HYBRID ROCK BIT

Abstract: A hybrid rock bit (10) which includes at least one cutter cone leg (18) which supports at least one disk cutter cone (20). Each disk cutter cone (20) includes a plurality of spaced apart cutting disk edges (30) which extend continuously around the periphery of the cone (20). At least one drag bit leg (26) is utilized, with the drag bit leg (26) including a plurality of diamond cutting elements (28) in one face thereof. The diamond cutting elements (28) are arranged to contact the borehole bottom during bit operation. Continuous disk cutters (30) are utilized on the cutter cone (20) to minimize "bouncing", or vertical movement of the rock bit (10) which can damage or fracture the diamond cutting elements (28).

Description: HYBRID ROCK BIT BACKGROUND OF THE INVENTION Rotary drill bits for rock drilling are well known in the prior -art. A common type of rotary drill bit utilizes a plurality of rolling cone cutters which are mounted to the drill bit body in a manner which will allow the cutters to roll along the bottom of a wellbore when the drill bit body is rotated. Such rolling cone cut¬ ters can be formed utilizing an integrated body of hardened steel with teeth or cutters formed about the exterior surface thereof. Another type of rolling cone cutter utilizes a steel body with a plurality of tungsten carbide or similar hardened inserts that protrude from the surface of the body in the manner of small knobs. Again, as the rolling cone cutters roll on the bottom of the wellbore, the teeth or inserts apply a highly compressive load to the bottom of the wellbore and fracture that bottom. The cutting action for such cutters is typically a combination of crushing action and chipping action. Another well known type of rotary rock bit is the so-called drag bit. Generally, drag bits include a set diamond cutter which includes a face which is embedded or "set" with numerous cutting OMPI diamonds. These cutting diamonds protrude from the surface of the bit a short distance and when the drill is rotated into the formation, they cut the formation utilizing a combination of compression and shearing action. The depth of penetration utilizing a diamond drag bit is limited by the weight on the bit, the number of diamonds uti¬ lized and the heat dissipating limitations of the bit. Hybrid rock bits which utilize combinations of drag bits and rolling cone cutters have been proposed in the prior art. One such example is United States Patent No. 3,174,564, issued to E. A. Morlan. The Morlan bit includes a cylindrical crown encrusted with set diamonds for cutting an annulus around a core. The set diamonds in the Morlan disclosure protrude from the matrix a small distance in a conventional manner. A plurality of rolling cone cutters with carbide inserts are mounted in special recesses around the cylindrical crown for cutting an outer annulus of a considerably greater area than the inner annulus cut by the diamonds ' . The set diamonds are used for their fine abrasive action in trimming the core and thereby minimizing breakage. Most of the cutting utilizing this bit is accomplished uti¬ lizing the rolling cone cutters. United States Patent No. 1,731,262, issued to Phipps and United States Patent No. 2,054,277, issued to Wright also disclose combinations of drag bits and rolling cone cutters; however, the drag bits utilized in both Phipps and Wright are steel drag teeth and are therefore limited in application to soft formations which can be cut efficiently with such a design. These steel drag teeth are imprac¬ tical for deep wells wherein formations of various hardness are encountered. Another example of a hybrid rock bit is disclosed in United States Patent No. 4,285,409, issued to James H. Allen. The Allen hybrid rock bit includes two rolling cone cutters and a single extended drag bit. The Allen hybrid bit utilizes the single drag bit with appropriately placed diamond cutter elements to remove the high points or ridges remaining in the formation on the bottom of the wellbore which are typically created by the action of rolling cone cutters. This is necessary due to the tendency of rolling teeth on each cone cutter to "track" in the bottom of the borehole and thus create ridges between the cutting area of each group of teeth. Various other modifications of a hybrid rock bit design which combines a diamond drag bit with a rolling cone cutter are disclosed in United States Patent No. 4,006,788, issued to Lloyd L. Garner; United States Patent No. 3,343,371, issued to William Baker m et al.; and United States Patent No. 