CN116464392A - Bit cutting structure, PDC bit with multilayer cutting structure and application of PDC bit - Google Patents

Abstract

The invention provides a bit cutting structure, a PDC bit with a multi-layer cutting structure and application thereof, wherein the PDC bit comprises a head part and a cutting unit, the cutting unit is fixedly arranged on the head part and comprises first cutting components, second cutting components and blades, the number of the blades is the sum of the number of the first cutting components and the number of the second cutting components, the blades are circumferentially arranged on the outer surface of the head part, chip grooves are formed between two adjacent blades, the first cutting components are respectively fixedly arranged on blades with the number corresponding to the first cutting components, and the second cutting components are fixedly arranged on blades with the number corresponding to the second cutting components; each cutting assembly comprises at least one group of cutting edges, and cutting teeth are arranged on the cutting edges and can perform cutting operation on the rock mass. The multi-layer cutting structure drill bit can effectively increase the single drilling length of the drill bit, reduce the number of tripping operations and prolong the service life of the drill bit under the conditions of complex difficult-to-drill stratum and enhanced drilling parameters.

Description

Bit cutting structure, PDC bit with multilayer cutting structure and application of PDC bit

Technical Field

The invention relates to the technical field of petroleum and natural gas drilling tools, in particular to a bit cutting structure, a PDC bit with a multi-layer cutting structure and application thereof.

Background

PDC drill bits are widely used in the oil and gas drilling industry due to a series of advantages of high rock breaking efficiency, long service life, good stability and the like, and the PDC drill bits are replaced by the PDC drill bits in soft to medium hard stratum. The PDC drill bit works under the conditions of low bit pressure and high rotating speed, and can obtain better technical and economic effects. The drilling speed is a consistent target of drilling, and during the drilling operation of the PDC drill bit, the drilling speed can keep high mechanical drilling speed by strengthening drilling parameters (drilling pressure, rotating speed, torque and the like) to achieve remarkable effect even if the PDC teeth are worn in half. However, under the working condition, the 'one-trip drilling' can not be realized in a specific stratum and a well section, and the drilling cost is high.

Disclosure of Invention

The present invention aims to address at least one of the above-mentioned deficiencies of the prior art. For example, one of the purposes of the present invention is to provide a cutting structure of a drill bit, a PDC drill bit with a multi-layer cutting structure and an application thereof, so that the drill bit can extend the service life of the drill bit without reducing the mechanical drilling speed of the drill bit under the condition of complex difficult-to-drill stratum drilling, especially strengthening drilling parameters (limit parameters), increase the single drilling length of the drill bit, reduce the number of tripping and tripping, reduce the drilling cost, and be hopeful to realize one drilling in specific stratum and well section.

In order to achieve the above object, the technical scheme of the present invention is as follows:

the invention provides a PDC drill bit with a multi-layer cutting structure, which comprises a head part and a cutting unit, wherein the cutting unit is fixedly arranged on the head part and comprises a plurality of first cutting assemblies, a plurality of second cutting assemblies and a plurality of blades, wherein the number of the blades is the sum of the number of the first cutting assemblies and the number of the second cutting assemblies, the plurality of blades are circumferentially arranged on the outer surface of the head part, chip grooves are formed between two adjacent blades, the plurality of first cutting assemblies are respectively fixedly arranged on blades corresponding to the plurality of first cutting assemblies, and the plurality of second cutting assemblies are respectively fixedly arranged on blades corresponding to the plurality of second cutting assemblies; each of the first and second cutting assemblies includes at least one set of cutting edges, each set of cutting edges having a plurality of cutting teeth mounted thereon, the cutting teeth being capable of performing cutting operations on a rock mass during drilling.

Optionally, each of the plurality of first cutting assemblies includes first, second and third cutting edges fixedly connected to each other, the first cutting edge having a contour outer diameter greater than a contour outer diameter of the second cutting edge, the second cutting edge having a contour outer diameter greater than a contour outer diameter of the third cutting edge.

Optionally, each of the plurality of second cutting assemblies includes fourth and fifth cutting edges fixedly connected to each other, the fourth cutting edge having a contour outer diameter equal to a contour outer diameter of the first cutting edge, and the fifth cutting edge having a contour outer diameter equal to a contour outer diameter of the third cutting edge.

Optionally, each of the plurality of first cutting assemblies includes a sixth cutting edge, and each of the plurality of second cutting assemblies includes a seventh cutting edge, the sixth cutting edge having a profile outer diameter that is greater than the profile outer diameter of the seventh cutting edge.

Optionally, the first cutting edge and the fourth cutting edge are provided with a plurality of first radial water holes, two ends of each of the first radial water holes penetrate through two sides of the first cutting edge and the fourth cutting edge, and the first radial water holes can communicate two adjacent chip grooves so as to reduce drilling resistance of drilling fluid to the cutting edges.

Optionally, the sixth cutting edge is provided with a plurality of second radial water holes, two ends of each of the plurality of second radial water holes penetrate through two sides of the sixth cutting edge, and the second radial water holes can communicate two adjacent chip grooves so as to reduce drilling resistance of drilling fluid to the cutting edge.

