A base plug tool and coiled tubing gas injection completion string and method of use thereof

Abstract

This invention provides a bottom plugging tool, a coiled tubing gas injection completion string, and its usage method. The bottom plugging tool includes an upper connector, an outer cylinder, and a plug connected sequentially from top to bottom. The upper connector and the outer cylinder are connected by a shear pin. The outer cylinder has an axial liquid phase channel and a radially arranged connecting hole. The axial liquid phase channel communicates with the annulus through the connecting hole. The outer cylinder also has a reciprocating motion mechanism, which closes and connects the axial liquid phase channel and the connecting hole when moving up and down axially. This bottom plugging tool integrates multiple functions, including a tubing plugging device for live drilling, a shear ball seat for packer setting, and a tubing cutting plugging device for live coiled tubing. It facilitates continuous construction during well completion operations and integrates live drilling, annulus protection fluid injection, packer setting, tubing cutting, and gas injection channel establishment during coiled tubing gas injection completion operations.

Description

Technical Field

[0001] This invention belongs to the field of oilfield enhanced oil recovery technology, specifically relating to a bottom plugging tool and a coiled tubing gas injection completion string and its usage method. It is applicable to situations where coiled tubing completion operations are required for gas injection wells in oilfields implementing CO2 flooding, foam-assisted oxygen-reduced air flooding, hydrocarbon gas flooding, and other gas injection development methods. Background Technology

[0002] During the initial gas drive test, conventional gas-tight tubing completion was used, which mainly had the following problems: high implementation cost, long completion cycle, high probability of leakage, high safety risk, and high cost of re-completion operation.

[0003] Using coiled tubing as completion tubing offers numerous advantages: it is made of stainless steel, providing excellent corrosion resistance and a long service life; it eliminates the need for thread gas seal testing, saving on testing costs and shortening the operation cycle, requiring only 1-2 days for a single completion operation; the completion string has only two sealing points, significantly reducing the chance of leakage and effectively ensuring wellbore safety; it allows for pressurized operation throughout, ensuring operational safety; the risk of re-completion is low, and the tubing has a high reuse rate. Research on coiled tubing gas injection string completion operations plays a crucial role in improving the integrity of injection wellbores and achieving safe gas injection throughout the entire lifecycle of injection wells.

[0004] However, when using coiled tubing for gas injection well completion, firstly, the well must be able to be run under pressure. Secondly, to protect the casing, the well generally requires a hydraulically set gas-tight packer. Before setting the packer, annular fluid must be injected into the annulus to protect the casing. Then, the packer must be set. Simultaneously, the technical challenge of cutting the coiled tubing under pressure must be addressed. Finally, a gas injection channel must be established. Conventional sliding sleeve tools and bottom plugging tools cannot meet these requirements.

[0005] The State Intellectual Property Office published patent CN110094180A on August 6, 2019, entitled "An Invention Patent for an Electrically Controlled Pressurized Sealing Device and Method." This patent includes a valve head, with a weighted rod connected to its lower end, a centralizer connected to its lower end, a control sub-section connected to its lower end, a motor reduction mechanism connected to its lower end, a release connector connected to its lower end, a slip connected to its lower end, a push block connected to its lower end, a metal support frame connected to its lower end, a sealing sleeve connected to its lower end, and a clamp anchoring claw connected to its lower end. The area above the release connector is the delivery unit, and the area below is the sealing section. It adopts a direct-reading structure, with ground-controlled sealing and release, ensuring accurate and reliable sealing. It can achieve sealing at any location within the tubing and tool section of the tubing string. Sealing is stable, fast, and highly efficient. However, this plugging tool has a single function and cannot simultaneously meet the integrated functions of running under pressure, injecting annular protective fluid, setting the packer, cutting the tubing under pressure, and establishing the gas injection channel. New completion tools need to be developed to meet the above-mentioned multiple functions of coiled tubing gas injection completion operations.

