A fishing tool for coiled tubing operations capable of determining the state of capture

Abstract

This invention relates to the field of oil and gas extraction engineering, and discloses a retrieval tube for coiled tubing operations that can determine the retrieval status. The retrieval tube includes an upper connector, a sliding rod, a spring, a slider, a connecting tube, slips, and a guide shoe tube. The slips are used to hold the fallen fish. The mechanical cooperation between the slider and the sliding rod causes a change in the opening and closing state of the fluid channel inside the tool after the fish is retrieved, resulting in a significant increase in the surface pump pressure, which is used to determine the retrieval status. This invention has a simple structure and can determine whether a fallen fish has been retrieved simply by changing the pump pressure, avoiding the uncertainty caused by relying on experience-based judgment. It is suitable for downhole retrieval operations in coiled tubing.

Description

Technical Field

[0001] This invention belongs to the field of downhole tools technology in oil and gas drilling engineering, and relates to a fishing tool for coiled tubing operations. Specifically, it is a new type of fishing cylinder that can determine the fishing status of fallen fish, and is mainly used for fishing downhole fish and determining the fishing status. Background Technology

[0002] In oil and gas field development, coiled tubing operations are widely used in well workover, fishing, and downhole operations due to their high efficiency, operational flexibility, and safety. Existing coiled tubing fishing tools typically rely on changes in pump pressure and suspended weight to determine whether a fish has been retrieved. However, pump pressure changes are small and the suspended weight signal is unstable. Furthermore, due to the complexity of downhole conditions and the varying sizes and conditions of fish, pump pressure changes are often insignificant, making it difficult for field personnel to accurately determine the retrieval status, leading to the risk of misjudgment or missed retrieval. In addition, the inability to accurately determine the retrieval status can result in repeated operations, tool damage, or increased operating costs.

[0003] Therefore, existing coiled tubing fishing tools suffer from insufficient reliability, low efficiency, and high operational risks in downhole fish retrieval operations. There is an urgent need for a new type of fishing tool that can intuitively determine whether a fish has been retrieved, in order to improve the safety and success rate of the operation. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem that existing coiled tubing fishing tools cannot accurately determine whether a fish has been caught during downhole operations, and to provide a new type of fishing tube that can intuitively determine the retrieval status.

[0005] To solve the above problems, the present invention adopts the following technical solution: The present invention provides a retrieval cylinder for coiled tubing operations that can determine the retrieval status, comprising a cylinder body, a retrieval mechanism, and a flow channel control mechanism. The retrieval mechanism is used to hold the fish downhole. The flow channel control mechanism, through mechanical structure design, changes the opening state of the fluid channel inside the tool when the fish is retrieved and when it is not, thereby creating a significant pump pressure difference on the surface, allowing operators to determine the retrieval status. The upper connector is externally threaded to the guide shoe cylinder and internally threaded to the slide rod. The slide rod is fitted with a spring and a slider, which can slide on the slide rod. The lower end of the slide rod has a built-in limit function. The slider and the connecting cylinder are connected by threads, and the lower end of the connecting cylinder is connected to the slip.

[0006] Compared with existing technologies, the retrieval cylinder of the present invention generates identifiable pump pressure change signals through mechanical structure, which can confirm whether the fish has been retrieved without relying on electronic sensors or experience judgment, effectively reducing operational risks and improving the reliability and success rate of downhole retrieval operations in coiled tubing.

[0007] Compared with the prior art, the advantages of the present invention are as follows: Compared with existing technologies, the retrieval tube of this invention, through its mechanical structure design, generates a significant pump pressure change when the fish is retrieved, thereby enabling intuitive judgment of the retrieval status and avoiding the uncertainty caused by relying on experience-based judgment. This tool has a simple and reliable structure, requiring no electronic sensors or complex detection devices; it functions solely through the mechanical cooperation between its components, reducing the risk of malfunctions during downhole operation. Simultaneously, this invention effectively reduces misjudgments and repetitive operations, improving the success rate and efficiency of coiled tubing retrieval operations. Furthermore, by accurately judging the state of the fish, it reduces tool damage and operational risks, further ensuring downhole safety. In addition, this retrieval tube is highly adaptable and can be applied to coiled tubing operations of different diameters and types, meeting the needs of various downhole conditions. Attached Figure Description

[0008] Figure 1 A schematic diagram of a retrieval cylinder for continuous tubing operations that can determine the retrieval status; Figure 2 The diagram shows a sliding rod. In the diagram, 21 is the main flow channel, 22 is the diversion hole, and 23 is the limiting structure. Figure 3 This is a longitudinal cross-sectional schematic diagram of the fishing tube of the present invention, showing the state in which the slider is in the sliding rod limit position and the diversion hole is exposed when the fish is not caught. In the figure, 8. Fish falls.