Optionally, the end head part is provided with a plurality of nozzles, and the openings of the nozzles are arranged in the chip removal groove so as to communicate the nozzles with the chip removal groove, and drilling fluid can flow into the chip removal groove through the nozzles.

Optionally, the mounting direction of the cutting teeth on the cutting edge is kept consistent, and the cutting teeth are plane teeth or non-plane teeth; the PDC drill bit further comprises a connecting portion, one end of the connecting portion is fixedly connected with the end head portion, and the other end of the connecting portion can be connected with a drill rod so that the PDC drill bit can be installed on the drill rod.

Optionally, the plurality of first cutting assemblies and the plurality of second cutting assemblies are disposed at intervals along a circumferential intersection of the tip portion to promote stability of the PDC bit during cutting operations.

In another aspect, the present invention provides the use of a PDC bit having a multi-layer cutting structure as described above in drilling operations, the use including first performing cutting operations using a cutting edge having a largest outside diameter of the profile, and after the cutting edge having the largest outside diameter of the profile wears, then performing composite cutting operations using a cutting edge having a second and/or smallest outside diameter of the profile to extend the single pass distance of the PDC bit.

In still another aspect, the present invention provides a cutting structure of a drill bit, the cutting structure of a drill bit including a cutting unit for mounting on an end portion of the drill bit, the cutting unit including a plurality of first cutting assemblies, a plurality of second cutting assemblies, and a plurality of blades, wherein the number of blades is a sum of the number of first cutting assemblies and the number of second cutting assemblies, the plurality of blades are circumferentially disposed on an outer surface of the end portion, junk slots are formed between two adjacent blades, the plurality of first cutting assemblies are fixedly mounted on blades corresponding to the plurality of first cutting assemblies, respectively, and the plurality of second cutting assemblies are fixedly mounted on blades corresponding to the plurality of second cutting assemblies, respectively; each of the first and second cutting assemblies includes at least one set of cutting edges, each set of cutting edges having a plurality of cutting teeth mounted thereon, the cutting teeth being capable of performing cutting operations on a rock mass during drilling.

Compared with the prior art, the invention has the beneficial effects that at least one of the following contents is included:

(1) The staggered blade structure can improve the working stability of the drill bit, disperse the lateral force of each cutting tooth of the drill bit, reduce the stress of the cutting tooth and the well wall and protect the cutting tooth; a multi-space blade structure is formed, so that the working stability of the drill bit is improved;

(2) The design of the multi-layer profile coverage tooth-distribution step cutting structure is that after the first layer profile coverage cutting teeth are worn, the two-stage drill bit formed by the second layer profile coverage cutting teeth and the low-wear drill bit inner cone continues to drill, the service time of the drill bit is prolonged, and the single-pass footage of the drill bit is increased;

(3) And reconstructing the double-stage drill bit structure, wherein the cutting teeth slightly worn in the original inner cone nose part of the drill bit and the second contour covered cutting teeth form a stepped double-stage cutting structure in the axial direction of the drill bit, namely after the first contour covered cutting teeth are worn, the whole drill bit is reconstructed into the double-stage drill bit structure. In the drilling process of the reconstructed double-stage drill bit, the central cutting part releases the confining pressure, so that the rock breaking difficulty of the outer rock cut by the second contour can be reduced, and the rock breaking efficiency is improved;

(4) The radial water hole structure of the stepped blade can improve the radial water force action in the cutting and drilling process of the drill bit and accelerate the abrasion of the rest blade body after the abrasion of the first profile cutting tooth, so that the second profile cutting tooth participates in cutting in time, and the normal drilling of the drill bit is restored;

(5) The novel PDC drill bit with the multi-layer profile coverage cutting tooth structure can effectively prolong the downhole operation time of the drill bit, increase the single drilling length of the drill bit, reduce the number of tripping and obtain better economic benefit under the conditions of complex difficult-to-drill stratum and reinforced drilling parameters.

Drawings

The foregoing and other objects and/or features of the invention will become more apparent from the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a schematic view of a PDC bit having a multi-layer cutting structure of exemplary embodiment 1 of the present invention.

FIG. 2 illustrates a top view of a PDC bit having a multi-layer cutting structure of exemplary embodiment 1 of the present invention.

Fig. 3 shows an enlarged view at a in fig. 1.

Fig. 4 shows an enlarged view at B in fig. 1.

FIG. 5 illustrates a cutter cover tooth layout diagram of a PDC bit having a multi-layered cutting structure of exemplary embodiment 1 of the present invention.

FIG. 6 illustrates a schematic view of an exemplary embodiment 1 of the present invention after wear of a first cutting edge in a PDC bit having a multi-layer cutting structure.

FIG. 7 illustrates a top view of a PDC bit having a multi-layer cutting structure of exemplary embodiment 1 of the present invention after wear of a first cutting edge.

FIG. 8 illustrates a schematic view of a cutter cover tooth layout after wear of a first cutting edge in a PDC bit having a multi-layer cutting structure in accordance with exemplary embodiment 1 of the present invention.

