a combined coiled tubing dredging tool. The coiled tubing vehicle 8 is the supply source of the coiled tubing and is connected to the injection head 1 through a surface manifold to provide power for lowering and recovering the coiled tubing. The injection head 1 is installed above the wellhead and is connected to the wellhead through a blowout preventer. It is the main operating equipment for lowering and recovering the coiled tubing. A clamping block is provided inside the injection head to clamp coiled tubing of different sizes.

[0038] The combined coiled tubing cleaning tool includes two sizes, 1.75 inches and 1.5 inches. The 1.75-inch coiled tubing is mainly used for the section from the tubing hanger 14 to the packer 11, while the 1.5-inch coiled tubing is used for the section from the packer 11 to the artificial bottom hole 13. The two are connected by a quick-connect joint 12 to form a complete coiled tubing string.

[0039] In the working fluid system, a low-friction working fluid with a density of 1.3 g / cm³ is selected and injected into the coiled tubing through a surface pump truck for circulating flushing and plug removal. The performance of the working fluid is adjusted according to the actual on-site situation to meet the operation requirements. The working fluid selected for this utility model has low friction, high temperature resistance, high dynamic shear force, and high pH value, which not only meets the requirements of the cleaning operation but also improves the safety and stability during the operation.

[0040] The wellhead pressure is controlled within 25 MPa. Considering the cost, a low-friction working fluid with a density of 1.3 g / cm³ (added with viscosity increasing and shear force enhancing agent + PH regulator + corrosion inhibitor) is selected. The apparent viscosity of the working fluid is 20 mPa·s to 40 mPa·s, the temperature resistance is ≥170 °C, the dynamic shear force is ≥6 Pa, and the PH is ≥9.5. The performance of the working fluid can be adjusted according to the actual on-site situation.

[0041] Preferably, two pump trucks of type 2000 or above are selected for the pump truck, one for standby and one for use, to provide sufficient pump pressure and displacement for the working fluid.

[0042] The auxiliary equipment includes surface metering equipment and a crane. The surface metering equipment selects 105 MPa level surface metering equipment to monitor parameters such as wellhead pressure and flow rate. The crane is used to lift heavy equipment such as the injection head and the drum to ensure the smooth handling and installation of equipment during the operation.

[0043] As Figures 1 to 5 shown, when using the cleaning system of this utility model to carry out the combined coiled tubing cleaning operation, the following steps are included:

[0044] S1. Well location selection: Select the oil and gas wells where the formation sand production causes the wellbore to be blocked according to the production dynamics as the target wells to carry out the combined coiled tubing cleaning operation.

[0045] Example: Well A is a high-pressure gas well with serious sand production and a significant reduction in production capacity. It is necessary to carry out the combined coiled tubing cleaning operation to restore the production capacity. The mid-depth of the pay zone of this well is 6150 m, the formation pressure is 114 MPa, the pressure coefficient is 1.6, the maximum shut-in pressure is 88 MPa, the packer 11 is a 5-inch permanent packer with an inner diameter of 48 mm, the length from the tubing hanger 14 to the packer 11 is 6000 m, and the length from the packer 11 to the artificial bottom hole 13 is 200 m.

[0046] S2. Construction preparation

[0047] S2.1 Coiled tubing selection

[0048] Select an appropriate coiled tubing length according to the completion string configuration of the target well.

[0049] Length of 1.75-inch coiled tubing = length from tubing hanger 14 to packer 11 + 500 m = 6500 m

[0050] Length of 1.5-inch coiled tubing = length from packer 11 to the artificial bottom hole 13 + 100 m = 300 m

[0051] S2.2 Selection of downhole tools

[0052] Jet tool string (from top to bottom): 1.75-inch coiled tubing + quick coupling 12 + 1.5-inch coiled tubing + 1.5-inch connector + 1.5-inch motor head assembly + 1.5-inch jet tool.

