CN111287664A

CN111287664A - PDC drill bit with dynamic stress interference principle

Info

Publication number: CN111287664A
Application number: CN202010296953.2A
Authority: CN
Inventors: 张春亮; 杨迎新; 包泽军
Original assignee: Chengdu Weiyi Petroleum Technology Co ltd; Southwest Petroleum University
Current assignee: Chengdu Weiyi Petroleum Technology Co ltd; Southwest Petroleum University
Priority date: 2020-04-15
Filing date: 2020-04-15
Publication date: 2020-06-16

Abstract

The invention provides a PDC drill bit with a dynamic stress interference principle, which comprises a drill bit body and at least two blades, wherein the blades are fixedly connected with the drill bit body or integrally formed; the impact teeth can generate impact motion; in the hybrid cutting unit, the positional relationship of the PDC teeth and the impact teeth is configured such that the PDC teeth are disposed rearward of the impact teeth in the circumferential direction in which the drill bit is rotated, and the range of the distance D between the PDC teeth and the impact teeth is: d is more than or equal to 4D and is more than or equal to D, and D is the diameter of the PDC teeth. The invention can solve the problems of poor cutting tooth invasion capability, low rock breaking efficiency and short working life of the drill bit when the drill bit drills into a hard stratum.

Description

PDC drill bit with dynamic stress interference principle

Technical Field

The invention relates to the technical fields of oil and gas drilling engineering, mining engineering, geological drilling, tunnel engineering and the like, in particular to a PDC drill bit with a dynamic stress interference principle.

Background

A drill bit is a tool that directly contacts rock during drilling and breaks the rock by cutting, impacting, etc. PDC (Polycrystalline Diamond Compact) bits, which are an important type of existing bit technologies, are increasingly used in oil drilling, geological and even construction. The PDC drill bit breaks rock in a cutting mode mainly through PDC teeth arranged on the drill bit, an ideal drilling rate can be obtained in soft to medium-hard strata, and the PDC drill bit is widely applied to oil and gas drilling.

With the development of shallow oil and gas resources being almost exhausted, the emphasis of oil and gas exploration and development gradually shifts to deep-layer, deep-sea and unconventional oil and gas (including shale gas). Typically, the rock material of deep formations is hard, abrasive and poorly drillable. PDC bits, drilling in these formations, often fail to achieve high rates of penetration, one of the most important reasons being limited by the plunging capacity of the PDC teeth. Particularly, with the increase of the depth of the stratum, the complexity of the stratum is higher and higher, such as a hard-plastic stratum, a hard-brittle stratum, a soft-hard interlayer, a gravel stratum and the like, the PDC teeth cannot effectively bite into the stratum, the drilling efficiency is low, and the PDC teeth are easily and rapidly worn. Particularly, the PDC teeth of the conventional PDC drill bit mainly comprise a polycrystalline diamond compact, the impact resistance of the PDC drill bit is weaker, when the PDC drill bit is drilled into complex stratums, the PDC teeth are easy to impact and break, and the cutting efficiency and the service life of the drill bit are greatly reduced due to the breaking of the compact. The main cause of compact collapse is the impact force from the downhole rock. Generally, the most likely locations on a drill bit where composite sheet chipping occurs are the crowns and the radial regions other than the crowns where the cutting speed is relatively high on the drill bit. After the excessive wearing and tearing of local radial zone internal PDC tooth on the drill bit, can add the work load that faces the tooth, and then take place the linkage failure of PDC tooth, in case the PDC tooth failure in great zone appears, the cutting ability of drill bit loses basically promptly.

Disclosure of Invention

The invention provides a PDC drill bit with a dynamic stress interference principle, which aims to solve the problems in the prior art that: when drilling into hard stratum, PDC teeth have poor invasion capability, low rock breaking efficiency and short working life of the drill bit.

The invention is realized by the following steps:

a PDC drill bit with a dynamic stress interference principle comprises a drill bit body and at least two blades, wherein the blades are fixedly connected with the drill bit body or integrally formed, a mixed cutting unit consisting of PDC teeth and impact teeth is arranged on the drill bit, and the PDC teeth and the impact teeth in the mixed cutting unit are respectively arranged on two adjacent blades; the impact teeth can generate impact motion; in the hybrid cutting unit, the positional relationship of the PDC teeth and the impact teeth is configured such that the PDC teeth are disposed rearward of the impact teeth in the circumferential direction in which the drill bit is rotated, and the range of the distance D between the PDC teeth and the impact teeth is: d is more than or equal to 4D and is more than or equal to D, and D is the diameter of the PDC teeth.

