A horizontal well coiled tubing extension tool and method

Abstract

The application provides a horizontal well coiled tubing extension tool and method, and belongs to the technical field of oil exploration and development equipment. The tool comprises at least two telescopic stepping mechanisms connected in series, each mechanism comprising a shell, a throttling sleeve, a piston assembly, a guide support mechanism and a reset mechanism. A pressure difference is generated in the throttling sleeve by liquid, which drives the axial movement of the piston assembly, and drives the radial extension of the support cylinder slider to support the well wall; when the pressure difference disappears, the reset spring pushes the shell to reset, and the support cylinder slider is retracted, realizing step-by-step advancement. Adjacent mechanisms are connected through a central flow channel, and can be continuously and cyclically extended. The tool does not require an electric control system, has a simple and reliable structure, can adapt to different well diameters, has high energy utilization efficiency, can effectively reduce friction and improve the running efficiency and operation depth of the coiled tubing in the horizontal well.

Description

Technical Field

[0001] This invention relates to the field of petroleum exploration and development equipment technology, specifically to a horizontal well coiled tubing extension tool and method. Background Technology

[0002] With the continuous advancement of petroleum exploration technology, horizontal well technology has been increasingly widely used in oil and gas development. Horizontal wells can significantly increase the contact area of ​​oil and gas reservoirs and improve single-well production, becoming an important technical means to enhance oilfield recovery. However, the operation of coiled tubing in horizontal wells faces many challenges, especially in deep wells, ultra-deep wells, highly deviated wells, and extended-range horizontal wells. As the length of the horizontal section and the depth of the well increase, the frictional resistance of the coiled tubing increases sharply during the sliding extension process, leading to difficulties in tubing string delivery and severely restricting the application of coiled tubing technology in complex well conditions.

[0003] Currently, the main technical means to solve the problem of coiled tubing extension include mechanical traction and hydraulic drive. Although some coiled tubing extension tools are available on the market, hydraulically controlled and hydraulically driven tools are still in their infancy. While related products from abroad are relatively mature in technology, they are expensive, have high procurement costs, and are subject to technological blockades and untimely service responses. Domestic research in this field is still in its early stages, and no mature hydraulically driven extension tools have yet been put into market application.

[0004] In the prior art, Chinese utility model patent CN206737853U discloses a hydraulically driven turbocharger traction device, which uses high-pressure fluid to drive a turbine to rotate, converting the rotational motion into linear traction force of rollers to solve the self-locking problem of coiled tubing. However, this technology is mainly applicable to high-torque scenarios, relies on precise matching of turbine speed and fluid pressure, has limited adaptability to different well conditions, and has a complex turbine mechanical structure, posing a challenge to reliability in the high-temperature and high-pressure environment downhole.

[0005] Chinese invention patent application CN117386292A discloses an electro-hydraulic integrated directional tool for coiled tubing drilling rigs. This tool uses a motor driven by ground commands to operate a bidirectional hydraulic pump, creating a pressure differential that drives a piston in reciprocating motion, thus achieving directional rotation of the downhole drilling tool. While this technology offers high precision in electro-hydraulic coordinated control, it relies excessively on the electronic control system. In harsh downhole environments such as high temperature and pressure, the reliability of electronic components is difficult to guarantee. Furthermore, the system is complex, has a relatively high failure rate, and incurs significant maintenance costs.

[0006] Chinese invention patent application CN119083927A discloses an oil horizontal well traction device, which adopts an expandable drive wheel set with a telescopic shaft structure and adapts to different well diameters through mechanical adjustment. Although the device has the advantage of modular design, it does not specify the specific implementation method of the hydraulic drive mechanism, mainly relies on mechanical adjustment to adapt to changes in well diameter, requires manual intervention, has a low degree of automation, and its adaptability under complex well conditions needs to be improved.

