CN114776226A

CN114776226A - PDC drill bit with different inner and outer parts and manufacturing method of PDC drill bit

Info

Publication number: CN114776226A
Application number: CN202210420292.9A
Authority: CN
Inventors: 刘维; 未九森; 高德利
Original assignee: China University of Petroleum Beijing
Current assignee: China University of Petroleum Beijing
Priority date: 2022-04-21
Filing date: 2022-04-21
Publication date: 2022-07-22
Anticipated expiration: 2042-04-21
Also published as: CN114776226B

Abstract

The invention provides a PDC drill bit with different inside and outside and a manufacturing method thereof, wherein the PDC drill bit with different inside and outside comprises: a bit center within a nose of a crown curve of the PDC bit and a bit shoulder outside of a nose of a crown curve of the PDC bit; the drill bit center part is provided with center part cutting teeth, and the drill bit shoulder part is provided with shoulder part cutting teeth; the average of the working areas of the central portion cutting teeth is less than the average of the working areas of the shoulder portion cutting teeth. The technical problem that the mechanical drilling speed and the rock breaking efficiency of the PDC drill bit are limited is solved through the PDC drill bit and the rock breaking method.

Description

PDC drill bit with different inner and outer parts and manufacturing method of PDC drill bit

Technical Field

The invention relates to the technical field of oil and gas drilling, in particular to a PDC drill bit with different inside and outside and a manufacturing method of the PDC drill bit.

Background

PDC (Polycrystalline Diamond Compact) bits are used to break underground rock, and are the main rock breaking tools in the field of oil and gas drilling engineering. The cutting structure of a PDC bit consists essentially of primary cutting teeth and crown curves. The main cutting teeth are located atThe first row of cutting teeth of each blade of the drill bit, which are firstly in contact with the stratum and undertake the main rock breaking task, are called main teeth for short. The crown curve is a curve formed by enveloping the highest points of all the main teeth; the gauge section of the drill bit is not counted in a crown curve, the crown curve only relates to a main tooth part for cutting broken rock and does not comprise teeth with non-rock breaking functions, such as gauge teeth at the gauge of the drill bit and non-first row teeth (also called secondary teeth) of each blade. The nose of the crown curve is tangent to the reference plane and is the axially highest position of the entire bit. As shown in FIGS. 1 and 2, the primary teeth on the crown curve of the PDC bit shown in FIG. 1 are

The circular teeth of (a); in FIG. 2, the inner band is the bit nose location and the outer band represents the maximum outer diameter of the bit, with the ratio of the inner band diameter to the outer band diameter typically being 30% to 80%. According to the radial position of the nose part, the cutting structure of the PDC drill bit can be divided into an inner part and an outer part: a bit center portion located inside the nose portion, and a bit shoulder portion located outside the nose portion.

Along with the continuous progress of drilling technology and tools, the rock breaking efficiency and the mechanical drilling speed of the PDC drill bit are also continuously improved. However, in recent years the rate of penetration of PDC bits has entered the bottleneck phase and has not made a significant breakthrough. Currently, the rate of penetration and the rock breaking efficiency of PDC bits are greatly limited in the following three specific applications.

In the first case, the default of the drilling engineer and the PDC bit manufacturer is that increasing the diameter of the PDC bit cutting teeth effectively increases the rate of penetration of the PDC bit. Under ideal drilling conditions, the rate of penetration of a PDC bit may be determined by the following equation:

ROP＝60×DOC×RPM (3)

wherein ROP (rate of penetration) is the rate of penetration of the drill bit, and ROP is in m/h; DOC (depth of cut per regression) is the depth of penetration of the PDC teeth, and the DOC is expressed in m/rev; RPM (revolutions per minute) is the rotational speed, and RPM is in rev/min.

As can be seen from equation 3: the mechanical drilling speed of the PDC drill bit is in positive correlation with the penetration depth of the cutting teeth; the size of the cutting teeth is improved, the cutting edge height and the depth of penetration of the cutting teeth are increased, and therefore the mechanical drilling speed of the PDC drill bit is effectively improved; the large-size cutting teeth can crush more rocks after rotating for one circle, massive volume crushing is facilitated, the rock crushing efficiency of the cutting teeth and the PDC drill bit is increased, and therefore the rock crushing effect of large-tooth fast cutting is achieved. However, at present, even if a large-size cutting tooth is adopted, the increase of the mechanical drilling rate of the PDC drill bit is not obvious, so that the mechanical drilling rate of the PDC drill bit enters the bottleneck period in recent years, and no significant breakthrough is made. In addition, the drill bit is easy to be held back, and once the torque energy is stored in the twisted pipe column and released, the rotating speed of the drill bit reaches 2-15 times of the normal value, so that the drill bit and the pipe column are subjected to severe torsional vibration, severe torque fluctuation is caused, and the PDC drill bit is an important reason for damage. The depth of the main teeth is controlled, the reaction torque is reduced, and the stick-slip is well inhibited. Baker Hughes corporation has discovered that stick-slip is a major cause of PDC bit failure in today's drilling applications. Thus, there has to be a compromise between aggressiveness of the cutting teeth and reaction torque, resulting in a balance between rate of penetration and bit stability durability.