[0053] S2.3 Selection of working fluid

[0054] Through fluid analysis, as the liquid density increases, the wellhead pressure decreases, and the pump pressure decreases accordingly at the same displacement. With the wellhead pressure control within 25 MPa, considering the cost comprehensively, a low-friction working fluid with a density of 1.3 g / cm³ (added with viscosity increasing and shear strength enhancing agent + PH regulator + corrosion inhibitor) is selected. The apparent viscosity of the working fluid is 20 mPa·s to 40 mPa·s, the temperature resistance is ≥170 °C, the dynamic shear force is ≥6 Pa, and the PH is ≥9.5. The performance of the working fluid can be adjusted according to the actual situation on site.

[0055] S2.4 Selection of surface metering equipment

[0056] The maximum shut-in pressure of Well A is 88 MPa, so surface metering equipment of 105 MPa level is selected.

[0057] S2.5 Selection of pump trucks

[0058] Well A is a high-pressure gas well with a maximum shut-in pressure of 88 MPa. Therefore, 2 pump trucks of type 2000 or above are selected, one for standby and one for use.

[0059] S2.6 Equipment installation

[0060] According to Figure 1 Prepare the corresponding auxiliary equipment according to the schematic diagram of the coiled tubing dredging operation and install it, and the pressure test is qualified. The surface metering equipment is installed according to the standard and the pressure test is qualified.

[0061] S3. Run the combined coiled tubing

[0062] S3.1 Run 1.5-inch coiled tubing to 300 m

[0063] Open the wax cleaning gate and lower the coiled tubing 10 to a well depth of 300m without starting the pump; after confirming the depth, close the 5 slips and half seal of the 1.5-inch blowout preventer and lock it manually.

[0064] S3.2 1.5 inch coiled tubing wellhead suspension

[0065] The flank flange of 1.5-inch blowout preventer 5 is depressurized to reduce the wellhead pressure above 1.5-inch semi-sealed to 0MPa; the 1.5-inch coiled tubing is depressurized to 0MPa on the ground, and the pressure change is observed; after the pressure is relieved, the clamping force of the injection head is adjusted to the minimum; the blowout preventer 6 is disassembled from any joint, and the injection head string is lifted up by the big hook to expose the 1.5-inch coiled tubing, which is 0.5m higher than the end face of the blowout preventer 6, and the injection head is re-clamped; the 1.5-inch coiled tubing is cut with a mechanical cutter, and the split straightening sleeve and 1.5-inch coiled tubing clamp are installed on the end face of the blowout preventer 6 before cutting; the outer wall and chamfer of the 1.5-inch coiled tubing are polished at the wellhead to ensure that the lower joint of the docking tool can be inserted relatively easily; then the 1.75-inch blowout preventer 2 is disassembled to the fixed seat on the drilling table 4, the injection head is supported by a leg, and the big hook is replaced with a 70-ton crane hook.

[0066] S3.3 Replacement of 1.75-inch coiled tubing

[0067] The injection head is hoisted to the ground, and the 1.5-inch drum is rewound around the continuous tubing. The 1.5-inch continuous tubing in the injection head is pulled out on the ground. The injection head clamping block is replaced with a 1.75-inch one. Two cranes are used to lower the 1.5-inch drum, replace it with a 1.75-inch drum, and connect it to the ground manifold.

[0068] S3.4 1.75 inch coiled tubing into the injection head

[0069] On the ground, first remove the upper 1.5-inch blowout preventer box 2 rubber core and replace it with a 1.75-inch rubber core; then pull the 1.75-inch coiled tubing into the injection head and conduct a ground water flow test on the 1.75-inch coiled tubing; the end of the 1.75-inch coiled tubing is connected to the quick-connect joint 12, specifically by pressing the pit with a pit joint pressing tool to connect it to the upper joint of the quick-connect joint 12.

[0070] S3.5 Wellhead Installation

[0071] Lift the injection head to the wellhead and replace it with a traveling block hook; then connect the injection head 1 to the blowout preventer box 2, and lift the injection head string with the traveling block; then lower the coiled tubing 0.5m out of the end face of the blowout preventer box 2 and prepare for tool docking.