[0009] Figure 4 This is a longitudinal cross-sectional schematic diagram of the fishing tube of the present invention, showing the state in which the slider moves upward to block the diversion hole after the fish is caught. In the figure, 8. Fish falls.

[0010] Figure 5 This is a graph comparing wellhead pressure changes over time. The horizontal axis represents time (in minutes), and the vertical axis represents surface pump pressure (in MPa). The blue curve represents the successful capture of the fish using the retrieval tube of this invention, operating at an initial well site pressure of approximately 25.5 MPa. At approximately point A, the pressure rapidly increased from 26 MPa to 32 MPa and remained stable, indicating successful capture. The yellow curve represents the use of traditional retrieval tools, where the pressure fluctuated slightly (±0.5 MPa) around 27.8 MPa without significant change, making it difficult to clearly determine the capture status. This graph demonstrates that this invention provides a clear capture status signal through a significant increase in wellhead pressure, making it suitable for actual well site operating environments. In the diagram: 1. Upper connector, 2. Shoe guide tube, 3. Sliding rod, 4. Spring, 5. Sliding block, 6. Connecting cylinder, 7. Locking clip, 8. Fish dropper. Detailed Implementation

[0011] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0012] Implementation Case 1 The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0013] Reference Figure 1 The structure of the present invention consists of 1. an upper connector, 2. a shoe guide tube, 3. a slide rod, 4. a spring, 5. a slider, 6. a connecting cylinder, and 7. a locking piece.

[0014] The upper connector 1 and the guide shoe tube 2 are connected by threads to form an external frame. The upper end of the slide rod 3 is fixed to the upper connector 1 by threads. The slider 5 is set on the slide rod 3 and can slide on the slide rod 3. It is restricted by the bottom limiting structure 23 of the slide rod 3 and will not slide off the slide rod 3. At the same time, the spring 4 acts downward to keep its initial position close to the bottom limiting of the slide rod 3. The slider 5 is connected to the connecting cylinder 6 by threads, and the connecting cylinder 6 is then connected to the slip 7 by threads. The slide rod 3, slider 4, spring 4, connecting cylinder 6 and slip 7 are all located inside the guide shoe tube. The slip 7 is used to contact the fallen fish to achieve the retrieval function. The slide rod 3 is provided with a diversion hole 22 to control the fluid channel and participate in the judgment of pump pressure changes.

[0015] The working principle of this invention is based on the mechanical cooperation between slider 5 and slide rod 3. By changing the opening and closing state of the diversion hole 22, the flowability of the internal fluid channel is altered, resulting in a significant change in the ground pump pressure, thus enabling the judgment of the fish catch status. The working process is described in detail below: Initial State (No Fish Retrieved): Before the retrieval tube is lowered into the well or before contacting the fish 8, spring 4 is in the extended state, pushing slider 5 downwards and stopping it at the limit position at the bottom of slide rod 3. At this time, the diversion hole 22 on slide rod 3 is fully exposed. Drilling fluid or working fluid pumped from the surface enters the main channel 21 of slide rod through the fluid channel of the upper connector, and flows out through the exposed diversion hole 22, entering the internal space of the guide shoe 2, and finally being discharged from the tool. The fluid flow path is unobstructed and the resistance is small, resulting in the surface pump pressure remaining at a low level. This low pump pressure state indicates that the tool has not yet caught the fish, and the operator can use this to determine whether the tool is in the preparation or lowering stage.

[0016] Contact with the fish: When the retrieval tube is lowered to the target location downhole via coiled tubing, the conical lower end of the guide shoe 2 first contacts and guides the fish 8 into the tool's interior. The fish 8 gradually enters the slips 7, and the wedge-shaped structure and serrated inner surface of the slips 7 begin to contact the outer surface of the fish 8. The operator applies an axial downward force through the coiled tubing, causing the slips 8 to expand or contract radially, firmly embedding into the surface of the fish, achieving initial gripping. At this point, the reaction force of the fish 8 begins to be transmitted upwards.