[0006] Meanwhile, the well is equipped with large-diameter packer tools, and the mechanical properties of coiled tubing are somewhat inferior to those of conventional tubing. Therefore, introducing coiled tubing into gas-driven injection well completion operations requires overcoming existing technical obstacles in order to maximize its advantages and meet the technical needs of the site. Summary of the Invention

[0007] The purpose of this invention is to provide a bottom plugging tool that overcomes the aforementioned technical problems existing in the prior art.

[0008] Another objective of this invention is to provide a coiled tubing completion string that solves a series of problems during coiled tubing completion, such as running the tubing under pressure, adding annular protective fluid, setting the packer, and cutting the tubing under pressure.

[0009] Another objective of this invention is to provide a method for using a continuous tubing gas injection completion string, which facilitates continuous construction during well completion operations.

[0010] Therefore, the technical solution provided by the present invention is as follows: A bottom plug tool, comprising an upper connector, an outer cylinder and a plug connected sequentially from top to bottom, wherein the upper connector and the outer cylinder are connected by a shear pin, and the outer cylinder is provided with an axial liquid phase channel and a connecting hole arranged radially, wherein the axial liquid phase channel is connected to the oil sleeve annulus through the connecting hole;

[0011] The outer cylinder is equipped with a reciprocating motion mechanism, which is used to close and connect the axial liquid phase channel and the connecting hole when moving up and down along the axial direction.

[0012] The reciprocating motion mechanism includes an upper sliding sleeve, a lower sliding sleeve, and a spring arranged sequentially from top to bottom. A reverse sealing ball is provided between the upper sliding sleeve and the lower sliding sleeve. One end of the spring is connected to the plug, and the other end of the spring is connected to the lower sliding sleeve. The upper sliding sleeve is sealed to the inner wall of the outer cylinder, and the lower sliding sleeve can reciprocate up and down along the axial direction.

[0013] A coiled tubing gas injection completion string includes a coiled tubing, a large-diameter anchor, and a connector. The large-diameter anchor is located at the wellhead and sleeved on the coiled tubing. The lower end of the coiled tubing is sequentially connected to a safety release device, a gas-tight packer, and a bottom plug tool via the connector.

[0014] The large-diameter anchor includes a housing, a threaded push rod, and a conical slip. The lower structure inside the housing matches the conical slip. The housing has a continuous pipe channel. The conical slip is located inside the housing and is circumferentially positioned within the continuous pipe channel. The lower oblique end of the threaded push rod is inserted into the housing and connected to the housing by threads. The lower oblique end of the threaded push rod is connected to the conical slip. The bottom end of the conical slip is provided with a metal seal.

[0015] A method for using a coiled tubing gas injection completion string includes the following steps:

[0016] Step 1) Run the coiled tubing gas injection completion string, and seal the coiled tubing with a bottom plug during the running-down process;

[0017] Step 2) After the tubing string is lowered, use a pump truck to inject annular protective fluid from the continuous tubing. By increasing the oil pressure, the connecting hole of the bottom plug tool will be exposed, thus achieving oil-jacket connection.

[0018] Step 3) After the annular protective fluid has circulated completely, the setting ball is added, the oil pipe is pressurized to achieve oil-jacket connection, and the gas-tight packer is set. After setting is completed, the seal is checked from the annulus. After the seal is qualified, the oil pipe is depressurized, the oil-jacket is disconnected, and the continuous tubing is plugged again.

[0019] Step 4) Hang and cut the pipe, restore the gas production tree, continue to pressurize the continuous pipe with the pump truck, cut the shear pin, detach the outer cylinder from the upper joint, and connect the oil jacket.

[0020] Step 5) Begin normal gas injection; construction complete.

[0021] In step 1), the lowering of the tubing is a pressurized operation. Under the elastic force of the spring, the sliding sleeve drives the reverse sealing ball to move upward, and achieves a one-way seal with the ball seat formed by the lower end of the upper sliding sleeve, thereby sealing the continuous tubing and meeting the requirements of pressurized drilling.