In the second case, for the exploration and development of oil and gas in the fields of unconventional, deep water and the like, more drilling energy is consumed for cutting rocks per unit volume; moreover, as well depths continue to increase, the drilling energy provided to PDC bits is relatively limited, subject to the limitations of current drilling processes and drilling equipment. By combining the factors, when the PDC drill bit drills in a deep stratum, the PDC drill bit has poor rock breaking effect and drilling efficiency, and the drilling period and the drilling cost are greatly increased.

In the third case, for very large diameters

The PDC drill bit has obvious limitation on the mechanical drilling speed and the rock breaking efficiency of the PDC drill bit.

In conclusion, the technical problems that the mechanical drilling speed and the rock breaking efficiency of the PDC drill bit are limited exist at present.

Disclosure of Invention

The invention aims to provide an inner-outer different PDC drill bit and a manufacturing method of the PDC drill bit, and aims to solve the technical problem that the mechanical drilling speed and the rock breaking efficiency of the PDC drill bit are limited.

The above object of the present invention can be achieved by the following technical solutions:

the invention provides a PDC drill bit with different inner and outer parts, which comprises: a bit center within a nose of a crown curve of the PDC bit and a bit shoulder outside of a nose of a crown curve of the PDC bit; the drill bit center part is provided with center part cutting teeth, and the drill bit shoulder part is provided with shoulder part cutting teeth;

the average of the working areas of the central portion cutting teeth is less than the average of the working areas of the shoulder portion cutting teeth.

In a preferred embodiment, the difference between the average of the working areas of the shoulder cutting teeth and the average of the working areas of the center cutting teeth is greater than or equal to 20% and less than or equal to 86% of the average of the working areas of the center cutting teeth.

In a preferred embodiment, the working area of the center portion cutting tooth is smaller than the working area of the shoulder portion cutting tooth.

In a preferred embodiment, the difference between the working area of the shoulder cutter and the working area of the center cutter is greater than or equal to 20% of the working area of the center cutter.

In a preferred embodiment, the central cutting tooth comprises at least 3 small area cutting teeth having a working area that is smaller than the working area of the other cutting teeth on the crown curve.

In a preferred embodiment, at least some of the central portion cutting teeth are cutting teeth having a pointed portion.

In a preferred embodiment, the cutting teeth with the pointed portions have a working area smaller than that of circular teeth having the same diameter, and the difference between the two is greater than or equal to 10% of the working area of the cutting teeth with the pointed portions.

In a preferred embodiment, at least a part of the shoulder cutting teeth are cutting teeth having a pointed tooth portion, or the shoulder cutting teeth are rounded teeth.

In a preferred embodiment, the cutting tooth having the pointed tooth portion is an axe-shaped tooth, a bent tooth, or a concave axe-shaped tooth.

The invention provides a manufacturing method of a PDC drill bit, which comprises the following steps:

making a bit body comprising a bit center portion and a bit shoulder, the bit center portion being located within a nose portion of a crown curve of the PDC bit, the bit shoulder being located outside of the nose portion of the crown curve of the PDC bit;

manufacturing a central cutting tooth and a shoulder cutting tooth, wherein the working area of the central cutting tooth is smaller than that of the shoulder cutting tooth;

the center portion cutting teeth are disposed in the bit center portion and the shoulder cutting teeth are disposed in the bit shoulders.

The invention has the characteristics and advantages that:

the PDC drill bit provided by the invention effectively improves the overall rock breaking efficiency and the mechanical drilling speed of the PDC drill bit, improves the rock breaking effect of the PDC drill bit, and has the following advantages:

(1) the high-speed rock breaking effect of 'large tooth fast cutting' is favorably exerted, and the great speed increase of the stratum with better drillability can be realized;

(2) the problem that the deep stratum is difficult to eat is effectively solved, and the drilling energy required by the PDC drill bit for rock breaking of the deep stratum is effectively reduced, so that the problems of low drilling speed and long period of the deep stratum are solved;

(3) the cutting teeth at the center of the drill bit are provided with the sharp tooth parts, so that the cutting teeth are beneficial to improving the biting effect, the working area is reduced, and the drilling energy required by the cutting teeth for rock breaking is effectively reduced, so that the retardation effect of the cutting teeth at the center of the drill bit is eliminated, and the rock breaking efficiency of the PDC drill bit is greatly improved;

(4) the cutting teeth at the center of the drill bit are provided with sharp tooth parts, so that the drill bit is beneficial to being eaten into a compact and hard stratum, the required bit pressure and torsional force are smaller, and the advantages are more obvious in drilling of a long horizontal section or a deep stratum;

(5) the cutting teeth at the center of the drill bit are provided with sharp tooth parts, so that the cutting teeth become sharp, the ridge height is increased, and the transverse stability of the drill bit is improved;

(6) the cutting teeth at the center of the drill bit are provided with sharp tooth parts, the working area of the cutting teeth is reduced, the reaction torque is reduced, and the drilling energy required by one rotation of the center of the drill bit is reduced;

(7) the cutting teeth at the center of the drill bit are provided with sharp tooth parts, so that the working area of the cutting teeth is reduced, the torque fluctuation is reduced, the torque of the drill bit is stabilized, and the vibration, the stick-slip and the bit bouncing and jumping of the drill bit are reduced;