With reference to fig. 2 and 3, a brief description of a hybrid cutting unit is given, in a bottom-hole overlay of the shaft face, in which the PDC and the punch have the same cutting area. On the drill bit, PDC teeth and impact teeth of the mixed cutting unit are adjacent in the drilling direction of the drill bit, the impact teeth are forward in the rotating direction, and the impact teeth rotate and follow. The well bottom covering tooth distribution diagram is that in any axial plane passing through the central line of the drill bit, the cutting profiles of the PDC teeth rotate around the central line of the drill bit and form an intersection line with the axial plane, the intersection line is a cutting profile line, and the cutting profile lines of all the PDC teeth are gathered together to form the well bottom covering tooth distribution diagram. The well bottom covering tooth distribution diagram directly reflects the important parameters of the PDC teeth, such as the positioning radius, the positioning height and the like. Similarly, the forming principle of the coverage map of a single blade is similar, and the description is omitted.

Among the above-mentioned scheme, the impact tooth sets up in the nearer position in PDC tooth the place ahead, and the produced rock stress field of the impact force that utilizes the impact tooth interferes or intersects with the produced stress field of PDC tooth cutting force mutually, makes PDC tooth the place ahead rock break failure in advance to reach and reduce PDC tooth cutting force, promote the purpose of drill bit at hard formation working property, strike the originally existing broken rock effect of tooth in addition, broken rock efficiency just can show the promotion. In addition, the impact load of striking the tooth directly acts on the rock, and does not act on blade PDC tooth, so, the impact force can not play negative effects to the PDC tooth on the drill bit, only can promote the breakage of rock, especially directly promotes the breakage of PDC tooth the place ahead rock, effectively reduces cutting load, finally makes the life of PDC tooth and the invasion ability of drill bit all promoted.

The mixed cutting unit is arranged on two adjacent blades, the impact teeth are arranged on the blades rotating in front as far as the two adjacent blades are concerned, the PDC teeth are arranged on the blades rotating behind, the space of the drill bit is fully utilized, meanwhile, the chip discharge grooves between the two blades are reserved, and rock debris can be smoothly carried into the annular space.

More preferably, the distance D between the PDC teeth and the impact teeth ranges from: d is more than or equal to 3D and is more than or equal to D, and D is the diameter of the PDC teeth.

Preferably, the distance D between the PDC teeth and the impact teeth ranges from: d is more than or equal to 2D and is more than or equal to D, and D is the diameter of the PDC teeth.

As a further preference, the axis of the impact tooth is not coincident with the normal of its set reference point. When the PDC teeth are arranged on the working face, the spatial position of the PDC teeth on the working face is firstly determined, the position is called a design reference point or an installation reference point, obviously, the point is on the working face, the normal line of the working face passing through the point is the normal line of the reference point, the concept is consistent with the basic mathematics, the understanding is easy, and the detailed description is not combined with the drawing for detail. Normally, when the impact tooth is provided, the axis of the impact tooth is aligned with the normal line. In the structure, the design that the normal line of the reference point is not parallel (not coincident) with the axis of the impact tooth can well optimize the impact angle of the impact tooth.

Preferably, the PDC teeth in the hybrid cutting unit correspond to the impact teeth one by one. That is, each impact tooth rotates following one PDC tooth.

As a preferred aspect of the present invention, the impact teeth include tapered teeth, wedge teeth, spoon teeth, ball teeth, and the like.

Preferably, the impact teeth are of an asymmetrical tooth form. Typically, the impact teeth are regular bodies of revolution (e.g., cone teeth, spherical teeth, etc., as are commonly used in roller cone bits), or are axisymmetric structures (e.g., wedge teeth), all of which are referred to as symmetrical tooth forms. The impact teeth are formed in an asymmetrical shape, and the direction of the blade penetration force can be changed without changing the impact direction.

The invention at least comprises the following beneficial effects:

1. in the mixed cutting unit, the close range setting of PDC tooth and invasion tooth makes the cutting stress field of impact stress field interference PDC tooth that the tooth produced of assaulting, forms the stress interference principle, makes PDC tooth the place ahead rock break failure in advance, reduces PDC tooth cutting force. Meanwhile, the stress interference principle reduces the rock strength in front of the PDC teeth, and is favorable for improving the invasion capacity of the cutting teeth.

2. In the mixed cutting unit, lateral cracks generated by the impact teeth tend to spread towards a PDC tooth working area, shear cracks generated by the PDC teeth also tend to develop towards an interference area with low energy consumption, and under the two trends, the rock is crushed in a large volume, so that the rock crushing efficiency is improved.

3. The mixed cutting unit is arranged on two adjacent blades, so that the space of the blades is fully utilized, and simultaneously, chip grooves between the blades are reserved. The rock debris generated by the rotating PDC teeth can smoothly enter the annular space.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a schematic diagram of a PDC bit according to an embodiment of the present invention.

Fig. 2 is a top view of fig. 1.

