CN115977546A - Cutting tooth, design method thereof and PDC (polycrystalline diamond compact) drill bit - Google Patents

Abstract

The invention discloses a cutting tooth and a design method thereof, and a PDC drill bit, and relates to the technical field of drilling drill bits for petroleum and natural gas and geological exploration, wherein the cutting tooth comprises the following components: a substrate having a first end face and a second end face; a cutter fixedly disposed on the first end face of the substrate, the cutter comprising: the first cutting structure is columnar and provided with a third end surface and a fourth end surface, and the fourth end surface is fixed with the first end surface; the second cutting structure is located in the third end face and is columnar, the radial cross section of the second cutting structure is smaller than that of the first cutting structure, the upper end face of the second cutting structure is provided with a linear ridge line, a first preset included angle theta is formed between the ridge line and the first end face, and the two side areas of the ridge line of the upper end face of the second cutting structure are respectively and gradually reduced along the direction of keeping away from the ridge line. The problem that the cutting teeth are easily abraded and damaged in the soft and hard interlayer and the strong abrasive stratum can be solved.

Description

Cutting tooth, design method thereof and PDC (polycrystalline diamond compact) drill bit

Technical Field

The invention relates to the technical field of drilling bits for petroleum, natural gas and geological exploration, in particular to a cutting tooth, a design method thereof and a PDC bit.

Background

At present, a PDC drill Bit (Polycrystalline Diamond Compact Bit) has become a main rock breaking drill Bit in the field of oil and gas drilling, and more than 90% of drilling footage of oil and gas wells worldwide is completed by the PDC drill Bit. The cutting teeth used by the PDC drill bit are polycrystalline diamond compacts, the common polycrystalline diamond compacts are cylindrical and are formed by sintering a polycrystalline diamond layer and a hard alloy substrate at high temperature and high pressure. The cylindrical cutting teeth break rock in a shearing mode in the working process, and have the characteristics of high drilling speed, high footage and the like in soft to medium-hard strata. However, in the stratum with high hardness, strong abrasiveness and tough interlayer, the commonly used cylindrical cutting teeth are difficult to be eaten into the stratum, have low rock breaking efficiency, serious abrasion and short service life, lead to low mechanical drilling speed of the drill bit and long drilling period, and undoubtedly increase the drilling cost.

Therefore, at present, a lot of researchers greatly improve the shape of the commonly used cylindrical cutting teeth, and develop various special-shaped cutting teeth, which can obviously improve the impact resistance and the wear resistance of the cylindrical cutting teeth and widen the application range of the polycrystalline diamond compact in a hard rock stratum. However, in the deep soft and hard interlayer and the strong abrasive stratum, the conventional special-shaped cutting teeth still have abrasion and collapse at different degrees, the drilling efficiency is still low, and the drilling efficiency cannot be effectively improved.

Disclosure of Invention

In order to overcome the above defects in the prior art, embodiments of the present invention provide a cutting tooth, a design method thereof, and a PDC drill bit, which can solve the problem that the cutting tooth is easily worn and damaged in a hard-soft interlayer and a strongly abrasive stratum.

The specific technical scheme of the embodiment of the invention is as follows:

a cutting tooth, comprising:

a substrate having corresponding first and second end faces;

a cutter fixedly disposed on the first end face of the substrate, the cutter being made of polycrystalline diamond, the cutter comprising: the first cutting structure is columnar and provided with a third end surface and a fourth end surface, and the fourth end surface is fixed with the first end surface; the second cutting structure is located in the third end face, the second cutting structure is columnar, the radial cross section of the second cutting structure is smaller than that of the first cutting structure, the upper end face of the second cutting structure is provided with a ridge line which is linear, a first preset included angle theta is formed between the ridge line and the first end face, and the two side areas of the ridge line of the upper end face of the second cutting structure are respectively and gradually reduced along the direction height of the ridge line.

Preferably, the base is made of cemented carbide, the cutting piece is fixedly arranged on the first end face of the base in a sintering mode, the cross section of the base in the radial direction is identical to the cross section of the first cutting structure in the radial direction in shape and size, and the cross section of the base in the radial direction is circular or approximately circular or oval or approximately oval.

Preferably, the center of the second cutting structure is the same as the center of the first cutting structure, the ridge line passes through the center of the second cutting structure, and two side regions of the ridge line of the upper end surface of the second cutting structure are symmetrical.

Preferably, the first preset included angle θ of the cutting tooth is greater than or equal to 0 degree, and α + θ is smaller than 90 degrees.