(8) the cutting teeth at the center of the drill bit are provided with the sharp tooth parts, the working area of the cutting teeth is reduced, the rock breaking amount of the drill bit rotating for one circle is reduced, the rock carrying and discharging and the shaft bottom cleaning are facilitated, the repeated cutting at the shaft bottom is reduced, and the rock breaking efficiency is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a typical crown curve for a PDC bit;

FIG. 2 is a top view of a typical crown curve for a PDC bit;

FIG. 3A is a schematic illustration of the working area of a 16mm diameter cutting tooth;

FIG. 3B is a schematic illustration of the working area of a 22mm diameter cutting tooth;

FIG. 4 is a graphical illustration of a programmed calculation of a typical working area for a first blade of a PDC bit;

FIG. 5 is a graph of an exemplary relationship between the resultant force F and the radial distance r of a PDC bit cutting element;

FIG. 6 is a schematic view of a circular tooth;

FIG. 7 is a schematic view of the structure of the hatchet-shaped teeth;

FIG. 8 is a schematic view of a configuration of a curved cutter tooth;

FIG. 9 is a schematic structural view of a concave hatchet-shaped tooth;

FIGS. 10-14 are schematic structural views of different PDC bits according to the present invention;

FIG. 15 is a schematic view of a horizontal drilling rig;

FIG. 16 is a schematic illustration of a comparison of rates of penetration;

FIG. 17 is a logic block diagram of PDC cutter working area calculation.

The reference numbers illustrate:

10. a nose portion; 11. a crown curve;

21. a drill bit center portion; 22. a drill shoulder;

30. cutting teeth; 301. a working surface;

31. a central portion cutting tooth; 32. shoulder cutting teeth;

40. a cutting tooth having a pointed tooth portion; 401. a sharp tooth part;

41. an axe-shaped tooth; 42. bending cutter teeth; 43. concave axe-shaped teeth;

44. a circular tooth;

51. a power propulsion device; 52. a rock holder; 53. a drill string centralizer; 54. a drill string; 55. a slide rail; 56. a base; 57. a drill bit; 58. a rectangular rock pillar; 59. a slurry outlet; 510. screening rock debris; 511. a rock debris groove; 512. a drilling pump; 513. a mud pit.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The inventor researches the first situation in the background art to find that: FIGS. 3A and 3B illustrate the working face 301 of the cutting tooth 30, the area of the working face 301 of the cutting tooth 30 being the working face of the cutting tooth 30, and a small size cutting tooth

Large size cutting teeth

A larger working area will result. According to equation 2, in the case of the same rock breaking stress, the cutting teeth in the center of the drill bit are subjected to a large force due to the large working area, and the corresponding force required for breaking rock is also large.

F＝A×σ (2)

Where A is the working area of contact between the cutting tooth and the rock, related to the location of the crown curve 11 at which the cutting tooth is located; and sigma is the rock breaking stress and is related to the rock characteristic parameters and the rock breaking motion mode.

The increase of the working area of the cutting teeth can obviously improve the retardation effect of the cutting teeth at the center of the drill bit, and the drill bit can consume more drilling energy when rotating for one circle. Thus, even with very large sized cutting teeth, the increase in rate of penetration of PDC bits is not significant, resulting in the rate of penetration of PDC bits entering a bottleneck period in recent years.

In addition, as the size of the cutting tooth increases and its working area increases, a greater reaction torque is also created. The reaction torque is too large, the PDC drill bit can stop rotating at any time to form a 'suppressed drill bit' until the pipe column accumulates enough torque to enable the drill bit to rotate again to shear the rock. Since the torque energy is stored in the twisted string, once released, the string behaves like a unwound spring, at which point the bit rotates at 2-15 times the normal speed, and the bit and string experience severe torsional vibration, a phenomenon known as stick-slip. Stick-slip vibrations will lead to severe torque fluctuations, an important cause of PDC bit damage.

Through a reasonable and innovative technical scheme, if the retardation effect of the large-size cutting teeth at the center of the bit can be reduced and the reaction torque of the large-size cutting teeth can be reduced, the large-tooth fast-cutting rock breaking effect of the formula 3 can be more favorably exerted, the stability and durability of the bit can be favorably improved, and the mechanical drilling speed and the rock breaking efficiency of the PDC bit can be effectively improved.

The inventors have studied the second case in the background art and found that: along with the continuous deepening of the well depth, the lithology of the stratum is more compacted and compact, the drillability of the stratum is deteriorated, and more drilling energy is consumed for cutting rocks in unit volume; due to the compaction and compaction of the stratum, the drilling energy required for breaking rock is continuously increased, so that the retardation effect of the cutting teeth at the center of the drill bit is amplified.

In deep formation drilling, if the retarding effect of the cutting teeth at the center of the drill bit can be reduced, for example: by means of the method for reducing the working area of the cutting teeth (according to the formula 2) and the design of the tooth form of the cutting teeth which are easier to bite into the compact stratum, the PDC drill bit consumes less drilling energy after rotating and cutting for one circle, and therefore the mechanical drilling speed and the rock breaking efficiency of the PDC drill bit for the deep stratum are effectively improved.

