Coiled tubing and tubing combined string connection tool and method of operation

Abstract

This invention relates to a tool and method for connecting a coiled tubing and tubing combination string. The tool includes a coiled tubing connector, a locking rotary joint, and a normally open safety valve. The coiled tubing connector is fitted over the coiled tubing and secures it. The locking rotary joint includes an upper tubing body, a lower tubing body, and a locking mechanism. The upper and lower tubing bodies are circumferentially rotatable and axially fixedly connected. The lower tubing body can rotate relative to the upper tubing body when the locking mechanism is in the unlocked position, and is locked and fixed to the upper tubing body when the locking mechanism is in the locked position. The upper end of the normally open safety valve can be threadedly connected to the lower end of the lower tubing body, and the lower end of the normally open safety valve can be threadedly connected to a conventional tubing string. This invention facilitates the connection of coiled tubing and conventional tubing strings and includes a built-in blowout preventer, significantly improving the running-in capability and depth of the combination string in ultra-long horizontal sections of wells, and reducing operating costs compared to conventional methods.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field construction technology, and in particular to a tool and method for connecting a coiled tubing and a tubing combination string. Background Technology

[0002] More than 40% of China's remaining oil and gas resources are located in deep strata below 5000m. In some areas, shale gas deposits have increased to depths of over 3000m, with well depths exceeding 5000m. Well sites are mostly situated in hilly areas. Existing mainstream 2-inch × 5000m coiled tubing equipment is insufficient to meet the operating well depths and transportation requirements in mountainous terrain. Furthermore, operating coiled tubing in long horizontal sections of deep shale gas wells presents challenges in terms of running-in and applying drilling pressure, as well as limitations in discharge capacity and incomplete cuttings removal. On the one hand, it is necessary to limit the total weight and dimensions of coiled tubing installation machines to address the transportation constraints in mountainous terrain. On the other hand, it is necessary to increase the diameter and length of the coiled tubing wound by the drum of the installation machine to extend the running depth and increase operational capacity. To meet the needs of deep shale gas development, a balance must be found between these two conflicting demands, or a new solution must be developed. In addition, the complex terrain conditions in some areas of tight oil development also make it difficult to transport large-diameter continuous pipe laying machines. The limited length of the large-diameter continuous pipe to be wound also requires special design of continuous pipe equipment and operation methods.

[0003] Therefore, for the shale gas or tight oil and gas wells with a maximum vertical depth of 5000m and a horizontal section length of 2000-3000m that are gradually increasing in number in China, the use of small-diameter coiled tubing for horizontal well sections is limited in terms of depth, operational capacity, and feasible process types; the weight and size of large-diameter coiled tubing workover rigs of 2.375in and above exceed the limits, making production, manufacturing, and transportation difficult under complex terrain conditions; and the inability of conventional tubing-based pressurized workover rigs to be continuously towed and circulated, and the high operating costs and low efficiency, these are problems that urgently need to be addressed.

[0004] Therefore, based on years of experience and practice in related industries, the inventor proposes a tool and method for connecting coiled tubing and tubing to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a tool and method for connecting a coiled tubing and a conventional tubing string, which can facilitate the connection of coiled tubing and conventional tubing strings, and has a built-in internal blowout preventer, which significantly improves the operational capability and application range, and reduces the operating cost.

[0006] The objective of this invention can be achieved using the following technical solutions:

[0007] This invention provides a tool for connecting a coiled tubing and a tubing assembly, comprising a coiled tubing connector, a locking rotary joint, and a normally open safety valve connected sequentially from top to bottom. The coiled tubing connector is used to fit over the coiled tubing and secure it. The locking rotary joint includes an upper tubing body, a lower tubing body, and a locking mechanism. The upper and lower tubing bodies are circumferentially rotatable and axially fixedly connected. The lower tubing body can rotate relative to the upper tubing body when the locking mechanism is in the unlocked position, and is locked and fixed to the upper tubing body when the locking mechanism is in the locked position. The upper end of the normally open safety valve can be threadedly connected to the lower end of the lower tubing body, and the lower end of the normally open safety valve can be threadedly connected to a conventional tubing assembly.

[0008] In a preferred embodiment of the present invention, the inner wall of the upper tube is provided with an annular groove, and the outer wall of the lower end of the upper tube is formed with a plurality of circumferentially spaced toothed grooves; an annular protrusion is provided on the outer wall of the lower tube, the annular protrusion being rotatably embedded in the annular groove, and a plurality of circumferentially spaced protrusions are formed on the outer wall of the lower tube below the annular protrusion; a retaining ring and a locking nut are also sleeved on the lower tube, the upper end of the retaining ring being formed with a plurality of circumferentially spaced toothed blocks, the protrusions being able to be embedded in the gap between two adjacent toothed blocks, and the toothed blocks being able to be inserted into the toothed grooves; the locking nut is threadedly connected to the lower tube, and the toothed grooves, protrusions, retaining rings and locking nut constitute a locking mechanism.

[0009] In a preferred embodiment of the present invention, an upper axial thrust bearing and a lower axial thrust bearing are respectively sleeved on both sides of the annular protrusion. The upper axial thrust bearing and the lower axial thrust bearing are both embedded in the annular groove and abut against the groove wall of the annular groove.

[0010] In a preferred embodiment of the present invention, the upper tube body includes an upper connecting pipe and an intermediate connecting pipe. The upper inner wall of the intermediate connecting pipe is threadedly connected to the lower outer wall of the upper connecting pipe. A limiting step is protruding from the lower inner wall of the intermediate connecting pipe. The space enclosed by the lower end face of the upper connecting pipe, the inner wall of the intermediate connecting pipe, and the limiting step forms an annular groove. A toothed groove is formed on the intermediate connecting pipe. The lower tube body includes a core tube and a lower connecting pipe. An annular protrusion is formed on the core tube. The lower end of the core tube extends out of the intermediate connecting pipe. The upper inner wall of the lower connecting pipe is threadedly connected to the lower outer wall of the core tube. A protrusion is formed on the lower connecting pipe. A retaining ring and a locking nut are both sleeved on the lower connecting pipe.

[0011] In a preferred embodiment of the present invention, the continuous tube connector has an upper slip and a lower slip that are radially retractable and have teeth on their inner walls. The upper slip and the lower slip are arranged at an interval between each other. Both the upper slip and the lower slip are arranged in a retracted state and the teeth can grip the continuous tube.

[0012] In a preferred embodiment of the present invention, the continuous tube connector further includes a first connector, a second connector, and a third connector connected sequentially from top to bottom. The first connector has a first inner conical surface with a downwardly expanding diameter. The outer wall of the upper clamp is a first outer conical surface that mates with the first inner conical surface. The upper clamp is inserted into the first connector in a contracted state. The upper outer wall of the second connector is threadedly connected to the lower inner wall of the first connector, and the upper end of the second connector can abut against the upper clamp. The second connector has a second inner conical surface with a downwardly expanding diameter. The outer wall of the lower clamp is a second outer conical surface that mates with the second inner conical surface. The lower clamp is inserted into the second connector in a contracted state. The upper outer wall of the third connector is threadedly connected to the lower inner wall of the second connector, and the upper end of the third connector can abut against the lower clamp.

