Variable-front-rake special-shaped PDC cutting tooth capable of effectively reducing cutting load under large cutting depth

Abstract

The invention relates to the field of drilling tools for petroleum and natural gas development, and discloses a variable-front-rake special-shaped PDC cutting tooth capable of effectively reducing cutting load under large cutting depth, which comprises a hard alloy matrix and a polycrystalline diamond layer, and the polycrystalline diamond layer is connected to the upper part of the hard alloy matrix; the upper surface of the polycrystalline diamond layer comprises a triangular plane, a plurality of fan-shaped planes and a plurality of cambered surfaces, a positive front rake ridge-shaped cutting edge is formed at the junction of the fan-shaped planes, and a negative front rake ridge-shaped cutting edge is formed at the junction of the cambered surfaces; the PDC tooth is simple in structure, the cutting teeth work at the negative front rake angle when the depth of depth is small, the cutting load is small, and the cutting edges at the negative front rake angle can pre-crush rock in front of the teeth when the depth of depth is large, so that the increase amplitude of the load of the PDC tooth is small, the rock breaking specific work of the PDC tooth is reduced, the drilling efficiency and the stability of the PDC tooth are improved, and the PDC tooth is particularly suitable for aggressive drilling operation of a deep stratum.

Description

Technical Field

[0001] The present invention belongs to the field of oil and gas exploration and development drilling tools, and is mainly used in the fields of oil exploration, geological excavation, energy extraction, etc., and specifically relates to a variable rake angle special-shaped PDC cutting tooth that can effectively reduce the cutting load at a large cutting depth. Background Art

[0002] In oil and gas extraction projects, PDC (polycrystalline diamond) drill bits are the most widely used rock-breaking tools, and PDC cutters are key components whose performance is directly related to drilling efficiency and cost. Existing studies have shown that the load of PDC teeth increases with the increase of rake angle and cutting depth, especially when the cutting depth is large, the problems of tooth collapse and tooth loss of the cutter occur frequently, which seriously affects the service life of the cutter and makes it difficult to meet the requirements of deep formation drilling and aggressive drilling parameter operations. In addition, the formation is objectively non-uniform in nature, with frequent alternations between soft and hard. The existing PDC teeth "single rake angle" cannot adapt to such complex and changeable working conditions, which easily causes the drill bit to vibrate violently and deflect, which not only reduces drilling efficiency, but also increases the risk of downhole accidents. Based on this, it is particularly necessary to develop a variable rake angle special-shaped PDC cutter that can effectively reduce the cutting load at a large cutting depth, adapt the cutting depth to the formation characteristics to the greatest extent, greatly reduce the fluctuation of cutting load, enhance the stability of the cutter, thereby increasing the service life of the PDC teeth and significantly improving the overall benefits of drilling operations.

[0003] The existing ridge-shaped teeth, axe-shaped teeth and triangular teeth are all designed with a single rake angle. When drilling, the ridge contacts the rock in a point load manner. Under the action of drilling pressure, the cutting depth continues to increase, and the load action form changes from point load to a mixed tensile shearing mode on both sides of the ridge. The ridge structure of the cutting tooth with a fixed rake angle can only be applied to a certain cutting depth range. When the cutting depth range is exceeded, the cutting load changes dramatically, which seriously reduces the service life of the cutting tooth. Therefore, it is considered to design a variable rake angle special-shaped PDC cutting tooth that can effectively reduce the cutting load at a large cutting depth. By superimposing positive and negative rake angles, the problem that the load of the conventional tooth shape increases with the increase of the rake angle and cutting depth is solved. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a PDC cutting tooth with a variable rake angle and a special shape which can effectively reduce the cutting load at a large cutting depth in view of the shortcomings of the prior art.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: a variable rake angle special-shaped PDC cutting tooth which can effectively reduce the cutting load under a large cutting depth, comprising a polycrystalline diamond layer and a cemented carbide substrate, the cross-section of the cemented carbide substrate is circular, the cross-section of the lower end face of the polycrystalline diamond layer is circular, the polycrystalline diamond layer is connected to the upper part of the cemented carbide substrate in a first direction, the upper surface of the polycrystalline diamond layer comprises a triangular plane, a plurality of fan-shaped planes and a plurality of arc surfaces, the triangular plane is located in the middle position of the upper part of the polycrystalline diamond layer, the plurality of fan-shaped planes are located on the periphery of the triangular plane, the arc surface is arranged on the side of the fan-shaped plane away from the triangular plane, a positive rake angle ridge-shaped cutting edge is formed at the junction between the fan-shaped planes, a negative rake angle ridge-shaped cutting edge is formed at the junction of the arc surfaces, and the arc surfaces are distributed along the periphery of the upper end face of the polycrystalline diamond layer, wherein the fan-shaped plane intersects with the cylindrical surface of the polycrystalline diamond layer to form an edge auxiliary cutting edge, and the arc surface intersects with the cylindrical surface of the polycrystalline diamond layer to form an edge cutting edge.

