A coiled tubing gas injection completion string and method of use

Abstract

The application provides a continuous pipe gas injection completion pipe string and a use method, and the pipe string comprises a large-diameter anchor packer, a continuous pipe and a connector, the large-diameter anchor packer is arranged at a wellhead, and the lower end of the continuous pipe is sequentially connected with a double safety shear joint, a gas seal packer, a setting ball seat and a reverse blocking sliding sleeve through the connector. The continuous pipe is used as a completion tubing, the number of leakage points is minimized, the gas seal performance of the pipe string is improved, the reverse blocking sliding sleeve meets the function of pressure drilling, the setting ball seat realizes setting of the packer by ball cutting of the sliding sleeve, the gas seal packer meets the gas seal performance, the double safety shear joint is designed to have two modes of ball hydraulic cutting and lifting load cutting, and double safety is provided for handling accidents, the large-diameter anchor packer guarantees running in of large-diameter packer tools, and suspension and sealing performance are taken into account, meanwhile, the continuous pipe body is processed by using a material with good corrosion resistance, and it is expected that the service life of the continuous pipe in the well can be improved to more than 8 years.

Description

Technical Field

[0001] This invention belongs to the field of oilfield enhanced oil recovery technology, specifically relating to a coiled tubing gas injection completion string and its usage method. It is applicable to situations where gas injection wells need to be completed when oilfields are developing reservoirs using gas injection methods such as CO2 flooding, foam-assisted oxygen-reduced air flooding, and hydrocarbon gas flooding. Background Technology

[0002] Gas drive, as a key technology for enhancing oil recovery, has been increasingly widely used in recent years. In early gas drive tests, well completion operations for injection wells mostly employed conventional gas-tight tubing or ordinary tubing. Taking gas-tight tubing as an example, the tubing string structure generally consists of a bell-shaped inlet, screen pipe, shear sleeve, plugger working cylinder, gas-tight packer, gas-tight tubing, tubing hanger, and injection wellhead, with anti-corrosion protective fluid injected into the annulus. From the perspective of injection wells where completion operations have been performed, the large number of tubing threads increases the probability of leakage. Furthermore, gas-tightness testing devices are often used to check the seal of each thread during tubing connection, resulting in high costs and long completion cycles. In addition, during re-completion or maintenance operations, the pressurized wellbore makes depressurization difficult, requiring the introduction of a gas well pressurization workover rig, which is costly and carries significant safety risks.

[0003] Domestic and international research results show that coiled tubing can be widely used in various technical operations in the oil and gas industry, such as drilling, completion, oil production, and well workover. It has advantages such as short operation cycle, low accident rate, minimal formation damage, and good re-entry performance. However, its application in gas injection wells is rarely reported. This is because large-diameter packers are used downhole, and the mechanical properties of coiled tubing are somewhat inferior to those of conventional tubing. Therefore, introducing coiled tubing into gas injection well completion operations requires overcoming existing technical obstacles in order to maximize its advantages and meet the technical requirements of the field.

[0004] The State Intellectual Property Office published patent CN106246148A on December 21, 2016, entitled "An Invention Patent for an Oil Production Method Using Coiled Tubes to Inject Air into Horizontal Wells." This patent describes a method of sequentially running a shear ball valve, a segmented packer, a ball-dropping sleeve, and another segmented packer into a horizontal well. In the vertical well section, a permanent packer, a sleeve, a movable sub, and a downhole safety valve are run for high-pressure gas injection completion. However, this patent does not take into account the limited yield strength of the coiled tubing. When the packer is unsealed, the required lifting tonnage exceeds the strength of the coiled tubing, which can cause the tubing to break. Summary of the Invention

[0005] The purpose of this invention is to provide a continuous tubing gas injection completion string that overcomes the aforementioned technical problems in the prior art.

[0006] Another objective of this invention is to provide a method for using a continuous tubing gas injection completion string, providing technical support for handling accidents when unexpected situations occur during the tripping process.

[0007] Therefore, the technical solution provided by the present invention is as follows:

[0008] A coiled tubing gas injection completion string includes a large-diameter anchor, coiled tubing, 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 double-safety shear joint, a gas-tight packer, a setting ball seat, and a reverse sealing sleeve via the connector.

