A type of bridge plug grinding shoe

Abstract

This invention discloses a grinding shoe for bridge plugs, belonging to downhole operation equipment. The grinding shoe of this invention includes a grinding shoe body, a power mechanism, and several cutting elements. All cutting elements are divided into two categories: movable cutting elements and fixed cutting elements. The movable cutting elements are movably arranged on the lower end face of the grinding shoe body and can move radially along the grinding shoe body. The fixed cutting elements are fixed on the lower end face of the grinding shoe body. The power mechanism drives the movable cutting elements to reciprocate radially along the grinding shoe body. The two types of cutting elements of this invention form interlaced scratches on the bridge plug. The filamentous iron filings generated during the grinding process easily break at the intersection points, thereby reducing the length of the iron filings and preventing them from forming tangled chips. The iron filings generated in this way are less likely to entangle, reducing the risk of stuck drill bits. At the same time, compared to granular iron filings, these iron filings are still filamentous but significantly larger in size, reducing wear on the cutting elements and improving the lifespan of the grinding shoe.

Description

Technical Field

[0001] This invention pertains to downhole operating equipment, and more particularly to downhole grinding equipment, specifically a grinding shoe for bridge plugs. Background Technology

[0002] Bridge plugs are downhole partitioning devices used to divide the wellbore into different sections along the axial direction, facilitating staged fracturing of each section and ultimately increasing production. After fracturing operations are completed, it is necessary to connect the oil and gas passages between the different sections. Therefore, all bridge plugs need to be drilled and ground away, which requires the use of grinding shoes. Grinding shoes are commonly used downhole grinding tools, with grinding elements on their lower end face to abut and grind the bridge plugs.

[0003] Currently, there are various types of shoe polishing products available. For example... Figure 1 As shown, some grinding shoes have cemented carbide particles welded onto the end face of the grinding shoe body. During the rotation of the grinding shoe, the cemented carbide particles continuously rub against the bridge plug, generating tiny iron filings. These iron filings are small and easily adhere to the outer wall of the circulating fluid, reducing the risk of stuck pipe. However, the grinding rate is low, and the grinding shoe itself experiences significant wear and has a short lifespan. Therefore, a single grinding shoe can only grind a limited number of bridge plugs, while each well often requires grinding dozens of bridge plugs. This necessitates frequent tubing string lifting and grinding shoe replacement, significantly increasing operating time and resulting in poor economic efficiency. Some grinding shoes have cemented carbide columns welded onto the end face of the grinding shoe body in a specific pattern. During use, these cemented carbide columns are inserted into the bridge plug. As the grinding shoe rotates, the cemented carbide columns cut the bridge plug, forming filamentous iron filings. This significantly shortens the grinding time and increases the lifespan of the grinding shoe. However, the iron filings are longer and prone to coiling and entanglement. Figure 2 As shown, these types of iron filings easily intertwine and accumulate in the wellbore, leading to stuck drill bits. To address this, some grinding shoes combine the features of the previous two types, arranging carbide pillars on the lower end face of the grinding shoe for rapid cutting and increased grinding speed. Simultaneously, crushed carbide particles are randomly arranged on the back of the carbide pillars to further grind the filamentous iron filings, ultimately forming smaller iron filings. This combination method achieves a higher grinding speed and lower risk of stuck drill bits, but still suffers from severe wear of the carbide particles, resulting in a shorter lifespan for individual grinding shoes. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a grinding shoe for bridge plugs. The grinding shoe of the present invention is equipped with two cutting elements. When the grinding shoe rotates, the two cutting elements form staggered scratches on the bridge plug. The iron filings are easily broken at the scratches, thereby significantly shortening the length of the iron filings and achieving the purpose of reducing the size of the filamentous iron filings. At the same time, it avoids the problem of excessive grinding of iron filings leading to large wear and short life of the grinding shoe itself.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A bridge plug grinding shoe, comprising:

[0007] The grinding shoe body has an axially extending blind hole inside, a water return groove on the outer wall, and a water eye communicating with the blind hole on the lower end face;

[0008] Several cutting elements are arranged circumferentially on the lower end face of the grinding shoe body. The cutting elements are divided into two categories: movable cutting elements and fixed cutting elements. The movable cutting elements are movably arranged on the lower end face of the grinding shoe body and can move radially along the grinding shoe body. The fixed cutting elements are fixed on the lower end face of the grinding shoe body.