[0017] Mechanical Movement Stage: As the slip 7 firmly grips the fish 8, the reaction force of the fish 8 is transmitted to the connecting sleeve 6 through the slip 7. Since the connecting sleeve 6 is fixedly connected to the slider 5 by threads, this force further drives the slider 5 to slide upward along the slide rod 3, compressing the spring 4. The slider 5 gradually covers the diversion hole 22 on the slide rod 3 until it is completely blocked. At this time, the bypass path of the internal fluid channel is closed, and the drilling fluid cannot be discharged through the diversion hole, but can only flow through the main flow channel 21 of the tool, resulting in a sharp increase in fluid flow resistance.

[0018] Pump pressure change and catch judgment stage: After the diversion orifice 22 is blocked, the ground pump pressure rises rapidly. This significant increase in pump pressure is due to the reduction in the effective flow area of ​​the fluid channel, resulting in increased back pressure encountered by the pumped liquid. The operator monitors the pump pressure changes in real time using a ground pressure gauge: if the pump pressure shows a significant and stable increase, it indicates that the fish 8 has been successfully caught by the catcher 7; conversely, if the pump pressure remains stable or fluctuates only slightly, it indicates that the catch has failed, and the tool position can be adjusted immediately without raising the tool or relying on experience for judgment. Figure 5 As shown, the retrieval tube of this invention operates at an initial well site pressure of approximately 25.5 MPa. After catching the fish, the pressure rapidly rises from 26 MPa to 32 MPa and remains stable, providing a clear retrieval signal. In contrast, the pressure of traditional tools fluctuates only slightly (±0.5 MPa) around 27.8 MPa, making it impossible to clearly determine the retrieval status. This mechanism avoids the uncertainties of traditional methods, improving operational efficiency and safety. The core of its working principle lies in using a mechanical structure to achieve passive detection, requiring no additional sensors or electronic components, resulting in a simple and reliable structure. Using wellhead pressure changes as a direct signal, it is suitable for high-deviation wells or complex well conditions in coiled tubing operations, ensuring high accuracy in judgment and reducing operational risks.

Claims

1. A fishing tool for coiled tubing operations, in which the state of capture can be determined, characterized in that, The system includes an upper connector (1), a sliding rod (3), a spring (4), a slider (5), a connecting cylinder (6), a locking device (7), and a shoe guide (2); wherein, the upper connector (1) and the shoe guide (2) are connected by threads to form an external frame; the upper end of the sliding rod (3) is fixed to the upper connector (1) by threads, the slider (5) can slide on the sliding rod (3), the spring (4) pushes the slider (5) downward, and the bottom of the sliding rod (3) is provided with a limiting structure to prevent the slider (5) from sliding out; the slider (5) is connected to the connecting cylinder (6) by threads, and the connecting cylinder (6) is connected to the connecting cylinder (6) by threads. The slip (7) is connected to the slide rod (3), the slider (5), the spring (4), the connecting cylinder (6), and the slip (7) are located inside the guide shoe cylinder (2); the slide rod (3) is provided with a diversion hole. In the initial state, the spring (4) pushes the slider (5) to the limit position, the diversion hole is exposed, and the fluid flows through the diversion hole; when the slip (7) grabs the fish, the slip (7) drives the slider (5) to move upward through the connecting cylinder (6), blocking the diversion hole, which is used to change the state of the downhole fluid channel, thereby generating a pump pressure change signal on the ground, which is used to determine whether the fish has been successfully grabbed.

2. A retrieval cylinder for coiled tubing operations capable of determining the retrieval status according to claim 1, characterized in that, The range of movement of the slider (5) on the slide bar (3) is limited by the bottom limiting structure of the slide bar (3).

3. A retrieval cylinder for coiled tubing operations capable of determining the retrieval status according to claim 1, characterized in that, The slider (5) is pushed downward by the spring (4) so ​​that its initial position is close to the bottom limit of the slider (3).

4. A retrieval cylinder for coiled tubing operations capable of determining the retrieval status according to claim 1, characterized in that, The diversion hole on the slide bar (3) remains open when the slider (5) is in its initial position, and is blocked when the slider (5) blocks the diversion hole, thereby enabling the judgment of the fish catch status.

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