[0009] The reverse sealing sleeve includes a body, a sleeve core, and a shear pin. The sleeve core is fixed inside the body by the shear pin. The sleeve core and the body are sealed by a sealing ring. The upper part of the body is provided with a step, and the sleeve core is located below the step.

[0010] The double-safety shearing joint includes an upper connector and a second body. The upper connector and the second body are connected by a shearing structure. The second body is provided with a shearing structure. Both the first and second shearing structures are sheared under the action of external force.

[0011] 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.

[0012] The body 2 is provided with a sliding sleeve core 2. The shearing structure 1 includes a shearing pin and an elastic claw. The elastic claw is located at the lower part of the upper connector. The inner side of the elastic claw is sealed to the sliding sleeve core 2 through a sealing ring 2. The outer side of the elastic claw is fixed to the body 2 through a shearing pin.

[0013] The second shearing structure includes a setting shear pin, and the second sliding sleeve core is fixedly connected to the second body through the setting shear pin.

[0014] A method for using a continuous tubing gas injection completion string: when the string cannot be pulled out of the hole smoothly, the string is lifted up, and when a certain load is exceeded, the shear pin is cut off, causing the upper connector two to detach from the body two, thus allowing the string to be released.

[0015] When it is impossible to release the grip by lifting the tubing string, first insert the setting ball, which sits into the second sliding sleeve core. Then, pressurize the oil pipe to cut the setting shear pin, causing the setting ball to move the second sliding sleeve core downward together, creating space. This allows the elastic claw to contract inward under elastic action, causing the shear pin to lose its fixation and the upper connector to detach from the second body, thus releasing the grip.

[0016] When adding protective fluid to the annulus, the setting ball is inserted, the oil pipe is pressurized, the gas-tight packer completes the sealing and setting, and then the protective fluid is injected.

[0017] The beneficial effects of this invention are:

[0018] The continuous tubing gas injection completion string provided by this invention uses continuous tubing as the completion tubing, which minimizes leakage points and improves the gas sealing performance of the string, providing key technical support for ensuring the safety of the injection wellbore and realizing gas injection throughout its entire life cycle.

[0019] This tubing string, with its reverse sealing sleeve, prevents formation pressure from entering the tubing during installation, effectively sealing the tubing and ensuring normal installation. Once the tubing is in place, the seal can be released by pressurizing the tubing, enabling live drilling. This fully leverages the advantages of continuous tubing for live operations, allowing for live tubing installation and removal throughout the injection well completion process. The operation is simple, significantly shortening the construction period and saving construction costs.

[0020] This invention employs a large-diameter anchor sealer, ensuring the insertion of large-diameter packer tools while also considering suspension and sealing performance. It overcomes the technical obstacles in the application of coiled tubing in gas-driven well completion operations, maximizing the advantages of coiled tubing.

[0021] This invention, considering the limited yield strength of the coiled tubing, employs a double-insurance shear joint to achieve release through two methods: ball-dropping hydraulic shearing and lifting load shearing. This avoids the problem of tubing breakage caused by the lifting tonnage exceeding the strength of the coiled tubing when using the lifting string for unsealing. It solves the technical problem of starting the packer tool in the coiled tubing gas injection string.

[0022] The following will provide a more detailed explanation in conjunction with the accompanying drawings. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of one embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of one implementation method of the reverse sealing sliding sleeve;

[0025] Figure 3 This is a schematic diagram of one implementation of a double-safety shear joint;

[0026] Figure 4 This is a schematic diagram of the structure of a large-diameter anchor seal.

[0027] Figure 5 This is a schematic diagram of the open state of the continuous tube channel of the large-diameter anchor sealer;

[0028] Figure 6 This is a schematic diagram of the closed state of the continuous pipe channel of the large-diameter anchor sealer.