[0072] S3.6 Coiled Tubing Docking

[0073] Lower the quick-connect joint 12 of the 1.75-inch coiled tubing slowly, align it with the 1.5-inch coiled tubing, slip the lower joint onto the coiled tubing, and then press the pit with a pit joint pressing tool to connect it to the lower joint of the quick-connect joint 12. Lift the injector head by 5 tons of hook load for a trial and observe the tensile bearing capacity at the connection.

[0074] S3.7 Lower the coiled tubing

[0075] Reduce the clamping force of the injector head to 0, slowly lower the injector head with the traveling block, connect the swivel joint of the blowout preventer pipe 6. After connection, restore the normal clamping force of the injector head, and loosen the half-closed and slips of the 1.5-inch blowout preventer 5; let water flow through the coiled tubing. After keeping the coiled tubing full of liquid, start to lower the coiled tubing; according to the construction design, lower the coiled tubing to the encountered resistance surface.

[0076] S4. Combined coiled tubing dredging

[0077] Circulate and flush for plug removal at a displacement of 150 L / min to 250 L / min, control the pressure and lower the coiled tubing with a jetting tool to 6200 m (artificial bottom hole). During the lowering process, when passing through variable diameter positions such as the wellhead, the lowering speed < 3 m / min, the normal lowering speed in the coiled tubing 10 ≤ 8 m / min, control the wellhead pressure of the coiled tubing operation at 26 MPa to 24 MPa, and test the hook load for normal lifting and lowering every 500 m of lowering.

[0078] S5. Pull out the combined coiled tubing

[0079] S5.1 Lift the coiled tubing to the wellhead

[0080] When lifting to a depth of 500 m, reduce the speed to 5 m / min; slowly lift the coiled tubing until the docking tool encounters resistance when lifted to the position of the rubber core of the blowout preventer box 2. After judging that it reaches the docking joint position according to the depth, lower the coiled tubing by 2 m; close the slips and half-closed of the 1.5-inch blowout preventer 5. After closing, relieve the pressure on the ground inside the coiled tubing, and relieve the pressure above the half-closed of the blowout preventer to 0 MPa through the 1.5-inch blowout preventer pressure relief pipeline; after confirming that the pressure is 0 MPa, disconnect the swivel joint of the blowout preventer pipe 6, adjust the clamping force of the injector head to the minimum, slowly lift the traveling block, and the 1.5-inch coiled tubing extends about 0.5 m out of the blowout preventer pipe 6; increase the clamping force of the injector head to the normal value again.

[0081] S5.2 Cut the coiled tubing

[0082] Centrally align the coiled tubing with a split-type centralizer on the upper end face of the blowout preventer box 2; install a 1.5-inch coiled tubing clamp above the centralizer; cut the coiled tubing with a mechanical cutter, and the cutting point is about 0.3 m to 0.5 m above the clamp.

[0083] S5.3 Recover the 1.75-inch coiled tubing

[0084] After cutting is completed, coiled tubing is injected under the injection head. Check the status of the 1.75-inch and 1.5-inch combination joints, and cut off the 1.75-inch coiled tubing above the joint to facilitate the recovery of the 1.75-inch coiled tubing. Remove the 1.75-inch blowout preventer to the platform, and switch the hook of the injection head to the crane hook. The crane lifts the injection head to the ground, and the drum recovers the 1.75-inch coiled tubing. Pull the 1.75-inch coiled tubing out of the injection head. Replace the clamping block of the injection head with a 1.5-inch configuration on the ground, and replace the sealing core of the upper blowout preventer box 2 with a 1.5-inch one.

[0085] S5.4 Replace the 1.5-inch coiled tubing

[0086] Two cranes lift down the 1.75-inch drum and replace it with a 1.5-inch drum, connect the surface manifold, and then thread the 1.5-inch coiled tubing into the injection head. Install a 1.5-inch recessed joint at the end of the coiled tubing 10.