[0006] Furthermore, the included angle between the negative rake angle ridge-shaped cutting edge and the triangular plane is β, and the range of β is 1°~89°.

[0007] Furthermore, the arc surface is located at the corner of the sector-shaped plane, and the arc surface occupies 10% to 80% of the area of ​​the sector-shaped plane.

[0008] Furthermore, the distance between the highest point of the negative rake angle ridge-shaped cutting edge and the triangular plane in the first direction ranges from 0 to 20 mm, and the distance between the lowest point and the triangular plane in the first direction ranges from 0.1 to 10 mm.

[0009] Furthermore, the arc surface is a concave surface, a convex surface or a plane surface, the fan-shaped plane is a plane surface, a convex surface or a concave surface, and the arc surface is symmetrically arranged, asymmetrically arranged or partially symmetrically arranged.

[0010] Furthermore, the thickness of the polycrystalline diamond layer is at least 15 mm.

[0011] Furthermore, the included angle between the two fan-shaped planes forming the positive rake angle ridge-shaped cutting edge is in the range of 91° to 179°.

[0012] Furthermore, the bottom surface of the polycrystalline diamond layer is provided with a plane, a protrusion or a groove, and the top surface of the cemented carbide substrate is a plane, a groove or a protrusion.

[0013] Furthermore, the polycrystalline diamond layer and the cemented carbide substrate are sintered at high temperature using a cobalt-containing metal binder.

[0014] Furthermore, the number of the fan-shaped planes is at least 3, and the number of the arc surfaces is at least 6.

[0015] The beneficial effects of the present invention are: a variable rake angle special-shaped PDC cutter which can effectively reduce the cutting load at a large cutting depth. When the cutting depth is small, only the negative rake angle ridge-shaped cutting edge contacts the rock, so that the tangential load amplitude of the cutting tooth is small. With the increase of drilling pressure, when operating at a large cutting depth, the tangential load of the conventional PDC cutter changes dramatically, which seriously affects the service life of the cutter. Therefore, a variable rake angle special-shaped PDC cutter which can effectively reduce the cutting load at a large cutting depth is designed. On the one hand, the rock is cut at a negative rake angle at the bottom of the tooth, so that the cutting load is reduced to a certain extent. At the same time, the bottom rock is crushed with a local strong point load to form an initial crack, release the rock stress, increase the rock crushing volume in a single cutting, and also reduce the cutting load. On the other hand, the positive rake angle ridge-shaped cutting edge can perform "ploughing" cutting on the pre-crushed rock, crush it with a local strong load at the ridge, and crush the rock by tensile shearing on the two side faces, so as to reduce the cutting load.

[0016] In summary, the combined effect of the three different forms of crushing makes the cutting load increase smaller when the cutting teeth are at a greater cutting depth, reducing the rock-breaking work ratio of the PDC teeth during the cutting process, and improving the drilling efficiency and stability of the PDC teeth. In addition, the upper surface structure of the polycrystalline diamond layer is distributed at equal intervals in the circumferential direction. When the ridge-shaped cutting edge on one side is worn to a certain extent, the cutting teeth can be rotated to switch to the unworn area for cutting work, so as to improve the rock-breaking efficiency of the cutting teeth and extend the service life of the PDC teeth. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention provides a structural schematic diagram of a special-shaped PDC cutting tooth with a variable rake angle that can effectively reduce the cutting load at a large cutting depth according to Example 1.

[0018] Figure 2 for Figure 1 main view.

[0019] Figure 3 for Figure 1 Top view of the .

[0020] Figure 4 for Figure 2 Cross-sectional view of .

[0021] Figure 5 for Figure 1 Left view of .

[0022] Figure 6 A schematic diagram of rock breaking using a positive rake angle at a large cutting depth according to Example 1 of the present invention is provided.

[0023] Figure 7 A schematic diagram of rock breaking using a negative rake angle at a small cutting depth in Example 1 is provided for the present invention.

