Steel ball fisher

Abstract

The invention relates to the technical field of downhole fallen object fishing, in particular to a steel ball fisher. The steel ball fisher comprises a barrel, a connecting structure used for being connected with a fishing pipe column is arranged at the upper end of the barrel, a first communicating hole communicated with an inner cavity of the barrel and the outside is formed in the side wall of the barrel, a magnetic suction head is arranged at the bottom of the barrel, an adsorption groove used for adsorbing a steel ball is formed in the bottom of the magnetic suction head, a reverse circulation water hole is formed in the magnetic suction head, and a second communicating hole is formed in the barrel. One end of the second communication hole is communicated with the outside of the barrel, and the other end is communicated with the reverse circulation water hole so as to form a local reverse circulation channel at the lower part of the fisher together with the reverse circulation water hole. The flushing fluid forms local reverse circulation flow at the lower part of the fisher, and the high-pressure flushing fluid quickly flows to drive a steel ball falling into a well to move towards the bottom of the fisher, so that the steel ball is easier to be in contact with a magnetic suction head at the bottom to be adsorbed, and the steel ball is adsorbed in an adsorption groove of the magnetic suction head to complete steel ball capturing, so that the steel ball capturing can be smoothly realized; the fishing success rate is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of underground object retrieval technology, and more particularly to a steel ball retrieval device. Background Technology

[0002] During oilfield development, steel balls can fall into the wellbore due to various reasons from downhole tools and equipment, accumulating at the bottom of the well or on top of other tools. This can hinder the implementation of downhole procedures, necessitating the removal of the fallen steel balls to ensure the smooth operation of these procedures. Currently, there are two methods for handling fallen steel balls: one is to grind the steel balls using a milling tool and then use well-washing fluid to remove the debris from the wellbore. However, this method has the problem that the steel balls rotate with the milling tool during the milling process, resulting in low milling efficiency and ineffective removal of the steel balls; the other method is to retrieve the steel balls from the wellbore using a retrieval tool.

[0003] Downhole magnetic retrievers are a commonly used tool for retrieving steel balls. A strong magnet is located at the bottom of the retriever's cylinder, attracting the steel ball. Current downhole magnetic retrievers use forward circulation well washing, utilizing the impact force of the washing fluid sprayed from the outlet to flush away debris adhering to the steel ball. After pump shutdown, the retriever is lowered to allow the steel ball to contact the strong magnet and be attracted. However, in actual well washing, some debris is too large to be flushed above the retriever, and after pump shutdown, the debris covers the steel ball again, making it difficult for the steel ball to contact the strong magnet, resulting in a low success rate for steel ball retrieval. Existing technology also uses downhole magnetic retrievers to retrieve steel balls through reverse circulation well washing. However, in practical applications, due to leakage in many formations, effective reverse circulation of the fluid cannot be achieved, thus also resulting in the problem of the steel ball not easily contacting the strong magnet and a low success rate for steel ball retrieval. In addition, the bottom of the downhole magnetic retrieval device currently in use uses a strong magnet to attract steel balls. Since the bottom surface of the strong magnet is flat, the steel balls are attracted to the flat surface, resulting in a small contact area. When pulling out of the well, the steel balls may fall off due to insufficient adhesion, leading to retrieval failure. Summary of the Invention

[0004] The purpose of this invention is to provide a steel ball retrieval device to solve the problem that existing downhole ball retrieval devices are not easy to retrieve steel balls and have a low retrieval success rate.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A steel ball retrieval device includes a cylinder with a connecting structure at the upper end for connecting a retrieval tube. A first connecting hole is provided on the side wall of the cylinder, connecting the inner cavity of the cylinder to the outside. A magnetic suction head is provided at the bottom of the cylinder, with an adsorption groove at the bottom of the magnetic suction head for adsorbing steel balls. A reverse circulation water hole is provided on the magnetic suction head. A second connecting hole is provided on the cylinder, with one end connected to the outside of the cylinder and the other end connected to the reverse circulation water hole, thus forming a local reverse circulation channel at the lower part of the retrieval device together with the reverse circulation water hole.

[0006] Furthermore, the first and second connecting holes are provided in multiples and are arranged alternately in the circumference of the cylinder.

[0007] Furthermore, all the first and second connecting holes are evenly distributed at intervals around the circumference of the cylinder.

[0008] Furthermore, the outlet of the second connecting hole is higher than the outlet of the first connecting hole.

[0009] Furthermore, the reverse circulation water holes are provided in multiple quantities and are evenly distributed on the same circumference, and the number of the second connecting holes is equal to that of the reverse circulation water holes and they are connected in a one-to-one correspondence.

