An equal-diameter expansion type fishing spear for oil and water well casing fishing

Abstract

The present application relates to oilfield workover tool technical field, especially to a kind of oil-water well casing fishing with slip equal-diameter expansion and contraction type fishing spear.The oil-water well casing fishing with slip equal-diameter expansion and contraction type fishing spear, including spear shaft being connected below upper joint by thread, the bottom end of spear shaft is the cone body that contracts upwards, spring and slip are sleeved on spear shaft, and spring pushes slip downward;The outer wall of the bottom end of slip is equipped with slip tooth being distributed along thread, and inner wall is the inclined surface being cooperated with cone body;The top end and bottom end of slip are evenly divided into multiple upper petal body and lower petal body, and synchronous same-diameter expansion and contraction are carried out when moving along spear shaft.The oil-water well casing fishing with slip equal-diameter expansion and contraction type fishing spear proposed in the present application, through respectively evenly dividing into petal-shaped the upper end and bottom end of slip to carry out equal-diameter opening and closing, keep the contact area of outer surface and the inner wall of fished part, improve the fit degree of slip and fished part;Slip tooth being distributed in thread form can be held on the surface of fished part by rotating slip.

Description

Technical Field

[0001] This invention relates to the field of oilfield well workover tools, and in particular to a retrieval spear with equal diameter expansion and contraction slips for retrieving oil and water well casings. Background Technology

[0002] In well workover operations in oilfields, retrieval equipment is needed to retrieve fish-shaped tools, tubing, or other tools from the casing. However, in existing technologies, when retrieving lightweight dredging tools and tubing in horizontal well operations, the outer end of the slips does not fit well against the inner wall of the fish-shaped tool being retrieved. This results in an inability to effectively grip the retrieved tool during the retrieval process, causing the retrieval string to fall midway, leading to a low retrieval success rate. Moreover, the commonly used threaded gripping spears can only grip the female threads of tools and tubing, offering limited functionality. Due to structural limitations, existing tools cannot be used for retrieved sizes of 7cm or less, and commonly used sliding spears, retractable spears, inverted spears, and telescopic spears are all unsuitable. To meet the requirements of different working conditions in well workover operations, short fish-shaped spears are usually modified from existing spear tools. However, due to insufficient machining precision and minimal structural changes, the modified tools still cannot overcome the problems of poor contact with the retrieved object, low retrieval success rate, and high construction costs during the retrieval process. Therefore, in order to address the above shortcomings, a new type of retrieval spear with equal diameter expansion and contraction for retrieval inside the casing of oil and water wells is proposed. Summary of the Invention

[0003] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a retrieval spear with equal-diameter expansion and contraction slips for retrieval inside oil and water well casings. This solves the problems of poor fit between the outer end of the slips and the inner wall of the fish being retrieved, as well as the inability to apply the spear in situations where the retrieval depth is less than or equal to 7 cm.

[0004] (II) Technical Solution To solve the above problems, the present invention provides a retrieval spear with equal-diameter expansion and contraction slips for retrieving oil and water well casings, comprising: The device comprises an upper connector and a spear shaft. The spear shaft passes through the upper connector from bottom to top and is fixed thereto. The outer wall of the bottom end of the spear shaft has an upwardly tapering conical surface. A slip is provided on the spear shaft, and the outer wall of the slip has evenly distributed slip teeth. The inner wall is an inclined surface that matches the conical surface at the bottom end of the spear shaft but in the opposite direction. The slip teeth are distributed in a threaded pattern on the surface of the slip, and the contact surface between the slip teeth and the object to be retrieved has a trapezoidal cross section. A spring is provided above the slip, which is fitted onto the spear shaft and pushes the slip downward. The bottom and top ends of the slip are evenly divided into several lower and upper segments, which are staggered. The lower segments at the bottom of the slip open and close as the slip moves up and down on the surface of the spear shaft. The upper segments open and close synchronously with the lower segments under their own elasticity, so that the upper and lower ends of the slip open and close synchronously with equal diameter, tightly fitting the object to be retrieved.

