WO2003080985A2

WO2003080985A2 - Stacked drill bit and toroidal reamer and method

Info

Publication number: WO2003080985A2
Application number: PCT/US2003/008382
Authority: WO
Inventors: Allen Kent Rives
Original assignee: Allen Kent Rives
Priority date: 2002-03-18
Filing date: 2003-03-18
Publication date: 2003-10-02
Also published as: AU2003218254A8; AU2003218254A1; WO2003080985A3

Abstract

The present invention relates to a combination of a drill bit (192) and a skewed toroidal reamer (190) carried on a drill bit shank (110), both free to independently rotate about their respective axes of rotation to drill and widen a bore. Since the toroidal reamer cutter body (190), is skewed and offset from the longitudinal axis of the drill string, only a portion of the cutter elements (131, 132, 133) engage the surface to be crushed at any given moment in the process and thus do not drag across the face of the formation to be cut but rather roll for a smooth, low-torque crushing of the formation. The drill bit-toroidal reamer assembly can be inserted through a restricted diameter to underream a bore similar to bi-center bit systems.

Description

STACKED DRILL BIT AND TOROIDAL REAMER AND METHOD FIELD OF INVENTION The present invention relates to a tool for earth drilling; specifically, to a low torque, high compressive force bit and toroidal reamer combination adapted to both drill and enlarge a bore. DESCRIPTION OF RELATED ART

The drilling industry, whether for utility construction, or for oil, gas and minerals extraction, has long sought a drill bit that can be used for extended periods of time without the need to change out the bit from excessive wear. Moving a drill bit assembly into and out of the bore is costly, unproductive time. The drilling industry also has sought small efficient bits and reamers that could withstand compressive loading and whose bearing systems would not fail from such excessive loading over long drilling runs.

As long appreciated, the rate of penetration (assuming constant rotational speed) improves as weight applied to the bit or weight on bit (WOB) is increased provided the drilling fluid can manage to keep the bit clean. Too often, however, the maximum WOB is not reachable because of the bearing size in smaller tri-cone rock bits. Similarly, rotational speed increases can increase penetration rates in soft formations; but in harder formations, there is an optimum rotational speed. Inserts can be damaged by too high rotational speed. Generally soft formation (steel teeth) bits may be run at 150 to 250 rpm while insert bits for hard formations are only run between 50 to 100 rpm. Ideally, a bit should be able to run throughout an extended range of weight on bit and rotational speed combinations. The greater the load placed on the drill bit, the greater the torque required stressing the entire drill string assembly and increasing the overall cost of operation. The present bit and toroidal reamer arrangement allows long-life, high compressive loading and high rotation speeds without the limitations of previously known drill bits. Prior reamers exhibit high torque from the tendency of the reamer body to drag around the outer periphery of the bore to widen it. In the present invention, the reamer continuously crushes the edge of the previously drilled hole to open up the bore to the desired size from the longitudinal force of the freely rotating reamer portion. The additional weight on the crushing surface of the reamer permits the reamer to work effectively and without excessive wear to create a bore of the desired diameter. Finally, since the reamer and bit combination can be combined to enter a casing substantially smaller than the diameter which can be cut by such combination, the present invention can be used to underream while drilling, like the much more expensive bi-center bits, without their attendant steering problems. For example, some rock formations, such as basalt, do not readily allow the use of PDC bi-center bits which scrape the rock to open or ream the bore. With the present invention, which engages the hard rock formation to be opened with a crushing and rolling engagement of the drill bit and the toroidal reamer, such rock can be more readily drilled. SUMMARY OF INVENTION