Preferably, the structural parameters of the cutting tooth satisfy the following relation:

Δh＝Rcosα-(L+r)·sin(α+θ)，

wherein α represents a cutting angle of the cutting tooth, R represents a radius of the first cutting structure, R represents a radius of the second cutting structure, L represents a distance from a center of a bottom surface of the second cutting structure to the ridge line, and Δ h represents a tooth height difference, that is, a distance from an end point B of one end of the lower height of the ridge line to an edge D of the third end surface of the first cutting structure in the Y-axis direction.

Preferably, the radius R of the first cutting structure is equal to 8.0mm and the radius R of the second cutting structure is equal to 6.5mm; or the radius R of the first cutting structure is equal to 9.5mm and the radius R of the second cutting structure is equal to 8mm; alternatively, the radius R of the first cutting structure is equal to 9.5mm and the radius R of the second cutting structure is equal to 6.5mm.

Preferably, the cutting angle α of the cutting tooth is between 5 and 30 degrees.

Preferably, the radius R of the first cutting structure is equal to 8.0mm, the radius R of the second cutting structure is equal to 6.5mm, the cutting angle α of the cutting tooth is equal to 15 degrees, the distance L from the center of the bottom surface of the second cutting structure to the ridge line is equal to 1.5mm, the first preset included angle θ is equal to 35 degrees, and the tooth height difference Δ h is equal to 1.6mm.

A PDC bit including a cutter as claimed in any one of the preceding claims.

A method of designing a cutting tooth as claimed in any one of the preceding claims, said method comprising the steps of:

selecting a radius R of the first cutting structure and a radius R of the second cutting structure;

obtaining a cutting angle alpha formed by the cutting teeth arranged on the PDC drill bit,

determining a distance L from the center of the bottom surface of the second cutting structure to a ridge line and a first preset included angle theta between the ridge line and the first end surface, wherein the first preset included angle theta is larger than or equal to 0 degree, and alpha + theta is smaller than 90 degrees;

determining a tooth height difference deltah according to the radius R of the first cutting structure, the radius R of the second cutting structure, a cutting angle alpha, a distance L from the center of the bottom surface of the second cutting structure to a ridge line and a first preset included angle theta between the ridge line and the first end surface, wherein a specific calculation formula is as follows:

Δh＝Rcosα-(L+r)·sin(α+θ)。

the technical scheme of the invention has the following remarkable beneficial effects:

1. the second cutting structure of this application cutting tooth has concentrated load in crest line department, makes the inside stress concentration district that forms of its place ahead rock, and the rock takes place to cut-tensile destruction more easily, improves the ability that the cutting tooth eats into the stratum, improves the broken rock efficiency of drill bit.

2. The cutting tooth utilizes the end part area with lower height of the ridge line of the first cutting structure to cut the edge area of the third end face of the second cutting structure, so that the first cutting structure and the second cutting structure jointly cut rock with the rail, and the defects of small single rock breaking volume and insufficient shaft bottom covering capacity of the first cutting structure are overcome.

3. The method has the advantages that the second cutting structure with the ridge line has strong aggressiveness and is not easy to impact and damage, the rock at the bottom of the well is crushed in advance, the stratum stress is released, the rock is easier to cut by the first cutting structure, and the rock crushing efficiency can be greatly improved; in addition, the second cutting structure with the ridge line can limit the depth of the first cutting structure which is eaten into the stratum, reduce the stick-slip effect and impact damage of the drill bit and prolong the service life of the drill bit.

Specific embodiments of the present invention are disclosed in detail with reference to the following description and drawings, indicating the manner in which the principles of the invention may be employed. It should be understood that the embodiments of the invention are not so limited in scope. Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments, in combination with or instead of the features of the other embodiments.

Drawings

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. In addition, the shapes, the proportional sizes, and the like of the respective members in the drawings are merely schematic for facilitating the understanding of the present invention, and do not specifically limit the shapes, the proportional sizes, and the like of the respective members of the present invention. Those skilled in the art, having the benefit of the teachings of this invention, may choose from the various possible shapes and proportional sizes to implement the invention as a matter of case.