The inventor researches the third situation in the background art and finds out that; for very large diameters

The PDC drill bit of fig. 2 shows that as the radial distance r from the center of the drill bit increases, the corresponding linear velocity (formula 1) also increases accordingly, so that the PDC drill bit has higher rock breaking capacity and rock breaking efficiency. Also, because the drillability of the drilled area tends to be relatively good, large diameter PDC bits typically employ large sized cutting teeth to increase the rate of penetration. However, the cutting teeth in the various regions of the crown curve 11 of the PDC bit still complete one revolution of the rotary shear rock breaking, and the effect of the blocking effect of the large-size cutting teeth at the center of the bit becomes significant.

By means of a reasonable and innovative technical scheme, if the retardation effect can be reduced, the mechanical drilling speed and the rock breaking efficiency of the large-diameter PDC drill bit can be effectively improved.

Typically, the cutting structure of a PDC bit will typically employ the same size and same profile of cutting elements at the center of the bit and at the shoulder 22 of the bit, i.e., the bit will have a uniform inner and outer set of teeth. As shown in fig. 1, the bit center and shoulder are both 16mm diameter circular teeth 44.

The inventor analyzes the defects of the PDC drill bit with 'uniform inside and outside' tooth arrangement and discovers that: the cutting teeth at the center of the bit of the PDC bit have a great retarding effect on the shearing and rock breaking effect of the entire bit. According to the barrel effect, the rock breaking effect of the cutting teeth at the center of the bit is a short plate for determining the mechanical drilling speed of the PDC bit.

This finding was made with respect to the retarding effect of the cutting teeth at the center of the PDC bit as follows:

according to the following steps of 1: according to the formula 1, the closer the cutting teeth are to the center of the drill bit, the slower the linear velocity is, the longer the time required for crushing rocks with the same arc length is, the lower the rock-breaking speed is and the poor effect is obtained.

Wherein, the first and the second end of the pipe are connected with each other,

is the linear velocity, r is the radial distance from the center of the bit, and ω is the angular velocity.

According to the following 2: as shown in FIG. 4, the closer the cutter is to the center of the bit, the larger the working area of the cutter. Typically, the crown curve 11 has an arc length at the bit center 21 that is much shorter than the arc length at the bit shoulder 22. Therefore, the number of teeth in the bit center 21 is much smaller than that in the bit shoulder 22 for the same width of the bottom projection surface, resulting in a larger cutting area of the cutting teeth in the bit center 21 than that in the bit shoulder 22. The first blade refers to the blade where the cutting tooth closest to the center of the drill bit is located.

According to equation 2, in the case that the rock breaking stress is the same, the cutting teeth in the center of the drill bit are subjected to a large force due to a large working area, and the corresponding force required to break rock is also large.

According to 3: as shown in fig. 5, the closer the cutter is to the bit center, the greater the resultant force F (weight on bit pressure and rotational Torque) the cutter experiences, and the greater the resulting Reactive Torque and Torque fluctuations, especially when lithology or weight on bit changes, which results in severe torsional fluctuations throughout the PDC bit.

According to 4: according to the formula 2, the closer the cutting tooth is to the center of the drill, the rock breaking stress is influenced by the rock breaking motion mode of the cutting tooth, and the greater the rock breaking stress is, the greater the rock breaking motion mode of the cutting tooth is, the greater the reaction force per unit working area of the cutting tooth is, the greater the energy required by the cutting tooth to break rock through rotary shearing is, that is, the greater the drilling energy is required to be consumed by the cutting tooth at the center of the drill compared with the cutting teeth in other areas. When the drill bit works underground, although the cutting teeth of each area of the crown curve 11 of the PDC drill bit complete one-circle rotary shearing rock breaking at the same time, the resistance of the cutting teeth of each area of the drill bit to the rotary shearing rock breaking of the drill bit is different. The central area of the drill bit needs to consume more drilling energy to complete the rotation due to large working area and high rock breaking stress.

Therefore, the region of the PDC drill bit cutting structure where the rock breaking efficiency is high is restricted by the central region of the drill bit where the rock breaking is inefficient (barrel effect), and the entire drill bit cannot exhibit the optimum rock breaking effect. On the contrary, if the retardation effect of the cutting teeth at the center of the bit can be reduced, the rock breaking efficiency and the mechanical drilling speed of the PDC bit can be effectively improved.

In order to solve the technical problem that the mechanical drilling speed and the rock breaking efficiency of the PDC drill bit are limited, the PDC drill bit is improved.

Scheme one

The present invention provides a PDC drill bit having different inner and outer shapes, as shown in fig. 10 to 14, the PDC drill bit including: a bit center 21 and a bit shoulder 22, the bit center 21 being located within the nose 10 of the crown curve 11 of the PDC bit, the bit shoulder 22 being located outside the nose 10 of the crown curve 11 of the PDC bit; the bit center 21 is arranged with center cutters 31, the bit shoulders 22 are arranged with shoulder cutters 32; the average of the working areas of the central portion cutting teeth 31 is smaller than the average of the working areas of the shoulder portion cutting teeth 32. Through the PDC drill bit with the different inside and outside, the problem that the deep stratum is difficult to eat is effectively solved, and the drilling energy required by rock breaking of the PDC drill bit in the deep stratum is effectively reduced, so that the problems of low drilling speed and long period of the deep stratum are solved.