FIG. 9 illustrates a schematic view of a PDC bit having a multi-layer cutting structure of exemplary embodiment 2 of the present invention.

FIG. 10 illustrates a top view of a PDC bit having a multi-layer cutting structure of exemplary embodiment 2 of the present invention.

Reference numerals illustrate:

1-nose head, 11-nozzle, 2-cutting unit, 21-blade, 22-first cutting assembly, 221-first cutting edge, 2211-first radial water eye, 222-second cutting edge, 223-third cutting edge, 224-sixth cutting edge, 2241-second radial water eye, 23-second cutting assembly, 231-fourth cutting edge, 232-fifth cutting edge, 233-seventh cutting edge, 24-cutting tooth, 3-connection, 4-junk slot, 5-third and fifth cutting edge envelope, 6-pre-wear first and fourth cutting edge envelope, 7-post-wear first and fourth cutting edge envelope, 8-second cutting edge envelope, 9-bit gage.

Detailed Description

Hereinafter, the bit cutting structure, the PDC bit having the multi-layered cutting structure, and the application thereof of the present invention will be described in detail with reference to exemplary embodiments.

In the description of the present application, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate description of the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present application.

The terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.

In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

The applicant found that the reason for the failure to achieve a "one pass" in a particular formation, well section, is that: in the drilling operation process of the PDC drill bit, the drilling parameters (drilling pressure, rotating speed, torque and the like) are strengthened, so that a remarkable effect is achieved, and the drilling with a high mechanical drilling rate can be maintained even if the PDC teeth are worn in half. However, under the working condition, the nose part and the shoulder PDC composite sheet of the blade of the drill bit are seriously damaged in a certain period of drilling due to the large impact load and high abrasion, so that the drill bit is ground down from the nose part to form a step, a ruler cannot be put into operation, the drill bit is scrapped, the service life of the drill bit is limited, and the drilling cost is high because one drilling operation cannot be realized in a specific stratum and a well section.

Based on the above, the invention provides a bit cutting structure, a PDC bit with a multi-layer cutting structure and an application thereof, wherein the PDC bit with the multi-layer cutting structure comprises a head part and a cutting unit, wherein the cutting unit is fixedly arranged on the head part and comprises a plurality of first cutting components, a plurality of second cutting components and a plurality of blades, the number of the blades is the sum of the number of the first cutting components and the number of the second cutting components, the plurality of blades are circumferentially arranged on the outer surface of the head part, chip grooves are formed between two adjacent blades, the plurality of first cutting components are fixedly arranged on blades corresponding to the plurality of first cutting components respectively, and the plurality of second cutting components are fixedly arranged on blades corresponding to the plurality of second cutting components respectively; each of the first and second cutting assemblies includes at least one set of cutting edges, each set of cutting edges having a plurality of cutting teeth mounted thereon, the cutting teeth being capable of performing cutting operations on a rock mass during drilling.

The novel PDC drill bit with the multi-layer profile coverage cutting tooth structure can effectively prolong the downhole operation time of the drill bit, increase the single drilling length of the drill bit, reduce the number of tripping and tripping operations and obtain better economic benefit under the conditions of complex difficult-to-drill stratum and enhanced drilling parameters.

Example embodiment 1

The present exemplary embodiment provides a PDC bit structure having a multi-layered cutting structure.

FIG. 1 illustrates a schematic view of a PDC bit having a multi-layer cutting structure of exemplary embodiment 1 of the present invention; FIG. 2 illustrates a top view of a PDC bit having a multi-layer cutting structure of exemplary embodiment 1 of the present invention; FIG. 3 shows an enlarged view at A in FIG. 1; FIG. 4 shows an enlarged view at B in FIG. 1; FIG. 5 illustrates a cutter cover tooth layout diagram of a PDC bit having a multi-layered cutting structure of exemplary embodiment 1 of the present invention; FIG. 6 illustrates a schematic view of an exemplary embodiment 1 of the present invention after wear of a first cutting edge in a PDC bit having a multi-layer cutting structure; FIG. 7 illustrates a top view of a PDC bit having a multi-layer cutting structure of exemplary embodiment 1 of the present invention after wear of a first cutting edge; FIG. 8 illustrates a schematic view of a cutter cover tooth layout after wear of a first cutting edge in a PDC bit having a multi-layer cutting structure in accordance with exemplary embodiment 1 of the present invention.

As shown in fig. 1 to 8, the PDC bit having a multi-layered cutting structure described in the present exemplary embodiment may include a tip portion 1, a cutting unit 2, and a connection portion 3, wherein one end of the tip portion 1 may be fixedly connected with the connection portion 3, the other end may be formed in a rounded shape, the cutting unit 2 may be fixedly mounted on the rounded head of the tip portion 1, and the connection portion 3 may be connected with a drill rod, thereby fixedly mounting the bit as a whole at the end of the drill rod. Various fixing connection modes such as welding, integral molding, etc. can be adopted among the end head part 1, the cutting unit 2 and the connecting part 3, and the invention is not limited to this.