[0007] Based on the current state of technological development, coiled tubing extension tools currently face the following technical challenges: First, existing turbine-driven tools have complex structures, requiring the conversion of rotary motion into linear motion, resulting in low energy conversion efficiency and stringent requirements for fluid pressure and flow matching. Second, while electro-hydraulic drive tools offer high control precision, the reliability and stability of electronic components are difficult to guarantee in the high-temperature and high-pressure downhole environment, increasing system complexity and failure risks. Third, existing mechanical traction devices often require manual adjustment to adapt to different well diameters, exhibiting low automation and lacking an effective hydraulic drive mechanism. Summary of the Invention

[0008] The purpose of this invention is to provide a horizontal well coiled tubing extension tool and method, which has a simple structure, high reliability, and can adapt to horizontal wells of different diameters, so as to overcome the shortcomings of the prior art and improve the efficiency of oil exploration and development.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A horizontal well coiled tubing extension tool, comprising:

[0011] At least two telescopic stepping mechanisms, each telescopic stepping mechanism comprising:

[0012] A housing, wherein a piston chamber is provided within the housing;

[0013] A throttling sleeve, disposed within the housing, has inlets and outlets of different diameters, used to generate a pressure differential as liquid passes through;

[0014] The piston assembly includes a piston rod connected to the throttling sleeve and a piston disposed in the piston chamber, and the piston assembly is axially movable under the action of the pressure difference;

[0015] The support mechanism includes a guide and a plurality of support cylindrical sliders. The guide is connected to the piston rod and is provided with a sliding track. The support cylindrical sliders can move along the sliding track. When the piston assembly moves axially, the support cylindrical sliders extend or retract radially.

[0016] A reset mechanism is provided to reset the piston assembly after the pressure differential disappears.

[0017] The at least two telescopic stepping mechanisms include a front extension structure and a rear extension structure;

[0018] The front-end extension structure includes a front-end extension housing, a front-end extension throttling sleeve, a front-end extension piston rod, a front-end extension piston, a front-end extension guide, a front-end extension support cylindrical slider, and a front-end extension return spring.

[0019] The rear extension structure includes a rear extension housing, a rear extension throttling sleeve, a rear extension piston rod, a rear extension piston, a rear extension guide, a rear extension support cylindrical slider, and a rear extension return spring.

[0020] The tail end of the front extension piston rod is connected to the rear extension housing;

[0021] A flow guide is provided at the connection between the front end extension structure and the rear end extension structure. The flow guide has a cylindrical hole for introducing liquid into the tail cavity of the rear end extension shell.

[0022] When the rear extension structure reaches the limit, the cylindrical hole on the flow guide is blocked by the rear extension housing, so that the liquid in the tail cavity of the rear extension housing is in a stable pressure state.

[0023] The front extension structure also includes a front extension bottom cylinder head, which is provided with a cavity and a pressure relief hole;

[0024] When the front extension return spring drives the front extension housing to the limit position, the cavity of the bottom cylinder head of the front extension is connected to the cavity of the rear extension housing, and the liquid in the cavity of the rear extension housing is discharged through the pressure relief hole to achieve pressure relief.

[0025] Among them, two adjacent telescopic stepping mechanisms are connected through a central flow channel. The piston rod of the first telescopic stepping mechanism pushes the housing of the second telescopic stepping mechanism to move, thereby achieving step-by-step extension.

[0026] Furthermore: the supporting cylindrical slider consists of three cylindrical sliders, evenly distributed around the circumference of the guide;

[0027] The three cylindrical sliders move synchronously along the sliding track, and when they extend radially, the top of each cylindrical slider is at the same distance from the center axis of the tool.

[0028] Furthermore, the sliding track is an inclined groove. When the guide moves axially, the supporting cylindrical slider moves obliquely upward or downward along the inclined groove to achieve radial extension or retraction.

[0029] Furthermore: the rear extension housing includes a detachably connected rear extension housing body and a pressure storage housing, the pressure storage housing being used to store liquid under stable pressure and being replaceable according to different well diameters.

[0030] Furthermore, it may include three or more telescopic stepping mechanisms connected in series, with power transmission between adjacent telescopic stepping mechanisms achieved through the connection between the piston rod and the housing.