The PDC bit has a bit center portion 21 with one or more center portion cutters 31 and a bit shoulder portion 22 with one or more shoulder portion cutters 32. The sum of the working areas of all the center cutters 31 of the PDC bit is smaller than the sum of the working areas of all the shoulder cutters 32. Further, the difference between the sum of the working areas of the shoulder cutting teeth 32 and the sum of the working areas of the central cutting teeth 31 is greater than or equal to 20% and less than or equal to 86% of the sum of the working areas of the central cutting teeth 31. As shown in fig. 2, the sum of the working areas of all the center section cutting elements 31 in the bit center section 21 and the sum of the working areas of all the shoulder center elements in the bit shoulders 22 form a "distinct inside and outside" bit cutting structure. More preferably, the difference between the sum of the working areas of the shoulder cutting elements 32 and the sum of the working areas of the central cutting elements 31 is less than or equal to 67.5% of the sum of the working areas of the central cutting elements 31.

The number of center cutting teeth 31 and shoulder cutting teeth 32 may or may not be equal. In one embodiment, the average of the working areas of the central portion cutting teeth 31 is less than the average of the working areas of the shoulder portion cutting teeth 32 and the difference between the average of the working areas of the shoulder portion cutting teeth 32 and the average of the working areas of the central portion cutting teeth 31 is greater than or equal to 20% and less than or equal to 86% of the average of the working areas of the central portion cutting teeth 31. Specifically, the sum of the working areas of all the center cutting teeth 31 of the bit center 21 is divided by the total number of teeth of the center cutting teeth 31 to obtain an average value a1 of the working areas of the center cutting teeth 31; similarly, the average a2 of the working areas of the shoulder cutters 32 is obtained by dividing the sum of the working areas of all the shoulder cutters 32 of the drill shoulder 22 by the total number of the shoulder cutters 32, and satisfies: a1 < A2, and preferably A1 × 70% ≧ A2-A1 ≧ A1 × 20%. More preferably, A1 × 67.5% ≧ A2-A1 ≧ A1 × 20%.

Further, the working area of the center cutting tooth 31 is smaller than the working area of the shoulder cutting tooth 32, i.e.: the working area of each center cutting tooth 31 is smaller than the working area of the shoulder cutting tooth 32. More closely, the difference between the working area of the shoulder cutter 32 and the working area of the center cutter 31 is greater than or equal to 20% of the working area of the center cutter 31.

The working areas of the central portion cutting teeth 31 may or may not be equal; the shoulder cutters 32 may or may not have equal working areas. The inventor makes further improvements to the PDC bit: the center cutter 31 of the PDC bit includes at least 3 small area cutters having a smaller working area than the other cutters on the crown curve 11. The working areas of the at least 3 small-area cutting teeth can be equal in pairs or unequal; preferably, the working areas of the at least 3 small area cutting teeth are mutually different. For example: the center section cutter 31 of the PDC bit includes 4 small area cutters, namely: the first, second, third and fourth cutting teeth, which are ranked from small to large in working area of the cutting teeth on the crown curve 11, all belong to the central portion cutting tooth 31.

The cutting structure of the PDC drill bit has the characteristic of 'internal and external dissimilarity', effectively solves the problem of retarding effect of the cutting teeth at the center of the drill bit on the overall rock breaking effect of the drill bit, and improves the rock breaking efficiency of the PDC drill bit. In one embodiment, the overall diameter of the PDC bit is 75mm to 720mm, and the number of blades of the PDC bit is 3 to 12. The diameter of the envelope circle of the center portion cutting teeth 31 and the diameter of the envelope circle of the shoulder portion cutting teeth 32 are each 8mm to 50mm, and specifically, may be 13mm, 16mm, 19mm, 22mm, 25mm, or 28 mm.

The inventor makes further improvements to the PDC bit: at least a part of the central portion cutting teeth 31 are cutting teeth 40 having a pointed portion. The cutting teeth 40 with the sharp-tooth parts are adopted for the central cutting teeth 31 in the PDC drill bit, so that the cutting effect of 'breaking through of sharp teeth' can be formed, the capability of the cutting teeth at the center of the drill bit to bite into the stratum is effectively improved, and the rock breaking efficiency of the cutting teeth at the center of the drill bit is effectively improved.

The tooth surface of the cutting tooth 40 having the pointed tooth portion is different from the continuous smooth arc tooth surface of the round tooth 44, and has obvious intermittent and connection characteristics including line, line connection, line segment connection with arc line, arc surface connection with arc surface, and the like. As shown in fig. 6 to 9, the cutting tooth 40 having the pointed tooth portion is preferably an axe-shaped tooth 41, a curved cutter tooth 42, or a concave axe-shaped tooth 43. The cutting tooth 40 having the pointed portion may be another shaped tooth.

Further, the cutting teeth 40 having the pointed portions have a working area smaller than that of the circular teeth 44 having the same diameter, and the difference therebetween is 10% or more of the working area of the cutting teeth 40 having the pointed portions of the circular teeth 44.

The rounded teeth 44 have a continuous smooth arcuate flank, and in some cases, the rounded teeth 44 are right circular cylindrical; in other cases, the projection of the rounded teeth 44 is a perfect circle, with a scoop-shaped concave configuration or a spherically convex configuration. In one embodiment, at least some of the shoulder cutters 32 are pointed cutters 40, or the shoulder cutters 32 are rounded teeth 44, i.e.: only all or part of the central portion cutting teeth 31 are cutting teeth 40 having a pointed portion, or part or all of the shoulder portion cutting teeth 32 and part or all of the central portion cutting teeth 31 are cutting teeth 40 having a pointed portion.