[0010] Furthermore, the second connecting hole is an oblique hole, and the reverse circulation water hole is an oblique hole with an inclination angle equal to that of the second connecting hole. The reverse circulation water hole and the second connecting hole are directly connected.

[0011] Furthermore, the adsorption grooves are provided in multiple places and are arranged at intervals at the bottom of the magnetic head.

[0012] Furthermore, all the adsorption grooves are of different sizes.

[0013] Furthermore, one of the adsorption grooves is located at the center of the magnetic head, and the remaining adsorption grooves are arranged around the central adsorption groove and are on the same circumference.

[0014] Furthermore, the reverse circulation water holes are provided in multiple and spaced apart, and all the reverse circulation water holes and the remaining adsorption grooves except for the central adsorption groove are on the same circumference.

[0015] Beneficial Effects: This invention is a pioneering creation. The steel ball retrieval device can be connected to the retrieval tubing string through the connecting structure at the upper end of the cylinder. High-pressure well-washing fluid is pumped into the retrieval tubing string. The well-washing fluid enters the inner cavity of the cylinder and is sprayed out through the first connecting hole into the annulus between the retrieval device and the casing. Since the magnetic suction head at the bottom of the retrieval device has a reverse circulation water hole, and the cylinder has a second connecting hole, one end of the second connecting hole is connected to the outside of the cylinder, and the other end is connected to the reverse circulation water hole, thus forming a local reverse circulation channel at the bottom of the retrieval device together with the reverse circulation water hole. Therefore, the well-washing fluid sprayed from the first connecting hole will continue to flow downward, and after being obstructed at the bottom of the well, it will flow back upward into the local reverse circulation channel. After passing through the local reverse circulation channel, it will return to the annulus between the retrieval device and the casing, and then flow back upward from the annulus to the surface. The well-washing fluid forms a local reverse circulation flow at the bottom of the retrieval device. The rapid flow of the high-pressure well-washing fluid can drive the steel ball that has been dropped into the well toward the bottom of the retrieval device, making it easier for the steel ball to contact the bottom magnetic head and be attracted. Thus, the steel ball is attracted into the attraction groove of the magnetic head, completing the steel ball capture. This can successfully capture the steel ball and greatly improve the retrieval success rate. Attached Figure Description

[0016] Figure 1 This is a front view of the steel ball retrieval device of the present invention; Figure 2 This is a cross-sectional view of the steel ball retrieval device of the present invention; Figure 3 This is a bottom view of the steel ball retrieval device of the present invention; In the diagram: 1. Cylinder; 2. Threaded structure; 3. Inner cavity of the cylinder; 4. First connecting hole; 5. Magnetic head; 6. Adsorption groove; 7. Reverse circulation water hole; 8. Second connecting hole. Detailed Implementation

[0017] The steel ball retrieval device provided by this invention is mainly used to solve the problem of existing downhole ball retrieval devices having difficulty retrieving steel balls and having a low retrieval success rate. The basic inventive concept of this invention is as follows: a steel ball retrieval device is connected to the bottom of the retrieval string, and a local reverse circulation channel is set at the bottom of the steel ball retrieval device. When high-pressure well-washing fluid is pumped into the retrieval string for forward circulation well-washing, the well-washing fluid forms a local reverse circulation flow at the bottom of the retrieval device after entering the annulus. That is, after entering the annulus, the well-washing fluid continues to flow downward, and then flows upward back into the local reverse circulation channel at the bottom of the retrieval device due to the obstruction at the bottom of the well. Then it returns to the annulus and flows upward back to the surface. During the reverse circulation of the well-washing fluid, the rapidly flowing well-washing fluid carries the fallen steel ball towards the bottom of the retrieval device, making it easier for the steel ball to contact and be attracted to the magnetic head at the bottom of the retrieval device, thereby successfully capturing the steel ball and greatly improving the retrieval success rate.

[0018] Based on the above inventive concept, the embodiments of the steel ball retrieval device of the present invention will be described in detail below.

[0019] like Figure 1-2 As shown, the steel ball retrieval device includes a cylindrical body 1, which is closed at the bottom and has an internal cavity 3 extending vertically. The upper end of the cylindrical body 1 has a connecting structure for connecting the retrieval tubing, specifically a threaded structure 2 on the upper wall of the internal cavity 3. A first connecting hole 4 is provided on the side wall of the cylindrical body 1, connecting the internal cavity 3 to the outside of the cylindrical body 1. A mounting groove is provided at the bottom of the cylindrical body 1, and a magnetic suction head 5 is embedded in the mounting groove. The magnetic suction head 5 is made of magnet, and its bottom has an adsorption groove 6 for adsorbing steel balls. The adsorption groove 6 is a spherical groove, providing a large contact area with the steel ball, resulting in greater adsorption force and more reliable adsorption. A reverse circulation water hole 7 is provided on the magnetic suction head 5, penetrating both ends of the magnetic suction head 5. A second connecting hole 8 is provided on the cylindrical body 1, with one end connected to the outside of the cylindrical body 1 and the other end connected to the reverse circulation water hole 7, thus forming a local reverse circulation channel at the bottom of the retrieval device together with the reverse circulation water hole 7.