[0009] The power mechanism is used to drive the moving cutting elements to reciprocate radially along the grinding shoe body.

[0010] As a specific embodiment of the present invention, the power mechanism includes:

[0011] A rotating shaft is arranged along the axis of the blind hole, and a cam is fixed at one end of the rotating shaft near the lower end face of the grinding shoe body;

[0012] A stabilizer fixed in a blind hole is used to straighten the rotating shaft;

[0013] A screw motor located in a blind hole is used to drive the shaft to rotate;

[0014] A T-shaped groove located on the side wall of the grinding shoe body and arranged radially along the grinding shoe body;

[0015] A linear groove located on the lower end surface of the grinding shoe body and arranged radially along the grinding shoe body, the linear groove being connected to the T-groove;

[0016] T-slots that mate with T-slots and linear slots are used to support moving cutting elements;

[0017] A spring used to push the T-shaped slider to move radially inward along the main body of the grinding shoe and abut against the outer wall of the cam ring.

[0018] In one specific embodiment of the present invention, there is an even number of cutting elements, wherein the number of movable cutting elements is equal to the number of fixed cutting elements, and the two are alternately distributed on the lower end face of the grinding shoe body.

[0019] Furthermore, the movable cutting elements are arranged in a ring array along the main body of the grinding shoe. Each movable cutting element is equipped with a T-slot, a T-slide block, a linear groove, and a spring. The outer ring wall of the cam has a ring array of protrusions equal in number to the movable cutting elements. This helps to reduce the eccentric force on the shaft and the stabilizer, thus extending the equipment's lifespan.

[0020] Furthermore, the linear groove connects the inside and outside of the blind hole, and the proximal end of the T-groove is located outside the proximal end of the linear groove. In this way, the linear groove can act as a movable water eye. When the T-slider slides in the linear groove, it will change the water output of each water eye, thereby frequently disturbing the fluid between the grinding shoe and the bridge plug and avoiding the formation of dead zones.

[0021] In one specific embodiment of the present invention, the movable cutting element includes multiple cutting edges, each of which is a pyramid (also known as a square pyramid or angle pyramid). This helps to reduce the resistance when the movable cutting element moves in different directions in the bridge plug. At the same time, the pyramid has a reduced diameter structure, and its sidewalls also exert strong pressure on the generated iron filings, which is beneficial to the breakage of the iron filings cut by the movable cutting element.

[0022] In one specific embodiment of the present invention, when the grinding shoe body is arranged vertically and the cutting element faces downward, the lower end of the cutting edge of the fixed cutting element is higher than the lower end of the cutting edge of the movable cutting element. Thus, during grinding, the movable cutting element penetrates the bridge plug to a greater depth than the fixed cutting element, ensuring that the metal chips generated by the fixed cutting element break at the intersection of the scratches, reducing the probability of chip formation.

[0023] In one specific embodiment of the present invention, the fixed cutting element adopts a cutting edge with a negative rake angle.

[0024] Beneficial effects: This invention features two types of cutting elements. The fixed cutting element rotates with the grinding shoe body, forming approximately circular scratches on the bridge plug body. The movable cutting element rotates with the grinding shoe body while moving radially along the grinding shoe body, forming approximately petal-shaped scratches on the bridge plug. The scratches of the two cutting elements intersect each other, and the resulting filamentous iron chips easily break at the intersection points, thereby reducing the length of the iron chips and preventing them from forming tangled chips. The iron chips produced in this way are less likely to entangle with each other, reducing the risk of drill jamming. At the same time, compared to granular iron chips, these iron chips are still filamentous but are significantly larger in size, reducing wear on the cutting elements and improving the life of the grinding shoe. Attached Figure Description

[0025] Figure 1 These are schematic diagrams of two existing shoe polishing techniques;

[0026] Figure 2 This is a schematic diagram of a type of lint.