The PDC drill bit provided by the invention has a PDC drill bit cutting structure with different inside and outside and sharp tooth breakthrough, can effectively improve the overall rock breaking efficiency and the mechanical drilling speed of the PDC drill bit, improves the rock breaking effect of the PDC drill bit, and has the following advantages:

(3) the cutting teeth at the center of the drill bit are provided with the sharp tooth parts 401, so that the cutting teeth are beneficial to improving the biting effect, the working area is reduced, and the drilling energy required by the cutting teeth for rock breaking is effectively reduced, so that the retardation effect of the cutting teeth at the center of the drill bit is eliminated, and the rock breaking efficiency of the PDC drill bit is greatly improved;

(4) the cutting teeth at the center of the drill bit are provided with the sharp tooth parts 401, so that the drill bit is beneficial to being eaten into a compact and hard stratum, the required bit pressure and torsional force are smaller, and the advantages are more obvious in drilling of a long horizontal section or a deep stratum;

(5) the cutting teeth at the center of the drill bit are provided with sharp tooth parts 401, and the cutting teeth become sharp, so that the ridge height is increased, and the transverse stability of the drill bit is improved;

(6) the cutting teeth at the center of the drill bit are provided with sharp teeth parts 401, the working area of the cutting teeth is reduced, the reaction torque is reduced, and the drilling energy required by one rotation of the center of the drill bit is reduced;

(7) the cutting teeth at the center of the drill bit are provided with sharp tooth parts 401, the working area of the cutting teeth is reduced, the torque fluctuation is reduced, the torque of the drill bit is stabilized, and the vibration, stick-slip and bit bouncing and jumping of the drill bit are reduced;

(8) the cutting teeth at the center of the drill bit are provided with the sharp tooth parts 401, the working area of the cutting teeth is reduced, the rock breaking amount of the drill bit rotating for one circle is reduced, rock carrying and discharging are facilitated, the shaft bottom is cleaned, repeated cutting of the shaft bottom is facilitated to be reduced, and the rock breaking efficiency is improved.

The inventor further optimizes the PDC drill bit:

as shown in fig. 10, the PDC bit is 222.3mm in diameter and includes 6 blades, and the bit center 21 is arranged with 9 curved cutter teeth 42 of 16mm in diameter; the other areas of the crown curve 11 are arranged with circular teeth 44 having a diameter of 16 mm. Further, the difference between the working areas of the rounded teeth 44 and the bent teeth 42 is 28.8% of the working area of the bent teeth 42.

As shown in fig. 11, the PDC bit is 215.9mm in diameter and includes 5 blades, and 8 curved cutter teeth 42 of 16mm in diameter are arranged in the bit center 21; the other areas of the crown curve 11 are arranged with hatchet-shaped teeth 41 having a diameter of 19 mm. The working area of the bending teeth 42 is smaller than that of the hatchet teeth 41, and further, the difference between the working areas of the hatchet teeth 41 and the bending teeth 42 is 45% of the working area of the bending teeth 42.

As shown in fig. 12, the PDC bit has a diameter of 311.2mm and includes 5 blades, and a bit center portion 21 is provided with 14 bent blades 42 having a diameter of 19 mm; the other areas of the crown curve 11 are arranged with hatchet-shaped teeth 41 having a diameter of 19 mm. The working area of the bending tooth 42 is smaller than that of the hatchet tooth 41, and further, the difference between the working areas of the hatchet tooth 41 and the bending tooth 42 is 41.9% of the working area of the bending tooth 42.

As shown in fig. 13, the PDC bit is 241.3mm in diameter and includes 4 blades, and the bit center 21 is arranged with 4 bent blades 42 19mm in diameter; the other areas of the crown curve 11 are arranged with circular teeth 44 having a diameter of 22 mm. Further, the difference in the working area of the rounded teeth 44 and the bent cutter teeth 42 is 64% of the working area of the bent cutter teeth 42.

As shown in fig. 14, the PDC bit is 215.9mm in diameter and includes 5 blades, and the bit center 21 is arranged with 7 curved cutter teeth 42 of 16mm in diameter; the other area of the crown curve 11 is arranged with axe-shaped teeth 41 having a diameter of 16 mm. The working area of the curved cutter tooth 42 is smaller than that of the axe-shaped tooth 41, and further, the difference between the working areas of the axe-shaped tooth 41 and the curved cutter tooth 42 is 25.8% of the working area of the curved cutter tooth 42.

The PDC drill bit is tested by the inventor, a full-size drill bit rock breaking experimental platform is designed and established, drilling parameters such as the drilling pressure, the drilling speed and the pumping pressure can be truly simulated, the mechanical drilling speed and the stability of the drill bit are suitable for researching the drilling performance of the drill bit, and the PDC drill bit has very important significance for optimizing the drilling parameters such as the drilling pressure and the rotating speed. The experiment platform mainly comprises a horizontal drilling machine and a measurement-while-drilling short joint arranged near a drill bit. The maximum bit weight of the horizontal drilling machine is 250KN, the maximum rotating speed is 160rev/min, and the maximum torque is 10000 N.m.