FIG. 1 is a schematic perspective view of a cutting tooth according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a design process for a cutter of a cutting tooth according to an embodiment of the present invention;

FIG. 3 is a front view of a cutting tooth in an embodiment of the present invention;

FIG. 4 is a perspective view of a cutter of a cutting tooth according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a PDC bit in an embodiment of the present invention;

FIG. 6 is a stress distribution diagram of a cutting tooth during rock breaking according to an embodiment of the present invention;

FIG. 7 is a stress profile of a conventional cylindrical cutting tooth during rock breaking in the prior art;

FIG. 8 is a graph comparing the cutting force with time during rock breaking for a cutter in accordance with an embodiment of the present invention and a conventional cylindrical cutter of the prior art.

Reference numerals of the above figures:

1. a substrate; 11. a first end face; 12. a second end face; 2. a cutting member; 21. a first cutting structure; 211. a third end face; 212. a fourth end face; 22. a second cutting structure; 221. a ridge line; 100. and (4) cutting teeth.

Detailed Description

The details of the present invention will become more apparent in light of the accompanying drawings and description of specific embodiments thereof. However, the specific embodiments of the present invention described herein are for the purpose of illustration only and are not to be construed as limiting the invention in any way. Any possible variations based on the present invention may be conceived by the skilled person in the light of the teachings of the present invention, and these should be considered to fall within the scope of the present invention. It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "mounted," "connected," and "connected" are to be construed broadly and may include, for example, mechanical or electrical connections, communications between two elements, direct connections, indirect connections through intermediaries, and the like. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In order to solve the problem that a cutting tooth is easy to wear and damage in a hard-soft interlayer and a strong abrasive stratum, a cutting tooth is provided in the present application, fig. 1 is a schematic perspective view of the cutting tooth in the embodiment of the present invention, fig. 2 is a schematic design process of a cutting element 2 of the cutting tooth in the embodiment of the present invention, fig. 3 is a front view of the cutting tooth in the embodiment of the present invention, fig. 4 is a schematic perspective view of the cutting element 2 of the cutting tooth in the embodiment of the present invention, and as shown in fig. 1 to 4, the cutting tooth may include: a substrate 1 and a cutter 2. Wherein the substrate 1 may have a first end face 11 and a second end face 12, respectively, the substrate 1 may be adapted to support the cutter 2. The cutting member 2 is fixedly arranged on said first end surface 11 of said substrate 1.

As shown in fig. 1 to 4, the substrate 1 may be made of cemented carbide, which may serve the purpose of saving polycrystalline diamond material, but may also be made of polycrystalline diamond.

The cutter 2 is made of polycrystalline diamond. When the substrate 1 is made of cemented carbide, the cutting member 2 is fixedly arranged on the first end surface 11 of the substrate 1 by means of sintering.

As shown in fig. 1, the cutter 2 may include: a first cutting structure 21 having a cylindrical shape, the first cutting structure 21 having a third end surface 211 and a fourth end surface 212, the fourth end surface 212 being fixed to the first end surface 11; a second cutting structure 22 located within the third end face 211, the second cutting structure 22 being cylindrical, a radial cross-section of the second cutting structure 22 being smaller than a radial cross-section of the first cutting structure 21. The third end surface 211 is a flat surface, and the fourth end surface 212 is sintered in cooperation with the first end surface 11. Further, the second cutting structure 22 is located in a middle region of the third end surface 211 of the first cutting structure 21, and the side wall of the second cutting structure 22 is located at a certain distance from the edge of the third end surface 211 of the first cutting structure 21.

As shown in fig. 1 and 3, the shape and size of the cross section of the base 1 in the radial direction are identical to the shape and size of the cross section of the first cutting structure 21 in the radial direction, so that the edge of the first cutting structure 21 is supported by the base 1, and the edge of the third end surface 211 of the first cutting structure 21 of the cutting tooth can be effectively prevented from being worn or cracked during rock breaking.

As shown in fig. 1 and 4, the upper end surface of the second cutting structure 22 has a linear ridge line 221, and the ridge line 221 divides the upper end surface of the second cutting structure 22 into left and right side regions. The length of the ridge line 221 spans the entire upper end face of the second cutting structure 22. The ridge line 221 may be parallel to the first end surface 11 of the substrate 1, i.e., a first preset included angle θ between the ridge line 221 and the first end surface 11 of the substrate 1 is equal to 0 degree. The ridge line 221 may also have a first predetermined included angle θ with the first end surface 11 of the substrate 1, where the first predetermined included angle θ is greater than 0 degree. The two side areas of the ridge line 221 of the upper end surface of the second cutting structure 22 are gradually reduced in height along the direction away from the ridge line 221. Both side regions of the ridge line 221 of the upper end surface of the second cutting structure 22 may be planar, and both side regions of the planar ridge line 221 have a certain inclination angle with the third end surface 211 of the first cutting structure 21.