[0013] In a preferred embodiment of the present invention, both the upper slip and the lower slip are tapered tubes with longitudinal cuts, the teeth are formed on the inner wall of the tapered tube, and the first outer tapered surface or the second outer tapered surface is formed on the outer wall of the tapered tube; multiple slits are formed on the tube wall of the tapered tube, and the slits extend to one end of the tapered tube.

[0014] In a preferred embodiment of the present invention, a plurality of radial holes are provided in the upper part of the first connecting pipe, and set screws are inserted in the radial holes, the set screws being able to abut against the outer wall of the continuous pipe.

[0015] In a preferred embodiment of the present invention, the normally open safety valve includes a sliding double-disc valve and a ball-throwing sliding sleeve. The sliding double-disc valve has a tubular structure and its upper end is threadedly connected to the lower pipe body. The sliding double-disc valve has a valve disc provided on its inner wall. The ball-throwing sliding sleeve is provided inside the sliding double-disc valve by a shear pin, and the valve disc can abut against the outer wall of the ball-throwing sliding sleeve to keep the valve disc in an open state. A stepped surface is provided on the lower inner wall of the ball-throwing sliding sleeve, and the stepped surface forms the ball seat of the ball-throwing sliding sleeve.

[0016] In a preferred embodiment of the present invention, the sliding double-disc valve includes an outer protective tube, an annular mounting groove is provided inside the outer protective tube, and a double-disc one-way valve, a gasket and a spring washer are arranged sequentially from top to bottom in the annular mounting groove. The upper end of the double-disc one-way valve and the lower end of the spring washer respectively abut against the two side walls of the annular mounting groove. The ball-throwing sliding sleeve is inserted into the inner through hole of the double-disc one-way valve and abuts against the valve disc in the double-disc one-way valve. The ball-throwing sliding sleeve is connected to the gasket by a shear pin.

[0017] In a preferred embodiment of the present invention, an annular receiving cavity is provided on the inner wall of the outer protective tube and below the annular mounting groove. The inner diameter of the annular receiving cavity is larger than the outer diameter of the throwing sleeve, the axial length of the annular receiving cavity is larger than the axial length of the throwing sleeve, and the inner diameter of the outer protective tube below the annular receiving cavity is smaller than the outer diameter of the throwing sleeve.

[0018] The present invention also provides a method for operating a coiled tubing and tubing combination string, the method comprising the following steps:

[0019] Depending on whether the wellhead needs to be pressurized throughout the oil and gas well operation, a tubing pressurized workover rig or a conventional workover rig should be used, and the corresponding workover wellhead equipment should be installed.

[0020] Depending on the required work process, after connecting the work tools to the conventional tubing, use a tubing pressurized workover rig or a conventional workover rig to run the conventional tubing into the well to the designed length.

[0021] A conventional tubing string of the designed length is temporarily suspended at the wellhead. Using the aforementioned continuous tubing and tubing combination string connection tool, a continuous tubing of the same diameter is connected to the conventional tubing string to form a working string.

[0022] The working string is lowered into place for operation;

[0023] After the operation is completed, the conventional tubing string is pulled out to the wellhead and temporarily suspended;

[0024] Remove the coiled tubing from the conventional tubing string;

[0025] Use a tubing pressurization device or a conventional workover rig to pull out the conventional tubing from the well one by one.

[0026] Shut down the well and await further instructions.

[0027] In a preferred embodiment of the present invention, removing the coiled tubing from the conventional tubing string specifically includes the following steps: after confirming that there is no pressure at the wellhead, the locking mechanism is adjusted to the unlocked position, and the connection thread between the normally open safety valve and the conventional tubing string is disassembled by rotation, thereby removing the coiled tubing and the connection tool between the coiled tubing and the tubing assembly string from the conventional tubing string.

[0028] In a preferred embodiment of the present invention, removing the coiled tubing from a conventional tubing string specifically includes the following steps: adjusting the normally open safety valve to the closed position;

[0029] Adjust the locking mechanism to the unlocked position;

[0030] Remove the coiled tubing, coiled tubing connector, and locking rotary joint from the wellhead by rotating to disconnect the threaded connection between the locking rotary joint and the normally open safety valve.

[0031] As described above, the connection tool and operation method of this invention, through the cooperation of the coiled tubing connector, the locking rotary joint, and the normally open safety valve, and by repeatedly switching between the unlocking and locking positions of the locking mechanism, can easily achieve the connection and disassembly of the coiled tubing and conventional tubing strings. Utilizing the normally open safety valve, internal blowout prevention can be achieved when the wellhead is pressurized, making it safer to use. It effectively solves the problem of previously being unable to complete the threaded connection of two types of tubing strings by rotating the coiled tubing or the tubing, and has a pre-installed internal blowout prevention function. It realizes the combination of a large-diameter connecting pipe with the same diameter as conventional tubing and a conventional tubing string to form a combined tubing string. During well operations, it can fully combine and utilize the high buckling resistance of the conventional tubing string to extend the running depth and apply drilling pressure, as well as the continuous dragging and circulation capabilities of the coiled tubing under pressure, etc., to complete various conventional or complex operation processes in deep, ultra-long horizontal sections of oil and gas wells. This forms a tight oil and gas coiled tubing combined tubing string operation technology adapted to complex terrain conditions, significantly improving operational capabilities and application scope, and reducing operating costs. Attached Figure Description

[0032] The following figures are intended only to illustrate and explain the present invention and do not limit the scope of the invention. Wherein:

[0033] Figure 1 : This is a structural diagram of the continuous tubing and tubing combination connection tool provided by the present invention.

[0034] Figure 2 : This is a structural diagram of the continuous tube connector provided by the present invention.

[0035] Figure 3 : This is a structural diagram of the locking rotary joint provided by the present invention.

[0036] Figure 4 : This is a structural diagram of the retaining ring provided by the present invention.

[0037] Figure 5 :for Figure 4 Sectional view along the middle AA.

[0038] Figure 6 : This is a structural diagram of the normally open safety valve provided by the present invention.

[0039] Figure 7 : This is a structural diagram of the working wellhead provided by the present invention.

[0040] Figure 8 : Another structural diagram of the working wellhead provided by the present invention.

[0041] Explanation of icon numbers:

[0042] 1. Continuous tube connector;

[0043] 11. First connecting pipe; 111. Radial hole; 12. Upper slip; 13. Second connecting pipe; 14. Lower slip; 15. Third connecting pipe;

[0044] 2. Locking rotary joint;

[0045] 21. Upper pipe body; 211. Annular groove; 212. Upper connecting pipe; 213. Intermediate connecting pipe; 2131. Toothed groove; 2132. Limiting step;

[0046] 22. Lower tube body; 221. Core tube; 2211. Annular protrusion; 222. Lower connecting pipe; 2221. Protrusion; 223. Upper axial thrust bearing; 224. Lower axial thrust bearing;

[0047] 23. Snap ring; 231. Tooth block;

[0048] 24. Tighten the nut;

[0049] 3. Normally open safety valve;

[0050] 31. Sliding sleeve double-disc valve

[0051] 311. Upper protective tube; 312. Lower protective tube; 3121. Annular flange; 3122. Annular receiving cavity;

[0052] 313. Annular mounting groove;

[0053] 314. Double-disc check valve; 3140. Disc-type check valve; 3141. Valve seat; 3142. Pin; 3143. Torsion spring; 3144. Valve disc; 3145. Valve body;

[0054] 315. Washer ring; 3151. Shear nail;