Horizontal drills are capable of simulating the drilling behavior of a full-size drill bit downhole. The horizontal drilling machine comprises a rock clamping device, a drilling power device, a high-pressure drilling pump, a rock debris collecting box and a data acquisition system. The rock clamping device can clamp 2000 multiplied by 350mm rock, and rock lithology can be set according to stratum environment. The drilling power plant consists of a feed system capable of providing the drill bit with a weight on bit of 0-250KN and a travel distance of 2m (limited to the rock length) and a rotation system capable of providing the drill bit with a rotational speed of maximally 160r/min and a torque of maximally 10000 n.m. In the experiment, the experiment purpose of accurately measuring various drilling behaviors of the drill bit can be realized by adjusting the parameters of the drilling machine. The data acquisition system of the full-size drill bit rock breaking experimental device can measure the bit pressure, the rotating speed, the torque, the footage, the pumping pressure, the flow, the axial vibration, the radial vibration and the circumferential vibration. The maximum data sampling rate of the data acquisition system is 1000 HZ. The rock debris collecting box can collect rock debris generated in the drilling process at every time, and the rock debris can be analyzed in the later period. The working principle is as follows: (1) installing rock in the rock clamping device; (2) the drilling power device clamps the drill rod and provides the bit pressure and the rotating speed for the drill bit in the drilling process; (3) buckling the drill bit and the drill rod; (4) pumping slurry into a drill rod by a high-pressure drilling pump in the drilling process, cooling and lubricating a drill bit and effectively discharging rock; (5) the data acquisition system is turned on prior to drilling: (6) and (5) after drilling is finished, collecting rock debris in the rock debris collecting box. Specifically, as shown in fig. 15, the horizontal drilling machine includes a power propulsion device 51, a rock gripper 52, a drill string centralizer 53, a drill string 54, a skid 55, a bed 56, a drill bit 57, a rectangular rock string 58, a mud outlet 59, a rock debris screen 510, a rock debris chute 511, a drill pump 512, and a mud pit 513.

Indoor test experiments are carried out on the PDC drill bit with the novel cutting structure design method and the conventional PDC drill bit through a full-size drill bit rock breaking experiment platform. The PDC drill bits used in the experiment have the same main tooth crown curve 11 and exposure value, the drill bit diameters are all 215.9mm (8.5-inch), the blade numbers are all 4, the only variable is a design method of a cutting structure, one is a design method of 'different inside and outside' and 'sharp tooth breakthrough' and the other is a conventional design method of 'same inside and outside'. Specifically, the PDC drill bit adopting the novel cutting structure design method adopts a cutting structure design method of "different inside and outside" and "sharp tooth breakthrough" shown in fig. 11, and has a drill bit diameter of 215.9mm, including 4 blades; the center of the drill bit uses 4 bent cutter teeth 42 with the diameter of 19mm, and the shoulder 22 of the drill bit uses round teeth 44 with the diameter of 22 mm. The bit diameter of a conventional PDC bit is 215.9mm, and 4 blades are arranged; the crown curve 11 of the drill bit adopts a traditional 'consistent inside and outside' tooth arrangement method; the same size (phi 19mm) and the same tooth form (circular) are used for the cutting teeth of the crown curve 11.

In the experiment, the rotating speed is set to be a constant value, the drilling pressure values are 1.5 tons and 2.5 tons, and as shown in figure 16, the novel bit adopts the PDC bit with different inner parts and outer parts, and compared with the conventional PDC bit, the speed is increased by over 60%.

The inventors have conducted field tests on this PDC bit.

Test one: the PDC drill bit has the characteristics of 'different inside and outside' and 'sharp tooth breakthrough', and field tests are performed on a C105 well in a Shandong Shengli oil field vehicle-western operation block by adopting the PDC drill bit shown in figure 13. Drilling the encountered stratum mainly comprises: the fourth line of the new kingdom is plain group, the recent lines are Ming Huan group and Liangtai group, and the ancient lines are Dong Ying group and Shahe street group. The test results are shown in Table 1, and the PDC drill bit adopting the novel cutting structure design method creates two records of the fastest mechanical drilling speed and the highest daily footage in the operation area of the Western-style vehicle! Compared with the bit data of the adjacent well C27-X2 well, the new bit achieves 160% speed increase.

TABLE 1 drill bit usage data comparison

And (2) testing II: in the Y941-X71 well in Shandong Shengli oil field, the PDC drill bit provided by the invention and the conventional PDC drill bit are used for the same-well test, the PDC drill bit shown in figure 14 is used firstly, and the conventional PDC drill bit is used after the drill bit is pulled out. The adopted PDC drill bit with different inside and outside has a cutting structure of ' different inside and outside and ' sharp tooth breakthrough ', the diameter of the drill bit is 215.9mm, and 5 blades are arranged; the center of the drill bit adopts 7 curved cutter teeth with the diameter of 16mm, and the shoulder of the drill bit adopts axe-shaped teeth with the diameter of 16 mm. The bit diameter of the conventional PDC bit is 215.9mm, and 5 blades are arranged; the curve of the crown part of the drill bit adopts a traditional 'consistent inside and outside' tooth arrangement method, and the cutting teeth of the curve of the crown part adopt the same size (phi 16mm) and the same tooth form (axe-shaped teeth). Drilling the encountered stratum mainly comprises: sandthree and Zhongsheng. As shown in table 2, the PDC drill bits having the different inner and outer surfaces achieved an increase in speed of 65% as compared to the conventional PDC drill bits.