In the present embodiment, the cutting unit 2 may include blades 21, first cutting assemblies 22, second cutting assemblies 23, and cutting teeth 24, wherein the number of blades 21 may be 5, 5 blades 21 are mounted on the outer surface of the tip part 1 in a circumferential distribution of the tip part 1, the number of first cutting assemblies 22 may be 3, and 3 first cutting assemblies are mounted on 3 of the 5 blades 21, respectively; the number of second cutting assemblies 23 may be 2, mounted on the other 2 of the 5 blades 21, respectively; the 3 first cutting assemblies 22 and the 2 second cutting assemblies 23 may be disposed at intervals intersecting each other, that is, the 2 second cutting assemblies 23 are not disposed adjacently, that is, at least 1 first cutting assembly 22 is disposed between the 2 second cutting assemblies 23, but the present invention is not limited thereto, and the number of blades 21, the first cutting assemblies 22, and the second cutting assemblies 23 may be other, so long as the number of blades 21 is equal to the sum of the first cutting assemblies 22 and the second cutting assemblies 23; the first cutting assemblies 22 and the second cutting assemblies 23 may also be disposed at non-intersecting intervals, that is, all of the first cutting assemblies 22 may be disposed adjacent to each other and all of the second cutting assemblies 23 may be disposed adjacent to each other.

Alternatively, the first cutting assembly 22 may include a first cutting edge 221, a second cutting edge 222, and a third cutting edge 223, with the first cutting edge 221, the second cutting edge 222, and the third cutting edge 223 being layered in a staggered configuration, wherein the first cutting edge 221 has a larger outer diameter profile than the second cutting edge 222, and the second cutting edge 222 has a larger outer diameter profile than the third cutting edge 223, that is, the first cutting edge 221 is higher than the second cutting edge 222, and the second cutting edge 222 is higher than the third cutting edge 223, as viewed in the bit placement direction of fig. 1.

Alternatively, the second cutting assembly 23 may include a fourth cutting edge 231 and a fifth cutting edge 232, the fourth cutting edge 231 and the fifth cutting edge 232 may be layered, the fourth cutting edge 231 having a profile outer diameter greater than that of the fifth cutting edge 232, and the fourth cutting edge 231 having a profile outer diameter equal to that of the first cutting edge 221, and the fifth cutting edge 232 having a profile outer diameter equal to that of the third cutting edge 223; that is, the fourth cutting edge 231 is higher than the fifth cutting edge 232 as seen in the bit placement direction in fig. 1, and the fourth cutting edge 231 is the same height as the first cutting edge 221, and the fifth cutting edge 232 is the same height as the third cutting edge 223.

In this embodiment, the number of the cutting teeth 24 may be plural, and the cutting teeth 24 are respectively installed on the rake face of each cutting edge, that is, the installation directions of the cutting teeth 24 on each cutting edge are kept consistent, and all the cutting teeth 24 face the cutting direction of the cutting edge, and the cutting teeth 24 can rotate along with the drill bit and cut and crush the rock wall at the bottom of the well under the driving of the cutting edge, so as to realize the drilling function of the drill bit; the cutting teeth 24 may be selected to be planar teeth or non-planar teeth, and the number of the cutting teeth 24 may be arbitrarily selected, and the present invention is not particularly limited.

The multi-stage cutting structure of the first cutting assembly 22 and the second cutting assembly 23 is actually formed by the nose and the outer multiple layer profile cover cutting teeth outside the nose of the crown of the drill bit, the first layer profile (i.e., the first cutting assembly 22) being disposed from the core-gage position of the drill bit entirely over the cutting teeth, the second layer profile (i.e., the second cutting assembly 23) being disposed from the nose-gage position of the crown over the cutting teeth, the envelope of the second layer profile cover cutting teeth not being higher than the inner profile of the first layer profile cover cutting teeth.

Optionally, a junk slot 4 may be formed between two adjacent blades 21 on the end head 1,7 nozzles 11 may be formed on the end head 1, the 7 nozzles 11 may be located in the junk slot 4, the nozzles 11 may be communicated with the drill pipe and the inside of the drill bit, drilling fluid introduced into the drill pipe may enter the drill bit and be sprayed out along the nozzles 11 and enter the junk slot 4, during drilling of the drill bit, cuttings generated by the cutting blade may enter the junk slot 4 first, and be mixed with drilling fluid sprayed out from the nozzles 11 and then be carried out of the wellbore along with upward flowback of the drilling fluid, thereby avoiding drilling sticking accidents caused by accumulation of cuttings in the pit; however, the present invention is not limited thereto, and the number of junk slots 4 may be any number of nozzles 11 depending on the number of blades 21.

Alternatively, blades 21 may be formed with a bit gage 9 at one end of the cutting assembly, and the outer surface of bit gage 9 may be provided with a wear layer or wear element to protect blades 21 from wear during drilling.