[0022] The specific process of step 2) is as follows: by increasing the oil pressure, the spring is compressed, and the lower sliding sleeve drives the reverse sealing ball to move downward. The reverse sealing ball separates from the ball seat formed at the lower end of the upper sliding sleeve, exposing the connecting hole and realizing the connection between the oil sleeve and the ball.

[0023] The specific process of step 3) is as follows: After the annular protective fluid is circulated, under the action of the spring, the sliding sleeve drives the reverse sealing ball to move upward, and achieves one-way sealing with the ball seat formed by the lower end of the upper sliding sleeve. The setting ball is put in, the oil pipe is pressurized, and under the action of the spring, the sliding sleeve drives the reverse sealing ball downward, and the connecting hole is exposed again, realizing the connection between the oil and the packer, setting the packer, and after the setting is completed, the seal is checked from the annulus.

[0024] After the seal is verified as qualified, the oil pipe is depressurized. Under the elastic force of the spring, the lower sliding sleeve drives the reverse sealing ball to move upward, and forms a ball seat with the lower end of the upper sliding sleeve to achieve a one-way seal, sealing the connecting hole and once again meeting the requirement of oil pipe pressure sealing.

[0025] The beneficial effects of this invention are:

[0026] The bottom plugging tool provided by this invention, through its reciprocating motion mechanism, enables repeated opening and closing of the channel between the tubing and casing, and integrates functions such as running the tubing under pressure, injecting annular protective fluid, setting the packer, cutting the tubing under pressure, and establishing the gas injection channel during coiled tubing gas injection completion operations.

[0027] This bottom plugging tool integrates multiple functions, including a pressurized tubing plug, a shear ball seat for setting the packer, and a pressurized tubing cutter plug for continuous tubing, providing convenience for continuous construction during well completion operations.

[0028] The coiled tubing completion string provided by this invention uses coiled tubing as the completion tubing, minimizing leakage points and improving the gas sealing performance of the string. This provides key technical support for ensuring wellbore safety and achieving gas injection throughout its entire lifecycle. The use of a large-diameter packer ensures the insertion of large-diameter packer tools while also considering suspension and sealing performance, overcoming technical obstacles in the application of coiled tubing in gas-driven well completion operations and maximizing the advantages of coiled tubing.

[0029] The following will provide a more detailed explanation in conjunction with the accompanying drawings. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of one embodiment of the continuous tubing gas injection completion string of the present invention;

[0031] Figure 2 This is a schematic diagram of the bottom plugging tool during pressurized drilling.

[0032] Figure 3 This is a schematic diagram of the bottom plug tool used when injecting circulating annular protective fluid;

[0033] Figure 4 This is a schematic diagram of the bottom plug tool used when setting the packer;

[0034] Figure 5 This is a schematic diagram of the bottom plug tool used when establishing an injection channel by cutting the pipe with pressure.

[0035] Figure 6 This is a schematic diagram of the structure of a large-diameter anchor seal.

[0036] Figure 7 This is a schematic diagram of the open state of the continuous tube channel of the large-diameter anchor sealer;

[0037] Figure 8 This is a schematic diagram of the closed state of the continuous pipe channel of the large-diameter anchor sealer.

[0038] In the diagram: 1. Plug; 2. Spring; 3. Outer cylinder; 4. Sliding sleeve; 5. Reverse sealing ball; 6. Connecting hole; 7. Upper sliding sleeve; 8. Sealing ring; 9. Shear pin; 10. Upper connector; 11. Continuous tube; 12. Connector; 13. Safety release; 14. Gas-tight packer; 15. Bottom plug tool; 16. Large-diameter anchor; 17. Setting ball; 18. Housing; 19. Threaded push rod; 20. Conical slip; 21. Metal seal; 22. Continuous tube channel. Detailed Implementation

[0039] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0040] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0041] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0042] Example 1:

[0043] This embodiment provides a bottom plugging tool, including an upper connector 10, an outer cylinder 3 and a plug 1 connected from top to bottom. The upper connector 10 and the outer cylinder 3 are connected by a shear pin 9. The outer cylinder 3 is provided with an axial liquid phase channel and a radially arranged connecting hole 6. The axial liquid phase channel is connected to the oil jacket annulus through the connecting hole 6.