[0024] In the figure: 1-polycrystalline diamond layer; 2-cemented carbide substrate; 3-triangular plane; 4-sector-shaped plane; 5-positive rake angle ridge-shaped cutting edge; 6-cambered surface; 7-negative rake angle ridge-shaped cutting edge; 8-edge cutting edge; 9-edge secondary cutting edge; 10-interfacing interface; 11-ridge. DETAILED DESCRIPTION

[0025] The present invention provides a PDC cutting tooth with a variable rake angle that can effectively reduce the cutting load at a large cutting depth. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] The invention is further described below by describing embodiments in conjunction with the accompanying drawings.

[0027] In the prior art, it is found that the ridge-shaped teeth and axe-shaped teeth of a single ridge change from the point load form of initial contact to the plowing form during stable cutting when breaking rocks. The cutting force fluctuates smoothly at a small cutting depth, but at a large cutting depth, the amplitude of the cutting load changes dramatically, seriously affecting the life of the cutting teeth. Therefore, it is considered whether it is possible to achieve a better rock breaking effect than the ridge-shaped teeth of a single ridge by adding other forms of load action to break rocks. At present, a variable rake angle special-shaped PDC cutting tooth that can effectively reduce the cutting load at a large cutting depth is designed. It uses local strong point load pre-crushing and plowing to break rocks, thereby improving the stability and service life of the PDC cutting tooth. The difference between the variable rake angle special-shaped PDC cutting teeth and the conventional plane teeth is that the rake angle of the conventional plane teeth is fixed at small cutting depth and large cutting depth, and the amplitude of the cutting load increases significantly with the increase of cutting depth, which seriously affects the life of the cutting teeth; while the rake angle of the variable rake angle special-shaped PDC cutting teeth will change when the cutting depth increases, so that the amplitude of the cutting load changes less, which is beneficial to extending the service life of the PDC teeth.

[0028] A variable rake angle special-shaped PDC cutting tooth which can effectively reduce cutting load under large cutting depth, comprises a polycrystalline diamond layer and a cemented carbide substrate, the cross section of the cemented carbide substrate is circular, the cross section of the lower end face of the polycrystalline diamond layer is circular, the polycrystalline diamond layer is connected to the upper part of the cemented carbide substrate in a first direction, the upper surface of the polycrystalline diamond layer comprises a triangular plane, a plurality of fan-shaped planes and a plurality of cambered surfaces, the triangular plane is located in the middle position of the upper part of the polycrystalline diamond layer, the plurality of fan-shaped planes are located at the periphery of the triangular plane, the cambered surface is arranged on the side of the fan-shaped plane away from the triangular plane, a positive rake angle ridge-shaped cutting edge is formed at the intersection between the fan-shaped planes, a negative rake angle ridge-shaped cutting edge is formed at the intersection of the cambered surfaces, and the cambered surfaces are distributed along the periphery of the upper end face of the polycrystalline diamond layer, wherein the fan-shaped plane intersects with the cylindrical surface of the polycrystalline diamond layer to form an edge auxiliary cutting edge, and the cambered surface intersects with the cylindrical surface of the polycrystalline diamond layer to form an edge cutting edge.

[0029] This embodiment 1 provides a PDC cutting tooth with a variable rake angle and a special shape that can effectively reduce the cutting load at a large cutting depth, such as Figure 1 As shown, it includes a polycrystalline diamond layer 1 and a cemented carbide substrate 2, the cross section of the lower end surface of the polycrystalline diamond layer 1 is circular, the polycrystalline diamond layer 1 is connected to the upper part of the cemented carbide substrate 2 by high temperature and high pressure sintering in the first direction, and the cross section of the cemented carbide substrate 2 is circular. The purpose is to reduce the volume of polycrystalline diamond that is not actually involved in cutting and breaking rocks, reduce costs while ensuring the rock breaking effect of the cutting teeth.