FIG. 3 is a schematic representation of a one-to-one correspondence of PDC teeth and impingement teeth in a hybrid cutting unit in a bottom hole overlay.

Fig. 4 is a schematic diagram of the principle of stress interference created by the hybrid cutting unit of the present invention.

Fig. 5 is a schematic diagram of the crushing effect of rock under the action of stress interference.

FIG. 6 is a graph of the rock breaking effect of PDC teeth in a conventional diamond bit.

FIG. 7 is a schematic view of an impact tooth having an asymmetrical configuration.

Icon: 1-PDC drill bits; 2-a blade; 21-PDC teeth; 22-impact teeth; 211-cutting stress field; 221-impact stress field; 11-a bit body; 3-a hybrid cutting unit; 4-chip removal groove; 5-impact seat.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Example (b):

referring to fig. 1-6, an embodiment of the present invention provides a PDC drill bit 1 with a dynamic stress interference principle. The PDC drill bit comprises a drill bit body 1 and at least two blades 2, wherein the blades 2 are fixedly connected with the drill bit body 1 or integrally formed, a mixed cutting unit 3 consisting of PDC teeth 21 and impact teeth 22 is arranged on the drill bit 1, and the PDC teeth 21 and the impact teeth 22 in the mixed cutting unit 3 are respectively arranged on the two adjacent blades 2; the impact teeth 22 are capable of producing an impact motion; in the hybrid cutting unit 3, the positional relationship of the PDC teeth 21 and the impact teeth 22 is configured such that the PDC teeth 21 are disposed rearward of the impact teeth 22 in the circumferential direction formed by rotation of the drill bit 1, and the range of the distance D between the PDC teeth 21 and the impact teeth 22 is: d is more than or equal to 4D and is more than or equal to D, and D is the diameter of the PDC teeth.

The tooth profile of the impact teeth 22 includes tapered teeth, wedge-shaped teeth, spherical teeth, edge wedge-shaped teeth, etc., and also includes teeth of asymmetrical configuration (see fig. 6). The materials of the impact teeth comprise artificial diamond, natural diamond, impregnated diamond, hard alloy, cubic boron nitride, ceramic and the like.

When the distances between the impact teeth 22 and the PDC teeth 21 in the hybrid cutting unit 3 are set within a small range, the following advantages can be obtained: firstly, an impact stress field 221 generated by the impact tooth 22 interferes with a cutting stress field 211 of the PDC tooth 21, the two fields are overlapped and interfere with each other (see fig. 4), so that rock in front of the PDC tooth 21 is promoted to break and fail in advance, and the cutting force of the PDC tooth 21 is reduced; secondly, the cracks generated by the impact teeth 22 tend to propagate towards the working area of the PDC teeth 21, and the shear cracks generated by the PDC teeth 21 also tend to develop in the stress interference area 200 which consumes less energy, which causes the rock to be crushed in a large volume (see fig. 5), which is beneficial to improving the rock breaking efficiency. In the rock breaking process of the conventional drill bit, a shearing slip band is generated in front of the PDC teeth 21, the rock is broken along the shearing slip band and consumes larger energy, the rock belongs to a brittle material, and before the rock is broken along the slip band, secondary breaking occurs under the extrusion effect of the PDC teeth 21, and larger volume breaking cannot be generated, as shown in fig. 6.

Referring to fig. 4 and 5, the impact direction of the impact teeth 22 may also be inclined toward the PDC teeth 21. Referring to fig. 3, in the hybrid cutting unit 3, the PDC teeth 21 and the impact teeth 22 are in one-to-one correspondence, so that the rock breaking efficiency is higher.

The impact teeth 22 may be provided separately or may be slidably connected to the bit body 1 through the tooth holder 5, see fig. 1.

Claims

1. A PDC drill bit with a dynamic stress interference principle comprises a drill bit body and at least two blades, wherein the blades are fixedly connected with the drill bit body or integrally formed; the impact teeth can generate impact motion; in the hybrid cutting unit, a positional relationship of the PDC teeth and the impact teeth is configured such that the PDC teeth are disposed rearward of the impact teeth in a circumferential direction formed by rotation of the drill bit, and a range of a distance D between the PDC teeth and the impact teeth is: d is more than or equal to 4D and is more than or equal to D, and D is the diameter of the PDC teeth.

2. The PDC bit of claim 1 wherein the axis of the percussive teeth is not coincident with the normal of the reference point to which they are set.

3. The PDC bit having a dynamic stress interference principle of claim 1 wherein the PDC teeth in the hybrid cutting unit correspond one-to-one to the percussive teeth.

4. The PDC bit of claim 1 wherein the percussive teeth comprise tapered teeth, wedge teeth, spoon teeth, ball teeth.

5. The PDC bit of claim 1 wherein the impact teeth are asymmetrically shaped.