[0044] The outer cylinder 3 is equipped with a reciprocating motion mechanism, which is used to close and connect the axial liquid phase channel and the connecting hole 6 when moving up and down along the axial direction. The upper connector 10 is sealed to the outer cylinder 3 by a sealing ring 8.

[0045] The bottom plugging tool 15 provided by this invention, through its reciprocating motion mechanism, enables repeated opening and closing of the channel between the tubing and casing. It integrates multiple functions, including a tubing plug for live drilling, a shearing ball seat for packer setting, and a live tubing cutter plug for the coiled tubing 11. This achieves integrated functionality for live drilling, annular fluid injection, packer setting, live tubing cutting, and establishing the gas injection channel during gas injection completion operations on the coiled tubing 11. By shearing the sliding sleeve, the ball seat moves downward, establishing the gas injection channel and achieving normal gas injection.

[0046] Example 2:

[0047] Based on Example 1, this example provides a bottom plugging tool, such as... Figure 2 As shown, the reciprocating motion mechanism includes an upper sliding sleeve 7, a lower sliding sleeve 4 and a spring 2 arranged sequentially from top to bottom. A reverse sealing ball 5 is provided between the upper sliding sleeve 7 and the lower sliding sleeve 4. One end of the spring 2 is connected to the plug 1 and the other end of the spring 2 is connected to the lower sliding sleeve 4. The upper sliding sleeve 7 is sealed to the inner wall of the outer cylinder 3, and the lower sliding sleeve 4 can reciprocate up and down along the axial direction.

[0048] Working principle of this invention:

[0049] During the tubing string lowering process, the spring force of spring 2 is used to achieve a one-way seal between the reverse sealing ball 5 and the upper sliding sleeve 7, meeting the requirements for pressurized drilling. After the tubing string is lowered, annular protective fluid is injected from the continuous tubing 11 using a pump truck. Spring 2 is compressed, and the reverse sealing ball 5 disengages from the ball seat, achieving oil-casing connection and enabling the injection of annular protective fluid. After the annular protective fluid circulation is completed, the packer is set by dropping the ball, and the seal is verified after setting. After the tubing is depressurized, the spring force of spring 2 is used to continue to achieve a one-way seal between the reverse sealing ball 5 and the ball seat, meeting the requirements for pressurized tubing plugging. The tubing is then suspended, cut, and the gas production tree is restored. Pressure is continued to be pumped into the continuous tubing 11 using a pump truck, shearing pin 9 and the ball seat are lowered, achieving oil-casing connection, ending the well completion operation, and normal gas injection begins.

[0050] Example 3:

[0051] This embodiment provides a continuous tubing gas injection completion string, such as... Figure 1 As shown, it includes a continuous tubing 11, a large-diameter anchor 16, and a connector 12. The large-diameter anchor 16 is located at the wellhead and sleeved on the continuous tubing 11. The lower end of the continuous tubing 11 is connected in sequence to a safety release handle 13, a gas-tight packer 14, and a bottom plugging tool 15 via the connector 12.