[0029] In the diagram: 1. Continuous tubing; 2. Connector; 3. Large-diameter anchor; 4. Double-safety shear joint; 5. Gas-tight packer; 6. Setting ball seat; 7. Reverse sealing sleeve; 8. Valve #1; 9. Valve #2; 10. Body 1; 11. Sleeve core 1; 12. Shear pin; 13. Sealing ring 1; 14. Upper connector; 15. Body 2; 16. Sleeve core 2; 17. Shear pin; 18. Elastic claw; 19. Sealing ring 2; 20. Housing; 21. Threaded push rod; 22. Conical slip; 23. Metal seal; 24. Continuous tubing channel; 25. Setting shear pin; 26. Setting ball. Detailed Implementation

[0030] 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.

[0031] 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.

[0032] 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.

[0033] Example 1:

[0034] This embodiment provides a continuous tubing gas injection completion string, such as... Figure 1 As shown, it includes a large-diameter anchor sealer 3, a continuous tube 1, and a connector 2. The large-diameter anchor sealer 3 is located at the wellhead and is sleeved on the continuous tube 1. The lower end of the continuous tube 1 is connected in sequence to a double-safety shear joint 4, a gas-tight packer 5, a setting ball seat 6, and a reverse sealing sliding sleeve 7 via the connector 2.

[0035] Among them, connector 2 is used to connect the upper continuous tube 1 and the lower matching tool; gas-tight packer 5 is used to seal the annulus of the oil sleeve and add annulus protection fluid; setting ball seat 6 is a conventional tool for use with hydraulic setting packer. With this tool, setting ball 26 is inserted, and pressure is applied through the oil pipe to achieve effective setting of the packer. If the pressure is further increased, the sliding sleeve core is cut off to achieve unobstructed oil pipe.

[0036] This invention uses continuous tubing 1 as the completion tubing, minimizing leakage points and improving the gas-tightness of the tubing string. This provides key technical support for ensuring wellbore safety and achieving full lifecycle gas injection. The reverse plugging sleeve 7 fulfills the function of running under pressure, and the setting ball seat 6 achieves the setting of the gas-tight packer 5 through ball-dropping shearing of the sleeve. The gas-tight packer 5 meets the gas-tightness requirements, and the double-insurance shearing joint 4 is designed with two methods: ball-dropping hydraulic shearing and lifting load shearing, providing double insurance for handling accidents. The large-diameter anchor sealer 3 ensures the insertion of large-diameter packer tools while taking into account suspension and sealing performance. At the same time, the continuous tubing 1 body is made of 2205 stainless steel with good corrosion resistance, which is expected to extend the downhole service life to more than 8 years.

[0037] Example 2:

[0038] Based on Example 1, this example provides a continuous tubing gas injection completion string, such as... Figure 2 As shown, the reverse sealing sleeve 7 includes a body 10, a sleeve core 11 and a shear pin 12. The sleeve core 11 is fixed inside the body 10 by the shear pin 12. The sleeve core 11 and the body 10 are sealed by a sealing ring 13. The upper part of the body 10 is provided with a step, and the sleeve core 11 is located below the step.

[0039] A step is provided between the sliding sleeve core 11 and the body 10, preventing the sliding sleeve core 11 from moving upward and the formation pressure from entering the tubing, thus effectively sealing the tubing and ensuring the normal insertion of the tubing string. When the tubing string is in place and it is necessary to release the seal, pressure is applied to the tubing to cut the pin, and the sliding sleeve core 11 is separated from the body 10, thereby releasing the seal.

[0040] The tubing string, through the reverse sealing sleeve 7, prevents formation pressure from entering the tubing during tubing insertion, effectively sealing the tubing and ensuring normal tubing insertion. Once the tubing string is in place, the sealing can be released by pressurizing the tubing, satisfying the requirement of running under pressure. This fully leverages the advantages of continuous tubing 1 for live drilling operations, enabling live tubing insertion and tripping operations throughout the injection well completion process. The operation is simple, greatly shortening the construction cycle and saving construction costs.

[0041] Example 3:

[0042] Based on Example 1, this example provides a continuous tubing gas injection completion string. The double-safety shear joint 4 includes an upper joint 14 and a second body 15. The upper joint 14 and the second body 15 are connected by a shear structure 1. The second body 15 is provided with a shear structure 2. Both the first shear structure and the second shear structure 2 are sheared under the action of external force.

