BE1019607A3 - ROTARY TREPAN. - Google Patents

Abstract

Rotary drill bit, comprising a body (1) substantially of revolution, having, at its periphery (3), at least one cavity (4) containing a cutting element (5), the cutting element having a substantially planar face which is applied to a substantially planar wall (6) of the cavity.

Description

FIELD OF THE INVENTION The invention relates to rotary bits, especially to bits for drilling wells in oil deposits or coring in such deposits.

The invention more particularly relates to an improved bit comprising a body substantially of revolution which comprises at its periphery, at least one cavity containing a cutting element.

State of the art

Rotary drill bits of the type defined above are commonly used for drilling wells in oil or gas deposits. In known drill bits of this type, the cutting elements are generally circular or elliptical cross-section cylinders which are partially embedded in semi-cylindrical cavities distributed around the periphery of the bit body (US-A-4,471,845).

In these known bits, a substantial part of each of the cylindrical cutting elements must be buried in the corresponding semi-cylindrical cavity to achieve sufficient anchoring of this cutting element in the bit body. The part of the cutting elements which is thus buried in the cavities of the bit body obviously does not participate in the drilling, which has an adverse effect on the cost of manufacturing the drill bit, on its efficiency and on its lifetime .

SUMMARY OF THE INVENTION The invention aims to remedy the disadvantages and disadvantages of known drill bits.

The invention more particularly aims to provide a rotary bit of the type comprising a body of revolution and cutting elements which are housed in cavities formed at the periphery of the body of the bit, said bit being designed so as to reduce the part of cutting elements that is buried in the cavities, without affecting the strength of the anchoring of the cutting elements in the body of the bit.

Another object of the invention is to provide a drill bit of the type defined above, whose efficiency and life are improved.

A further object of the invention is to reduce the manufacturing cost of rotary bits without compromising their efficiency and their lifetime.

Accordingly, the invention relates to a rotary bit, comprising a body substantially of revolution, having, at its periphery, at least one cavity containing a cutting element, said bit being characterized in that the cavity comprises a substantially flat wall and the cutting element has a substantially planar face which is applied to the flat wall of the cavity.

Detailed description of the invention

In a manner known per se for the known rotary bits, the body of the bit according to the invention is of revolution and is intended to be equipped with cutting elements designed for drilling wells, for example in oil or gas deposits. For this purpose, the rear portion of the bit body is normally arranged to be attached to a drill string coupled to a motor.

The shape of the body of the bit according to the invention is not critical for the definition of the invention. It may for example be cylindrical or conical or comprise a cylindrical part and a conical or frustoconical part.

The body of the bit according to the invention comprises at least one cavity hollowed at its periphery. Said cavity generally has an elongate profile and is arranged transversely to the axis of rotation of the bit body, substantially tangentially to the peripheral surface of said body. Nozzles may be provided through the end face of the bit body for the projection of a drilling fluid. The said nozzles are not critical for the definition of the invention.

The cutting element can be any cutting element commonly used in rotary bits. It can in particular be a cutting element PDC or an infiltrated cutting element. The cutting elements PDC (abbreviation of the English expression "Polycrystalline Diamond Compacts") are well known in drilling technology. They comprise a polycrystalline diamond pellet on a cemented tungsten carbide substrate and are usually obtained by compressing a mixed diamond and cobalt powder on the tungsten carbide substrate. The infiltrated cutting elements are also well known in drilling technology and are usually obtained from a diamond powder and tungsten carbide, which is infiltrated with a metal binder.

In the bit according to the invention, the cutting element is housed and anchored in the cavity of the bit body. Anchoring can be obtained by any suitable means. Brazing is preferred in the case where the cutting element is a PDC element.

According to the invention, the cavity comprises a plane wall and the cutting element has a flat face, which is applied against the flat wall of the cavity.

In general, the bit according to the invention comprises several cavities containing cutting elements and these cavities are then preferably uniformly distributed at the periphery of the body of the bit. In this embodiment of the invention, all cavities may have a planar wall as defined above, the cutting element they contain then having a planar face which is applied to the flat wall of the cavity. In a variant, only a portion of the cavities and cutting elements are in accordance with the invention. In this variant, it is recommended that a significant number of cavities and cutting elements are in accordance with the invention. This significant number may for example be greater than one third of the total number of cavities. It is preferably at least 50% (advantageously 80%) of the total number of cavities. In practice, it is preferred that all the cavities and cutting elements are in accordance with the invention.

In a preferred embodiment of the invention, the planar wall of the cavity is substantially parallel to the axis of rotation of the bit body.

In a preferred embodiment of the preferred embodiment defined above, the planar wall of the cavity is substantially parallel to the axis of rotation of the bit body and is connected to the peripheral surface of the body forming with this an angle less than 90 degrees. By definition, the angle characterizing this variant of the invention is the angle formed between the plane wall of the cavity and a plane tangent to the body of the bit along the line of intersection of this plane wall with the peripheral surface of the hole. bit body. In this preferred embodiment of the invention, the aforementioned angle is normally greater than 2 degrees (or even 3 degrees). It is advantageously at least equal to 5 degrees (preferably 8 degrees). It is desirable that it does not exceed 45 degrees (preferably 35 degrees). Normally, the optimum angle will depend on various parameters, such as the shape and size of the bit body and the type of cutting elements selected, and it must be determined in each particular case by those skilled in the art. In practice, angles of 10 to 45 degrees (preferably 15 to 30 degrees) are generally well suited in the majority of cases.