[0052] This invention uses continuous tubing 11 as the completion tubing, minimizing leakage points, improving the gas-tightness of the tubing, and ensuring wellbore safety. A large-diameter anchor 16 ensures the insertion of large-diameter packers while also providing suspension and sealing performance; a gas-tight packer 14 seals the annulus and injects annulus protection fluid; a safety release 13, when the tubing cannot be retrieved, uses tubing pressure shearing to release the release, allowing the upper tubing to be retrieved first before handling the lower tools. A bottom plugging tool 15 solves a series of problems during continuous tubing 11 gas injection completion, including running the tubing under pressure, injecting annulus protection fluid, setting the packer, cutting the tubing under pressure, and establishing the gas injection channel, providing comprehensive technical support for continuous tubing 11 gas injection completion wellbore setup.

[0053] Example 4:

[0054] Based on Example 3, this example provides a coiled tubing completion string. The large-diameter anchor 16 includes a housing 18, a threaded push rod 19, and a conical slip 20. The lower structure inside the housing 18 matches the conical slip 20. The housing 18 has a coiled tubing channel 22. The conical slip 20 is located inside the housing 18 and is circumferentially positioned within the coiled tubing channel 22. The lower inclined end of the threaded push rod 19 is inserted into the housing 18 and is threadedly connected to the housing 18. The lower inclined end of the threaded push rod 19 is connected to the conical slip 20. The bottom end of the conical slip 20 is provided with a metal seal 21.

[0055] Figure 6 This represents the final working state of the large-diameter packer 16. The large-diameter packer 16 facilitates the passage of large-diameter packing tools while also ensuring the suspension and sealing performance of the continuous tubing 11 injection string. For example... Figure 1 As shown, the large-diameter anchor seal 16 is located at the wellhead and is connected by threaded connections.

[0056] like Figure 7 As shown, the threaded push rod 19 is in the retracted preset state, and it is temporarily fixed relative to the housing 18 by the thread. At this time, the central hole (continuous tube channel 22) of the housing 18 is in the open state, which satisfies the normal insertion of large-diameter tools such as the gas-tight packer 14. At this time, the conical slip 20 and the metal seal 21 are in the non-working state.

[0057] After the continuous injection tubing 11 is lowered to the predetermined position, as follows Figure 8As shown, the threaded push rod 19 is screwed into the housing 18 through the connecting thread. The threaded push rod 19, together with the conical slip 20 and the metal seal 21, enters the internal space of the housing 18. Under the action of the conical tilt angle, it achieves engagement with the continuous tube 11. As the weight of the continuous tube 11 is released, the conical slip 20 is suspended from the continuous tube 11. At the same time, under the further action of the conical tilt angle, the metal seal 21 is compressed, and finally the seal with the continuous tube 11 is achieved.

[0058] Example 5:

[0059] This embodiment provides a method for using a coiled tubing gas injection completion string, including the following steps:

[0060] Step 1) Run the coiled tubing gas injection completion string, and during the running-down process, use the bottom plug tool 15 to plug the coiled tubing 11;

[0061] Step 2) After the tubing string is lowered, use a pump truck to inject annular protective fluid into the continuous tubing 11. By increasing the oil pressure, the connecting hole 6 of the bottom plug tool 15 is leaked out, thus achieving oil jacket connection.

[0062] Step 3) After the annular protective fluid circulation is complete, the setting ball 17 is added, the oil pipe is pressurized to achieve oil-jacket connection, and the gas-tight packer 14 is set. After the setting is completed, the seal is checked from the annulus. After the seal is qualified, the oil pipe is depressurized, the oil-jacket is not connected, and the continuous tube 11 is sealed again.

[0063] Step 4) Suspend and cut the pipe, restore the gas production tree, continue pressurizing the continuous pipe 11 using the pump truck, cut the shear pin 9, disengage the outer cylinder 3 from the upper connector 10, and connect the oil jacket; Figure 5 As shown;

[0064] Step 5) Begin normal gas injection; construction complete.

[0065] In step 1), the lowering of the tubing is a pressurized operation. Under the elastic force of the spring 2, the sliding sleeve 4 drives the reverse sealing ball 5 to move upward, and forms a one-way seal with the ball seat at the lower end of the upper sliding sleeve 7, thereby sealing the continuous tube 11 and meeting the requirements of pressurized drilling.