[0005] Preferably, the outer wall of the upper connector is provided with a plurality of guide and straightening wings evenly distributed along the circumference, and the upper and lower ends of the guide and straightening wings are chamfered.

[0006] Preferably, the spear shaft and the upper connector are connected by threads, and the position of the guide and straightening wing corresponds to the position of the upper thread of the spear shaft.

[0007] Preferably, the guide straightening wing is provided with a plurality of fixing screws that penetrate the guide straightening wing evenly. The bottom end of the fixing screw is round, and the thread of the spear shaft is provided with a plurality of recessed fixing grooves. The position and shape of the fixing grooves are matched with the fixing screws.

[0008] Preferably, the spear shaft has a vertical through hole in the middle, through which the liquid in the upper connector flows to flush the lower part of the spear shaft.

[0009] Preferably, the middle section of the card is uniformly provided with several radial rectangular grooves along the circumference, the two ends of the rectangular grooves are circular, and the top or bottom of the rectangular grooves are provided with radial through slits. The top and bottom of the card (5) are divided into upper and lower petals by the through slits.

[0010] Preferably, the lower end of the slip is provided with a plurality of radial limiting grooves evenly distributed along the circumference, and the outer wall of the bottom end of the spear shaft is provided with a plurality of protruding limiting blocks evenly distributed along the circumference, the number, size and shape of the limiting blocks being matched with the limiting grooves.

[0011] Preferably, the spring is a rectangular spring, with a coil of spring pressed together at each of the upper and lower ends to form a ring.

[0012] (III) Beneficial Effects The present invention provides a retrieval spear with equal-diameter expansion and contraction slips for retrieving oil and water well casings. By uniformly dividing the upper and lower ends of the slips into petals, they open and close with equal diameter when in contact with the spear shaft. When the slips expand outward, they can maintain the parallelism between the outer surface of the slip and the inner wall of the retrieved object, increasing the contact area between the slip teeth and the retrieved object and improving the fit between the slip and the retrieved object. Through the threaded distribution of the slip teeth, it can hold the object on the surface of the retrieved object by rotating the slips when the retrieved size depth is less than or equal to 7cm, achieving a tight fit for retrieval. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the equal-diameter expansion and contraction retrieval spear for oil and water well casing retrieval according to the present invention; Figure 2 This is a schematic diagram of the upper connector structure of the equal-diameter expansion and contraction retrieval spear for retrieval inside the casing of oil and water wells according to the present invention. Figure 3This is a schematic diagram of the fixing screw structure of the equal-diameter expansion and contraction type fishing spear for fishing inside the casing of oil and water wells according to the present invention. Figure 4 This is a schematic diagram of the spear shaft structure of the equal-diameter expansion and contraction type retrieval spear for oil and water well casing retrieval according to the present invention. Figure 5 This is a schematic diagram of the spring structure of the equal-diameter expansion and contraction retrieval spear with slips for retrieval inside the casing of oil and water wells according to the present invention. Figure 6 This is a schematic diagram of the slip structure of the equal-diameter expansion and contraction type retrieval spear for retrieval inside the casing of oil and water wells according to the present invention.

[0014] Among them, 1. upper connector; 2. fixing screw; 3. spear rod; 4. spring; 5. clip; 6. limiting block; 7. limiting groove; 8. guide straightening wing. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0016] In the description of this invention, it is necessary to understand that the orientation or positional relationship indicated by terms such as "upper", "lower", "inner", "outer", "top", and "bottom" are based on the orientation or positional relationship shown in the accompanying drawings. The purpose is only to facilitate the description of this invention and to simplify the description. It is not intended to indicate or imply that the component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0017] like Figure 1-6 As shown, this invention provides a collapsible, equal-diameter, expandable retrieval spear for internal casing retrieval in oil and water wells, specifically comprising: an upper connector 1 and a spear shaft 3. The spear shaft 3 is inserted into the upper connector 1 from bottom to top and fixed thereto. The upper connector 1 primarily serves a connecting function, connecting the device to the upper component within the tool string, thereby fixing the device in the working position. The spear shaft 3 is used to connect the upper connector 1 and the lower anchoring mechanism to the upper connector 1 to form a single body.