[0020] The first connecting hole 4 is an inclined hole sloping downwards and outwards. From the perspective of the well-washing fluid flow direction, the opening of the first connecting hole 4 that connects to the inner cavity 3 of the cylinder is the inlet, and the opening that connects to the outside of the cylinder 1 is the outlet. The second connecting hole 8 is an inclined hole sloping upwards and outwards. From the perspective of the well-washing fluid flow direction, the lower end of the second connecting hole 8 is the inlet, and the upper end is the outlet. The outlet of the second connecting hole 8 is higher than the outlet of the first connecting hole 4, which can extend the length of the local reverse circulation channel and further improve the driving force of the well-washing fluid reverse circulation flow on the steel ball.

[0021] Three first connecting holes 4 are provided, located at the same height on the cylinder 1 and evenly distributed on the same circumference to ensure the uniformity of the circumferential distribution of the washing fluid when it is injected into the annulus through the first connecting holes 4. Three second connecting holes 8 are also provided, located at the same height on the cylinder 1 and evenly distributed on the same circumference to maximize the uniformity of the reverse circulation flow of the washing fluid in the circumferential direction. Preferably, the first and second connecting holes are arranged alternately on the circumference of the cylinder 1 to ensure smooth and rapid circulation of the washing fluid. More preferably, all the first and second connecting holes are evenly distributed on the circumference of the cylinder 1 to further improve the uniformity of the circumferential flow of the washing fluid, ensuring rapid overall circulation of the washing fluid.

[0022] The number of reverse circulation water holes 7 and the number of second connecting holes 8 are equal and they are connected one-to-one. The reverse circulation water holes 7 are inclined holes, and the inclination angle is equal to that of the second connecting holes 8. The reverse circulation water holes 7 and the second connecting holes 8 are directly opposite each other and connected. Together, they form a straight hole that extends from bottom to top, which is more conducive to the rapid passage of the washing fluid, accelerates the circulation speed of the washing fluid, and makes it easier for the washing fluid to drive the steel ball upward.

[0023] like Figure 3As shown, multiple adsorption grooves 6 are provided at the bottom of the magnetic head 5. All the adsorption grooves 6 are arranged at intervals on the magnetic head 5, enabling the adsorption of multiple steel balls at once, reducing the number of well-washing cycles. Preferably, the sizes of each adsorption groove 6 are different. The steel balls move towards the magnetic head 5 under the influence of the well-washing fluid, randomly forming spherical contact with the multiple adsorption grooves 6. The adsorption grooves 6 are randomly matched according to the size of the steel balls, ensuring reliable adsorption of multiple steel balls simultaneously by the magnetic head 5. One adsorption groove 6 is located at the center of the magnetic head 5, and the remaining adsorption grooves 6 are arranged around the central adsorption groove 6 on the same circumference. This arrangement fully utilizes the bottom surface area of ​​the magnetic head 5, providing as many adsorption grooves 6 as possible to adsorb more steel balls at once, and allows the steel balls to match the suitable adsorption groove 6 more quickly, improving capture efficiency. All the reverse circulation water holes 7 and the other adsorption grooves 6 except for the central adsorption groove 6 are on the same circumference, so that each adsorption groove 6 is located near the reverse circulation water hole 7. The closer to the reverse circulation water hole 7, the faster the liquid flow rate, thereby accelerating the movement speed of the steel ball towards the adsorption groove 6 and completing the matching and bonding with the adsorption groove 6 more quickly.

[0024] The working principle of this invention is as follows: Connect the upper end of the steel ball retriever to the retrieval string. Lower the steel ball retriever to a position 0.2m above the fallen steel ball through the retrieval string. Start the well-washing fluid circulation device to allow the well-washing fluid to enter from the inner cavity of the retrieval string. After reaching the inner cavity 3 of the steel ball retriever, it enters the annulus between the retriever and the casing through the first connecting hole 4 and is sprayed downwards. Due to the obstruction at the bottom of the well, it flows upwards back into the reverse circulation water hole 7 on the magnetic suction head 5 and the second connecting hole 8 at the bottom of the cylinder 1. Then it returns to the annulus between the retriever and the casing and flows upwards back to the surface through the annulus. This creates a local reverse circulation flow of the well-washing fluid at the bottom of the retriever. The rapid flow of the well-washing fluid drives the fallen steel ball toward the bottom of the retriever. Multiple adsorption grooves 6 and the fallen steel ball randomly form a spherical contact. Under the action of magnetic force, steel balls of different diameters are tightly adsorbed in the adsorption grooves 6. The steel ball capture is completed. Finally, the fallen steel ball is retrieved out of the well by using the steel ball retriever.