[0066] like Figure 1 As shown, the bottom plug tool 15 is installed at the tail end of the gas-tight packer 14. During drilling, considering pressurized operations, the tubing needs to be plugged, such as... Figure 2 As shown, during the lowering of the tubing, under the elastic force of the spring 2, the sliding sleeve 4 drives the reverse sealing ball 5 to move upward, and forms a ball seat with the lower end of the upper sliding sleeve 7 to achieve a one-way seal, which meets the requirements of drilling under pressure.

[0067] Example 6:

[0068] Based on Example 5, this example provides a method for using a continuous tubing gas injection completion string. The specific process of step 2) is as follows: by increasing the oil pressure, the spring 2 is compressed, and the sliding sleeve 4 drives the reverse sealing ball 5 to move downward. The reverse sealing ball 5 separates from the ball seat formed at the lower end of the upper sliding sleeve 7, exposing the connecting hole 6, thus realizing the connection between the oil sleeve and the casing.

[0069] like Figure 3 As shown, the outer cylinder 3 is designed with a large axially opening hole, and the connecting hole 6 is a small hole opened radially along the outer cylinder 3. There are two small holes, set at 180°, which are connected to the large axially opening hole. The sliding sleeve 4 is located in the large axially opening hole. Figure 2 In this state, the reverse sealing ball 5 and the lower end of the upper sliding sleeve 7 are in a sealed state. Figure 2 Liquid coming from the upper part cannot enter below the reverse sealing ball 5, that is, it cannot enter the connecting hole 6. Only when the reverse sealing ball 5 and the upper sliding sleeve 7 move downwards at the same time, and the lower ends of the reverse sealing ball 5 and the upper sliding sleeve 7 lose their seal, can the liquid enter the connecting hole 6 to complete the filling of the annular protective fluid.

[0070] Example 7:

[0071] Based on Example 5, this example provides a method for using a continuous tubing gas injection completion string, such as... Figure 4 As shown, the specific process of step 3) is as follows: After the annular protective fluid circulation is completed, under the elastic force of spring 2, the sliding sleeve 4 drives the reverse sealing ball 5 to move upward, and achieves one-way sealing with the ball seat formed by the lower end of the upper sliding sleeve 7. The setting ball 17 is put in, the oil pipe is pressurized, and under the elastic force of spring 2, the sliding sleeve 4 drives the reverse sealing ball 5 to move downward, and the connecting hole 6 is exposed again to realize the connection between the oil and the packer. After the setting is completed, the seal is checked from the annulus.

[0072] After the seal is verified as qualified, the oil pipe is depressurized. Under the elastic force of spring 2, the sliding sleeve 4 drives the reverse sealing ball 5 to move upward, and forms a ball seat with the lower end of the upper sliding sleeve 7 to achieve a one-way seal, sealing the connecting hole 6, and once again meeting the requirement of oil pipe pressure sealing.

[0073] In summary, this invention solves a series of problems during gas injection completion of coiled tubing 11 wells, such as running in under pressure, adding annular protective fluid, setting packers, cutting tubing under pressure, and establishing gas injection channels, and provides technical support for wellbore support for gas injection completion of coiled tubing 11 wells.

[0074] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A bottom plugging tool, characterized in that: It includes an upper connector, an outer cylinder and a plug connected in sequence from top to bottom. The upper connector and the outer cylinder are connected by shear pins. The outer cylinder is provided with an axial liquid phase channel and a connecting hole arranged radially. The axial liquid phase channel is connected to the oil jacket annulus through the connecting hole. The outer cylinder is equipped with a reciprocating motion mechanism, which is used to close and connect the axial liquid phase channel and the connecting hole when moving up and down along the axial direction. The reciprocating motion mechanism includes an upper sliding sleeve, a lower sliding sleeve, and a spring arranged sequentially from top to bottom. A reverse sealing ball is provided between the upper sliding sleeve and the lower sliding sleeve. One end of the spring is connected to the plug, and the other end of the spring is connected to the lower sliding sleeve. The upper sliding sleeve is sealed to the inner wall of the outer cylinder, and the lower sliding sleeve can reciprocate up and down along the axial direction.