[0018] The spear shank 3 is connected to the upper connector 1 by a thread, and the position of the guide wing 8 corresponds to the position of the upper thread of the spear shank 3. Multiple guide wing 8s are evenly arranged circumferentially on the outer wall of the upper connector 1, and the upper and lower ends of the guide wing 8 have chamfered structures. The guide wing 8s are mainly used to straighten the device during downhole operations. During downhole operations, the guide wing 8s will contact the well wall as the device shakes. When the guide wing 8 contacts the well wall, it will support the upper connector 1 in the opposite direction. Through the combined action of the guide wing 8s in different directions, the upper connector 1 is always fixed in the middle position inside the well, facilitating subsequent alignment with the object being retrieved. During the movement of the upper connector 1 along the casing, when the casing bends or there are debris, the chamfered structures at the front and rear of the guide wing 8 will contact the bend and debris to guide the upper connector 1, allowing it to move smoothly up and down along the casing.

[0019] It should be noted that the guide and straightening wing 8 is evenly provided with several fixing screws 2 that penetrate the guide and straightening wing 8. The bottom end of the fixing screw 2 is round, and the thread of the spear rod 3 is provided with several concave fixing grooves. The position and shape of the fixing grooves are matched with the fixing screw 2. After the fixing screw 2 is installed on the guide and straightening wing 8, the round head of the fixing screw 2 will fall into the fixing groove on the surface of the spear rod 3 and cooperate with the fixing groove to clamp the spear rod, preventing the spear rod 3 from loosening during operation. After the fixing groove is installed on the thread of the spear rod 3 and the round head of the fixing screw 2 fixes the groove, when the spear rod 3 loosens, the thread will contact the round head of the fixing screw to generate friction, thereby preventing the spear rod 3 from loosening further and improving the stability of the device. Generally, in order to simplify the structure of the device and reduce the processing difficulty, the number of guide and straightening wings 8 on the surface of the upper connector 1 is generally six. When arranging the fixing screws 2, they are usually arranged symmetrically around the spear rod 3. A common installation method is to evenly install three fixing screws 2 on each of the guide and centralizing wings 8 in two opposite directions, for a total of six fixing screws 2 arranged in two groups to clamp the spear rod 3. In actual work, the number of guide and centralizing wings 8 and fixing screws 2 can be modified according to the size and weight of the upper connector 1 and the spear rod 3, so that the spear rod 3 and the upper connector 1 can still be stably connected during downhole operations.

[0020] In this invention, the outer wall of the bottom end of the spear shaft 3 has an upwardly tapered conical surface. The spear shaft 3 is equipped with a slip 5, and the outer wall of the slip 5 has evenly distributed slip teeth. The inner wall is an inclined surface that matches the conical surface at the bottom end of the spear shaft 3 but in the opposite direction. After the slip 5 is installed on the spear shaft 3, during the salvage operation, the spear shaft 3 and the slip extend into the object to be salvaged, and the slip 5 is pushed downwards. The inner wall of the slip 5 engages with the conical surface at the bottom end of the spear shaft 3, pushing the slip 5 outwards. At this time, the slip teeth on the outer wall of the slip 5 contact and adhere to the inner wall of the object to be salvaged. As the slip 5 is gradually pushed downwards, the pressure exerted by the slip teeth on the inner wall of the object to be salvaged gradually increases, engaging with the inner wall and fixing the slip 5 to the object to be salvaged. At this point, lifting the upper connector 1 can lift the slip 5 and the object to be salvaged, thus achieving the salvage operation.