[0025] When applied, this invention creates a localized reverse circulation flow of the well-washing fluid at the bottom of the retrieval device, which drives the steel ball that has been dropped into the well toward the bottom of the retrieval device. This makes it easier for the steel ball to contact the magnetic suction head at the bottom and be attracted, thus successfully capturing the steel ball and greatly improving the retrieval success rate.

[0026] Of course, the present invention is not limited to the embodiments described above.

[0027] For example, in other embodiments, the number of the first and second connecting holes can be flexibly adjusted. The number of the first and second connecting holes can be equal or unequal. The first and second connecting holes can also not be arranged alternately in the circumferential direction of the cylinder. For example, two second connecting holes are provided between two adjacent first connecting holes. All the first and second connecting holes are arranged at intervals in the circumferential direction of the cylinder, and the distance between two adjacent connecting holes can also be unequal. The liquid outlet of the second connecting hole can also be flush with the liquid outlet of the first connecting hole or slightly lower than the liquid outlet of the first connecting hole.

[0028] For example, in other embodiments, all the reverse circulation water holes can be arranged irregularly on the magnetic suction head and may not be on the same circumference; the reverse circulation water holes can also be vertical holes extending vertically. In this case, there is an angle change at the connection between the reverse circulation water holes and the second connecting hole, which affects the flow speed of the well washing fluid, which can be compensated for by increasing the pressure.

[0029] For example, in other embodiments, the magnetic suction head may be provided with only one or two adsorption grooves. The specific number can be flexibly adjusted according to the size of the steel ball to be retrieved. In principle, the bottom surface area of ​​the magnetic suction head should be utilized as much as possible to provide as many adsorption grooves as possible. When there are multiple adsorption grooves, some adsorption grooves may be the same size, or all adsorption grooves may be the same size. The arrangement of the adsorption grooves may also be changed. For example, all adsorption grooves may be set in one ring, or the adsorption grooves may be arranged in two rings, so that the reverse circulation water hole is located between the two rings of adsorption grooves in the radial direction.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A steel ball retrieval device, characterized in that: The device includes a cylinder with a connecting structure at the upper end for connecting to the retrieval string. The cylinder has a first connecting hole on its side wall that connects the inner cavity of the cylinder to the outside. The bottom of the cylinder has a magnetic suction head with an adsorption groove at the bottom for adsorbing steel balls. The magnetic suction head has a reverse circulation water hole. The cylinder has a second connecting hole, one end of which connects to the outside of the cylinder, and the other end connects to the reverse circulation water hole, thus forming a local reverse circulation channel at the bottom of the retrieval device together with the reverse circulation water hole.

2. The steel ball retrieval device according to claim 1, characterized in that: The first and second connecting holes are provided in multiples and are arranged alternately around the circumference of the cylinder.

3. The steel ball retrieval device according to claim 2, characterized in that: All the first and second connecting holes are evenly distributed around the circumference of the cylinder.

4. The steel ball retrieval device according to any one of claims 1-3, characterized in that: The outlet of the second connecting hole is higher than the outlet of the first connecting hole.

5. The steel ball retrieval device according to any one of claims 1-3, characterized in that: The reverse circulation water holes are provided in multiple quantities and are evenly distributed on the same circumference. The number of the second connecting holes is equal to that of the reverse circulation water holes and they are connected in a one-to-one correspondence.

6. The steel ball retrieval device according to any one of claims 1-3, characterized in that: The second connecting hole is an oblique hole, and the reverse circulation water hole is an oblique hole with an inclination angle equal to that of the second connecting hole. The reverse circulation water hole and the second connecting hole are directly opposite and connected.

7. The steel ball retrieval device according to any one of claims 1-3, characterized in that: The magnetic suction head has multiple adsorption grooves arranged at intervals at the bottom.

8. The steel ball retrieval device according to claim 7, characterized in that: All the adsorption grooves are of different sizes.

9. The steel ball retrieval device according to claim 8, characterized in that: One of the adsorption grooves is located at the center of the magnetic head, and the other adsorption grooves are arranged around the central adsorption groove and are on the same circumference.

10. The steel ball retrieval device according to claim 9, characterized in that: The reverse circulation water holes are provided in multiple and spaced apart, and all the reverse circulation water holes and the remaining adsorption grooves except for the central adsorption groove are on the same circumference.

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