[0031] The present invention also provides a method for extending coiled tubing in horizontal wells, using the aforementioned coiled tubing extension tool, characterized by comprising the following steps:

[0032] S1: Liquid is introduced. The liquid generates a pressure difference through the throttling sleeve of the front extension structure, which pushes the piston assembly of the front extension structure forward. The supporting cylindrical slider of the front extension structure extends radially and supports the well wall, while compressing the return spring.

[0033] S2: The liquid continues to enter the rear extension structure through the central flow channel. The pressure difference generated by the throttling sleeve of the rear extension structure pushes the piston assembly of the rear extension structure forward. The supporting cylindrical slider of the rear extension structure extends radially and supports the well wall.

[0034] S3: After the rear extension structure reaches the limit, the liquid is in a stable pressure state in the shell cavity of the rear extension structure, maintaining the supporting function of the rear extension structure.

[0035] S4: Stop the liquid flow, the pressure difference of the throttling sleeve of the front extension structure disappears, the return spring pushes the shell of the front extension structure to move forward, the supporting cylindrical slider retracts radially, and the forward movement is achieved;

[0036] S5: After the front extension structure is reset to the limit, the liquid in the cavity of the rear extension structure housing is discharged through the pressure relief hole, the reset spring of the rear extension structure pushes the housing to reset, and the support cylindrical slider retracts radially.

[0037] S6: Reintroduce liquid and repeat the cycle of S1-S5 to achieve continuous step extension.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] I. This invention adopts a pure mechanical hydraulic drive method, which directly drives the piston assembly to move through the pressure difference of the throttling sleeve, eliminating the need for power conversion of rotating machinery such as turbines and avoiding complex mechanical transmission structures. The entire tool does not rely on an electronic control system and achieves pressure stabilization and pressure relief control entirely through mechanical structures, completely solving the problem of poor reliability of electronic components in the high temperature and high pressure environment downhole, and significantly improving the stability and service life of the tool.

[0040] Second, this invention achieves a fully automatic cyclic stepping process through the combination of hydraulic differential drive and reset spring, and can work continuously without manual intervention; the supporting cylindrical slider can adapt to different well diameters within a certain stroke range, and the applicable well diameter range can be further expanded by replacing the pressure storage shell and bottom cylinder head, thus solving the problem of frequent manual adjustment required by the prior art.

[0041] Third, this invention directly converts liquid pressure energy into axial propulsion force, avoiding the conversion loss from rotational motion to linear motion, resulting in high energy utilization efficiency; the pressure difference generated by the throttling sleeve can fully utilize the liquid kinetic energy, reducing the stringent requirements on pump pressure and flow rate, and obtaining greater traction force under the same conditions.

[0042] Fourth, this invention employs three evenly distributed support cylindrical sliders that extend and retract synchronously. The distance from the top of each slider to the central axis of the tool is always the same, ensuring that the tool maintains good centering in the wellbore, avoiding eccentricity and vibration caused by uneven support, and improving the feeding efficiency of coiled tubing.

[0043] V. The telescopic stepping mechanism of the present invention adopts a modular design, which can connect two, three or more mechanisms in series according to actual needs, flexibly adjust the stepping stroke, meet the operation requirements of different depths and horizontal section lengths, and has good scalability and versatility. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall structure of the horizontal well coiled tubing extension tool of the present invention;

[0045] Figure 2 This is a schematic diagram of the overall external outline of the present invention;

[0046] Figure 3 This is a schematic diagram illustrating the cooperation between the cylindrical slider and the guide of the present invention;

[0047] Figure 4 for Figure 1 Schematic diagram of section AA;

[0048] Figure 5 This is a cross-sectional schematic diagram of the throttling sleeve of the present invention.