[0021] The spear shaft 3 has a vertical through-hole in the middle, through which liquid from the upper connector 1 flows to flush the area below. During the retrieval process, due to the complex downhole environment, the surface of the object being retrieved often contains accumulated sand, mud, gravel, and other debris. If retrieval is carried out directly, this debris can get stuck between the slips 5 and the object, affecting the fit between the device and the object and the stability of the retrieval, thus reducing the success rate. During the retrieval process, when the device reaches above the object, water can be injected into the upper connector 1. The water flows through the through-hole inside the spear shaft 3 to flush the object, the surrounding well wall, and the environment. Cleaning the surrounding environment before retrieval effectively improves the tightness of the fit between the slips 5 and the object, increasing the retrieval success rate.

[0022] To improve the efficiency of the device, a spring 4 is usually installed above the slip 5. The spring 4 is fitted onto the spear 3 and pushes the slip 5 downward. During operation, the slip 5 is constantly compressed and pushed downward by its own elastic force. When the device is performing a salvage operation, the spear 3 drives the slip 5 downward to contact the object being salvaged. At this time, the slip 5 is in an expanded state under the action of the spring 4, with a diameter larger than the object being salvaged. The bottom end of the slip 5 contacts the object and pushes upward, while the spear 3 extends into the object. After the slip 5 is pushed upward, the inner wall of the slip gradually separates from the bottom end of the spear 3. Without the support of the conical surface, the slip 5 gradually... When the diameter of slip 5 is smaller than that of the object being retrieved, slip 5 moves downward into the object. At this point, slip 5 loses its support below and moves downward along the spear shaft 3 under the action of spring 4, then contacts the conical surface at the bottom of the spear shaft 3 and expands again. This causes the slip teeth on the outer wall of slip 5 to contact the inner wall of the object being retrieved. As the spear shaft 3 pulls slip 5 upward, the gravity of the object being retrieved acts on the inner wall and slip teeth, causing slip 5 to fit against the object and grasp it. Then, by continuing to pull the spear shaft 3 upward, the downhole tool can be retrieved.

[0023] The spring 4 is a rectangular spring, with a coil of spring at each of its upper and lower ends compressed to form a ring. Compared to ordinary springs, rectangular springs have higher strength and better fatigue resistance under axial pressure, resulting in a longer service life. By compressing one end of the spring 4 at both ends, the contact area between the spring 4 and the upper connector 1 and the slip 5 is increased, and the force is distributed more evenly. This prevents damage to the spring 4 or wear of the upper connector 1 and the slip 5 due to excessive local pressure, further improving the service life and operational stability of the device.

[0024] It is important to note that the locking teeth are arranged in a spiral pattern on the surface of the locking teeth 5, and the cross-section of the contact surface between the locking teeth and the object to be retrieved is trapezoidal. When the weight of the object to be retrieved is insufficient to form a firm connection between the locking teeth 5 and the object, the spiral pattern of the locking teeth allows the locking teeth to rotate synchronously while the tool string is being lifted. This causes the locking teeth to contact and grip the inner wall of the object while rotating, creating a "hole" in the inner wall of the object. As the locking teeth rotate, the sidewalls of the locking teeth rub against the inner wall of the object, forming a groove that matches the shape of the locking teeth. The engagement of the locking teeth and the groove allows for the gripping of the object with insufficient weight and the retrieval operation. Similarly, for situations where the retrieval depth does not exceed 7cm, the target can also be retrieved by rotating and lifting the tool string.