[0043] Because the yield strength of the coiled tubing 1 is limited, a double-safety shear joint 4 was designed. The gas-tight packer 5 is generally released by lifting the tubing string. When the lifting tonnage exceeds the strength of the coiled tubing 1, it will cause the tubing to break. The double-safety shear joint 4 is designed with two methods: ball-dropping hydraulic shearing and lifting load shearing. When the packer releases and there is an overload phenomenon that makes it impossible to pull out the tubing string, it can be sheared in advance to pull out the upper tubing string first, and then deal with the lower tool. This solves the technical problem of pulling out the packer tool in the gas injection tubing string of the coiled tubing 1.

[0044] Example 4:

[0045] Based on Example 1, this example provides a continuous tubing gas injection completion string, such as... Figure 4 As shown, the large-diameter anchor seal 3 includes a housing 20, a threaded push rod 21, and a conical slip 22. The lower structure inside the housing 20 matches the conical slip 22. A continuous pipe channel 24 is provided inside the housing 20. The conical slip 22 is located inside the housing 20 and is circumferentially located in the continuous pipe channel 24. The lower inclined end of the threaded push rod 21 is inserted into the housing 20 and is threadedly connected to the housing 20. The lower inclined end of the threaded push rod 21 is connected to the conical slip 22. A metal sealing element 23 is provided at the bottom end of the conical slip 22.

[0046] Figure 4 This represents the final working state of the large-diameter packer 3. The large-diameter packer 3 facilitates the passage of large-diameter packing tools while also ensuring the suspension and sealing performance of the continuous tubing 1 injection string. For example... Figure 1 As shown, the large-diameter anchor seal 3 is located at the wellhead, specifically between valve 8 (1#) and valve 9 (2#), and is a threaded connection.

[0047] like Figure 5 As shown, the threaded push rod 21 is in the retracted preset state, and it is temporarily fixed relative to the housing 20 through the thread. At this time, the central channel (continuous tube channel 24) of the housing 20 is in the open state, which satisfies the normal insertion of large-diameter tools such as the gas-tight packer 5. At this time, the conical slip 22 and the metal seal 23 are in the non-working state.

[0048] After the continuous injection tubing 1 is lowered to the predetermined position, as follows Figure 6As shown, the threaded push rod 21 is screwed into the housing 20 through the connecting thread. The threaded push rod 21, together with the conical slip 22 and the metal seal 23, enters the internal space of the housing 20. Under the action of the conical tilt angle, it achieves engagement with the continuous tube 1. As the weight of the continuous tube 1 is released, the conical slip 22 is suspended from the continuous tube 1. At the same time, under the further action of the conical tilt angle, the metal seal 23 is compressed, and finally the seal with the continuous tube 1 is achieved.

[0049] Example 5:

[0050] Based on Example 3, this example provides a continuous tubing gas injection completion string, such as... Figure 3 As shown, the second body 15 is provided with a second sliding sleeve core 16. The first shearing structure includes a shearing pin 17 and an elastic claw 18. The elastic claw 18 is located at the lower part of the upper connector 14. The inner side of the elastic claw 18 is sealed to the second sliding sleeve core 16 through a second sealing ring 19. The outer side of the elastic claw 18 is fixed to the second body 15 through the shearing pin 17.

[0051] The second shearing structure includes a setting shear pin 25, and the second sliding sleeve core 16 is fixedly connected to the second body 15 by the setting shear pin 25.

[0052] If the lower gas-tight packer 5 experiences overload upon release and the tubing cannot be removed, the upper tubing can be removed first using the double-safety shear joint 4, followed by the removal of the lower tool. The specific process is as follows:

[0053] When the tubing is lifted, if the load exceeds a certain level, the shear pin 17 is cut off, and the upper connector 14 is disengaged from the body 2 15, thus releasing the load. Alternatively, the setting ball 26 can be inserted, the sliding sleeve core 2 16 can be seated, the oil pipe can be pressurized, the setting shear pin 25 can be cut off, the setting ball 26 and the sliding sleeve core 2 16 can move downward together, making room, the elastic claw 18 can contract inward under the elastic action, lose its fixation to the shear pin 17, and the upper connector 14 can be disengaged from the body 2 15, thus releasing the load.