[0049] In the diagram: 1. Rear-end extended piston rod; 2. Rear-end extended bottom cylinder head; 3. Rear-end extended housing; 4. Rear-end extended return spring; 5. Rear-end extended piston; 6. Rear-end extended support cylindrical slider; 7. Rear-end extended guide; 8. Rear-end extended throttle sleeve; 9. Flow guide; 10. Front-end extended bottom cylinder head; 11. Front-end extended housing; 12. Front-end extended return spring; 13. Front-end extended piston; 14. Front-end extended support cylindrical slider; 15. Front-end extended guide; 16. Front-end extended piston rod; 17. Front-end extended throttle sleeve; 18. Front-end extended sealing ring; 19. Front-end extended connector. Detailed Implementation

[0050] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0052] Reference Figures 1 to 5 The horizontal well coiled tubing extension tool provided by this invention includes two telescopic stepping mechanisms based on the same principle: a front-end extension structure and a rear-end extension structure. The front-end extension structure mainly includes a front-end extension connector 19, a front-end extension throttling sleeve 17, a front-end extension piston rod 16, a front-end extension piston 13, a front-end extension guide 15, a front-end extension support cylindrical slider 14, a front-end extension return spring 12, a front-end extension housing 11, a front-end extension bottom cylinder head 10, and a front-end extension sealing ring 18. The rear-end extension structure mainly includes a rear-end extension throttling sleeve 8, a rear-end extension piston rod 1, a rear-end extension piston 5, a rear-end extension guide 7, a rear-end extension support cylindrical slider 6, a rear-end extension return spring 4, a rear-end extension housing 3, a rear-end extension bottom cylinder head 2, and a flow guide 9.

[0053] The front-end extension throttling sleeve 17 is disposed inside the front-end extension housing 11, such as Figure 5As shown, the inlet diameter of the front-end extended throttling sleeve 17 is larger than the outlet diameter. This variable diameter structure causes a pressure drop when the liquid passes through, thus creating a pressure difference across the two ends of the front-end extended throttling sleeve 17. The front-end extended piston rod 16 is threaded to the front-end extended throttling sleeve 17, and the front-end extended piston 13 is fixed to the front-end extended piston rod 16, located within the piston chamber of the front-end extended housing 11. The front-end extended guide 15 is fixedly connected to the front-end extended piston rod 16, and the outer surface of the front-end extended guide 15 is provided with three oblique grooves, such as... Figure 3 As shown. Three front-end extension support cylindrical sliders 14 are evenly distributed around the circumference of the front-end extension guide 15. Each front-end extension support cylindrical slider 14 fits into a corresponding groove and can slide along the groove. A cylindrical hole is opened on the front-end extension housing 11 at the position corresponding to the front-end extension support cylindrical slider 14, allowing the front-end extension support cylindrical slider 14 to extend radially. The front-end extension return spring 12 is sleeved on the front-end extension piston rod 16, with one end abutting against the front-end extension piston 13 and the other end abutting against the inner end face of the front-end extension housing 11.

[0054] The internal structure of the rear extension structure is basically the same as that of the front extension structure, except that the tail end of the front extension piston rod 16 is threadedly connected to the rear extension housing 3 to form a power transmission relationship. A flow guide 9 is located at the connection between the front and rear extension structures. The flow guide 9 has a cylindrical hole for introducing liquid from the central flow channel of the front extension structure into the tail cavity of the rear extension housing 3. The tail of the rear extension housing 3 has a dedicated liquid storage cavity, and the side wall of this cavity has a through hole that mates with the cylindrical hole of the flow guide 9.

[0055] like Figure 4 As shown in the AA cross-sectional view, the three rear-end extension support cylindrical sliders 6 are evenly distributed at 120 degrees on the circumference. This arrangement ensures stable support and good centering of the tool in the wellbore. Each rear-end extension support cylindrical slider 6 is cylindrical in shape, with its axis aligned with the radial direction of the tool. The inner end of the rear-end extension support cylindrical slider 6 fits into the groove of the rear-end extension guide 7, and the outer end can extend from the cylindrical hole of the rear-end extension housing 3.