[0025] like Figure 6As shown, the bottom and top of the slip 5 are evenly divided into several lower and upper lobes, which are staggered. The lower lobes at the bottom of the slip 5 open and close as the slip 5 moves up and down on the surface of the spear shaft 3. The upper lobes open and close synchronously with the lower lobes under their own elasticity, so that the upper and lower ends of the slip 5 open and close synchronously with equal diameter, making a tight fit with the object being retrieved. The reason why commonly used retrieval devices do not have a good fit with the object being retrieved is that the outer wall of the slip 5 expands through the inclined plane. While expanding, the diameter of the top of the slip 5 remains unchanged, causing the part of the slip 5 that contacts the inner wall of the object being retrieved to be in an inclined state. This means that the slip teeth on the slip 5 cannot fully contact the inner wall of the object being retrieved, reducing the degree of fit between the slip 5 and the inner wall of the object being retrieved. By evenly dividing the upper and lower ends of the slip 5 into several upper and lower lobes, when the bottom end of the slip 5 expands outward under the action of the cone surface at the bottom end of the spear shaft 3, the lower lobe first contacts the cone surface at the bottom end of the spear shaft 3 and expands outward. Then, through the elasticity of the slip 5 itself, the outward expansion force is transmitted to the upper lobe at the top. After being subjected to force, the upper lobe performs an outward expansion action synchronously with the lower lobe, so that the top and bottom ends of the slip 5 expand synchronously. At this time, since the upper and lower ends expand outward at the same time, the part of the bottom end of the slip 5 that contacts the inner wall of the object being retrieved always maintains its original direction and will not tilt with the object being retrieved. The slip teeth on the bottom end surface of the slip 5 fully contact the inner wall of the object being retrieved, so that the slip teeth on the surface of the slip 5 are subjected to uniform force, thereby improving the tightness of the fit between the slip 5 and the object being retrieved. The staggered distribution of the upper and lower lobes prevents the Slip 5 from being completely sheared radially due to the overlap of the boundary lines of the upper and lower lobes. The staggered distribution of the upper and lower lobes ensures that the Slip 5 remains a complete whole while achieving synchronous expansion and contraction at both ends, resulting in uniform stress on the Slip 5 and preventing local breakage due to uneven stress during expansion.

[0026] The slip 5 features several radial rectangular grooves evenly distributed along its circumference in its middle section. The ends of these grooves are circular, and radial through-slits are located at the top or bottom of each groove. These through-slits divide the slip 5 into upper and lower lobes. The rectangular grooves significantly reduce the slip 5's weight and the device's counterweight. Furthermore, the combination of the grooves and through-slits divides the slip 5 into upper and lower lobes. Each upper and lower lobe connects only to a portion of the strip-shaped sidewall of the slip 5. When the slip 5 expands outwards, each upper and lower lobe at the bottom only needs to overcome the elasticity of the connected strip-shaped sidewall to drive the lobe's top lobed structure to synchronously expand and contract with equal diameter. This greatly reduces the difficulty of achieving equal diameter expansion and contraction, improving the device's efficiency.

[0027] It should be noted that the lower end of the slip 5 is uniformly provided with several radial limiting grooves 7 along the circumference, and the outer wall of the bottom end of the spear 3 is uniformly provided with several protruding limiting blocks 6 along the circumference. The number, size, and shape of the limiting blocks 6 are all matched with the limiting grooves 7. During operation, the limiting blocks 6 are inserted into the limiting grooves 7. When the top of the limiting groove 7 contacts the limiting block 6, the limiting block 6 holds the slip 5 against it, preventing the slip 5 from continuing to move downward along the spear 3, thus preventing the slip 5 from moving too far downward and detaching from the spear 3. At the same time, when the rotating tool string is in contact with the inner wall of the object being retrieved, since the spear 3 and the upper connector 1 are connected by threads and clamped by fixing screws 2, the upper connector 1 will drive the spear 3 to rotate synchronously with the tool string. At this time, the side wall of the limiting block 6 contacts the side of the limiting groove 7, transmitting the steering force transmitted by the tool string to the slip 5, thereby driving the slip 5 to rotate and make a hole in the inner wall of the object being retrieved, thus gripping the inner wall of the object being retrieved. To ensure that the device itself has sufficient strength, the position of the limiting groove 7 is usually connected to the through seam where the bottom end of the slip 5 connects to the rectangular groove. The limiting groove 7 evenly divides the part with the slip teeth at the bottom end of the slip 5 into several petals.

[0028] During the processing, it is necessary to consider the thread direction between the upper connector 1 and the spear rod 3, as well as the thread direction of the slip teeth distributed in a threaded manner at the bottom of the slip 5. Under normal circumstances, the tightening direction of the two should be the same to ensure that the upper connector 1 and the spear rod 3 are always tightened when the rotating tool string is "drilling" the inner wall of the object being retrieved, so as to avoid the upper connector 1 and the spear rod 3 from loosening and falling off during the operation, and to improve the stability of the device during the operation.