[0087] S5.5 Connect the 1.5-inch coiled tubing at the wellhead

[0088] Lift the injection head to the drill floor 4 and replace it with a hook to lift the injection head; connect the 1.75-inch blowout preventer, lower the 1.5-inch coiled tubing 0.5 m out of the end face of the blowout preventer; slowly lower the coiled tubing 10 to connect the 1.5-inch coiled tubing, tighten the joint, test pull 3 t, and paint and mark the joint.

[0089] S5.6 Lift the 1.5-inch coiled tubing out of the well

[0090] Loosen the 1.5-inch slips and half seal; the injection head lifts the coiled tubing. Pay attention to controlling the pulling force when the joint passes through the gooseneck and drum of the injection head to prevent the joint from breaking. After the remaining 50 m of coiled tubing 10, slow down the lifting speed. When the remaining 10 m of coiled tubing 10, try to close the paraffin removal gate; the coiled tubing exits the well, and close the paraffin removal gate.

[0091] S6. Construction is completed

[0092] Remove the wellhead equipment and surface process, restore the original appearance of the well site, and the construction operation is completed.

Claims

1. A combined coiled tubing dredging tool, characterized in that, It includes a first-size coiled tubing, a quick-connect joint (12), and a second-size coiled tubing connected in sequence. Among them, the quick-connect joint (12) includes an upper joint (121) and a lower joint (124). The upper joint (121) is located at the upper end of the quick-connect joint (12) for connecting with the first-size coiled tubing, and the lower joint (124) is located at the lower end of the quick-connect joint (12) for connecting with the second-size coiled tubing. The first-size coiled tubing is used between the tubing hanger (14) and the packer (11) section, and the second-size coiled tubing is used for the section from the packer (11) to the artificial bottom hole (13). The diameter of the first-size coiled tubing is larger than that of the second-size coiled tubing.

2. The combined coiled tubing dredging tool according to claim 1, wherein The first-size coiled tubing is a 1.75-inch to 2-inch coiled tubing.

3. The combined coiled tubing dredging tool according to claim 2, wherein The second-size coiled tubing is a 1-inch to 1.5-inch coiled tubing.

4. The combined coiled tubing dredging tool according to claim 3, characterized in that The packer (11) is a 5-inch permanent packer.

5. The combined coiled tubing dredging tool according to claim 1, wherein The length of the first-size coiled tubing is equal to the length from the tubing hanger (14) to the packer (11) plus 500 m to 1000 m.

6. The combined coiled tubing dredging tool according to claim 1, wherein, The length of the second-size coiled tubing is equal to the length from the packer (11) to the artificial bottom hole (13) plus 100 m to 300 m.

7. The combined coiled tubing dredging tool according to claim 1, characterized in that, Both the upper joint (121) and the lower joint (124) are pit joints, and at least two O-ring seals are provided at the upper part of the pit joint.

8. A dredging system, characterized in that, It includes a wellhead device, a coiled tubing system, and a wellbore cleaning tool string connected in sequence. Among them, the combined coiled tubing wellbore cleaning tool described in any one of claims 1 to 7 is adopted in the coiled tubing system. The coiled tubing system and the wellbore cleaning tool string are placed in the wellbore, and the coiled tubing system is used to transport the working fluid in the working fluid system to the wellbore cleaning tool string part.

9. The dredging system according to claim 8, characterized in that, The wellhead device includes a blowout preventer box (2), a first-size blowout preventer, a second-size blowout preventer, and a Christmas tree (7). Among them, the Christmas tree (7) is located at the wellhead, the blowout preventer box (2) is installed above the Christmas tree (7), and both the first-size blowout preventer and the second-size blowout preventer are installed between the Christmas tree (7) and the blowout preventer box (2).

10. The dredging system according to claim 8, characterized in that, The coiled tubing system includes an injector head (1), a coiled tubing truck (8), and the combined coiled tubing wellbore cleaning tool described in any one of claims 1 to 7. Among them, the coiled tubing truck (8) is connected to the injector head (1) through a surface manifold. The injector head (1) is installed above the wellhead and is connected to the wellhead through a blowout preventer.

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