Optionally, the first cutting edge 221 and the fourth cutting edge 231 may be further provided with a plurality of first radial water holes 2211, the first radial water holes 2211 penetrate through two sides of the first cutting edge 221 and the fourth cutting edge 231 along the thickness direction of the first cutting edge 221 and the fourth cutting edge 231, that is, the first radial water holes 2211 may communicate two adjacent junk slots 4, during the rotary drilling process of the drill bit, the drilling fluid ejected from the nozzle 11 may circulate between each junk slot 4 along the first radial water holes 2211, so that the additional radial resistance applied by the drilling fluid to the cutting edges during the rotary drilling process of the drill bit is reduced, and the cutting of the drill bit to the rock wall at the bottom of the well is smoother; the number of the first radial water holes 2211 can be any number, which is not limited in the present invention.

As shown in fig. 5 and 8, since the contour outer diameters of the third cutting edge and the fifth cutting edge are identical, the envelope trajectories thereof coincide, i.e., the third and fifth cutting edge envelopes 5 in fig. 5 and 8, and since the contour outer diameters of the first cutting edge and the fourth cutting edge are identical, the envelope trajectories thereof coincide, i.e., the pre-wear first and fourth cutting edge envelopes 6 in fig. 5 and the post-wear first and fourth cutting edge envelopes 7 in fig. 8, the envelope of the second cutting edge is the second cutting edge envelope 8 in fig. 5 and 8; the outer diameter of the profile of the first and fourth cutting edge envelopes 6 before the drill is worn is maximized, in which case the cutting operation is mainly performed by means of the first and fourth cutting edges, the outer diameter of the profile of which gradually decreases as the first and fourth cutting edges are worn, and the envelopes are finally formed into the first and fourth cutting edge envelopes 7 after the wear, in which case the cutting operation is mainly performed by means of the second, third and fifth cutting edges.

As can be understood from the above arrangements of the cutting edges and the drilling principle of the drill bit according to fig. 1 to 8, when the drill bit performs drilling operation, firstly, the first cutting edge 221 and the fourth cutting edge 231 with the largest outline outer diameter are used to perform cutting operation on the rock wall at the bottom of the well, and at this time, the second cutting edge 222, the third cutting edge 223 and the fifth cutting edge 232 are in an inactive state because the outline outer diameter is smaller and cannot contact the rock wall; as the cutting operation proceeds, the first cutting edge 221 and the fourth cutting edge 231 also wear, and the outer diameters of the profiles thereof gradually decrease, and when the outer diameters of the profiles (i.e., the heights in fig. 1) of the first cutting edge 221 and the fourth cutting edge 231 wear to be identical to the second cutting edge 222 (as shown in fig. 6 and 7), the second cutting edge 222 and the third cutting edge 223 form a two-stage drill bit structure, the second cutting edge 222 starts to contact the bottom wall of the well, and at this time, the cutting operation is performed by means of the second cutting edge 222, and when the wear degree is further increased, the second cutting edge 222 also wears until the third cutting edge 223 starts to contact the bottom wall of the well, and the third cutting edge 223 can continue to perform the cutting operation on the bottom wall of the well. The multi-layer staggered structure design of the cutting edge can perform composite cutting operation, prolong the service life of the drill bit and increase the single-pass length of the drill bit.

Example embodiment 2

The present exemplary embodiment provides another PDC bit structure having a multi-layered cutting structure.

FIG. 9 illustrates a schematic view of a PDC bit having a multi-layer cutting structure of exemplary embodiment 2 of the present invention; FIG. 10 illustrates a top view of a PDC bit having a multi-layer cutting structure of exemplary embodiment 2 of the present invention.

As shown in fig. 9 and 10, the PDC bit having a multi-layered cutting structure described in the present exemplary embodiment may include a tip portion 1, a cutting unit 2, and a connection portion 3, wherein one end of the tip portion 1 may be fixedly connected with the connection portion 3, the other end may be formed in a rounded shape, the cutting unit 2 may be fixedly mounted on the rounded head of the tip portion 1, and the connection portion 3 may be connected with a drill rod, thereby fixedly mounting the bit as a whole at the end of the drill rod. Various fixing connection modes such as welding, integral molding, etc. can be adopted among the end head part 1, the cutting unit 2 and the connecting part 3, and the invention is not limited to this.

In the present embodiment, the cutting unit 2 may include blades 21, first cutting assemblies 22, second cutting assemblies 23, and cutting teeth 24, wherein the number of blades 21 may be 8, the 8 blades 21 are mounted on the outer surface of the tip part 1 in a circumferential distribution of the tip part 1, the number of first cutting assemblies 22 may be 4, and the 4 first cutting assemblies are mounted on 4 of the 8 blades 21, respectively; the number of second cutting assemblies 23 may be 4, mounted on the other 4 of the 8 blades 21, respectively; the 4 first cutting assemblies 22 and the 4 second cutting assemblies 23 may be disposed at an interval intersecting each other, that is, the 4 second cutting assemblies 23 are not disposed adjacently, that is, 1 first cutting assembly 22 is disposed between 2 second cutting assemblies 23, but the present invention is not limited thereto, and the number of blades 21, first cutting assemblies 22, and second cutting assemblies 23 may be other, so long as the number of blades 21 is equal to the sum of the first cutting assemblies 22 and the second cutting assemblies 23; the first cutting assemblies 22 and the second cutting assemblies 23 may also be disposed at non-intersecting intervals, that is, all of the first cutting assemblies 22 may be disposed adjacent to each other and all of the second cutting assemblies 23 may be disposed adjacent to each other.