As shown in fig. 1 to 4, the cross-section of the substrate 1 in the radial direction and the cross-section of the first cutting structure 21 in the radial direction have a circular or approximately circular or elliptical or approximately elliptical shape. The shape of the cross-section of the second cutting structure 22 in the radial direction may be the same as the shape of the cross-section of the first cutting structure 21 in the radial direction. Further, the center of the second cutting structure 22 is the same as the center of the first cutting structure 21, the ridge line 221 passes through the center of the second cutting structure 22, and two side regions of the ridge line 221 of the upper end surface of the second cutting structure 22 are symmetrical.

As shown in fig. 2, when the cutting tooth cuts the formation, the cutting tooth moves in the X direction, and the formation is cut from the end region of the first cutting structure 21 where the height of the ridge line 221 is low to the edge region of the third end surface 211 of the second cutting structure 22. Wherein the cutting angle of the cutting tooth is α, which is the angle between the third end face 211 of the second cutting structure 22 and the Y-axis. The sum of the cutting angle alpha of the cutting tooth and a first preset included angle theta between the ridge line 221 and the first end face 11 is smaller than 90 degrees, and the first preset included angle theta is larger than or equal to 0 degree.

In order to obtain the highest rock breaking efficiency and service life, the structural parameters of the cutting tooth need to satisfy the following relational expression:

Δh＝Rcosα-(L+r)·sin(α+θ)，

where α denotes a cutting angle of the cutting tooth, R denotes a radius of the first cutting structure 21, R denotes a radius of the second cutting structure 22, L denotes a distance from the center o of the bottom surface of the second cutting structure 22 to the ridgeline 221A, and Δ h denotes a tooth height difference, that is, a distance from the end point B of the end having the lower height of the ridgeline 221 to the edge D of the third end surface 211 of the first cutting structure 21 in the Y-axis direction.

In the above structure, the cross section of the substrate 1 in the radial direction and the cross section of the first cutting structure 21 in the radial direction have a circular shape, and the cross section of the second cutting structure 22 in the radial direction has a circular shape. The center of the second cutting structure 22 is the same as the center of the first cutting structure 21, and the ridge line 221 passes through the center of the second cutting structure 22.

In the above structure, several suitable combinations of the radius of the first cutting structure 21 and the radius of the second cutting structure 22 may be as follows: the radius R of the first cutting structure 21 is equal to 8.0mm and the radius R of the second cutting structure 22 is equal to 6.5mm; alternatively, the radius R of the first cutting structure 21 is equal to 9.5mm and the radius R of the second cutting structure 22 is equal to 8mm; alternatively, the radius R of the first cutting structure 21 is equal to 9.5mm and the radius R of the second cutting structure 22 is equal to 6.5mm.

In the above structure, further, the cutting angle α of the cutting tooth is controlled to be between 5 degrees and 30 degrees.

In a specific embodiment, the radius R of the first cutting structure 21 is equal to 8.0mm, the radius R of the second cutting structure 22 is equal to 6.5mm, the cutting angle α of the cutting tooth is equal to 15 degrees, the distance L from the center of the bottom surface of the second cutting structure 22 to the ridge line 221 is equal to 1.5mm, the first preset included angle θ is equal to 35 degrees, and the tooth height difference Δ h is equal to 1.6mm.

The second cutting structure 22 of this application cutting tooth has concentrated load in crest line 221 department, makes the inside stress concentration district that forms of its place ahead rock, and the rock takes place to cut-tensile destruction more easily, improves the ability that the cutting tooth eats into the stratum, improves the broken rock efficiency of drill bit. The cutting tooth cuts from the end area with the lower height of the ridge line 221 of the first cutting structure 21 to the edge area of the third end face 211 of the second cutting structure 22, so that the first cutting structure 21 and the second cutting structure 22 jointly cut rock along the track, and the defects of small single rock breaking volume and insufficient bottom hole covering capacity of the single first cutting structure 21 are overcome. The method has the advantages that the second cutting structure 22 with the ridge line 221 is strong in aggressiveness and not prone to impact damage, the rock at the bottom of the well is broken in advance, stratum stress is released, the rock is cut more easily by the first cutting structure 21, and rock breaking efficiency can be improved greatly; in addition, the second cutting structure 22 with the ridgeline 221 can limit the depth of the first cutting structure 21 to penetrate into the formation, reduce the "stick-slip effect" and impact damage of the drill bit, and improve the service life of the drill bit.