TABLE 2 drill bit usage data comparison

And (3) testing three: the PDC drill bits with different inner and outer parts are adopted for field application in Y3-X14 wells of the Sinkiang pseudo-songorian basin. The PDC drill bits different in inside and outside are identical to the PDC drill bits different in inside and outside in test two. Drilling the encountered stratum mainly comprises: hull wall group and clear river group. The test results are shown in table 3, and the PDC drill bits of Harliberton enterprises in foreign countries are adopted in the peripheral adjacent wells Y3-X2, so that the speed is increased by 125% by adopting the different PDC drill bits in the foreign countries; compared with a Schlumberger PDC drill bit imported from foreign countries which is adopted in the surrounding adjacent well Y3-P16, the speed is increased by 330%.

TABLE 3 comparison of the results of the drill bit imported from abroad

Scheme two

The invention provides a manufacturing method of a PDC drill bit, which comprises the following steps: manufacturing a drill bit body, wherein the drill bit body comprises a drill bit central part 21 and a drill bit shoulder part 22, the drill bit central part 21 is positioned in the nose part 10 of the crown curve 11 of the PDC drill bit, and the drill bit shoulder part 22 is positioned outside the nose part 10 of the crown curve 11 of the PDC drill bit; manufacturing a central cutting tooth 31 and a shoulder cutting tooth 32, wherein the working area of the central cutting tooth 31 is smaller than that of the shoulder cutting tooth 32; the center cutter 31 is disposed in the bit center 21 and the shoulder cutter 32 is disposed in the bit shoulder 22.

To effectively distinguish the working area of the cutter at the center and shoulder of the bit, the working area of the cutter on the PDC bit crown curve 11 can be calculated as follows. Specifically, the working area calculation of the PDC drill bit cutting tooth distribution design is realized by a modern computer numerical method by taking two computer languages of python and C + + as carriers and a computer graphic method. As shown in fig. 17, for a given PDC bit tooth arrangement design result parameter, 9 key calculation parameters including a radial position R, a rotation angle θ, and a height H of each PDC cutting tooth, a back inclination angle α, a side rotation angle β, and an assembly angle γ of a spatial direction rotation angle of a working surface of each PDC cutting tooth, a serial number in an overall tooth arrangement structure, and preset generalized drilling parameters including a mechanical drilling rate and a bit rotation speed are input into a calculation program, and an ideal drilling process of a full-size bit rotating around a bit axis is simulated by combining a PDC bit geometry and a PDC bit kinematics related theory and using spatial coordinate transformation. By carrying out the Boolean difference calculation of the continuous PDC cutting teeth and the stratum rock mass, the size of the working area of each PDC cutting tooth of the PDC drill bit tooth distribution structure design under the drilling parameter state can be obtained.

The manufacturing method of the PDC drill bit can calculate the working area of the PDC drill bit teeth in any different shapes, and compared with calculation programs and calculation methods designed by other researchers, the manufacturing method of the PDC drill bit has the advantages of being high in calculation speed, convenient to use, strong in universality and good in stability due to the fact that a bottom programming language of C + + and a glue programming language of python are used.

The above description is only a few embodiments of the present invention, and those skilled in the art can make various changes or modifications to the embodiments of the present invention according to the disclosure of the application document without departing from the spirit and scope of the present invention.

Claims

1. An inside and outside distinct PDC drill bit, comprising: a bit center within a nose of a crown curve of the PDC bit and a bit shoulder outside of a nose of a crown curve of the PDC bit; the drill bit center portion is provided with center portion cutting teeth, and the drill bit shoulder portion is provided with shoulder portion cutting teeth;

2. The inside-outside differential PDC bit of claim 1 wherein the difference between the average of the working areas of the shoulder cutters and the average of the working areas of the center cutters is greater than or equal to 20% and less than or equal to 86% of the average of the working areas of the center cutters.

3. The distinct inside and outside PDC bit of claim 1, wherein the working area of the center section cutter is less than the working area of the shoulder section cutter.

4. The distinct inside and outside PDC bit of claim 3, wherein the difference between the working area of the shoulder cutter and the working area of the center cutter is greater than or equal to 20% of the working area of the center cutter.

5. The dissimilar PDC bit of claim 1, wherein the central cutting elements comprise at least 3 small area cutting elements having a working area less than the working area of the other cutting elements on the crown curve.

6. The PDC bit of claim 1 wherein at least some of the central cutting teeth are pointed cutting teeth.

7. The PDC drill bit of claim 6 wherein the cutting elements having a pointed portion have a working area less than a working area of a circular tooth of the same diameter by a difference of 10% or more.

8. The distinct inside and outside PDC drill bit of claim 6 wherein at least some of the shoulder cutters are pointed cutters or the shoulder cutters are rounded cutters.

9. The dissimilar PDC bit of any one of claims 6 to 8, wherein the cutting teeth having the pointed tooth portion are hatchet, curved cutter or concave hatchet teeth.

10. A method of manufacturing a PDC bit, comprising:

making a bit body comprising a bit center portion and bit shoulders, the bit center portion being located within a nose portion of a crown curve of the PDC bit, the bit shoulders being located outside of the nose portion of the crown curve of the PDC bit;