[0030] Further, in this embodiment 1, if Figure 2 , 3As shown, the triangular plane 3 is located in the middle position of the upper part of the polycrystalline diamond layer 1, the multiple fan-shaped planes 4 are located at the periphery of the triangular plane 1, the arc surface 6 is arranged on the side of the fan-shaped plane 4 away from the triangular plane 3, and the intersection between the fan-shaped planes 4 forms a positive rake angle ridge-shaped cutting edge 5, which is linear and has a length of 3mm; the intersection of the arc surfaces 6 forms a negative rake angle ridge-shaped cutting edge 7, which is linear and has a length of 2.78mm; the arc surface 6 is distributed along the periphery of the upper end face of the polycrystalline diamond layer 1, wherein the arc surface 6 intersects with the cylindrical surface of the cutting tooth to form an edge cutting edge 8 and an edge auxiliary cutting edge 9, which are arc-shaped, and the arc surface 6 is located at the corner of the fan-shaped plane 4, and the arc surface 6 occupies 10% of the area of ​​the fan-shaped plane 4, the arc surface 6 is a concave surface, and the fan-shaped plane 4 is a plane; among the three fan-shaped planes 4, the top is the first fan-shaped plane 4, and the next clockwise directions are the second fan-shaped plane 4 and the third fan-shaped plane 4 respectively. Among them, there are six arc surfaces 6, starting from the upper right corner, and the clockwise direction is respectively the first, second, third, fourth, fifth and sixth arc surfaces 6. The first and second fan-shaped planes 4 intersect at 170° to form a first positive rake angle ridge-shaped cutting edge 5. Similarly, the second and third fan-shaped planes 4 and the third and first fan-shaped planes 4 form the second and third positive rake angle ridge-shaped cutting edges 5 respectively. The arc surfaces 6 are symmetrically arranged. When the cutting depth is small, only the ridge-shaped cutting edge with negative rake angle contacts the rock, so that the tangential load amplitude of the cutting tooth is small. When the cutting depth is large, the cutting tooth cuts the rock with negative rake angle at the bottom of the tooth, so that the cutting load is reduced to a certain extent. At the same time, the bottom rock is crushed with local strong point load to form initial cracks to release rock stress and increase the rock crushing volume in a single cutting. In addition, the ridge-shaped cutting edge with positive rake angle can perform "ploughing" cutting on the pre-crushed rock, crush it with local strong load at the ridge, and crush the rock with tensile shear on the two side edges, which can reduce the cutting load. The fan-shaped plane has good conductivity, and the crushed rock chips can be discharged in time and will not accumulate in front of the cutting tooth to affect the cutting effect, thereby increasing the service life of the cutting tooth.

[0031] Further, in this embodiment 1, if Figure 4 , 5 As shown, the angle between the negative rake angle ridge-shaped cutting edge 7 and the triangular plane 3 is β, and the range of β is 1°~89°. The distance between the highest point of the negative rake angle ridge-shaped cutting edge 7 and the triangular plane 3 in the first direction is 1mm, and the distance between the lowest point and the triangular plane 3 in the first direction is 0.5mm. The bottom surface of the polycrystalline diamond layer 1 is set as a plane, and the top surface of the cemented carbide substrate 2 is a plane. The interface 10 between the polycrystalline diamond layer 1 and the cemented carbide substrate 2 is connected by a cobalt-containing metal mold adhesive at high temperature and high pressure. The thickness of the polycrystalline diamond layer 1 is 10mm and the diameter is 15.88mm. The polycrystalline diamond layer 1 set in this way has high strength, and the cobalt-containing metal mold interface 10 has high stability and is not easy to fall off.

[0032] Further, in this embodiment 1, if Figure 6 , 7 As shown, in the process of cutting and crushing rocks of the present invention, when the cutting depth is small, the rake angle β is a negative value, only the negative rake angle ridge-shaped cutting edge 7 contacts the rock, and the tangential load of the cutting tooth changes slightly; with the increase of drilling pressure, when operating at a larger cutting depth, the conventional teeth cause drastic changes in the tangential load due to the increase in cutting depth, which seriously affects the service life of the cutting teeth. In the present invention, on the one hand, the cutting teeth cut the rock at a negative rake angle at the bottom of the tooth, so that the cutting load is reduced to a certain extent. At the same time, the negative rake angle ridge-shaped cutting edge 7 performs local strong "point load" pre-crushing on the inside of the rock. Microcracks develop and expand into the rock under the tooth with the contact point as the center, forming initial cracks, releasing rock stress, increasing the rock crushing volume in a single cutting, and also reducing the cutting load; on the other hand, the positive rake angle ridge-shaped cutting edge 5 with a positive β value performs "ploughing" cutting on the crushed rock, crushes it with a local strong load at the ridge, and crushes the rock by tensile shearing on the two side edges, which can reduce the cutting load. In summary, the combined effect of the three different forms of crushing makes the cutting load increase smaller when the cutting teeth are at a greater cutting depth, reducing the rock-breaking work ratio of the PDC teeth during the cutting process, and improving the drilling efficiency and stability of the PDC teeth. In addition, the upper surface structure of the polycrystalline diamond layer is distributed at equal intervals in the circumferential direction. When the ridge-shaped cutting edge on one side is worn to a certain extent, the cutting teeth can be rotated to switch to the unworn area for cutting work, so as to improve the rock-breaking efficiency of the cutting teeth and extend the service life of the PDC teeth, which is suitable for aggressive drilling operations in deep formations.