[0055] 316. Spring washers;

[0056] 32. Throwing slide;

[0057] 100. Wellhead main valve;

[0058] 200. Suspended and semi-sealed double-gate blowout preventer;

[0059] 300, Standard four-gate blowout preventer;

[0060] 400, Spray Protector;

[0061] 500, Injection Head;

[0062] 600. Tubing live working device; 601. Suspension and annular sealing mechanism; 602. Stepping axial feed mechanism;

[0063] 700. Support frame;

[0064] 800, Gooseneck Frame. Detailed Implementation

[0065] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0066] like Figures 1 to 6 As shown, this embodiment provides a tool for connecting a coiled tubing and a tubing assembly, including a coiled tubing connector 1, a locking rotary joint 2, and a normally open safety valve 3 connected sequentially from top to bottom. The coiled tubing connector 1 is used to fit over the coiled tubing and secure it. The locking rotary joint 2 includes an upper tubing body 21, a lower tubing body 22, and a locking mechanism. The upper tubing body 21 and the lower tubing body 22 are circumferentially rotatable and axially fixedly connected. The lower tubing body 22 can rotate relative to the upper tubing body 21 when the locking mechanism is in the unlocked position, and is locked and fixed to the upper tubing body 21 when the locking mechanism is in the locked position. The upper end of the normally open safety valve 3 can be threadedly connected to the lower end of the lower tubing body 22, and the lower end of the normally open safety valve 3 can be threadedly connected to a conventional tubing assembly.

[0067] During operation, the conventional tubing string is lowered into the well to the designated position and temporarily suspended at the wellhead. The coiled tubing is then lowered to a certain distance above the conventional tubing string using the injection head 500. The coiled tubing connector 1 is connected to the coiled tubing to secure it. The locking rotary joint 2 is threadedly connected to the coiled tubing connector 1. The lower end of the normally open safety valve 3 is threadedly connected to the upper end of the conventional tubing string. Then, the injection head 500 is lowered into the coiled tubing so that the lower thread of the locking rotary joint 2 aligns with the upper thread of the normally open safety valve 3. The locking mechanism of the locking rotary joint 2 is adjusted to the unlocked position, allowing the lower end of the lower tubing body 22 and the upper tubing body 21 to rotate relative to each other and engage with the upper thread of the normally open safety valve 3. Finally, the locking mechanism is adjusted to the locked position. This connection tool can then be used to connect the coiled tubing and the conventional tubing string to form a combined tubing string.

[0068] After the operation is completed, the conventional tubing string is pulled out and temporarily suspended at the wellhead, and the locking mechanism is adjusted to the unlocked position. If there is no pressure at the wellhead, the coiled tubing and connecting tools can be removed from the conventional tubing string by rotating and disassembling the connecting thread between the normally open safety valve 3 and the conventional tubing string. If there is pressure at the wellhead, the normally open safety valve 3 needs to be adjusted to the closed position to prevent the fluid in the well from flowing back up, thus achieving the internal blowout prevention function in the tubing string. Then, the coiled tubing, coiled tubing connector 1, and locking rotary joint 2 can be removed from the conventional tubing string by disassembling the connecting thread between the locking rotary joint 2 and the normally open safety valve 3.

[0069] Therefore, the connection tool in this embodiment, through the cooperation of the continuous tubing connector 1, the locking rotary joint 2 and the normally open safety valve 3, and by switching the unlocking position and locking position of the locking mechanism multiple times, can easily realize the connection and disassembly of the continuous tubing and the conventional tubing string. With the setting of the normally open safety valve 3, blowout prevention can be achieved in the tubing string when the wellhead is pressurized, making it safer to use. It effectively solves the problem of not being able to complete the threaded connection of two types of tubing strings using either rotating coiled tubing or tubing, and has a built-in internal blowout preventer. It enables the combination of a large-diameter connecting pipe with the same diameter as conventional tubing to form a combined tubing string. During well operations, it can fully combine and utilize the high buckling resistance and locking capacity of conventional tubing to extend the running depth and apply drilling pressure, as well as the continuous dragging and circulation capabilities of coiled tubing under pressure. This allows for the completion of various conventional or complex operations in deep, ultra-long horizontal sections of oil and gas wells, forming a tight oil and gas coiled tubing combined tubing operation technology adapted to complex terrain conditions. This significantly improves operational capabilities and application scope (specifically, it improves the running-in capability and depth of combined tubing strings in ultra-long horizontal sections of wells), and reduces operational costs compared to conventional methods.

[0070] It should be noted that the "up" and "down" positions mentioned in the text refer to the orientation of the connection tool according to... Figure 1 The diagram shows the vertical orientation of the tool when it is placed vertically. The terms "top," "bottom," "upper," "lower," and similar expressions used in this article are for illustrative purposes only and do not represent the only possible implementation. In actual use, the connecting tool can be placed vertically or horizontally. Generally, the connecting tool is placed horizontally in most working states, depending on the working depth. If the horizontal section of the oil and gas well is long, the connecting tool is placed horizontally; if the horizontal section is short, the connecting tool is placed vertically.

[0071] In the specific implementation, to facilitate the switching of the locking mechanism between the unlocked and locked positions, such as... Figures 3 to 5 As shown, the inner wall of the upper tube 21 is provided with an annular groove 211, and the lower outer wall of the upper tube 21 is formed with a plurality of circumferentially spaced toothed grooves 2131. An annular protrusion 2211 is provided on the outer wall of the lower tube 22, and the annular protrusion 2211 is rotatably embedded in the annular groove 211. A plurality of circumferentially spaced protrusions 2221 are formed on the outer wall of the lower tube 22, below the annular protrusion 2211. A retaining ring 23 and a locking nut 24 are also fitted onto the lower tube 22. The upper end of the retaining ring 23 is formed with a plurality of circumferentially spaced toothed blocks 231. The protrusions 2221 can be embedded in the gap between two adjacent toothed blocks 231, and the toothed blocks 231 can be inserted into the toothed grooves 2131. The locking nut 24 is threadedly connected to the lower tube 22. The toothed grooves 2131, protrusions 2221, retaining ring 23, and locking nut 24 constitute a locking mechanism.

[0072] When connecting the continuous tubing to the conventional tubing string and activating the rotation function of the locking rotary joint 2, the locking nut 24 can be loosened to disengage the upper end face of the locking nut 24 from the lower end face of the retaining ring 23 and maintain a certain gap. This gap should be greater than the axial engagement length between the toothed block 231 and the toothed groove 2131. Then, the retaining ring 23 is moved downward to disengage the toothed block 231 from the toothed groove 2131. At this time, under the action of external force, the lower tubing 22 can rotate relative to the upper tubing 21, and the locking mechanism is in the unlocked position. When the locking function of the locking rotary joint 2 needs to be activated, the retaining ring 23 is moved axially upwards, and the protrusion 2221 is inserted into the gap between two adjacent toothed blocks 231, so that the toothed blocks 231 are inserted into the toothed grooves 2131 and maintained in engagement. Then, the locking nut 24 is tightened, so that the upper end face of the locking nut 24 abuts against the lower end face of the retaining ring 23. At this time, the locking mechanism is in the locked position, and the upper tube body 21 and the lower tube body 22 cannot rotate relative to each other. In this way, by repeatedly operating the locking nut 24 and the retaining ring 23, the locking function and rotation function of the locking rotary joint 2 can be switched multiple times, which is simple and convenient.