Alternatively, the first cutting assembly 22 may include a sixth cutting edge 224, the second cutting assembly 23 may include a seventh cutting edge 233, and the sixth cutting edge 224 and the seventh cutting edge 233 may constitute a layered structure, with the sixth cutting edge 224 having a larger outer diameter profile than the seventh cutting edge 233, that is, the sixth cutting edge 224 is higher than the seventh cutting edge 233 as viewed in the bit placement direction in fig. 9.

In this embodiment, the number of the cutting teeth 24 may be plural, and the cutting teeth 24 are respectively installed on the rake face of each cutting edge, that is, the installation directions of the cutting teeth 24 on each cutting edge are kept consistent, and all the cutting teeth 24 face the cutting direction of the cutting edge, and the cutting teeth 24 can rotate along with the drill bit and cut and crush the rock wall at the bottom of the well under the driving of the cutting edge, so as to realize the drilling function of the drill bit; the cutting teeth 24 may be selected to be planar teeth or non-planar teeth, and the number of the cutting teeth 24 may be arbitrarily selected, and the present invention is not particularly limited.

The multi-stage cutting structure of the first cutting assembly 22 and the second cutting assembly 23 is actually formed by the nose and the outer multiple layer profile cover cutting teeth outside the nose of the crown of the drill bit, the first layer profile (i.e., the first cutting assembly 22) being disposed from the core-gage position of the drill bit entirely over the cutting teeth, the second layer profile (i.e., the second cutting assembly 23) being disposed from the nose-gage position of the crown over the cutting teeth, the envelope of the second layer profile cover cutting teeth not being higher than the inner profile of the first layer profile cover cutting teeth.

Optionally, a junk slot 4 can be formed between two adjacent blades 21 on the end head 1,6 nozzles 11 can be formed on the end head 1, the 6 nozzles 11 are all positioned in the junk slot 4, the nozzles 11 can be communicated with the drill rod and the inside of the drill bit, drilling fluid introduced into the drill rod can enter the drill bit and be sprayed out along the nozzles 11 and enter the junk slot 4, during the drilling process of the drill bit, the cuttings generated during the cutting operation of the cutting blade on the rock wall at the bottom of the well can firstly enter the junk slot 4 and be mixed with drilling fluid sprayed out of the nozzles 11 and then be carried out of the well bore along with the upward flowback of the drilling fluid, so that the drilling accident caused by the accumulation of the cuttings in the well is avoided; however, the present invention is not limited thereto, and the number of junk slots 4 may be any number of nozzles 11 depending on the number of blades 21.

Alternatively, blades 21 may be formed with a bit gage 9 at one end of the cutting assembly, and the outer surface of bit gage 9 may be provided with a wear layer or wear element to protect blades 21 from wear during drilling.

Optionally, the sixth cutting edge 224 may further be provided with a plurality of second radial water holes 2241, and the second radial water holes 2241 penetrate through two sides of the sixth cutting edge 224 along the thickness direction of the sixth cutting edge 224, that is, the second radial water holes 2241 may communicate two adjacent junk slots 4, during the rotary drilling process of the drill bit, the drilling fluid ejected from the nozzle 11 may circulate between each junk slot 4 along the second radial water holes 2241, so that the additional radial resistance applied by the drilling fluid to the cutting edge during the rotary drilling process of the drill bit is reduced, and the cutting of the drill bit to the bottom wall of the well is smoother; the number of the second radial water holes 2241 may be any number, which is not limited in the present invention.

As can be understood from the above arrangement of the cutting edges and the drilling principle of the drill bit in fig. 9 and 10, when the drill bit performs drilling operation, firstly, the sixth cutting edge 224 with the largest outline outer diameter is used to perform cutting operation on the rock wall at the bottom of the well, and at this time, the seventh cutting edge 233 is in an inactive state because the outline outer diameter is smaller and cannot contact the rock wall; as the cutting operation proceeds, the sixth cutting edge 224 is worn, and the outer diameter of the profile thereof is gradually reduced, and when the outer diameter of the profile of the sixth cutting edge 224 (i.e., the height in fig. 9) is worn to be the same as the seventh cutting edge 233, the seventh cutting edge 233 comes into contact with the bottom wall, and at this time, the cutting operation is mainly performed by means of the seventh cutting edge 233. The multi-layer staggered structure design of the cutting edge can perform composite cutting operation, prolong the service life of the drill bit and increase the single-pass length of the drill bit.

Example embodiment 3

The present exemplary embodiment provides the use of the PDC bit having a multi-layered cutting structure described in the above exemplary embodiment 1 or 2 in drilling operations.