[0027] Figure 3 This is a schematic diagram of a specific embodiment of the present invention;

[0028] Figure 4 yes Figure 3 A schematic diagram of the lower end of the main body of the grinding shoe;

[0029] Figure 5 yes Figure 3 A structural diagram showing the removal of the lower end face of the main body of the grinding shoe;

[0030] Figure 6 yes Figure 5 A schematic diagram of the main body of the grinding shoe after disassembling the T-shaped slider, rotating shaft, and cam;

[0031] Figure 7 yes Figure 5 Schematic diagram of the combined structure of the central shaft and cam;

[0032] Figure 8 yes Figure 5 Schematic diagram of the combined structure of the T-shaped slider and the movable cutting element;

[0033] Figure 9 yes Figure 8 Schematic diagram of a medium pyramid;

[0034] Figure 10 yes Figure 3 A schematic diagram showing the state of the fixed cutting element cutting the bridge plug;

[0035] In the figure: grinding shoe body 100; blind hole 110; water return groove 120; water eye 130; cutting element 200; movable cutting element 210; pyramid 211; fixed cutting element 220; rotating shaft 310; cam 320; T-slot 330; linear groove 340; T-slider 350; centralizer 360. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0037] Please refer to Figures 3-9 This document illustrates the structure of a specific embodiment of the bridge plug grinding shoe of the present invention. The bridge plug grinding shoe of the present invention includes a grinding shoe body 100 and cutting elements 200. Several cutting elements 200 are circumferentially distributed on the lower end face of the grinding shoe body 100 and are used for cutting the bridge plug. The upper end of the grinding shoe body 100 is provided with a connecting portion for connection to an upper tubing column; the grinding shoe body 100 has an axially extending blind hole 110; a water eye 130 is provided on the lower end face of the grinding shoe body 100, communicating with the blind hole 110; and a return water groove 120 is provided on the outer wall of the grinding shoe body 100. In use, liquid is introduced into the tubing column from the ground and the tubing column is rotated. The cutting elements 200 abut against the bridge plug and rotate together with the upper tubing column, thereby continuously cutting the bridge plug and generating iron filings. Simultaneously, the liquid sprays out through the blind hole 110 and the water eye 130, cooling the cutting elements 200 and carrying the iron filings to the ground, preventing drill jamming. These are standard configurations for existing polishing shoes. The number of water inlets 130 and the shape and number of return water channels 120 can be determined as needed, and will not be detailed here.

[0038] This invention improves upon existing grinding shoes. The cutting elements 200 of this invention are divided into two types: a movable cutting element 210 and a fixed cutting element 220. The movable cutting element 210 is movably arranged on the lower end face of the grinding shoe body 100 and can move radially along the grinding shoe body 100, while the fixed cutting element 220 is fixed to the lower end face of the grinding shoe body 100. Simultaneously, the grinding shoe of this invention also includes a power mechanism for driving the movable cutting element 210 to reciprocate radially along the grinding shoe body 100. During use, the grinding shoe body 100 rotates synchronously with the upper tubing column. The fixed cutting element 220 forms an approximately circular scratch on the bridge plug body. The movable cutting element 210, while rotating with the upper tubing column, also moves radially back and forth along the grinding shoe body 100 under the drive of the power mechanism, thereby forming an approximately petal-shaped scratch on the bridge plug. In this way, the scratches of the movable cutting element 210 and the fixed cutting element 220 intersect each other, and the resulting filamentous iron chips are easily broken at the intersection point, thereby reducing the length of the iron chips and preventing them from forming rolled chips. The iron chips generated in this way are not easy to entangle with each other, reducing the risk of drill jamming. At the same time, compared with granular iron chips, these iron chips are still filamentous and obviously larger in size, reducing the wear on the cutting element 200 and helping to improve the life of the grinding shoe.