[0029] To facilitate installation and disassembly, a hexagonal groove is usually provided at the top of the spear shaft 3, which allows a hexagonal wrench to be directly inserted into the hexagonal groove to rotate the spear shaft 3 for installation and disassembly.

[0030] Normally, when the number of rectangular grooves on the surface of the slip 5 is six during the processing, it can adapt to most working conditions in existing downhole salvage operations. In each of the six rectangular grooves, one of the two adjacent rectangular grooves has a radial through slit at the top and the other has a radial through slit at the bottom, so that the top and bottom of the slip 5 are divided into three upper and lower lobes respectively, and the upper and lower lobes are staggered. When the slip 5 moves up and down along the spear shank 3, each lobe of the slip 5 only needs to overcome the elasticity of the two strip-shaped slip 5 sidewalls connected to it to perform equal-diameter expansion and equal-diameter contraction.

[0031] In actual operation, as the size of the slip 5 increases, in order to reduce its weight and the stress that the device needs to overcome during expansion and contraction, the number of rectangular grooves on the surface of the slip 5 can be appropriately increased to further reduce its weight. Simultaneously, the shape and distribution of the upper and lower lobes are set according to the required performance, and through-slits are machined at the corresponding positions of the rectangular grooves to divide the top and bottom of the slip 5.

[0032] During the manufacturing process, in order to ensure that the teeth on the outer wall of the bottom of the slip 5 are distributed in a threaded manner, a uniform thread is usually first machined on the outer wall of the slip 5 at the location where the teeth are distributed, in accordance with the distribution direction of the teeth. Then, a limiting groove 7 and a corresponding through slot are machined at the bottom of the slip 5 to evenly divide the bottom of the slip 5 into multiple lower segments. Finally, a milling cutter is used to longitudinally cut the remaining threads on the surface of the slip 5, dividing the threads into individual slip teeth. At this point, the slip teeth are distributed in a threaded manner on the surface of the slip 5.

[0033] The oil and water well casing retrieval spear with equal-diameter expansion and contraction slips provided by this invention can improve the fit between the slip teeth and the inner wall of the fish being retrieved, and can also be used normally in situations where the retrieved object is lightweight and the retrieval depth is less than or equal to 7cm. The specific operation process of this device is as follows: Step 1: Select appropriate size and shape of clamps according to the work requirements, assemble them according to the device structure, and then install the upper connector on the tool string.

[0034] Step 2: Lower the device along with the tool string into the casing to the retrieval location. During this process, the guide and centering wings on the outer wall of the upper connector will help to center the device, keeping it consistently in the middle position of the casing.

[0035] Step 3: Fill the tool string with water to rinse the object being retrieved. At this time, the water in the tool string flows downward through the through hole between the upper connector and the spear shaft, rinsing the surface of the object being retrieved and the surrounding casing environment, washing away the debris attached to the surface of the object being retrieved and the inner wall of the casing.

[0036] Step 4: Continue with the following tool string to insert the slip into the inner wall of the object being retrieved. Initially, the slip is located at the bottom of the spear shaft and is in an expanded state under the action of the spring. At this time, the bottom end of the slip contacts the top of the object being retrieved, pushing the slip upward while the spear shaft extends into the object. The bottom end of the slip gradually separates from the conical surface at the bottom of the spear shaft and contracts inward under its own elasticity. When the diameter of the bottom end of the slip is smaller than the diameter of the object being retrieved, the slip moves downward with the spear shaft and extends into the object being retrieved.

[0037] Step 5: Under the action of the spring and the spear shaft, the slip expands at the same diameter to grip the inner wall of the object being retrieved. At this time, under the action of the spring, the slip moves downward along the spear shaft, and its bottom end gradually engages with the conical surface at the bottom of the spear shaft, causing the slip to expand again. The slip teeth on the outer wall of the slip then adhere to the inner wall of the object being retrieved.