[0073] Preferably, to improve the tensile strength of the locking rotary joint 2 under axial load, an upper axial thrust bearing 223 and a lower axial thrust bearing 224 are respectively fitted on both sides of the annular protrusion 2211. Both the upper and lower axial thrust bearings 224 are embedded in the annular groove 211 and abut against the groove wall of the annular groove 211. This ensures that the lower tube 22 can rotate smoothly relative to the upper tube 21 under a certain axial load.

[0074] For ease of processing and installation, the upper pipe body 21 includes an upper connecting pipe 212 and an intermediate connecting pipe 213. The upper inner wall of the intermediate connecting pipe 213 is threadedly connected to the lower outer wall of the upper connecting pipe 212. A limiting step 2132 is protruding from the lower inner wall of the intermediate connecting pipe 213. The space formed by the lower end face of the upper connecting pipe 212, the inner wall of the intermediate connecting pipe 213, and the limiting step 2132 constitutes an annular groove 211 (the lower end face of the lower connecting pipe 222 and the limiting step 2132 respectively constitute the two side walls of the annular groove 211). A toothed groove 2131 is formed on the intermediate connecting pipe 213. The lower pipe body 22 includes a core tube 221 and a lower connecting pipe 222. An annular protrusion 2211 is formed on the core tube 221, and the lower end of the core tube 221 extends out of the intermediate connecting pipe 213. The upper inner wall of the lower connector 222 is threadedly connected to the lower outer wall of the core tube 221. A protrusion 2221 is formed on the lower connector 222, and a retaining ring 23 and a locking nut 24 are both fitted onto the lower connector 222. It can be understood that sealing rings are sandwiched between the upper connector 212 and the intermediate connector 213, as well as between the core tube 221 and the upper connector 212, the intermediate connector 213, and the lower connector 222, to ensure sealing at each point.

[0075] More specifically, the upper part of the upper pipe 212 is provided with an internal thread, which is screwed into the lower end of the continuous pipe connector 1; the lower outer surface of the upper pipe 212 is an external thread structure, which is screwed into the internal thread on the upper part of the intermediate pipe 213; the lower outer surface and the lower inner surface of the upper pipe 212 are also provided with annular sealing grooves for installing O-ring seals; the lower end face of the upper pipe 212 abuts against the upper end face of the upper axial thrust bearing 223; the upper pipe 212 is generally a stepped through hole structure, the lower inner surface of the upper pipe 212 is a stepped structure, and the shoulder should maintain a certain gap with the upper end face of the core tube 221 to avoid affecting the rotation of the lower tube 22. The intermediate connector 213 has a stepped through-hole structure, with an internally threaded upper inner surface that screws into the upper connector 212. Its lower limiting step 2132 abuts against the lower axial thrust bearing 224 to restrict its axial downward movement. The inner wall of the limiting step 2132 has grooves and is fitted with a sealing ring. Each toothed groove 2131 is formed on the lower outer surface of the intermediate connector 213, and each toothed groove 2131 connects to the lower end face of the intermediate connector 213.

[0076] The core tube 221 has a stepped through-hole structure, installed inside the intermediate connector 213 and extending a certain length beyond the lower end face of the intermediate connector 213. Generally, an internal hexagonal structure is provided on the upper inner surface of the core tube 221 to facilitate fixing the core tube 221 using relevant tools when connecting it to the lower connector 222. The middle of the outer surface of the core tube 221 is the aforementioned annular protrusion 2211. A gap should be left between the outer diameter of the annular protrusion 2211 and the inner surface of the intermediate connector 213 (specifically, the bottom of the annular groove 211) to avoid affecting the rotation of the core tube 221. Two sets of thrust bearings are respectively fitted onto the upper and lower parts of the annular protrusion 2211 and abut against the end faces of the thrust bearings. An O-ring sealing structure and external connecting threads are provided on the lower outer surface of the core tube 221. The lower connecting pipe 222 has a stepped internal through-hole structure. The upper inner surface of the lower connecting pipe 222 is threaded and engages with the lower external thread of the core tube 221. The shoulder of the internal through-hole abuts against the lower end face of the core tube 221. The aforementioned protrusion 2221 is formed on the upper outer wall of the lower connecting pipe 222. The protrusion 2221 can be locked in the upper straight groove of the retaining ring 23 (that is, in the gap between two adjacent tooth blocks 231). Generally, the protrusion 2221 is square and its outer surface is arc-shaped. The outer diameter of the protrusion 2221 should be the same as the outer diameter of the intermediate connecting pipe 213. The lower outer surface of the lower connecting pipe 222 has an external thread structure and engages with the upper thread of the normally open safety valve 3.

[0077] The aforementioned retaining ring 23 has a through-hole structure and is fitted onto the outside of the lower connecting pipe 222. The upper part of the retaining ring 23 has multiple toothed blocks 231, which can cross-mesh with the toothed grooves 2131 on the lower outer surface of the intermediate connecting pipe 213. The lower end face of the retaining ring 23 can abut against the upper end face of the locking nut 24. The locking nut 24 has a through-hole structure and a fully threaded inner surface, which screws onto the threads on the outer surface of the lower connecting pipe 222.

[0078] Of course, the locking mechanism described above can also adopt other structural forms, as long as it can easily realize the locking and unlocking functions between the upper tube 21 and the lower tube 22. This embodiment is only for illustrative purposes.

[0079] Furthermore, since the coiled tubing is connected to the conventional tubing string via this connection tool, the coiled tubing connector 1 should be a heavy-duty type to withstand greater tensile loads.

[0080] To improve the tensile strength of continuous tubing, such as Figure 2 As shown, the continuous tube connector 1 has an upper slip 12 and a lower slip 14 that can retract radially and have teeth on their inner walls. The upper slip 12 and the lower slip 14 are arranged at an interval between each other. Both the upper slip 12 and the lower slip 14 are in a retracted state and the teeth can grip the continuous tube.

[0081] During installation, after inserting the continuous tube into the continuous tube connector 1, the upper clamp 12 and lower clamp 14 are adjusted to their retracted positions, allowing the jaws of each clamp to grip the outer surface of the continuous tube, thus securing it. By incorporating two sets of wedge-shaped clamp structures inside the continuous tube connector 1, the jaws of these structures grip the outer surface of the continuous tube fitted inside the connector 1, preventing axial movement between the connector 1 and the continuous tube. Furthermore, with two sets of wedge-shaped clamp structures, when simultaneously gripping the continuous tube, it can withstand higher axial tensile loads, resulting in more reliable performance.

[0082] Furthermore, to facilitate adjustment of the clamps to a retracted state during installation, the continuous pipe connector 1 also includes a first connector 11, a second connector 13, and a third connector 15 connected sequentially from top to bottom. The first connector 11 has a first inner conical surface with a downwardly expanding diameter. The outer wall of the upper clamp 12 is a first outer conical surface that mates with the first inner conical surface. The upper clamp 12 is inserted into the first connector 11 in a retracted state. The upper outer wall of the second connector 13 is threaded to the lower inner wall of the first connector 11, and the upper end of the second connector 13 can abut against the upper clamp 12. The second connector 13 has a second inner conical surface with a downwardly expanding diameter. The outer wall of the lower clamp 14 is a second outer conical surface that mates with the second inner conical surface. The lower clamp 14 is inserted into the second connector 13 in a retracted state. The upper outer wall of the third connector 15 is threaded to the lower inner wall of the second connector 13, and the upper end of the third connector 15 can abut against the lower clamp 14.