[0039] The fixed cutting element 220 of the present invention can be the cutting element 200 commonly used in existing grinding shoes, for example... Figure 4 As shown, the fixed cutting element 220 includes multiple cutting edges, each with a V-shaped lower end to facilitate penetration into the bridge plug when the grinding shoe body 100 is subjected to axial pressure. The specific forms of the cutting edges are varied; for example, their rake angle can be negative, positive, or zero. In some embodiments, cutting edges with negative rake angles are selected, such as... Figure 10 As shown, after the chips are generated, they are subjected to strong compression from the rake face of the cutting edge (the surface where the cutting edge directly contacts the chips during cutting). Under this compression, the chips are more likely to break at mechanically weak points such as the intersection of scratches. The larger the negative rake angle, the stronger the compression effect of the rake face on the chips, which is more conducive to chip breakage. However, under the same axial pressure conditions, the depth of the cutting edge penetrating the bridge plug will decrease with the increase of the angle, resulting in a decrease in cutting speed. Therefore, a smaller angle, such as 18°, is generally chosen.

[0040] The movable cutting element 210 of the present invention rotates around the grinding shoe body 100 and moves radially along the grinding shoe body 100 during use. In some embodiments, the cutting edge of the movable cutting element 210 is a pyramid 211, such as... Figure 8 and Figure 9As shown, each movable cutting element 210 includes multiple arrayed pyramids 211, each with a sharp tip for easy insertion into the bridge plug. The base of the pyramid 211 can be a regular hexagon, octagon, etc. Thus, the sidewalls of the pyramid 211 have multiple sharp edges, facilitating movement in various directions within the bridge plug to form scratches. Simultaneously, the pyramid 211 gradually narrows from its base to its tip, and its sidewalls exert strong pressure on the generated iron filings, promoting the breakage of the iron filings cut by the movable cutting element 210. Furthermore, in some embodiments, the grinding shoe body 100 is arranged vertically with the cutting element 200 facing downwards. The lower end of the cutting edge of the fixed cutting element 220 is higher than the lower end of the cutting edge of the movable cutting element 210. During grinding, the depth to which the movable cutting element 210 penetrates the bridge plug is greater than the depth to which the fixed cutting element 220 penetrates the bridge plug. Therefore, the iron filings generated by the fixed cutting element 220 will inevitably break at the intersection of the scratches, reducing the probability of shavings forming.

[0041] In this invention, a power mechanism is used to drive the movable cutting element 210 to reciprocate radially along the grinding shoe body 100. In some embodiments, the power mechanism includes a rotating shaft 310, a cam 320, a T-slot 330, a linear groove 340, a T-slider 350, a stabilizer 360, a screw motor (not shown in the figure), and a spring (not shown in the figure). The rotating shaft 310 is arranged axially along the blind hole 110. The stabilizer 360 is used to stabilize the rotating shaft 310, positioning it on the center line of the blind hole 110. A cam 320 is fixed to one end of the rotating shaft 310 near the lower end face of the grinding shoe body 100. The screw motor is a common component in existing drilling equipment, which uses liquid to actuate the screw to rotate it, thereby outputting torque. Its specific structure is not detailed here. In this invention, the screw motor is located in the blind hole 110 and is used to drive the rotating shaft 310 to rotate, thereby driving the cam 320 to rotate. The T-slot 330 is located on the side of the grinding shoe body 100. The linear groove 340 is located on the lower end face of the grinding shoe body 100 and is arranged radially along the grinding shoe body 100. Simultaneously, the linear groove 340 communicates with the T-groove 330. The T-slider 350 is clearance-fitted with the T-groove 330 and the linear groove 340, thus allowing it to slide along the T-groove 330 and the linear groove 340, thereby driving the movable cutting element 210 to move radially along the grinding shoe body 100. A spring is used to push the T-slider 350 to move radially inward along the grinding shoe body 100 and abut against the annular outer wall of the cam 320. Therefore, with the cooperation of the spring, when the cam 320 rotates, the movable cutting element 210 will reciprocate radially along the grinding shoe body 100.