[0054] Example 6:

[0055] This embodiment provides a method for using a continuous tubing gas injection completion string. When the string cannot be pulled out of the hole smoothly, the string is lifted up. When the load exceeds a certain level, the shear pin 17 is cut off, causing the upper connector 14 to detach from the body 15, thus allowing the string to be released.

[0056] The gas-tight packer 5 is generally released by lifting the tubing string. When the gas-tight packer 5 is overloaded and the tubing string cannot be lifted out, it can be pre-cut by using the double-safety shear joint 4, that is, the shear pin 17 is cut off by lifting the tubing string, so that the upper joint 14 is separated from the body 15, and the upper tubing string is lifted out first.

[0057] Example 7:

[0058] Based on Example 6, this example provides a method for using a continuous tubing gas injection completion string. When it is impossible to release the string by lifting it, first insert the setting ball 26, set the sliding sleeve core 16, and then pressurize the tubing to shear the setting shear pin 25. This causes the setting ball 26 to move the sliding sleeve core 16 downwards, creating space so that the elastic claw 18 can contract inwards under elastic action. The shear pin 17 loses its fixation, causing the upper connector 14 to detach from the body 15, thus releasing the string.

[0059] This invention takes into account the limited yield strength of the continuous tube 1 and uses a double-safety shear joint 4 to shear and remove the upper tube first. When the tonnage of the unsealing gas seal packer 5 exceeds the strength of the continuous tube 1, it will cause the tube to break. Therefore, when the packer unsealing causes overload and the tube cannot be removed, the upper tube can be removed. Instead, the setting ball 26 is inserted and the sliding sleeve core 16 is seated. Then, pressure is applied through the oil pipe to shear the setting shear pin 25, causing the setting ball 26 to drive the sliding sleeve core 16 downward together, making room for the elastic claw 18 to contract inward under the elastic action. The shear pin 17 loses its fixation, causing the upper joint 14 to separate from the body 15.

[0060] When the annulus is filled with protective fluid, the setting ball 26 is inserted, the oil pipe is pressurized, and the gas-tight packer 5 completes the sealing and setting. Then, protective fluid is injected. This achieves annular sealing of the oil jacket.

[0061] 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 coiled tubing completion string, characterized in that: It includes a large-diameter anchor, a coiled tubing, 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 double-safety shear joint, a gas-tight packer, a setting ball seat, and a reverse sealing sleeve via the connector. The double-safety shearing joint includes an upper joint and a second body. The upper joint and the second body are connected by a shearing structure. The second body is provided with a shearing structure. Both the shearing structure and the shearing structure are sheared under the action of external force. The body 2 is provided with a sliding sleeve core 2. The shearing structure 1 includes a shearing pin and an elastic claw. The elastic claw is located at the lower part of the upper connector. The inner side of the elastic claw is sealed to the sliding sleeve core 2 through a sealing ring 2. The outer side of the elastic claw is fixed to the body 2 through a shearing pin. The second shearing structure includes a setting shear pin, and the second sliding sleeve core is fixedly connected to the second body through the setting shear pin; When the drill string cannot be pulled out smoothly, the drill string is lifted up. When the load exceeds a certain level, the shear pin is cut off, so that the upper connector two is separated from the body two, and the drill string can be released. When it is impossible to release the grip by lifting the tubing string, first insert the setting ball, which sits into the second sliding sleeve core. Then, pressurize the oil pipe to cut the setting shear pin, causing the setting ball to move the second sliding sleeve core downward together, creating space. This allows the elastic claw to contract inward under elastic action, causing the shear pin to lose its fixation and the upper connector to detach from the second body, thus releasing the grip.

2. The coiled tubing completion string according to claim 1, characterized in that: The reverse sealing sleeve includes a body, a sleeve core, and a shear pin. The sleeve core is fixed inside the body by the shear pin. The sleeve core and the body are sealed by a sealing ring. The upper part of the body is provided with a step, and the sleeve core is located below the step.

3. The coiled tubing completion string according to claim 1, 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 1, characterized in that: When adding protective fluid to the annulus, the setting ball is inserted, the oil pipe is pressurized, the gas-tight packer completes the sealing and setting, and then the protective fluid is injected.

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