[0056] The working process of this invention can be divided into the following continuous position states. In the initial position, the liquid is not introduced into the extension tool, all components are in the initial state, the front extension support cylindrical slider 14 and the rear extension support cylindrical slider 6 are retracted into the front extension housing 11 and the rear extension housing 3, and the tool as a whole does not move.

[0057] When fluid is introduced, it enters through the front extension connector 19 and initially acts on the front extension throttling sleeve 17. Due to the variable diameter structure of the front extension throttling sleeve 17, a pressure drop occurs as the fluid passes through, creating a pressure difference across the two ends of the front extension throttling sleeve 17. This pressure difference pushes the front extension throttling sleeve 17 forward, driving the front extension piston rod 16, the front extension guide 15, and the front extension piston 13 forward together via a threaded connection. During the forward movement of the front extension guide 15, because the groove on the front extension guide 15 is angled, the front extension support cylindrical slider 14 is forced to slide obliquely upward along the groove of the front extension guide 15, thereby generating a radially outward component motion. This causes the front extension support cylindrical slider 14 to extend from the cylindrical hole of the front extension housing 11 until it contacts the well wall and generates a supporting force. Simultaneously, the forward movement of the front extension piston 13 compresses the front extension return spring 12, allowing the front extension return spring 12 to store elastic potential energy, preparing for subsequent return actions.

[0058] The liquid continues to flow through the central channel of the front-end extended piston rod 16, through the cylindrical hole on the guide 9, and into the cavity at the tail of the rear-end extended housing 3. Upon reaching the rear-end extended throttling sleeve 8, the liquid also generates a pressure difference, pushing the rear-end extended throttling sleeve 8, the rear-end extended piston rod 1, the rear-end extended guide 7, and the rear-end extended piston 5 forward. The rear-end extended support cylindrical slider 6 extends radially on the same principle, providing support to the wellbore. The rear-end extended piston 5 also compresses the rear-end extended return spring 4 to store energy. When the rear-end extended piston 5 of the rear-end extended structure reaches its limit position, the cylindrical hole on the guide 9 is blocked by the end face of the rear-end extended housing 3, preventing the liquid from continuing to enter the tail cavity of the rear-end extended housing 3. At this point, the liquid inside the cavity is sealed and in a stable pressure state. This stable pressure state ensures that the rear-end extended support cylindrical slider 6 is stably supported on the wellbore.

[0059] Next, the fluid flow is stopped, and the pressure difference at the front extension throttling sleeve 17 disappears. At this time, the front extension return spring 12 releases its stored elastic potential energy, pushing the front extension piston 13 and the front extension housing 11 forward. Since the front extension guide 15 and the front extension piston rod 16 are fixed, and the tail end of the front extension piston rod 16 is connected to the rear extension housing 3, the rear extension structure is now fixed to the well wall by its extended rear extension support cylindrical slider 6. Therefore, the front extension housing 11 moves forward relative to the front extension guide 15. This relative motion causes the front extension support cylindrical slider 14 to slide downward along the groove of the front extension guide 15, generating a radially inward component motion. The front extension support cylindrical slider 14 retracts into the front extension housing 11, releasing its support to the well wall. The forward movement of the front extension housing 11 realizes the forward movement of the entire tool.

[0060] When the front extension return spring 12 pushes the front extension housing 11 to the limit position, the previously closed space between the front extension bottom cylinder head 10 and the rear extension housing 3 opens, and their cavities become connected. At this time, the liquid in the tail cavity of the rear extension housing 3, which is under stable pressure, flows into the cavity of the front extension bottom cylinder head 10 through the cylindrical hole on the rear extension housing 3, and then is discharged to the outside of the tool through the pressure relief hole on the front extension bottom cylinder head 10, thus achieving pressure relief. After losing the support of liquid pressure, the rear extension return spring 4 releases its elastic potential energy, pushing the rear extension piston 5 and the rear extension housing 3 to return to their original position. The rear extension support cylindrical slider 6 also retracts into the rear extension housing 3. During the return process, the guide 9 squeezes the remaining liquid in the cavity of the rear extension housing 3, causing it to be completely discharged.