Fig. 6 is an experimental graph of cutting force of a cutting tooth in a rock breaking process according to an embodiment of the present invention, and fig. 7 is an experimental graph of cutting force of a conventional cylindrical cutting tooth in the prior art, as shown in fig. 6 and 7, under the same cutting conditions, cutting is performed from an end region of a ridge line 221 of a first cutting structure 21 with a relatively low height to an edge region of a third end surface 211 of a second cutting structure 22, and a maximum Mises stress generated by the cutting tooth in the present application in rock is 468.7MPa, while a maximum Mises stress generated by the conventional cylindrical cutting tooth in the prior art in rock is 367.5MPa. Obviously, the cutting tooth in this application can produce bigger stress in rock to stress concentration phenomenon appears more easily in step form prong position, more does benefit to the rock breakage, improves broken rock efficiency.

Fig. 8 is a graph comparing the cutting force with time during rock breaking of the cutting tooth according to the embodiment of the present invention and the conventional cylindrical cutting tooth of the prior art, and as shown in fig. 8, the average value of the cutting force during rock breaking of the cutting tooth of the present application is 1882.05N and the standard deviation is 132.94, while the average value of the cutting force during rock breaking of the conventional cylindrical cutting tooth of the prior art is 1840.92N and the standard deviation is 482.98. Although the average cutting force values of the two cutting teeth during rock breaking are relatively close, the standard deviation of the cutting force of the cutting teeth in the application is 72.48 percent smaller than that of the conventional cylindrical cutting teeth in the prior art. This shows that the fluctuation degree of cutting force is littleer at broken rock in-process of the cutting tooth in this application, is favorable to reducing PDC drill bit moment of torsion fluctuation and harmful vibration, can improve PDC drill bit's job stabilization nature, extension working life.

The present application further provides a PDC bit, and fig. 5 is a schematic structural diagram of a PDC bit according to an embodiment of the present invention, and as shown in fig. 5, the PDC bit may include a cutter 100 as described in any one of the above. The cutters 100 may be distributed in the nose or shoulder of the PDC bit. The cutting teeth 100 arranged on the nose or the shoulder utilize the excellent rock breaking performance of the second cutting structure 22 with the ridge line 221 to firstly cut rock at the bottom of a well, break the original mechanical state of the rock, enable the rock to be broken more easily, and improve the rock breaking efficiency of the drill bit. The broken rock advantage of first cutting structure 21 and second cutting structure 22 has been integrateed to the cutting tooth, and simultaneously, the double cloth tooth design of PDC drill bit can effectively be avoided in both integrated designs, reduces the thickness of PDC drill bit wing, concentrates on sharp cutting member 2 with the energy, and low weight-on-bit can obtain high drilling rate. In addition, the blade structure can be more open, and the chip groove structure can also be wider, so that a smooth hydraulic flow passage can be formed, and the higher mechanical drilling speed can be adapted to the stronger rock debris removing capacity.

The application also provides a design method of the cutting tooth, which comprises the following steps:

selecting a radius R of the first cutting structure 21 and a radius R of the second cutting structure 22;

obtaining a cutting angle alpha formed by the cutting teeth arranged on the PDC drill bit,

determining a distance L from the center of the bottom surface of the second cutting structure 22 to a ridge line 221 and a first preset included angle theta between the ridge line 221 and the first end surface 11, wherein the first preset included angle theta is greater than or equal to 0 degree, and alpha + theta is smaller than 90 degrees;

determining the tooth height difference Δ h according to the radius R of the first cutting structure 21, the radius R of the second cutting structure 22, the cutting angle α, the distance L from the center of the bottom surface of the second cutting structure 22 to the ridge line 221, and a first preset included angle θ between the ridge line 221 and the first end surface 11, wherein the specific calculation formula is as follows:

Δh＝Rcosα-(L+r)·sin(α+θ)。

by means of the method, the cutting tooth structure parameters in the application can be rapidly designed aiming at specific lithology of the stratum, so that the cutting tooth can obtain the highest rock breaking efficiency and the service life.

All articles and references disclosed, including patent applications and publications, are hereby incorporated by reference for all purposes. The term "consisting essentially of 8230comprises the elements, components or steps identified and other elements, components or steps which do not materially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, components, or steps herein also contemplates embodiments that consist essentially of such elements, components, or steps. By using the term "may" herein, it is intended to indicate that any of the attributes described that "may" include are optional. A plurality of elements, components, parts or steps can be provided by a single integrated element, component, part or step. Alternatively, a single integrated element, component, part or step may be divided into separate plural elements, components, parts or steps. The disclosure of "a" or "an" to describe an element, ingredient, component or step is not intended to foreclose other elements, ingredients, components or steps.