[0083] Specifically, the interior of the entire continuous tube connector 1 has a stepped through-hole structure. The aforementioned first inner conical surface is formed on the inner surface of the middle part of the first connecting tube 11. The upper clamp 12 is installed inside the first connecting tube 11. The taper of the first inner conical surface and the first outer conical surface should be the same, and the two can fit together. The first connecting tube 11 is connected to the upper external thread of the second connecting tube 13 through internal thread engagement. The upper end face of the second connecting tube 13 abuts against the lower end face of the upper clamp 12. By tightening the connecting threads of the first connecting tube 11 and the second connecting tube 13, the upper clamp 12 is driven to contract radially, thereby gripping the continuous tube.

[0084] Similarly, the aforementioned second inner conical surface is formed on the middle inner surface of the second connector 13. The taper of the second inner conical surface and the second outer conical surface should be the same, and they can fit together. The lower inner surface of the second connector 13 has a threaded structure, which engages with the upper external thread of the third connector 15. The upper end face of the third connector 15 abuts against the lower end face of the lower slip 14. By tightening the connecting threads of the second connector 13 and the third connector 15, the lower slip 14 contracts radially, thereby further gripping the continuous tube. Generally, two O-ring grooves are provided on the inner surface of the third connector 15 for installing O-ring seals to ensure the sealing between the continuous tube connector 1 and the continuous tube. The interior of the third connector 15 has a step to limit the axial position of the continuous tube and the continuous tube connector 1. The lower outer wall of the third connector 15 has an external threaded structure for connecting with the locking rotary joint 2.

[0085] To ensure smooth radial contraction of the slips, both the upper slip 12 and the lower slip 14 are conical tubes with longitudinal slits. Teeth are formed on the inner wall of the conical tube, and a first or second outer conical surface is formed on the outer wall. Multiple slits are formed on the wall of the conical tube, extending to one end. Due to the presence of the longitudinal slits and multiple slits, each slip has a multi-lobed structure with gaps between each lobe, giving the conical tube a certain degree of elasticity. Variations in the width of the longitudinal slits and the gap widths of the slits allow for overall radial contraction or expansion of the slips.

[0086] Regarding the upper slip 12, when the second connector 13 and the first connector 11 are screwed together, the upper slip 12 will move upward. As the diameter of the first inner conical surface gradually decreases upward, each segment of the upper slip 12 will be compressed, causing the upper slip 12 to be in a contracted state. The distance between the cusps of the opposite teeth in the upper slip 12 decreases to grip the continuous tube, preventing the continuous tube from moving and achieving a secure fastening. The entire continuous tube connector 1, through the double slip structure, utilizes the gripping action of the upper teeth of each slip to ensure that the continuous tube remains fixed regardless of whether it is subjected to upward or downward forces, making the fastening of the continuous tube more reliable. Moreover, when the continuous tube is subjected to upward tension, each slip will be pulled upward along the inner conical surface, making the grip increasingly tighter. This not only achieves a secure fastening of the continuous tube, but also allows the continuous tube to withstand greater tension due to the gripping of the double slip structure, making the fastening even more reliable.

[0087] To further enhance the tightening effect on the continuous tube, multiple slits are typically used, including staggered first slits and second slits. The first slits extend upwards to the upper end of the tapered tube, and the second slits extend downwards to the lower end of the tapered tube. During the screwing in of the corresponding connector and the contraction of the slips, the staggered first and second slits ensure more uniform contraction deformation of the slips. This allows the teeth within each slip to grip the cable more evenly, preventing some teeth from being tightly engaged while others are loosely engaged, thus securing the continuous tube more firmly.

[0088] To further improve the tensile strength of the continuous tube, multiple radial holes 111 are formed in the upper wall of the first connecting pipe 11. Set screws are inserted into the radial holes 111 and can abut against the outer wall of the continuous tube. In actual use, indentations can also be formed on the outer surface of the continuous tube, and set screws can be tightened into the corresponding indentations to further secure the continuous tube.

[0089] The normally open safety valve 3 mentioned above can provide internal blowout prevention when the wellhead is pressurized after the operation is completed. Under normal circumstances, the normally open safety valve 3 is in the open position, and the internal passage of the normally open safety valve 3 is open, allowing normal fluid flow without affecting normal operation. After the operation is completed, when the wellhead is pressurized, the normally open safety valve 3 is adjusted to the closed position so that the liquid in the tubing cannot flow back up, thus playing a blowout prevention role and ensuring safety.

[0090] Furthermore, such as Figure 6As shown, the normally open safety valve 3 includes a sliding double-disc valve 31 and a ball-throwing sliding sleeve 32. The sliding double-disc valve 31 has a tubular structure and its upper end is threadedly connected to the lower pipe body 22. The sliding double-disc valve 31 has a valve disc 3144 provided on its inner wall. The ball-throwing sliding sleeve 32 is provided inside the sliding double-disc valve 31 by a shear pin 3151, and the valve disc 3144 can abut against the outer wall of the ball-throwing sliding sleeve 32 to keep the valve disc 3144 in an open state. A stepped surface is provided on the lower inner wall of the ball-throwing sliding sleeve 32, and the stepped surface forms the ball seat of the ball-throwing sliding sleeve 32.

[0091] Before the ball is thrown, the shear pin 3151 is not broken. The throwing sleeve 32 pushes open the valve disc 3144, and the valve disc 3144 remains open, so that the normally open safety valve 3 is in the open position, and the normally open safety valve 3 can flow normally. When the steel ball matching the throwing sleeve 32 is put into the continuous tube and pumped in, the steel ball is carried to the ball seat inside the throwing sleeve 32. Under the action of pressure difference, the shear pin 3151 is sheared, the throwing sleeve 32 moves axially downward, and the valve disc 3144 is closed, so that the normally open safety valve 3 is adjusted to the closed position, and the fluid in the control column cannot flow back up.

[0092] More specifically, the sliding double-disc valve 31 includes an outer protective tube, within which an annular mounting groove 313 is formed. Within the annular mounting groove 313, a double-disc one-way valve 314, a washer 315, and a spring washer 316 are arranged sequentially from top to bottom. The upper end of the double-disc one-way valve 314 and the lower end of the spring washer 316 respectively abut against the two side walls of the annular mounting groove 313. The ball-throwing sliding sleeve 32 is inserted into the inner through-hole of the double-disc one-way valve 314 and abuts against the valve disc 3144 within the double-disc one-way valve 314. The ball-throwing sliding sleeve 32 is connected to the washer 315 via a shear pin 3151.

