This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 61/016,243, filed Dec. 21, 2007, the full disclosure of which is hereby incorporated by reference herein.
1. Field of Invention
The disclosure herein relates in general to rolling cone earth boring bits, and in particular to the shape and orientation of compacts used on the cones.
2. Description of Prior Art
Drilling systems having earth boring drill bits are used in the oil and gas industry for creating wells drilled into hydrocarbon bearing substrata. Drilling systems typically comprise a drilling rig (not shown) used in conjunction with a rotating drill string wherein the drill bit is disposed on the terminal end of the drill string and used for boring through the subterranean formation.
Drill bits typically are chosen from one of two types, either drag bits or roller cone bits. Rotating the bit body with the cutting elements on the outer surface of the roller cone body crushes the rock and the cuttings may be washed away with drilling fluid. A rolling cone earth boring bit has a bit body with typically three legs. A bearing pin depends from each leg and a cone mounts rotatably to each bearing pin. The cones have rows of cutting teeth on the outer surface of the cone. In one type, the cutting elements comprise teeth machined into the surface of the cone. In another type, the cutting elements comprise carbide compacts or inserts that are pressed-fitted into mating holes in the cone surface.
Compacts generally have a cylindrical base that is inserted into a hole and a protruding cutting tip. The cutting tips may have chisel, hemispherical, ovoid or other shapes. Particularly on the heel row, which is located near the gage surface of each cone, the compacts may have asymmetrical shoulder surfaces for engaging the sidewall of the bore hole. Depending upon the formation being drilled, different shapes are utilized for aggressiveness of cutting and durability.
- SUMMARY OF INVENTION
One example of a roller cone bit is provided in side view in FIG. 1, which illustrates a bit 11 having a body 13 with a leg 15. Roller cone bits typically comprise three legs 15. A cone 17 rotatably mounts to a bearing pin (not shown) of each leg 15. Each cone 17 has a plurality of inserts 19, arranged in at least one inner row. A plurality of outer or heel row compacts 21 are adjacent to a gage surface 23 of each cone 17. In the embodiment shown, heel row compacts 21 are generally ovoid, although different shapes could be used.
BRIEF DESCRIPTION OF DRAWINGS
Disclosed herein is an earth boring drill bit having a roller cone with cutting inserts on the outer surface of the roller cone. The inserts comprise a generally circular base and a peal. The sides of the inserts comprise four faces that extend from the base to the peak. Each face has a generally triangular configuration wherein a portion of its surface is generally planar. The region where adjacent sides join is rounded thereby defining ridges. The four substantially similar sides form four ridges that meet at the crest. A first set of two ridges form on opposite sides of the base with respect to one another and are substantially parallel. A second set of two ridges also form on opposite sides with respect to one another and are also parallel. The inserts are oriented on the cone in rows so that the first set of ridges is aligned with the cone axis and the second set of ridges is aligned with the row.
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 side perspective view of a roller cone bit.
FIG. 2 provides a bottom view of a roller cone bit having shaped inserts.
FIG. 3 is an overhead view of an insert for a roller cone bit.
FIG. 4 shows a side view of a roller cone bit having an embodiment of inserts of the present disclosure.
FIG. 5 illustrates in a perspective view a roller cone bit having embodiment of an insert of the present disclosure.
FIGS. 6-8 depict examples of insert embodiments.
- DETAILED DESCRIPTION OF INVENTION
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.
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 thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
A bottom view of an embodiment of an earth boring bit 30 is provided in FIG. 2. The bit 30 comprises three cutter cones 32 wherein each cone includes rows of inserts formed thereon. The outermost or heel row is formed on the heel surface 34 and includes heel row teeth 36. As shown, the heel row teeth 36 have a generally hemispherical configuration. Inner rows 40, 42 are formed on each cone between the heel row and the nose of each cone 32. The inner row 40 includes inserts 46 disposed on its outer surface. The inner row 42 proximate to the nose of the cone 32 also includes inserts 44. In the embodiment shown, the inserts 44, 46 resemble a four sided pyramid.
FIG. 3 provides an overhead view of an example of a pyramid shaped insert 52. As shown, the insert 52 has a generally circular base 53 with its sides 54 extending upward towards a crest 58. Each side 54 may have substantially the same dimension. The surface 55 of each side 54 can be generally planar, include contours, or have both planar and contoured portions. The respective surfaces 55 of adjacent sides are depicted as being angled roughly 90° to one another. The sides 54 join each adjacent side along a rounded ridge 56, the ridge 56 extends from the base 53 and terminates at the crest 58. Here, the circular base 53 is shown with each side 54 (also referred to herein as a face) extending upward in a generally triangular fashion and terminating at the crest 58. The insert surface 55 is curved where the adjacent sides 54 meet thereby giving the ridge 56 a curved cross section. Other embodiments exist wherein the ridge 56 cross section is defined by the sides 54 intersecting at an angle.