2. A coiled tubing completion string, characterized in that: It includes a coiled tubing, a large-diameter anchor, and a connector. The large-diameter anchor is located at the wellhead and sleeved on the coiled tubing. The lower end of the coiled tubing is connected in sequence to a safety release device, a gas-tight packer, and the bottom plugging tool as described in claim 1 via the connector.

3. The coiled tubing completion string according to claim 2, characterized in that: The large-diameter anchor includes a housing, a threaded push rod, and a conical slip. The lower structure inside the housing matches the conical slip. The housing has a continuous pipe channel. The conical slip is located inside the housing and is circumferentially within the continuous pipe channel. The lower inclined end of the threaded push rod is inserted into the housing and connected to the housing by threads. The lower inclined end of the threaded push rod is connected to the conical slip. The bottom end of the conical slip is provided with a metal seal.

4. The method of using a coiled tubing completion string according to claim 3, characterized in that: Includes the following steps: Step 1) Run the coiled tubing gas injection completion string, and seal the coiled tubing with a bottom plug during the running-down process; Step 2) After the tubing string is lowered, use a pump truck to inject annular protective fluid from the continuous tubing. By increasing the oil pressure, the connecting hole of the bottom plug tool will be exposed, thus achieving oil-jacket connection. Step 3) After the annular protective fluid has circulated completely, the setting ball is added, the oil pipe is pressurized to achieve oil-jacket connection, and the gas-tight packer is set. After setting is completed, the seal is checked from the annulus. After the seal is qualified, the oil pipe is depressurized, the oil-jacket is disconnected, and the continuous tubing is plugged again. Step 4) Hang and cut the pipe, restore the gas production tree, continue to pressurize the continuous pipe with the pump truck, cut the shear pin, detach the outer cylinder from the upper joint, and connect the oil jacket. Step 5) Begin normal gas injection; construction complete.

5. The method of using a coiled tubing completion string according to claim 4, characterized in that: In step 1), the lowering of the tubing is a pressurized operation. Under the elastic force of the spring, the lower sliding sleeve drives the reverse sealing ball to move upward, and achieves a one-way seal with the ball seat formed by the lower end of the upper sliding sleeve, thereby sealing the continuous tubing and meeting the requirements of pressurized drilling.

6. The method of using a coiled tubing completion string according to claim 4, characterized in that: The specific process of step 2) is as follows: by increasing the oil pressure, the spring is compressed, and the lower sliding sleeve drives the reverse sealing ball to move downward. The reverse sealing ball separates from the ball seat formed at the lower end of the upper sliding sleeve, exposing the connecting hole and realizing the connection between the oil sleeve and the ball.

7. The method of using a coiled tubing completion string according to claim 4, characterized in that: The specific process of step 3) is as follows: After the annular protective fluid is circulated, under the action of the spring, the sliding sleeve drives the reverse sealing ball to move upward, and achieves one-way sealing with the ball seat formed by the lower end of the upper sliding sleeve. The setting ball is put in, the oil pipe is pressurized, and under the action of the spring, the sliding sleeve drives the reverse sealing ball downward, and the connecting hole is exposed again, realizing the connection between the oil and the packer, setting the packer, and after the setting is completed, the seal is checked from the annulus. After the seal is verified as qualified, the oil pipe is depressurized. Under the elastic force of the spring, the lower sliding sleeve drives the reverse sealing ball to move upward, and forms a ball seat with the lower end of the upper sliding sleeve to achieve a one-way seal, sealing the connecting hole and once again meeting the requirement of oil pipe pressure sealing.

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