[0093] Generally, for ease of processing and installation, the outer protective tube includes an upper protective tube 311 and a lower protective tube 312 arranged vertically. The upper inner wall of the upper protective tube 311 can be threaded to the lower outer wall of the lower connecting tube 222, and the upper inner wall of the lower protective tube 312 is threaded to the lower outer wall of the upper protective tube 311. An annular flange 3121 is provided on the inner wall of the lower protective tube 312. The space enclosed between the lower end face of the upper protective tube 311, the inner wall of the lower protective tube 312, and the annular flange 3121 constitutes the aforementioned annular mounting groove 313. The double-disc check valve 314 is composed of two identical disc-type check valves 3140 connected in series. The disc-type check valve 3140 includes an O-ring, a valve seat 3141, a pin 3142, a torsion spring 3143, a valve disc 3144, and a valve body 3145, which is the basic structure of the disc-type check valve 3140 known in the continuous tubing technology industry. The double-disc check valve 314 is placed in the annular mounting groove 313. The upper end face of the valve seat 3141 of the upper disc check valve 3140 abuts against the lower end face of the upper protective tube 311 for limiting. The lower end face of the valve body 3145 of the lower disc check valve 3140 abuts against the upper end face of the gasket 315. The outer surfaces of the valve seat 3141 and the valve body 3145 form a sealing fit with the inner surface of the lower protective tube 312. The inner surfaces of the valve seat 3141 and the valve body 3145 form a sealing fit with the outer surface of the ball-throwing sleeve 32.

[0094] After the ball-throwing sleeve 32 pushes open the valve disc 3144 of the disc-type check valve 3140, the normally open safety valve 3 is in the open position. The ball-throwing sleeve 32 can protect the valve disc 3144 and valve seat 3141 of the disc-type check valve 3140 from the erosion and corrosion of the working fluid. After the ball is thrown, the shear pin 3151 is sheared, and the ball-throwing sleeve 32 is pulled out from the disc-type check valve 3140 and moves downward. The valve disc 3144 of the disc-type check valve 3140 rotates 90° under the action of the torsion spring 3143 to block the internal passage of the normally open safety valve 3, controlling the fluid in the well to prevent it from flowing back. At this time, the normally open safety valve 3 can only circulate in the forward direction.

[0095] The washer 315 has an axial through-hole structure. Its upper end face abuts against the lower end face of the valve body 3145 of the lower disc-type check valve 3140 and is installed in the annular mounting groove 313. The middle part of the washer 315 has multiple radially distributed through holes in the circumferential direction to accommodate the shear pins 3151. The lower inner and outer surfaces of the washer 315 are provided with O-ring grooves for installing O-rings. The inner surface of the washer 315 is sealed to the outer surface of the ball-throwing sleeve 32. The spring washer 316 is a C-shaped spring washer. Its upper end face abuts against the lower end face of the washer 315, and its lower end face abuts against the upper end face of the annular flange 3121. The C-shaped spring washer has a certain degree of elasticity and compressibility in the axial direction, which can compensate for the installation gap and ensure the axial compression of the double-disc check valve 314, making its performance more reliable. The aforementioned ball-throwing sleeve 32 has a stepped internal through-hole structure, and its internal stepped surface should be a conical stepped surface to serve as the ball seat for throwing. The ball-throwing sleeve 32 is inserted into the axial internal through-hole of the valve seat 3141 and the valve body 3145, keeping the valve disc 3144 in an open state. A ring-shaped shear pin groove is provided on the lower outer surface of the ball-throwing sleeve 32. After the shear pin 3151 passes through the radial through-hole of the washer ring 315, part of its body is inserted into the shear pin groove to axially limit the ball-throwing sleeve 32. The upper end face of the ball-throwing sleeve 32 generally leaves a small gap with the lower inner stepped end face of the upper protective tube 311.

[0096] Preferably, an annular receiving cavity 3122 is provided on the inner wall of the outer protective tube and below the annular mounting groove 313. The inner diameter of the annular receiving cavity 3122 is larger than the outer diameter of the ball-throwing sleeve 32, and the axial length of the annular receiving cavity 3122 is larger than the axial length of the ball-throwing sleeve 32. Furthermore, the inner diameter of the outer protective tube below the annular receiving cavity 3122 is smaller than the outer diameter of the ball-throwing sleeve 32. Specifically, the annular receiving cavity 3122 is formed on the lower protective tube 312, which has a stepped internal through-hole structure. Its upper part is connected to the upper protective tube 311 by threads, and its lower outer surface has a threaded structure for connection with the oil pipe. The portion above the annular flange 3121 is used to accommodate the double-disc check valve 314, and the annular receiving cavity 3122 is located below the annular flange 3121. Since the inner diameter of the outer protective tube below the annular receiving cavity 3122 is smaller than the outer diameter of the ball-throwing sliding sleeve 32, when the ball is thrown, the ball-throwing sliding sleeve 32 can fall into the annular receiving cavity 3122, thus preventing the ball-throwing sliding sleeve 32 from falling to the bottom of the well.

[0097] Furthermore, this embodiment also provides a method for operating a coiled tubing and tubing combination string, which includes the following steps:

[0098] S1. Depending on whether the wellhead needs to be pressurized throughout the oil and gas well operation, use the tubing pressurized workover rig 600 or a conventional workover rig, and install the corresponding workover wellhead equipment.

[0099] S2. According to the required operation process, after connecting the operation tool to the conventional tubing, use the tubing pressurized operation device 600 or the conventional workover rig to run the conventional tubing into the well to the designed length.

[0100] S3. Temporarily suspend the conventional tubing string of the designed length at the wellhead, and connect the continuous tubing and the conventional tubing string of the same diameter to form a complete working string using the aforementioned continuous tubing and tubing combination string connection tool.

[0101] S4. Lower the working string to carry out the operation;

[0102] S5. After the operation is completed, pull out the conventional tubing string to the wellhead and temporarily suspend it;

[0103] S6. Remove the coiled tubing from the conventional tubing string;

[0104] S7. Use a 600 tubing pressurized workover rig or a conventional workover rig to pull out the conventional tubing from the well one by one.

[0105] S8, shut in the well and await further instructions.

[0106] The entire operation method utilizes the aforementioned connecting tools to easily connect coiled tubing and conventional tubing strings of the same diameter. The combined operation string formed by connecting the coiled tubing and conventional tubing strings can fully utilize the characteristics and operational advantages of both coiled tubing and conventional tubing strings during well operations. This allows for the safe and rapid relocation of surface equipment, the smooth running of the combined string into long horizontal sections and the provision of effective drilling pressure, and the ability to continuously drag under pressure and circulate at high displacement during operations to avoid stuck drill accidents. It can implement various operational processes, including both conventional and complex ones, and significantly improves operational efficiency while reducing operational costs.

[0107] Furthermore, the above operating methods differ slightly for both unpressurized and pressurized operations, as detailed below:

[0108] For wellhead pressureless or kill conditions before and after conventional tubing tripping, refer to Figures 1 to 7 The more specific steps are as follows:

[0109] In step S1, more specifically, a conventional workover rig is used, and a suspended and semi-sealed double gate blowout preventer 200 is installed above the wellhead main valve 100.

[0110] In step S2, more specifically, after connecting the work tool to the conventional tubing according to the required work process, conventional tubing is run into the well using a conventional workover rig. The designed length of the run-in conventional tubing string should not be shorter than the length of the horizontal section of the workover well.

[0111] In step S3, more specifically, when using a conventional workover rig to run a conventional tubing string to the designed length, a suspension and semi-sealed double-gate blowout preventer 200 is used to temporarily suspend and seal the conventional tubing string at the wellhead (e.g., Figure 7 (As shown), then a continuous tubing of the same diameter as the conventional tubing is passed sequentially through the injection head 500, the blowout preventer box 400, and the standard four-gate blowout preventer 300. Then, the locking rotary joint 2 in the above-mentioned connecting tool is adjusted to a rotatable state. Then, the upper and lower ends of the connecting tool are connected to the continuous tubing and the conventional tubing string respectively to form a complete working tubing string. Subsequently, the locking rotary joint 2 is adjusted to a locked state, the wellhead is connected, and the working tubing string is ready to be run in.

