PDC CUTTER WITH OVAL CROSS-SECTION

Abstract

A drag bit having cutting elements, wherein the cross section of the cutting elements is an oval shape, wherein in one embodiment the major axis is perpendicular to the surface of the drag bit blade. A method is also included, wherein the method comprises using a milling bit having an oval cross section that thereby produces pockets in the drag bit blades for receiving the oval shaped cutting elements. Use of the oval bit also results in a half oval formed at the closed end of the pocket.

Description

RELATED APPLICATIONS

This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 60/947,591, filed Jul. 2, 2007, the full disclosure of which is hereby incorporated by reference herein.

BACKGROUND

1. Field of Invention

The disclosure herein relates to contoured cutting teeth for use with a drilling bit. More specifically, the present disclosure concerns oval shaped cutting teeth disposed in a correspondingly formed pocket, wherein the pocket is situated on the cutting surface of a drag bit. The present disclosure also concerns a method for forming the pockets on the face of a drill bit.

2. Description of Prior Art

With respect to FIG. 1, an example of a drag bit 10 is shown in a perspective view. The drag bit 10 shown in FIG. 1 includes a body 13 on one end connectable to a drilling system (not shown) through a threaded connection 11 and an upper surface 12 on the opposite end. Formed on the upper surface 12 of the bit 10 are a series of blades 14. The blades comprise a raised portion of material having a generally rectangular cross-section that extends roughly from the center portion of the surface 12 and longitudinally extend radially outward from the surface and down along a side of the bit 10. Pockets 16 are formed on the upper surface of the blade, wherein the respective axes of the pockets are generally parallel with other pockets on the individual blade. Typically, the pockets comprise a hollowed out trough portion of the upper surface of the blade 14, wherein the pockets are formed to receive a cutting element 18 therein. The cutting elements can be attached in any number of ways, such as welding and brazing or other attachment means. The cutting element has a generally cylindrical shape with a cutting face on one end rounded on its other end. It is well known in the prior art to add polycrystalline diamond compact, i.e., PDC, on the face of the cutting element 18. The cutting element body is typically formed of a relatively hard material such as sintered tungsten carbide. The PDC layer may be mounted directly on the mounting body or on an intermediate carrier also generally made from a sintered tungsten carbide.

The bit body 10 is usually comprised of either a tungsten carbide matrix or various forms of steel. When the body is made of steel, the pocket receiving the stud is generally in the shape of a cylinder to receive the cylindrically shaped cutting element 18.

Drilling systems typically utilize the weight on bit to press down into the rock; the weight on bit pressing on the rock combined with the torque crushes the rock to bore through the rock. Continued turning of the drill string pushes the teeth through the rock by the combined forces of the weight on bit and the torque.

SUMMARY OF INVENTION

The present disclosure concerns a drag bit and a method for creating a drag bit. In one embodiment, the drag bit comprises a blade on its cutting face, with at least one pocket formed on the blade. The pocket has a cutting element disposed within, wherein the cutting element has an oval cross section. The terminal end of the pocket and the back end of the cutting element may have corresponding shapes resembling a half portion of an oval.

A method as included herein for forming the pockets on the blade of the drag bit. The method involves utilizing a milling element comprising an oval shaped end and shaft connecting the end to a milling device. The oval shaped end is used for forming pockets on the blade surface of the cutting bit.

BRIEF DESCRIPTION OF DRAWINGS

Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a traditional drag bit.

FIGS. 2a and 2b provide a perspective view and a side view of a cutting element of the present disclosure.

FIG. 3 illustrates a perspective view of a cutting element of the present disclosure combined with a drag bit.

FIG. 4 illustrates a side view of an oval end mill used for creating pockets in a drag bit.

FIG. 5 illustrates a cross-sectional view of a drag bit blade having oval shaped pockets formed therein.

FIG. 6 is a perspective view of milling devices forming cutter pockets.

FIG. 7 is a side partial sectional view of a drilling system having a drag bit with oval shaped cutting elements forming a wellbore.

While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be through and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.