With the PDC bit structure having the multi-layered cutting structure described in the exemplary embodiment 1, as shown in fig. 5 and 8, since the contour outer diameters of the third cutting edge and the fifth cutting edge coincide, the envelope trajectories thereof coincide, i.e., the third and fifth cutting edge envelopes 5 in fig. 5 and 8, and since the contour outer diameters of the first cutting edge and the fourth cutting edge coincide, the envelope trajectories thereof coincide, i.e., the pre-wear first and fourth cutting edge envelopes 6 in fig. 5 and the post-wear first and fourth cutting edge envelopes 7 in fig. 8, the envelope of the second cutting edge is the second cutting edge envelope 8 in fig. 5 and 8; the outer diameter of the profile of the first and fourth cutting edge envelopes 6 before the drill is worn is maximized, in which case the cutting operation is mainly performed by means of the first and fourth cutting edges, the outer diameter of the profile of which gradually decreases as the first and fourth cutting edges are worn, and the envelopes are finally formed into the first and fourth cutting edge envelopes 7 after the wear, in which case the cutting operation is mainly performed by means of the second, third and fifth cutting edges.

As can be understood from the above arrangements of the cutting edges and the drilling principle of the drill bit according to fig. 1 to 8, when the drill bit performs drilling operation, firstly, the first cutting edge 221 and the fourth cutting edge 231 with the largest outline outer diameter are used to perform cutting operation on the rock wall at the bottom of the well, and at this time, the second cutting edge 222, the third cutting edge 223 and the fifth cutting edge 232 are in an inactive state because the outline outer diameter is smaller and cannot contact the rock wall; as the cutting operation proceeds, the first cutting edge 221 and the fourth cutting edge 231 also wear, and the outer diameters of the profiles thereof gradually decrease, and when the outer diameters of the profiles (i.e., the heights in fig. 1) of the first cutting edge 221 and the fourth cutting edge 231 wear to be identical to the second cutting edge 222 (as shown in fig. 6 and 7), the second cutting edge 222 and the third cutting edge 223 form a two-stage drill bit structure, the second cutting edge 222 starts to contact the bottom wall of the well, and at this time, the cutting operation is performed by means of the second cutting edge 222, and when the wear degree is further increased, the second cutting edge 222 also wears until the third cutting edge 223 starts to contact the bottom wall of the well, and the third cutting edge 223 can continue to perform the cutting operation on the bottom wall of the well. The multi-layer staggered structure design of the cutting edge can perform composite cutting operation, prolong the service life of the drill bit and increase the single-pass length of the drill bit.

With the PDC bit structure having the multi-layered cutting structure described in exemplary embodiment 2, as shown in fig. 9 and 10, when the drill bit performs drilling operation, firstly, the sixth cutting edge 224 with the largest profile outer diameter is used to perform cutting operation on the rock wall at the bottom of the well, and at this time, the seventh cutting edge 233 is in an inactive state because the profile outer diameter is smaller, and cannot contact the rock wall; as the cutting operation proceeds, the sixth cutting edge 224 is worn, and the outer diameter of the profile thereof is gradually reduced, and when the outer diameter of the profile of the sixth cutting edge 224 (i.e., the height in fig. 9) is worn to be the same as the seventh cutting edge 233, the seventh cutting edge 233 comes into contact with the bottom wall, and at this time, the cutting operation is mainly performed by means of the seventh cutting edge 233. The multi-layer staggered structure design of the cutting edge can perform composite cutting operation, prolong the service life of the drill bit and increase the single-pass length of the drill bit.

In summary, the inventive dislocation blade structure can improve the working stability of the drill, disperse the lateral force of each cutting tooth of the drill, reduce the stress of the cutting tooth and the well wall, and protect the cutting tooth; a multi-space blade structure is formed, so that the working stability of the drill bit is improved; the design of the multi-layer profile coverage tooth-distribution step cutting structure is that after the first layer profile coverage cutting teeth are worn, the two-stage drill bit formed by the second layer profile coverage cutting teeth and the low-wear drill bit inner cone continues to drill, the service time of the drill bit is prolonged, and the single-pass footage of the drill bit is increased; and reconstructing the double-stage drill bit structure, wherein the cutting teeth slightly worn in the original inner cone nose part of the drill bit and the second contour covered cutting teeth form a stepped double-stage cutting structure in the axial direction of the drill bit, namely after the first contour covered cutting teeth are worn, the whole drill bit is reconstructed into the double-stage drill bit structure. In the drilling process of the reconstructed double-stage drill bit, the central cutting part releases the confining pressure, so that the rock breaking difficulty of the outer rock cut by the second contour can be reduced, and the rock breaking efficiency is improved; the radial water hole structure of the stepped blade can improve the radial water force action in the cutting and drilling process of the drill bit and accelerate the abrasion of the rest blade body after the abrasion of the first profile cutting tooth, so that the second profile cutting tooth participates in cutting in time, and the normal drilling of the drill bit is restored; the novel PDC drill bit with the multi-layer profile coverage cutting tooth structure can effectively prolong the downhole operation time of the drill bit, increase the single drilling length of the drill bit, reduce the number of tripping and obtain better economic benefit under the conditions of complex difficult-to-drill stratum and reinforced drilling parameters.