[0061] After completing one cycle, fluid is reintroduced, the tool returns to the second position, and the next step cycle begins. Through this cyclical action, continuous step extension of coiled tubing in a horizontal well is achieved.

[0062] To accommodate different wellbore diameters, this invention features an adjustable support stroke. Since the travel distance of the front extension guide 15 within the front extension housing 11 is limited, the radial extension distance of the front extension support cylindrical slider 14 is also correspondingly limited. Within the designed wellbore diameter range, the front extension support cylindrical slider 14 can contact the well wall at different extension positions, automatically adapting to changes in wellbore diameter. When used in a smaller wellbore, the front extension bottom cylinder head 10 and the pressure storage portion of the rear extension housing 3 can be replaced. For ease of replacement, the rear extension housing 3 can be designed as two parts: the rear extension housing 3 body and the pressure storage housing, connected by threads. Thus, when adapting to different wellbore diameters, only the pressure storage housing and the front extension bottom cylinder head 10 need to be replaced; the main difference between these two components is the location of the pressure stabilizing and venting holes.

[0063] This invention can also realize the series connection of multiple telescopic stepping mechanisms. Since the front extension structure and the rear extension structure have the same principle, and the front extension piston rod 16 and the rear extension piston rod 1 have the same size specifications, one or more identical structures can be connected after the rear extension structure. When the extension tool is expanded from two parts to three parts, the stepping stroke increases accordingly. To realize the series connection of the three parts, it is only necessary to replace the rear extension bottom cylinder head 2 in the rear extension structure with the front extension bottom cylinder head 10, and connect the third extension structure to the tail end of the rear extension piston rod 1. Since the pressure of the liquid will decrease when it passes through each extension structure, in order to ensure that all rear extension support cylindrical sliders 6 and front extension support cylindrical sliders 14 can reliably extend and support the well wall, it is necessary to appropriately increase the pressure of the input liquid.

[0064] A key feature of this invention is the use of a purely mechanical structure for pressure stabilization and relief control, eliminating the need for electrically controlled valves. Pressure stabilization is achieved by mechanically sealing the cylindrical hole of the flow guide 9 with the end face of the rear extended housing 3, while pressure relief is achieved through the mechanical connection between the front extended bottom cylinder head 10 and the cavity of the rear extended housing 3. This design avoids reliability issues of electronic components in the high-temperature, high-pressure environment downhole, significantly improving the stability and service life of the tool.

[0065] In practical applications, this invention can be connected to the front end of coiled tubing and operated using a high-pressure fluid-driven tool provided by a surface pumping station. The traction force generated by the tool effectively overcomes the sliding friction of the coiled tubing in horizontal well sections, enabling smooth tubing string delivery. In addition to its basic extension function, this invention can also carry various detection equipment or working tools, expanding its application range downhole.

[0066] As can be seen from the above description of specific embodiments, the horizontal well coiled tubing extension tool provided by the present invention has a simple structure, reliable operation, and a high degree of automation. It can effectively solve the problem of sending coiled tubing into horizontal wells and has broad application prospects.