4,359,112, issued to Lloyd L. Garner et al. Each of the aforementioned patents discloses a hybrid rock bit which includes a combination drag bit and rolling cone cutter. Each of the aforementioned known hybrid rock bits which includes diamond drag bit cutters is particularly sensitive to overloading and sudden vertical movement of the drill bit which can shatter or fracture the diamond cutters. While diamond cutting tools are extremely hard and can handle abrasive wear for long periods of time, they are also exceedingly susceptible to fracture or breakage when subjected to these sudden impacts. SUMMARY OF THE INVENTION It is therefore one object of the present invention to pro¬ vide an improved hybrid rock bit. It is another object of the present invention to provide an improved hybrid rock bit which includes both rolling cone cutters and drag bit cutters. It is yet another object of the present invention to provide an improved hybrid rock bit including a drag bit cutter which minimi¬ zes vertical movement of the bit during operation whereby stress frac¬ ture of the drag bit cutters is minimized. It is yet another object of the present invention to provide an improved hybrid rock bit including a drag bit cutter which can be utilized in formations of varying hardness. The foregoing objects are achieved as is now described. The hybrid rock bit of the present invention includes at least one cutter cone leg which supports at least one disk cutter cone. Each disk cutter cone includes a plurality of spaced apart cutting disk edges which extend continuously around the periphery of the cone. At least one drag bit leg is utilized, with the drag bit leg including a plura¬ lity of diamond cutting elements in one face thereof. The diamond cutting elements are arranged to contact the borehole bottom during iRE OMPI ° bit operation. Continuous disk cutters are utilized on the cutter cone to minimize "bouncing", or vertical movement of the rock bit which can damage or fracture the diamond cutting elements. BRIEF DESCRIPTION OF THE DRAWINGS The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself; however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in con- junction with the accompanying drawings, wherein: Figure 1 is a perspective view of the hybrid rock bit of the present invention; and Figure 2 is an end view of the hybrid rock bit of Figure 1. DETAILED DESCRIPTION OF THE INVENTION With reference now to the figures and in particular with reference to Figure 1, there is depicted a preferred embodiment of a hybrid rock bit generally designated at reference numeral 10, which includes a bit body 12 having a pin end 14 and a cutting end 16. A pair of opposed roller cone legs 18 are utilized to support cutter cones 20 and 22. Disposed adjacent to cutter cones 20 and 22 in the depicted embodiment, and diametrically opposed from each other, are drag bit legs 24 and 26 which extend from bit body 12 and which serve to support diamond insert cutter blanks 28. Preferably a plurality of diamond insert cutting blanks 28 are utilized and they are positioned in the face of drag bit legs 24 and 26 in a manner which will be explained in detail herein. As those skilled in the art will appre¬ ciate, hybrid rock bit 10 also preferably includes hydraulic nozzles or openings which communicate with a central chamber within bit body 12 and which provide a channel for cutting fluid or drilling mud to be applied to the bottom of the wellbore, cooling the cutting implements and removing cuttings from the wellbore. Diamond insert cutter blanks 28 are preferably fabricated from a tungsten carbide substrate with a diamond layer sintered to a face of the substrate, the diamond layer being composed of a poly- OMPI C/Λ. crystalline material. One such synthetic polycrystalline diamond material is manufactured by the Specialty Material Department of General Electric Company of Worthington, Ohio under the trademark name of Stratapax. As can be seen in Figure 1, cutter cones 20 and 22 do not include a plurality of teeth or carbide inserts in the manner of most well known cutter cones. Cutter cones 20 and 22 each include a plura¬ lity of spaced apart disk edges 30 which extend continuously around the periphery thereof and which are utilized to at least partially support the weight of the drill bit and drill pipe above the bit and to shear and grind rock from the bottom of the wellbore. In one embo¬ diment of novel hybrid rock bit 10 of the present invention, cutter cones 20 and 22 may be deliberately skewed to enhance the shearing action of cutting disk edges 30. The utilization