[0033] Based on the disclosure of the present invention, those skilled in the art should understand that equivalent structures do not deviate from the spirit and scope of the disclosure of the present invention, and that various changes, substitutions and modifications made to the embodiments disclosed in the present invention do not deviate from the spirit and scope of the disclosure of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications or equivalent substitutions can be made without departing from the technical solution of the present invention, which are all regarded as the protection scope of the present invention.

Claims

1. A PDC cutting tooth with a variable rake angle and a special shape that can effectively reduce cutting load at a large cutting depth, comprising a polycrystalline diamond layer (1) and a cemented carbide substrate (2), characterized in that: The cross section of the cemented carbide substrate (2) is circular, the cross section of the lower end surface of the polycrystalline diamond layer (1) is circular, the polycrystalline diamond layer (1) is connected to the upper part of the cemented carbide substrate (2) in a first direction, the upper surface of the polycrystalline diamond layer (1) comprises a triangular plane (3), a plurality of fan-shaped planes (4) and a plurality of arc surfaces (6), the triangular plane (3) is located in the middle of the upper part of the polycrystalline diamond layer (1), the plurality of fan-shaped planes (4) are located on the periphery of the triangular plane (3), and the arc surfaces (6) are arranged on the fan-shaped planes (4). The fan-shaped plane (4) is located on one side away from the triangular plane (3), a positive rake angle ridge-shaped cutting edge (5) is formed at the intersection between the fan-shaped planes (4), and a negative rake angle ridge-shaped cutting edge (7) is formed at the intersection between the cambered surfaces (6), and the cambered surfaces (6) are distributed along the periphery of the upper part of the polycrystalline diamond layer (1), wherein the fan-shaped plane (4) intersects with the cylindrical surface of the polycrystalline diamond layer (1) to form an edge auxiliary cutting edge (9), and the cambered surface (6) intersects with the cylindrical surface of the polycrystalline diamond layer (1) to form an edge cutting edge (8).

2. The variable rake angle special-shaped PDC cutting tooth capable of effectively reducing cutting load at a large cutting depth according to claim 1, characterized in that: The included angle between the negative rake angle ridge-shaped cutting edge (7) and the triangular plane (3) is β, and the range of β is 1° to 89°.

3. The variable rake angle special-shaped PDC cutting tooth capable of effectively reducing cutting load at a large cutting depth according to claim 2, characterized in that: The arc surface (6) is located at the corner of the sector-shaped plane (4), and the arc surface (6) occupies 10% to 80% of the area of ​​the sector-shaped plane (4).

4. The variable rake angle special-shaped PDC cutting tooth capable of effectively reducing cutting load at a large cutting depth according to claim 2, characterized in that: The distance between the highest point of the negative rake angle ridge-shaped cutting edge (7) and the triangular plane (3) in the first direction ranges from 0 to 20 mm, and the distance between the lowest point and the triangular plane (3) in the first direction ranges from 0.1 to 10 mm.

5. The variable rake angle special-shaped PDC cutting tooth capable of effectively reducing cutting load at a large cutting depth according to claim 2, characterized in that: The arc surface (6) is a concave surface, a convex surface or a plane surface, and the fan-shaped plane (4) is a plane surface, a convex surface or a concave surface.

6. The variable rake angle special-shaped PDC cutting tooth capable of effectively reducing cutting load at a large cutting depth according to claim 1, characterized in that: The thickness of the polycrystalline diamond layer (1) is at least 15 mm.

7. The variable rake angle special-shaped PDC cutting tooth capable of effectively reducing cutting load at a large cutting depth according to claim 6, characterized in that: The included angle of the two fan-shaped planes (4) forming the positive rake angle ridge-shaped cutting edge (5) is in the range of 91° to 179°.

8. The variable rake angle special-shaped PDC cutting tooth capable of effectively reducing cutting load at a large cutting depth according to claim 7, characterized in that: The bottom surface of the polycrystalline diamond layer (1) is provided with a plane, a protrusion or a groove, and the top surface of the cemented carbide substrate (2) is a plane, a groove or a protrusion.

9. The variable rake angle special-shaped PDC cutting tooth capable of effectively reducing cutting load at a large cutting depth according to claim 1, characterized in that: The polycrystalline diamond layer (1) and the cemented carbide substrate (2) are formed by high-temperature sintering using a cobalt-containing metal binder.

10. The variable rake angle special-shaped PDC cutting tooth capable of effectively reducing cutting load at a large cutting depth according to claim 8, characterized in that: The number of the fan-shaped planes (4) is at least 3, and the number of the arc surfaces (6) is at least 6.

Images