[0038] Step Six: Lift and rotate the tool string to grip the object being retrieved. As the tool string rotates, the jaws rub against the inner wall of the object, creating a narrow slit. Once the jaws engage with the slit, the weight of the object is evenly distributed across the jaws.

[0039] Step 7: Continue lifting to bring the salvaged object out of the casing and complete the salvage operation.

[0040] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A type of retrieval spear with equal-diameter expansion and contraction slips for retrieving oil and water well casings, characterized in that, include: The upper connector (1) and the spear shaft (3) are connected. The spear shaft (3) is inserted into the upper connector (1) from bottom to top and fixed to the upper connector (1). The outer wall of the bottom end of the spear shaft (3) is a tapered surface that tapers upward. The spear shaft (3) is provided with a slip (5). The outer wall of the bottom end of the slip (5) is evenly provided with slip teeth. The inner wall is an inclined surface that matches the tapered surface at the bottom end of the spear shaft (3) and is opposite in direction. The slip teeth are distributed in a spiral pattern on the surface of the slip (5). The cross section of the contact surface between the slip teeth and the object being retrieved is trapezoidal. A spring (4) is provided above the slip (5), and the spring (4) is sleeved on the spear rod (3) to push the slip (5) downward. The bottom and top of the slip (5) are evenly divided into several lower and upper petals. The upper and lower petals are staggered. The lower petals at the bottom of the slip (5) move up and down on the surface of the spear rod (3) as the slip (5) moves up and down. The upper petals open and close synchronously with the lower petals under their own elasticity, so that the upper and lower ends of the slip (5) open and close synchronously with the same diameter and fit tightly with the salvaged object.

2. The oil and water well casing retrieval spear with equal-diameter expansion and contraction slips as described in claim 1, characterized in that, The upper connector (1) has multiple guide and straightening wings (8) evenly arranged along the circumference on its outer wall, and the upper and lower ends of the guide and straightening wings (8) are chamfered.

3. The oil and water well casing retrieval spear with equal-diameter expansion and contraction slips as described in claim 2, characterized in that, The spear shaft (3) is connected to the upper connector (1) by a thread, and the position of the guide straightening wing (8) corresponds to the position of the upper thread of the spear shaft (3).

4. The oil and water well casing retrieval spear with equal-diameter expansion and contraction slips as described in claim 3, characterized in that, The guide straightening wing (8) is evenly provided with a number of fixing screws (2) that penetrate the guide straightening wing (8). The bottom end of the fixing screw (2) is round. The thread of the spear shaft (3) is provided with a number of recessed fixing grooves. The position and shape of the fixing grooves are matched with the fixing screws (2).

5. The oil and water well casing retrieval spear with equal-diameter expansion and contraction slips as described in claim 4, characterized in that, The spear shaft (3) has a vertical through hole in the middle, and the liquid in the upper connector (1) flows through the through hole of the spear shaft (3) to flush the lower part.

6. The oil and water well casing retrieval spear with equal-diameter expansion and contraction slips as described in claim 5, characterized in that, The middle section of the card (5) is uniformly provided with several radial rectangular grooves along the circumference. The two ends of the rectangular grooves are circular. The top or bottom of the rectangular grooves are provided with radial through slits. The top and bottom of the card (5) are divided into upper and lower petals by the through slits.

7. The oil and water well casing retrieval spear with equal-diameter expansion and contraction slips as described in claim 6, characterized in that, The lower end of the clasp (5) is provided with several radial limiting grooves (7) evenly distributed along the circumference, and the outer wall of the bottom end of the spear rod (3) is provided with several protruding limiting blocks (6) evenly distributed along the circumference. The number, size and shape of the limiting blocks (6) are all matched with the limiting grooves (7).

8. The oil and water well casing retrieval spear with equal-diameter expansion and contraction slips as described in claim 7, characterized in that, The spring (4) is a rectangular spring, with a spring coil pressed into a ring at each of the upper and lower ends of the spring (4).

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