The embodiments in the present specification are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered in the protection scope of the present invention.

Claims (10)

1. A cutting tooth, comprising:

a substrate having corresponding first and second end faces;

a cutter fixedly disposed on the first end face of the substrate, the cutter being made of polycrystalline diamond, the cutter comprising: the first cutting structure is columnar and provided with a third end surface and a fourth end surface, and the fourth end surface is fixed with the first end surface; the second cutting structure is located in the third end face, the second cutting structure is columnar, the radial cross section of the second cutting structure is smaller than that of the first cutting structure, the upper end face of the second cutting structure is provided with a ridge line which is linear, a first preset included angle theta is formed between the ridge line and the first end face, and the two side areas of the ridge line of the upper end face of the second cutting structure are respectively and gradually reduced along the direction height of the ridge line.

2. The cutting tooth as set forth in claim 1 wherein said base is made of cemented carbide, said cutting member being fixedly disposed on said first end surface of said base by sintering, said base having a cross-section in a radial direction substantially the same as a cross-section of said first cutting structure in the radial direction in shape and size, said base having a cross-section in the radial direction substantially the same as a cross-section of said first cutting structure in the radial direction in shape of a circle or an approximately ellipse.

3. The cutting tooth as set forth in claim 2 wherein the center of said second cutting structure is the same as the center of said first cutting structure, said ridge line passes through the center of said second cutting structure, and regions on both sides of said ridge line on the upper face of said second cutting structure are symmetrical.

4. The cutting tooth as set forth in claim 1 wherein the cutting angle α of the cutting tooth, the first predetermined included angle θ being greater than or equal to 0 degrees and α + θ being less than 90 degrees.

5. A cutting tooth as set forth in claim 3, wherein the structural parameters of the cutting tooth satisfy the following relationship:

Δh＝Rcosα-(L+r)·sin(α+θ)，

wherein α represents a cutting angle of the cutting tooth, R represents a radius of the first cutting structure, R represents a radius of the second cutting structure, L represents a distance from a center of a bottom surface of the second cutting structure to the ridge line, and Δ h represents a tooth height difference, that is, a distance from an end point B of one end of the lower height of the ridge line to an edge D of the third end surface of the first cutting structure in the Y-axis direction.

6. The cutting tooth as set forth in claim 5 wherein the radius R of the first cutting structure is equal to 8.0mm and the radius R of the second cutting structure is equal to 6.5mm; or the radius R of the first cutting structure is equal to 9.5mm and the radius R of the second cutting structure is equal to 8mm; alternatively, the radius R of the first cutting structure is equal to 9.5mm and the radius R of the second cutting structure is equal to 6.5mm.

7. The cutting tooth as set forth in claim 5 wherein the cutting tooth has a cutting angle α of between 5 and 30 degrees.

8. A cutting tooth according to claim 5, characterized in that the radius R of the first cutting structure is equal to 8.0mm, the radius R of the second cutting structure is equal to 6.5mm, the cutting angle α of the cutting tooth is equal to 15 degrees, the distance L from the center of the bottom surface of the second cutting structure to the ridge line is equal to 1.5mm, the first predetermined angle θ is equal to 35 degrees, and the tooth height difference Δ h is equal to 1.6mm.

9. A PDC bit comprising the cutter of any one of claims 1 to 8.

10. A method of designing a cutting tooth as claimed in any one of claims 1 to 8, characterized in that the method comprises the steps of:

selecting a radius R of the first cutting structure and a radius R of the second cutting structure;

obtaining a cutting angle alpha formed by the cutting teeth arranged on the PDC drill bit,

determining a distance L from the center of the bottom surface of the second cutting structure to a ridge line and a first preset included angle theta between the ridge line and the first end surface, wherein the first preset included angle theta is larger than or equal to 0 degree, and alpha + theta is smaller than 90 degrees;

determining a tooth height difference deltah according to the radius R of the first cutting structure, the radius R of the second cutting structure, a cutting angle alpha, a distance L from the center of the bottom surface of the second cutting structure to a ridge line and a first preset included angle theta between the ridge line and the first end surface, wherein a specific calculation formula is as follows:

Δh＝Rcosα-(L+r)·sin(α+θ)。

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