of a continuous disk edge, as opposed to a plurality of tooth inserts has been found to enhance the usable lifetime of hybrid rock bit 10 by minimizing the bouncing or vertical movement associated with the operation of known roller cutter cones, which may subject diamond insert cutter blanks 28 to vertical stress and subsequent fractures. When the vertical move- ment is minimized or substantially eliminated by the utilization of continuous disk cutting edges, the probability of fractures or cracking of diamond insert cutter blanks 28 is effectively minimized, unexpectedly increasing the efficiency of the operation of hybrid rock bit 10. Referring now to Figure 2, there is depicted an end view of hybrid rock bit 10 which will serve to illustrate the preferred place¬ ment of diamond insert cutter blanks 28. Those skilled in the art will appreciate that the continuous cutting disk edges 30 disposed about the periphery of cutter cones 20 and 22, in an embodiment without a substantial amount of skew, will result in a plurality of concentric paths being cut into the borehole bottom. Careful place¬ ment of diamond insert cutter blanks 28, at the points geometrically between spaced apart continuous cutting disk edges 30 of cutter cones 20 and 22 will result in the application of diamond insert cutter blanks 28 to the ridges formed by the action of the cutting disk edges 30 of cutter cones 20 and 22. Thus, diamond insert cutter blanks 28 OMPI can be utilized to remove these ridges and assure removal of detritus material from the borehole and the maximum efficient progress of rock bit 10 in the hole. In an alternate embodiment of the present inven¬ tion, drag bit legs 24 and 26 may be altered to permit diamond insert cutter blanks 28 to be mounted at a point even with the extension of disk edges 30, or below or above disJc edges 30 to vary the penetration parameters of hybrid rock bit 10 in correlation with the hardness of the formation being drilled. Additionally, it is anticipated that drag bit legs 24 and 26 may be movably mounted to bit body 12 to per- mit the extension of diamond insert cutter blanks 28 to be altered in situ utilizing hydraulic or pneumatic controls. Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modification of the disclosed embodiment as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover any such modifications or embodiments that fall within the true scope of the invention. What is claimed is:

Claims: 1. A hybrid rock bit comprising: a rock bit body having a pin end at a first end thereof and a cutting end at a second end thereof, said cutting end comprising: at least one drag bit leg extending from said cutting end and having a plurality of diamond cutting elements positioned in a face thereof and arranged to contact a borehole bottom in a plurality of substan¬ tially concentric circles; at least one cutter cone leg coextending with said at least one drag bit leg; a journal extending from said at least one cutter cone leg; and a disk cutter cone mounted on said journal having a plurality of spaced apart cutting disk edges extending continuously around the periphery thereof wherein both vertical movement of said rock bit body during operation thereof and damage to said plurality of diamond cutting elements is minimized. 2. The hybrid rock bit according to claim 1 wherein said cutting end includes two drag bit legs and two cutter cone legs arranged in alternate fashion. 3. A hybrid rock bit comprising: a rock bit body having a pin end at a first end thereof and a cutting end at a second end thereof, said cuttng end comprising: at least one cutter cone leg extending from said cutting end; a journal extending from said at least one cutter cone leg; a disk cutter cone mounted on said journal having a plurality of spaced apart cutting disk edges extending continuously around the periphery thereof; and at least one drag bit leg coextending with said at least one cutter cone leg from said cutting end, said at least one drag bit leg having a plurality of diamond cutting elements positioned in a face thereof and being arranged to contact a borehole bottom at a plurality of concentric ridges resultant from the removal of cuttings by said plurality of spaced apart cutting disk edges. 4. The hybrid rock bit according to claim 3 wherein said cutting end includes two drag bit legs and two cutter cone legs arranged in alternate fashion. OMPI

Inventors: GARNER LLOYD L, GARNER, LLOYD, L.
Applicants: ROCK BIT IND INC, ROCK BIT INDUSTRIES U.S.A., INC.
Application year: 1984
Main classification: E21B10
IPC codes: E21B10