With reference now to FIG. 2a a perspective view of one embodiment of a cutting element 20 in accordance with the present disclosure is provided. In this embodiment, the cutting element 20 includes a body 21 a cutting face 22 on its front portion. The body 21 cross section, the face 22, and the face 22 perimeter have a generally oval configuration. Lines D₁ and D₂ are provided on the cutting face 22 respectively illustrating prolate and oblate lengths, where the prolate (or elongate) length exceeds the oblate length. Although the oval face 22 as shown in FIG. 2a is substantially symmetric about both D₁ and D₂, the oval shape as disclosed herein includes ovals symmetric about one of either D₁ or D₂, or asymmetric about both D₁ and D₂.

As shown, the face 22 is largely planar and substantially perpendicular to the axis A of the cutting element 20. Additionally, the end portion 24 of the cutting element 20 is shown having a half oval shape. More specifically, as can be seen in the side view of FIG. 2b, the cutting element 20 of this embodiment has an end 24 wherein the terminal section of the end is oval. Other embodiments of this cutting element may include hemispherical or one having a flat face. It should be pointed out that the half oval contour of the end 24 of the cutting element 20 is not limited to the dimensions shown in the figure, but can include any number of oval shapes with an infinite number of combinations of major axis and minor axis.

An insert 26 is shown in side view optionally disposed on the entire surface of the face 22. The insert 26 may comprise any number of hard or super hard, materials typically used in conjunction with cutting elements of earth boring drag bits. Examples include PDC material, sintered tungsten carbide, and any other hard or super hard material useful in drag bit applications.

FIG. 3 is a perspective view of a portion of a drag bit 25 having an embodiment of the cutting element 20 of FIGS. 2a and 2b. The drag bit 25 comprises a cutting blade 28 extending from a bit body 27 thereby defining a cutting face 29 on the forward and rearward sides of the blade 28. A top surface 33 extends between the respective upper terminal ends of the cutting face 29. The cutting face 29 is illustrated in FIG. 3 as substantially perpendicular to the bit body 27, however the cutting face 29 can instead be oblique to the bit body 27. Additionally, the top surface 33 is shown as parallel to the bit body 27 and substantially planar, however the top surface 33 is not limited to this configuration. The blade 28 includes a pocket 30 formed thereon correspondingly contoured to the cutting element 20 oval shape. Securing the cutting element 20 in the pocket 30 may be done in any number of methods, including brazing, welding, and cementing.

In FIG. 4, a side view of a mill bit 32 is illustrating that includes a tip 34 having a largely frusto-oval cross section. For the purposes of discussion herein, a frusto-oval means oval shaped along at least a portion of the member, the remaining portion of the member can be truncated or have a non-oval shape. In the embodiment of FIG. 4, the oval cross section of the tip 34 truncates where it attaches to a shaft 36. Optionally however, the present disclosure includes embodiments wherein the tip 34 is oval, frusto-oval, egg shaped, elliptical, frusto-elliptical, or entirely oval. The shaft 36 is coupled with a milling machine thereby providing rotational energy for engaging the tip 34. Accordingly, the pockets 30 of FIG. 5 may be formed using the oval shaped tip 34 of the milling device of this disclosure.

FIG. 6 provides a perspective view a milling operation using the mill bit 32. Here a pocket is formed on a drag bit by energizing or activating the milling device 31 thereby rotating the mill bit 32. The milling device 31 and rotating mill bit 32 are disposed adjacent the blade to be cut and positioned proximate to where the cutter pocket 30 is to be formed. The rotating mill bit 32 is then urged into the blade 28 and across the top surface 33 to form the pocket 30. Preferably the mill bit 32 is oriented parallel to the cutting face 29 of the blade 28. Cutting across the top surface 33 rather than parallel to the top surface 33 allows mill bit 32 insertion into the space 37 separating adjacent blades 28. While rotating the mill bit 32, the milling device 31 urges the mill bit 32 longitudinally transverse to the surface of the cutting face 29 until a desired length of pocket 30 is formed within the upper surface of the blade 28. The oval shape of the tip 34 thereby not only provides an oval cross section, but also forms a half oval in the closed end of the pocket 30.