FIG. 4, which illustrates a portion of a cone 60 in side view, provides some examples of the orientation of the inserts on the face of the cone. The cone 60 also comprises a lower row 67 with inserts 68. The lower row 67 of inserts 68 circumscribes the axis A of the cone 60 and is disposed proximate to the heel row 62. With reference now to the inserts 68 in the lower row 67, each insert 68 has a first set of ridges running parallel to the row 67. The ridges in this first set are referred to as the linear ridge 70. A reference line L has been provided illustrating the row path. Similarly, a second set of ridges on the insert 68 extend substantially parallel with the axis A of the cone 60 and roughly perpendicular to the reference line L. This second set of ridges is referred to here as the axial ridge 72. The axis A is provided in dashed outline for reference. Also in the embodiment of FIG. 4, the inserts 76 disposed on an upper row 74 also include a first and second set of ridges, wherein one set of ridges runs generally parallel with the line defining the path of the upper row 74, and the other set of ridges on the insert 76 runs generally parallel with the axis of the cone 60. In an embodiment of a roller cone bit described herein, the inserts on a cone of a roller cone bit comprise four sided pyramid shaped inserts with one set of ridges running generally parallel to its respective row and the other set of ridges running generally parallel with the axis of the cone. For the purposes of discussion herein, generally parallel includes an alignment of up to about 15° from parallel. Additionally, the line defining the path of the upper row 74 coincides with the rotational path of the associated roller cone.
Aligning the ridges as described herein opens the insert face towards grooves or open space on the cone surface. As the insert penetrates the displaced material, the material is mechanically pushed into the open space and not trapped between adjacent inserts. The material trapped between conventional inserts, such as axially aligned chisels, may cause balling in shale thereby impeding its penetration rate. The axially and circumferentially aligned pyramid inserts also have a more streamlined shape allowing them to better withstand the sliding induced by cone offset and non-true-rolling cone geometry. Additionally, durability is enhanced with the disclosed cutting structure. Optionally, this advantageous result of the pyramid shape may be enhanced by strategically placed grooving between inserts to further enhance material flow. Moreover, inserts disposed proximate to the heel area may comprise a three sided pyramid due to the difficulty of displacement of material toward the gage of the bit.
A schematic drawing of a side view of an embodiment of a cone cutter 32 a is provided in FIG. 5. The cutter cone 32 a includes an outer heel surface 34 a on which are formed heel row teeth 36 a. As shown, the heel row teeth 36 a are generally hemispherical in shape, but can have other shapes as well. Also included is an adjacent heel row 48 having a pyramid shaped insert 50. The insert 50 also includes an upward and downward ridge substantially aligned with the adjacent heel row 48 and a corresponding perpendicular ridge substantially parallel to the axis of the cutter cone 32 a. Inner rows 40 a, 42 a are shown coaxially disposed between the adjacent heel row 48 and the nose of the cone 32 a. Corresponding inserts 44 a, 46 a are provided on these inner rows. As shown, the inserts 44 a, 46 a also have ridges that are aligned with their corresponding row as well as aligned with the axis of the cone 32 a.
Alternative insert embodiments are provided in FIGS. 6 through 8. In FIG. 6, an insert 80 is shown in perspective view having a first ridge 81 formed on the insert 80 upper surface. A second ridge 82, also on the insert 80 upper surface, intersects the first ridge 81 proximate the crest or uppermost portion of the insert 80. In this embodiment the insert 80 is asymmetric, thus the first and second ridges have different lengths.
In FIG. 7, an insert 83 shown in perspective view includes first and second ridges 84, 85 on its upper surface. Faces 86 are on the upper surface disposed between adjacent ridges 84, 85 extending between the insert 83 base and its upper crest. The adjacent faces 86 join at an angle to define a ridges 84, 85 having a cross section with an angled edge. Although shown as a rectangular base, circular and rounded base configurations exist.
The insert 87 in FIG. 8 includes a leading side 88 and a trailing side 93. In this embodiment the leading side 88 is oriented to first contact the excavated material. The insert 87 includes a first ridge 89 aligned generally perpendicular to the cone direction of rotation. The first ridge 89 extends over a substantial portion of the insert 87 outer surface. Also included is a second ridge 90 that is generally aligned with or parallel to the cone rotational direction. The second ridge 90 is shown extending from the insert 87 base, along the leading side 88, and terminating at the first ridge 89. Faces 91, 92 are on the leading side 88 between the first ridge 89 and second ridge 90. The faces 91, 92 may be planar or have a curved surface. However, the second ridge 90 should protrude outward from the leading side 88 so as to first penetrate formation. The sloping surfaces of the faces 91, 92 direct the displaced material outward and away from the next following insert. In the embodiment of FIG. 8, the trailing side 93 is shown having a consistent surface absent ridges or other contours. Accordingly, the present disclosure includes inserts whose a shaped surface is only on the leading side that performs a majority of the cutting or excavating action.
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. For example, the scope of this disclosure includes roller cone bits having different numbers of roller cones as well as inserts comprising pyramids having other than four sides. Additionally, the ridges' intersection is not limited to the embodiments disclosed, but can include intersections on the insert having a large range of radii, including an intersection forming a point on the insert crest. 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.