[0112] In step S4, more specifically, the working tubing is lowered using the injection head 500 to perform the operation, during which the tubing can be continuously lowered and circulated under pressure.

[0113] In step S5, more specifically, after the operation is completed, the injection head 500 is used to pull the entire coiled tubing out of the wellhead, and the suspension and semi-sealed double gate blowout preventer 200 is used to temporarily suspend and seal the conventional tubing string at the wellhead.

[0114] In step S6, more specifically, after confirming that the wellhead is depressurized, first disconnect the connection between the standard four-gate blowout preventer 300 and the suspended and semi-sealed double-gate blowout preventer 200, lift the injection head 500, and then adjust the locking rotary joint 2 in the above-mentioned connecting tool to a rotatable state (that is, adjust the locking mechanism to the unlocked position). By rotating, disassemble the connection thread between the normally open safety valve 3 and the conventional tubing, and then remove the coiled tubing and connecting tool from the conventional tubing string.

[0115] In step S7, more specifically, under the condition of no pressure at the wellhead, conventional workover rigs are used to pull out the conventional tubing from the well one by one.

[0116] In step S8, more specifically, the wellhead main valve 100 is closed, and subsequent operation instructions are awaited.

[0117] When the wellhead is pressurized before operation or the process design requires operation under full pressurization, refer to Figures 1 to 6 as well as Figure 8 The more specific steps are as follows:

[0118] In step S1, more specifically, a tubing live-line working device 600 is used and installed above the wellhead main valve 100, such as... Figure 8 As shown.

[0119] In step S2, more specifically, after connecting the working tool to the conventional tubing according to the required operating process, the conventional tubing is run under pressure using the tubing live-line working device 600. The designed length of the run-in conventional tubing string should not be shorter than the length of the horizontal section of the working well.

[0120] In step S3, more specifically, when the conventional tubing string is run under pressure to the designed length using the tubing live-line working device 600, the suspension and annular sealing mechanism 601 built into the tubing live-line working device 600 is activated to temporarily suspend and seal the conventional tubing string at the wellhead. Then, the support frame 700 with the gooseneck 800 is installed on the upper part of the tubing live-line working device 600, and the continuous tubing of the same diameter as the conventional tubing on the continuous tubing machine drum is pulled along the gooseneck 800 into the support frame 700. Next, the locking rotary joint 2 in the connecting tool is adjusted to a rotatable state, and then the upper and lower ends of the connecting tool are connected to the continuous tubing and the conventional tubing string respectively to form a complete working tubing string. Subsequently, the locking rotary joint 2 is adjusted to a locked state, the wellhead is connected, and preparation is made to run the working tubing string.

[0121] In step S4, more specifically, the stepping axial feed mechanism 602 built into the tubing live working device 600 is used to lower the working tubing string under pressure for operation. During the operation, the tubing string can be continuously raised and lowered under pressure and circulated.

[0122] In step S5, more specifically, after the operation is completed, the stepping axial feed mechanism 602 built into the tubing live working device 600 is used to pull the entire coiled tubing out of the wellhead under pressure, and the suspension and annular sealing mechanism 601 built into the tubing live working device 600 is used to temporarily suspend and seal the conventional tubing string at the wellhead. The connecting tools must be located inside the support frame 700.

[0123] In step S6, more specifically, a steel ball matching the ball-throwing sleeve 32 built into the normally open safety valve 3 is delivered and pumped onto the surface, and the normally open safety valve 3 is adjusted to the closed state by surface pressure control. The locking rotary joint 2 in the connecting tool is adjusted to a rotatable state, and the connecting thread between the locking rotary joint 2 and the normally open safety valve 3 is disassembled by rotation, thereby removing the coiled tubing, coiled tubing connector 1, locking rotary joint 2, and support frame 700 from the wellhead, leaving the normally open safety valve 3 in the closed state and the conventional tubing string at the wellhead.

[0124] In step S7, more specifically, under pressurized conditions at the wellhead, the tubing pressurized operation device 600 is used to remove the remaining conventional tubing from the well one by one.

[0125] In step S8, more specifically, the wellhead main valve 100 is closed, and subsequent operation instructions are awaited.

[0126] In summary, the connection tools and operating methods described in this embodiment are particularly suitable for deep, long horizontal sections of oil and gas wells. They offer advantages such as smooth installation of large-diameter coiled tubing and tubing combination strings in deep, long horizontal sections of oil and gas wells, continuous pressurized dragging, and high-volume coiled tubing circulation. This is especially suitable for operations in deep shale gas, tight oil wells in complex terrains, and deep, long horizontal sections of oil and gas wells. On the one hand, it effectively solves the problems of rapid, high-strength connection between coiled tubing and conventional tubing strings, as well as issues related to blowout prevention within the tubing. On the other hand, it addresses the issues of reasonable matching and coordinated operation of large-diameter coiled tubing equipment and conventional tubing equipment, as well as general construction procedures. By connecting large-size coiled tubing and oil tubing to form a combined working string, the technical advantages of both coiled tubing and conventional oil tubing are well inherited and complemented. This effectively avoids the shortcomings of conventional oil tubing, such as the inability to continuously raise and lower the string under pressure and circulation, low operating efficiency, and the limitations of large-size coiled tubing equipment due to complex terrain, which restricts the length of coiled tubing that can be transported and the depth of the working well. This approach meets the application conditions of coiled tubing technology in deep, long horizontal sections of oil and gas wells in complex terrain. Furthermore, the effective combination of the two types of tubing can further expand the operational capabilities and application scope of combined tubing, enabling high-level and high-quality development of deep, long horizontal sections of shale gas and tight oil and gas wells.

[0127] The above are merely illustrative embodiments of the present invention and are not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A coiled tubing and tubing combination string connection tool, characterized by, The continuous pipe connector, the locking rotary joint and the normally open safety valve are sequentially connected from top to bottom. The continuous pipe connector is used to be sleeved on the continuous pipe and can fasten the continuous pipe, the locking rotary joint comprises an upper pipe body, a lower pipe body and a locking mechanism, the upper pipe body is connected with the lower pipe body in a manner that the upper pipe body can rotate in a circumferential direction and is fixed in an axial direction, the lower pipe body can rotate relative to the upper pipe body when the locking mechanism is in an unlocking position and is locked and fixed with the upper pipe body when the locking mechanism is in a locking position, and the upper end of the normally open safety valve can be threadedly connected with the lower end of the lower pipe body, and the lower end of the normally open safety valve can be used to be threadedly connected with a conventional tubing string.

2. The continuous pipe and tubing combined string connecting tool according to claim 1, wherein an inner wall of the upper pipe body is provided with an annular groove, an outer wall of a lower end of the upper pipe body is formed with a plurality of tooth grooves which are uniformly distributed in a circumferential direction, an annular protrusion is protruded on an outer wall of the lower pipe body, the annular protrusion is rotatably embedded in the annular groove, and a plurality of protruding blocks which are uniformly distributed in a circumferential direction are formed on the outer wall of the lower pipe body and below the annular protrusion; a snap ring and a locking nut are further sleeved on the lower pipe body, an upper end of the snap ring is formed with a plurality of tooth blocks which are uniformly distributed in a circumferential direction, the protruding blocks can be embedded in intervals between adjacent two tooth blocks, and the tooth blocks can be inserted into the tooth grooves, and the locking nut is threadedly connected with the lower pipe body, and the tooth grooves, the protruding blocks, the snap ring and the locking nut constitute the locking mechanism.