[0067] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A horizontal well coiled tubing extension tool, characterized in that, include: At least two telescopic stepping mechanisms, each telescopic stepping mechanism comprising: A housing, wherein a piston chamber is provided within the housing; A throttling sleeve, disposed within the housing, has inlets and outlets of different diameters, used to generate a pressure differential as liquid passes through; The piston assembly includes a piston rod connected to the throttling sleeve and a piston disposed in the piston chamber, and the piston assembly is axially movable under the action of the pressure difference; The support mechanism includes a guide and a plurality of support cylindrical sliders. The guide is connected to the piston rod and is provided with a sliding track. The support cylindrical sliders can move along the sliding track. When the piston assembly moves axially, the support cylindrical sliders extend or retract radially. A reset mechanism is provided to reset the piston assembly after the pressure differential disappears. The at least two telescopic stepping mechanisms include a front extension structure and a rear extension structure; the front extension structure includes a front extension housing, a front extension throttling sleeve, a front extension piston rod, a front extension piston, a front extension guide, a front extension support cylindrical slider, and a front extension return spring. The rear extension structure includes a rear extension housing, a rear extension throttling sleeve, a rear extension piston rod, a rear extension piston, a rear extension guide, a rear extension support cylindrical slider, and a rear extension return spring. The tail end of the front extension piston rod is connected to the rear extension housing; A flow guide is provided at the connection between the front end extension structure and the rear end extension structure. The flow guide has a cylindrical hole for introducing liquid into the tail cavity of the rear end extension housing. When the rear end extension structure reaches the limit position, the cylindrical hole on the flow guide is blocked by the rear end extension housing, so that the liquid in the tail cavity of the rear end extension housing is in a stable pressure state. The front end extension structure also includes a front end extension bottom cylinder head, which has a cavity and a pressure relief hole. When the front extension return spring drives the front extension housing to the limit position, the cavity of the bottom cylinder head of the front extension is connected to the cavity of the rear extension housing, and the liquid in the cavity of the rear extension housing is discharged through the pressure relief hole to achieve pressure relief. Among them, two adjacent telescopic stepping mechanisms are connected through a central flow channel. The piston rod of the first telescopic stepping mechanism pushes the housing of the second telescopic stepping mechanism to move, thereby achieving step-by-step extension.

2. The horizontal well coiled tubing extension tool according to claim 1, characterized in that, The supporting cylindrical slider consists of three cylindrical sliders, which are evenly distributed around the circumference of the guide. The three cylindrical sliders move synchronously along the sliding track, and when they extend radially, the top of each cylindrical slider is at the same distance from the center axis of the tool.

3. The horizontal well coiled tubing extension tool according to claim 1, characterized in that, The sliding track is an inclined groove. When the guide moves axially, the supporting cylindrical slider moves obliquely upward or downward along the inclined groove to achieve radial extension or retraction.

4. The horizontal well coiled tubing extension tool according to claim 1, characterized in that, The rear extension housing includes a detachably connected rear extension housing body and a pressure storage housing. The pressure storage housing is used to store liquid under stable pressure and is replaced according to different well diameters.

5. The horizontal well coiled tubing extension tool according to claim 1, characterized in that, It includes three or more telescopic stepping mechanisms connected in series, and power is transmitted between adjacent telescopic stepping mechanisms through the connection between the piston rod and the housing.

6. A method for extending coiled tubing in a horizontal well, using the coiled tubing extension tool as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: Liquid is introduced. The liquid generates a pressure difference through the front extension throttling sleeve, which pushes the front extension piston to move forward axially. The front extension guide moves accordingly, causing the front extension support cylindrical slider to extend radially along the sliding track and support the well wall, while compressing the front extension return spring. S2: The liquid continues to enter the rear extension structure through the central flow channel. After passing through the rear extension throttling sleeve, a pressure difference is generated, which pushes the rear extension piston to move forward axially. The rear extension guide moves accordingly, causing the rear extension support cylindrical slider to extend radially along the sliding track and support the well wall. S3: After the rear extension structure reaches the limit, the cylindrical hole on the guide is blocked by the rear extension shell, and the liquid is in a stable pressure state in the tail cavity of the rear extension shell, maintaining the supporting effect of the rear extension support cylindrical slider on the well wall. S4: Stop the liquid flow, the pressure difference at the front extension throttling sleeve disappears, the front extension return spring pushes the front extension housing forward, and the front extension support cylindrical slider retracts radially, thus achieving forward movement; S5: After the front extension housing is reset to the limit, the cavity of the bottom cylinder head of the front extension is connected to the cavity of the rear extension housing. The liquid in the cavity of the rear extension housing is discharged through the pressure relief hole on the bottom cylinder head of the front extension. The rear extension reset spring pushes the rear extension housing to reset, and the rear extension support cylindrical slider retracts radially. S6: Reintroduce liquid and repeat the cycle of S1-S5 to achieve continuous step extension.

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