In the preferred embodiment described above, the cross-section of the cavity increases from the peripheral surface of the bit body to the posterior face of the cavity. This constructive feature of the cavity provides two advantages. On the one hand, it ensures a good anchoring of the cutting element in the cavity; on the other hand, it optimizes the efficiency of the cutting element.

In the bit according to the invention, the profile of the cross section of the cavity is not critical for the definition of the invention. However, according to the invention, it is preferred that the cross section of the cavity be substantially rectangular or trapezoidal. A rectangular cross section is preferred.

Similarly, the profile of the cross section of the cutting element is not critical for the definition of the invention. However, according to the invention, it is preferred that the cross section of the cutting element is substantially semi-elliptical or, preferably, semi-circular.

The rotary bit according to the invention has applications for drilling all types of wells for various applications. It is especially suitable for drilling deep wells in oil or gas deposits or for coring in such deposits.

Brief description of the figures

Particularities and details of the invention will appear in the course of the following description of the appended figures.

Figure 1 is a perspective view of a rotary bit of the prior art;

Fig. 2 is an exploded cross-sectional view of a cutting element of the bit of Fig. 1;

Figure 3 is a perspective view of a drill bit according to the invention;

Figure 4 shows the drill bit of Figure 3, without cutting elements;

FIG. 5 shows a cavity of the bit of FIG. 3 and its cutting element, in axial longitudinal section; and

Figure 6 is a section along the plane VI-VI of Figure 5.

In these figures, the same reference notations designate identical elements.

Detailed description of a drill bit of the prior art

Figures 1 and 2 show a rotating bit of the prior art. This known bit comprises a substantially cylindrical body 1 having a front face 2 and a peripheral surface 3. The front face 2 is provided, in the usual manner, nozzles (not shown) for projecting a drilling fluid. The rear face 9 of the body 1 is arranged to be fixed to a drill string, not shown. In Figure 1, the arrow X designates the direction of rotation of the body 1 during normal use of the bit.

Cavities 4 are formed through the peripheral surface 3. The cavities 4 have a semi-cylindrical profile and they are positioned so that their longitudinal axis is substantially tangential to the peripheral surface 3 and substantially perpendicular to the axis of rotation of the body. 1. The longitudinal peripheral surface of the cavities 4 thus has a semi-cylindrical profile.

A cylindrical cutting element 5 (for example in PDC) is housed and anchored in each of the cavities 4.

FIG. 2 shows that one half of the cutting element 5 is buried inside the semicircular cavity 4. Only the other half of the cutting element protrudes beyond the peripheral surface 3 and is active during the use of the trephine. The portion of the cutting element 5, which is buried in the cavity 4 is inactive, which is a drawback and harms the effectiveness of the bit.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Figures 3 to 6 show a trephine according to the invention. In this bit the cavities 4 comprise a flat wall 6. This flat wall 6 is substantially parallel to the axis of rotation of the body 1 of the bit and it is connected to the peripheral surface 3 forming with it an angle approximately equal to 25 degrees. It follows that, perpendicular to the wall 6, the cross section of the cavity 4 is substantially rectangular and increases from the front face 7 of the cavity (on the surface 3) to the rear wall 8 thereof . In this embodiment of the bit, the terms "front face" and "rear wall" of the cavity 4 are defined relative to the direction of rotation X of the body 1 of the bit.

The cutting element 5 is semi-cylindrical and therefore has a flat longitudinal face. It is housed in the cavity 4 so that its flat longitudinal face rests on the flat wall 6 of the cavity 4. The attachment of the cutting element 5 in the cavity 4 can be achieved by any suitable means of anchoring known. The cutting element 5 is advantageously a PDC element, brazed in the cavity 4.

Claims (10)

A rotary bit, comprising a body substantially of revolution, having, at its periphery, at least one cavity containing a cutting element, characterized in that the cavity (4) comprises a substantially planar wall (6) and the cutting element ( 5) has a substantially planar face which is applied to the flat wall of the cavity. 2. Drill according to claim 1, characterized in that said flat wall (6) of the cavity (4) is substantially parallel to the axis of rotation of the body (1). 3. Drill according to claim 2, characterized in that the plane wall (6) of the cavity (4) is connected to the peripheral surface (3) of the body (1), forming therewith an angle less than 90 degrees. 4. Drill bit according to claim 3, characterized in that the aforesaid angle is from 10 to 45 degrees. 5. Drill bit according to any one of claims 1 to 4, characterized in that the cross section of the cavity (4) is substantially rectangular. 6. Drill bit according to any one of claims 1 to 5, characterized in that the cross section of the cutting element (5) is substantially semi-circular or semi-elliptical. 7. Drill bit according to any one of claims 1 to 6, characterized in that the cutting element (5) is a PDC element. 8. Drill bit according to any one of claims 1 to 7, characterized in that the body (1) of the bit is cylindrical. 9. Drill bit according to any one of claims 1 to 8, characterized in that the end face (2) of the body (1) of the bit comprises nozzles for the projection of a drilling fluid. A drill bit according to any one of claims 1 to 9 for drilling wells in oil or gas deposits or coring in such deposits.