3. The continuous pipe and tubing combined string connecting tool according to claim 2, wherein an upper axial thrust bearing and a lower axial thrust bearing are respectively sleeved on two sides of the annular protrusion, and the upper axial thrust bearing and the lower axial thrust bearing are embedded in the annular groove and abut against groove walls of the annular groove.

4. The continuous pipe and tubing combined string connecting tool according to claim 3, wherein the upper pipe body comprises an upper adapter and an intermediate adapter, an inner wall of an upper end of the intermediate adapter is threadedly connected with an outer wall of a lower end of the upper adapter, a lower end inner wall of the intermediate adapter is protruded with a limiting step, and a space surrounded by a lower end surface of the upper adapter, an inner wall of the intermediate adapter and the limiting step constitutes the annular groove, and the tooth grooves are formed on the intermediate adapter; the lower pipe body comprises a core pipe and a lower adapter, the annular protrusion is formed on the core pipe, and a lower end of the core pipe extends out of the intermediate adapter, an inner wall of an upper end of the lower adapter is threadedly connected with an outer wall of a lower end of the core pipe, the protruding blocks are formed on the lower adapter, and the snap ring and the locking nut are both sleeved on the lower adapter.

5. The continuous pipe and tubing combined string connecting tool according to claim 1, wherein the continuous pipe connector has an upper slip and a lower slip which can be radially contracted and have inner walls with dies, the upper slip and the lower slip are arranged in an upper-lower interval, the upper slip and the lower slip are arranged in a contracted state, and the dies can bite the continuous pipe.

6. The continuous pipe and tubing combined string connecting tool according to claim 5, wherein The continuous pipe connector further comprises a first adapter pipe, a second adapter pipe and a third adapter pipe connected in sequence from top to bottom, the first adapter pipe has a first inner taper surface with a diameter gradually increasing downward, the outer wall of the upper slip is a first outer taper surface matched with the first inner taper surface, and the upper slip is arranged in the first adapter pipe in a contracted state; the outer wall of the upper end of the second adapter pipe is threadedly connected with the inner wall of the lower end of the first adapter pipe, and the upper end of the second adapter pipe can abut against the upper slip; the second adapter pipe has a second inner taper surface with a diameter gradually increasing downward, the outer wall of the lower slip is a second outer taper surface matched with the second inner taper surface, and the lower slip is arranged in the second adapter pipe in a contracted state; the outer wall of the upper end of the third adapter pipe is threadedly connected with the inner wall of the lower end of the second adapter pipe, and the upper end of the third adapter pipe can abut against the lower slip.

7. The continuous pipe and tubing combined string connecting tool according to claim 6, wherein the upper slip and the lower slip are both taper pipes with longitudinal cuts, the dies are formed on the inner wall of the taper pipe, and the first outer taper surface or the second outer taper surface is formed on the outer wall of the taper pipe; a plurality of slits are formed on the wall of the taper pipe, and the slits extend to one of the ends of the taper pipe.

8. The continuous pipe and tubing combined string connecting tool according to claim 6, wherein a plurality of radial holes are formed in the upper wall of the first adapter pipe, and a plurality of set screws are arranged in the radial holes and can abut against the outer wall of the continuous pipe.

9. The continuous pipe and tubing combined string connecting tool according to claim 1, wherein the normally open safety valve comprises a sliding sleeve double flap valve and a ball sliding sleeve, the sliding sleeve double flap valve is a tubular structure, the upper end of the sliding sleeve double flap valve is threadedly connected with the lower pipe body, the sliding sleeve double flap valve has a valve flap formed on the inner wall thereof, the ball sliding sleeve is arranged in the sliding sleeve double flap valve through a shear pin, and the valve flap can abut against the outer wall of the ball sliding sleeve to keep the valve flap in an open state; a step surface is formed on the inner wall of the lower end of the ball sliding sleeve, and the step surface forms a ball seat of the ball sliding sleeve.

10. The continuous pipe and tubing combined string connecting tool according to claim 9, wherein the sliding sleeve double flap valve comprises an outer sleeve, an annular mounting groove is formed in the outer sleeve, a double flap one-way valve, a spacer ring and a spring washer are arranged in the annular mounting groove in sequence from top to bottom, the upper end of the double flap one-way valve and the lower end of the spring washer abut against the two side groove walls of the annular mounting groove respectively, the ball sliding sleeve is arranged in the inner through hole of the double flap one-way valve and abuts against the valve flap in the double flap one-way valve, and the ball sliding sleeve is connected with the spacer ring through the shear pin.

11. The continuous pipe and tubing combined string connecting tool according to claim 10, wherein An annular accommodating cavity is arranged on the inner wall of the outer protective pipe below the annular mounting groove, the inner diameter of the annular accommodating cavity is greater than the outer diameter of the ball-throwing sliding sleeve, the axial length of the annular accommodating cavity is greater than the axial length of the ball-throwing sliding sleeve, and the inner diameter of the outer protective pipe below the annular accommodating cavity is less than the outer diameter of the ball-throwing sliding sleeve.

12. A method of operating a coiled tubing and tubing combination string, the method comprising: The method for operating the continuous pipe and tubing combined pipe string comprises the following steps: According to whether the wellhead needs to be under pressure during the oil and gas well operation, a tubing under pressure operating device or a conventional workover rig is used, and a matching operating wellhead device is installed; According to the operation process to be implemented, the operation tool is connected with the conventional tubing, and then the tubing under pressure operating device or the conventional workover rig is used to lower the conventional tubing into the well to a designed length; The conventional tubing string of the designed length is temporarily hung at the wellhead, the continuous pipe and the conventional tubing string of the same pipe diameter are connected into one operation pipe string through the continuous pipe and tubing combined pipe string connecting tool according to any one of claims 1 to 11; The operation pipe string is lowered to perform the operation; After the operation is completed, the conventional tubing string is pulled out to the wellhead and temporarily hung; The continuous pipe is removed from the conventional tubing string; The tubing under pressure operating device or the conventional workover rig is used to pull out the conventional tubing in the well one by one; The well is closed, and subsequent operation instructions are waited.

13. The method for operating the continuous pipe and tubing combined pipe string according to claim 12, wherein The continuous pipe is removed from the conventional tubing string specifically comprising the following steps: After confirming that the wellhead is not under pressure, the locking mechanism is adjusted to the unlocked position, the connection threads of the always-open safety valve and the conventional tubing string are rotated and disassembled, and the continuous pipe and the continuous pipe and tubing combined pipe string connecting tool are removed from the conventional tubing string.

14. The method for operating the continuous pipe and tubing combined pipe string according to claim 12, wherein The continuous pipe is removed from the conventional tubing string specifically comprising the following steps: The always-open safety valve is adjusted to the closed position; The locking mechanism is adjusted to the unlocked position; The connection threads of the locking type rotary joint and the always-open safety valve are rotated and disassembled, and the continuous pipe, the continuous pipe connector and the locking type rotary joint are removed from the wellhead.

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