[0042] In some embodiments, the number of cutting elements 200 is even, and the number of movable cutting elements 210 is equal to the number of fixed cutting elements 220, for example... Figure 3As shown, there are six cutting elements 200 in total, including three movable cutting elements 210 and the rest fixed cutting elements 220. The movable and fixed cutting elements 210 are alternately distributed on the lower end face of the grinding shoe body 100. Each movable cutting element 210 is arranged in a circular array along the grinding shoe body 100. Each movable cutting element 210 is equipped with a T-slot 330, a T-slide 350, a linear groove 340, and a spring. Multiple protrusions are arranged in a circular array on the annular outer wall of the cam 320, the number of which is equal to the number of movable cutting elements 210. Figure 5 and Figure 7 As shown, at the same time, the forces exerted by each protrusion on each T-slider 350 are more similar, and the eccentric force borne by the rotating shaft 310 during operation is smaller, which helps to reduce the eccentric force on the centralizer 360, thereby extending its service life. Furthermore, in some embodiments, the linear groove 340 connects the inside and outside of the blind hole 110, and the proximal end (the end closest to the center) of the T-slider 330 is located outside the proximal end of the linear groove 340. Thus, the linear groove 340 can act as a movable water eye. During the movement of the T-slider 350, the flow area of ​​the movable water eye will change, causing the water volume in each water eye 130 to change continuously, thereby frequently disturbing the fluid between the cutting element 200 and the bridge plug, reducing the dead zone. This helps to promptly flush the generated iron filings out of the grinding shoe area, avoiding the risk of iron filings accumulating and becoming entangled.

[0043] The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the protection scope of the present invention.

Claims

1. A grinding shoe for bridge plugs, characterized in that, include: The grinding shoe body (100) has an axially extending blind hole (110) inside, a water return groove (120) on the outer wall, and a water eye (130) communicating with the blind hole (110) on the lower end face. A number of cutting elements (200) are arranged circumferentially on the lower end surface of the grinding shoe body (100). The cutting elements (200) are divided into two types: movable cutting elements (210) and fixed cutting elements (220). The movable cutting elements (210) are movably arranged on the lower end surface of the grinding shoe body (100) and can move radially along the grinding shoe body (100). The fixed cutting elements (220) are fixed on the lower end surface of the grinding shoe body (100). A power mechanism is provided to drive the movable cutting element (210) to reciprocate radially along the grinding shoe body (100); The power mechanism includes: A rotating shaft (310) is arranged axially along the blind hole (110), and a cam (320) is fixed at one end of the rotating shaft (310) near the lower end face of the grinding shoe body (100). A straightener (360) fixed in the blind hole (110) is used to straighten the rotating shaft (310). A screw motor located in the blind hole (110) is used to drive the rotating shaft (310) to rotate; A T-groove (330) is located on the side wall of the grinding shoe body (100) and arranged radially along the grinding shoe body (100). A linear groove (340) is located on the lower end surface of the grinding shoe body (100) and arranged radially along the grinding shoe body (100), the linear groove (340) being connected to the T-groove (330); A T-slider (350) that is in clearance fit with the T-slot (330) and the linear slot (340) is used to support the movable cutting element (210). A spring for pushing the T-shaped slider (350) to move radially inward along the grinding shoe body (100) and abutting against the annular outer wall of the cam (320); There are an even number of cutting elements (200), wherein the number of movable cutting elements (210) is equal to the number of fixed cutting elements (220), and the two are alternately distributed on the lower end face of the grinding shoe body (100); The movable cutting elements (210) are arranged in a ring array along the grinding shoe body (100). Each movable cutting element (210) is equipped with a T-slot (330), a T-slide block (350), a linear groove (340), and a spring. The cam (320) has a ring array of protrusions on its outer ring wall, which are equal in number to the movable cutting elements (210). The linear groove (340) connects the inside and outside of the blind hole (110), and the proximal end of the T-groove (330) is located outside the proximal end of the linear groove (340).

2. The grinding shoe for bridge plugs according to claim 1, characterized in that, The active cutting element (210) includes multiple cutting edges, and each cutting edge is a pyramid (211).

3. A grinding shoe for bridge plugs according to claim 1 or 2, characterized in that, When the grinding shoe body (100) is arranged vertically and the cutting element (200) faces downward, the lower end of the cutting edge of the fixed cutting element (220) is higher than the lower end of the cutting edge of the movable cutting element (210).

4. A grinding shoe for bridge plugs according to claim 1 or 2, characterized in that, The fixed cutting element (220) employs a cutting edge with a negative rake angle.

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