Although the present invention has been described above with reference to the exemplary embodiments and the accompanying drawings, it should be apparent to those of ordinary skill in the art that various modifications can be made to the above-described embodiments without departing from the spirit and scope of the claims.

Claims (11)

1. A PDC drill bit having a multi-layer cutting structure, characterized in that the PDC drill bit includes a tip portion and a cutting unit, wherein,

the cutting unit is fixedly arranged on the end head and comprises a plurality of first cutting assemblies, a plurality of second cutting assemblies and a plurality of blades, wherein the number of the blades is the sum of the number of the first cutting assemblies and the number of the second cutting assemblies, the plurality of blades are circumferentially arranged on the outer surface of the end head, chip grooves are formed between two adjacent blades, the plurality of first cutting assemblies are respectively and fixedly arranged on the blades corresponding to the plurality of first cutting assemblies, and the plurality of second cutting assemblies are respectively and fixedly arranged on the blades corresponding to the plurality of second cutting assemblies;

each of the first and second cutting assemblies includes at least one set of cutting edges, each set of cutting edges having a plurality of cutting teeth mounted thereon, the cutting teeth being capable of performing cutting operations on a rock mass during drilling.

2. The PDC bit having a multi-layered cutting structure of claim 1 wherein each of the plurality of first cutting assemblies comprises first, second and third cutting edges fixedly coupled to one another, the first cutting edge having a contour outer diameter greater than a contour outer diameter of the second cutting edge, the second cutting edge having a contour outer diameter greater than a contour outer diameter of the third cutting edge.

3. The PDC bit having a multi-layered cutting structure of claim 2 wherein each of the plurality of second cutting assemblies comprises fourth and fifth cutting edges fixedly coupled to one another, the fourth cutting edge having a contour outer diameter equal to a contour outer diameter of the first cutting edge and the fifth cutting edge having a contour outer diameter equal to a contour outer diameter of the third cutting edge.

4. The PDC bit having a multi-layer cutting structure of claim 1 wherein each of the number of first cutting assemblies comprises a sixth cutting edge and each of the number of second cutting assemblies comprises a seventh cutting edge, the sixth cutting edge having a contour outer diameter that is greater than a contour outer diameter of the seventh cutting edge.

5. The PDC bit having a multi-layered cutting structure of claim 3 wherein the first and fourth cutting edges are provided with a plurality of first radial pockets, each of the plurality of first radial pockets extending through both sides of the first and fourth cutting edges, the first radial pockets being capable of communicating adjacent ones of the junk slots to reduce drilling resistance of drilling fluid to the cutting edges.

6. The PDC bit with multi-layer cutting structure of claim 4 wherein a plurality of second radial water holes are provided on the sixth cutting edge, two ends of each of the plurality of second radial water holes penetrate through two sides of the sixth cutting edge, and the second radial water holes can communicate two adjacent junk slots to reduce drilling resistance of drilling fluid to the cutting edge.

7. The PDC bit having a multi-layered cutting structure of claim 1 wherein the tip section is provided with a plurality of nozzles, the openings of the nozzles being positioned within the junk slots to communicate the nozzles with the junk slots, drilling fluid being able to flow into the junk slots through the nozzles.

8. The PDC bit having a multi-layered cutting structure of claim 1 wherein the mounting direction of the cutting teeth on the cutting edge remains consistent, the cutting teeth being either planar teeth or non-planar teeth;

the PDC drill bit further comprises a connecting portion, one end of the connecting portion is fixedly connected with the end head portion, and the other end of the connecting portion can be connected with a drill rod so that the PDC drill bit can be installed on the drill rod.

9. The PDC bit having a multi-layered cutting structure of claim 1 wherein the plurality of first cutting assemblies and the plurality of second cutting assemblies are disposed at circumferentially intersecting intervals along the tip portion to promote stability of the PDC bit during cutting operations.

10. Use of the PDC bit having a multi-layered cutting structure of any of claims 1-9 in a drilling operation, the use comprising first performing a cutting operation using a cutting edge having a largest profile outer diameter, and after the cutting edge having the largest profile outer diameter wears, performing a compound cutting operation using a cutting edge having a second and/or smallest profile outer diameter to extend the single pass distance of the PDC bit.

11. The drill bit cutting structure is characterized by comprising a cutting unit which is used for being installed on the end part of a drill bit, wherein the cutting unit comprises a plurality of first cutting assemblies, a plurality of second cutting assemblies and a plurality of blades, the number of the blades is the sum of the number of the first cutting assemblies and the number of the second cutting assemblies, the plurality of blades are circumferentially arranged on the outer surface of the end part, junk slots are formed between two adjacent blades, the plurality of first cutting assemblies are respectively fixedly installed on blades corresponding to the plurality of first cutting assemblies, and the plurality of second cutting assemblies are respectively fixedly installed on blades corresponding to the plurality of second cutting assemblies;

each of the first and second cutting assemblies includes at least one set of cutting edges, each set of cutting edges having a plurality of cutting teeth mounted thereon, the cutting teeth being capable of performing cutting operations on a rock mass during drilling.