FIG. 6 illustrates both the milling device 31 with the oval mill bit 32 and a currently used milling tool 3 with an associated bit 4. One of the advantages of using the mill bit 32 having the oval end piece over current methods of manufacturing is the difference in milling bit orientation. The current method of milling cutter pockets orient the milling bit 4 and milling tool 3 parallel to the blades. This involves reaching the bit 4 past a blade that is forward of the blade being cut with the milling tool. The milling bit 4 thus needs to be sufficiently long to clear the forward blade while cutting. Reaching past the forward blade requires a longer than necessary milling bit which results in a weak tooling because of the extra clearance requirements. To accommodate the weaker tooling, feed torque and speed must be reduced which results in a comprised quality of tooling.

Thus, an advantage of using the tool as described herein is that alternate tooling is shorter and the quality of the hole is increased. Quality attributes include cutter pocket surface finish as well as preciseness and/or accuracy of pocket placement. The shorter tooling of the mill bit 32 compared to the prior art bit 4 herein described provides a stronger cutting device and minimizes clearance issues with the bit center. Moreover, cutting elements having an oval cross section are less susceptible to damage than a cylindrically shaped cutting element. Oval shaped cutting elements have a cross sectional area exceeding cylindrical elements and therefore have increased strength. Thus smaller ovals could be used in a cutting bit thereby increasing cutter number on the same blade profile.

FIG. 7 illustrates a side partial sectional view of the drag bit 25 used with a drilling system 38 for forming a wellbore 39. Here the drag bit 25 is attached via a threaded connection to a drill string 40 on the lower end of a drill string 40. The drill string 40 is connected on its upper end to a top drive 42. The top drive 42 provides rotational torque to the drill string 40 and drag bit 25 for drilling through a formation forming the wellbore 39.

The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. For example, the face 22 can be faceted instead of residing within a single plane, and may be oblique to the axis A of the cutting element 20. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims. While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.

Claims

1. A drag bit for use in earth boring operations comprising:

a drag bit body having a cutting surface on one end and a drill string connection on an opposite end;

a blade formed on the bit body cutting surface; and

a cutting element provided with the blade, the cutting element having an oval cutting face perimeter.

2. The drag bit of claim 1, further comprising a cutter pocket formed in the blade correspondingly shaped to the cutting element, the cutting element disposed in the cutter pocket.

3. The drag bit of claim 1, further comprising a plurality of blades on the bit body and a plurality of cutting elements on the blades.

4. The drag bit of claim 1 further comprising a PDC insert affixed to the cutting face.

5. The drag bit of claim 1 further comprising a cutting element having an oval shaped perimeter on the drag bit body between the cutting surface and the drill string connection.

6. The drag bit of claim 1 further comprising a drill string having an upper end and a lower end, the drill string lower end affixed to the drill string connection and a top drive connected to the drill string upper end.

7. The drag bit of claim 1, wherein the cutting face surface includes an elongate section, wherein the elongate section oriented substantially perpendicular to the blade.

8. A method of forming a cutter pocket on a blade of a drag bit used in earth boring operations, the drag bit having a body, the blade extending from the bit body and having a top surface and sides surfaces, the side surfaces extending from the bit body to the top surface, the method comprising:

activating a milling device having an oval shaped milling bit, thereby rotating the oval shaped milling bit;

positioning the oval shaped milling bit adjacent the blade at a location where the side surface and top surface converge; and

forming a cutter pocket having an oval shaped perimeter by moving the activated oval shaped milling bit through the blade.

9. The method of claim 8, further comprising orienting the milling bit normal to the blade top surface.

10. The method of claim 8 wherein a shaft connects the oval shaped milling bit to the milling device, the method further comprising positioning the milling bit shaft above the blade top surface before moving the activated oval shaped milling bit through the blade.

11. The method of claim 8 wherein the back end of pocket is oval shaped.

12. The method of claim 8 further comprising forming a multiplicity of pockets

13. The method of claim 8 further comprising adding an oval shaped cutting element to the cutter pocket.

14. The method of claim 8 wherein the milling bit width exceeds its length.

15. The method of claim 8, wherein the milling bit length exceeds its width.

16. The method of claim 8, wherein the drag bit comprises a multiplicity of blades on the bit body thereby defining spaces between adjacent blades, the method further comprising disposing the oval shaped milling bit within the space between adjacent blades.

17. The method of claim 8 further comprising including the drag bit with a drilling system and forming a wellbore.