The present invention is a drill bit providing a stack of cutters positioned generally along the longitudinal axis of the bore to provide cutting and reaming as the tool is rotated. Both cutters are rotatably supported on the body of the tool, the lower bit being generally of smaller diameter than the upper reamer cutter body so that the lower cutter body (bit body) initiates the cutting or crushing of the bore while the upper reamer body widens the bore to the desired diameter. By adjusting the axis of rotation of the upper body, the present invention may be used as a bi- centered bit assembly at a substantial fraction of the cost of these types of bits. Unlike the bi-centered bits, the present bit and toroidal reamer combination can accept substantial compressive loading without spiraling or deviating from the desired drill course. In summary, the present invention is an new drill bit-reamer assembly having an annular body or drill bit shank adapted to be coupled at one end to a drill string assembly, which may be either a drill string, drill collars or mud motor. The drill bit shank or body has a number of bearing raceways which cooperate with a first toroidal cutter body providing a plurality of bearing races on its inner surface; and sizeable bearings, larger than those found on drill bits of comparable sizes or diameters, which both retain the toroidal cutter body on drill bit shank and allow rotation thereof. Attached to the drill bit shank or body is an extension of the journal which provides a connection to a second cutter or drill bit body and also provides a plurality of bearing races on an inner surface of said second cutter body, and a number of bearings rotatably supporting the second cutter body on said journal. Alternatively, the second cutter body could be formed as a generally spherical body without a fluid passageway therethrough, without departing from the spirit or purpose of the invention disclosed herein. Alternatively, a standard drill bit may be attached to the extension of the toroidal reamer journal, all in a manner well known in the drilling industry. When the toroidal first cutter body and the second cutter are combined, the driller will be able to connect this drill bit and reamer system to the drill string or downhole mud motor, insert the assembly into the bore and drill for extended periods of time and utilizing greater than normal WOB without experiencing the early failure like those of current bit technology because of the low-torque, large bearing design of the present invention. Since the arrangement also permits drilling a hole larger than the diameter of the tool itself, the present invention can be used in place of a bi-center bit system at a fraction of the cost for underreaming while drilling. Additionally, the present apparatus may be used with a stabilizer interposed between the reamer and the drill bit to ream a previously drilled hole after being inserted in a restricted diameter drill string or casing. Since the reamer can be inserted past the restricted internal diameter of the restriction, it may be used to follow a drill bit or a bull nose in a manner well known to those in the drilling industry to ream a previously drilled hole.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view of one embodiment of the present invention in a bore.

Fig. 2 is a cross-sectional view of another embodiment of the present invention in a bore.

Fig. 3 is a cross-sectional side view of multi-cutter bodied drill bit-reamer combination.

Fig. 4 is a cross-sectional side view of an alternative multi-cutter bodied drill bit reamer combination with a standard drill bit.

Fig. 5 is a cross-sectional side view of another alternative embodiment of the toroidal reamer used for reaming below a restricted inner diameter. DETAILED DESCRIPTION

In Fig. 1 , the bit shank 110 provides threaded surface 112 for connection to either a drill string or a mud motor to provide rotation to the bit shank 110. A longitudinal passage 113 is provided in the bit shank to permit fluid communication into the bit shank 110 and through the jetting nozzle 114 provided through the shank body and through the passage 115 to the passage 116 to the bore face BF. The jetting nozzles or passages 114 and 116 are standard in the industry and may be fashioned with hardened materials to avoid erosion of the jetting nozzles from the abrasive effects of the fluid exiting the bit shank 110.

Upper cutter body 190 is retained by bearings 120 inserted through passage 117 into a raceway formed on the interior of the toroidal cutter body 190 and external surface for the bit shank 110. The bearings 120 are retained in place by cap head screw 111 which is inserted into the passage way after insertion of the retainer bearings 120. The upper cutter body 190 is rotatably carried by thrust bearings 130 and further supported by roller bearings 140. All bearing surfaces are packed with grease upon assembly and are protected from drilling fluids from O-ring 121 at the proximal end of the cutter body 190 and O-ring 122 at the distal end of the cutter body 190. Further, in a manner well known in this art, all bearing surfaces are connected to pressure compensated grease reservoirs (not shown) to provide constant lubrication of each bearing race during use. The drill bit shank 110 is threaded 118 for a cutter journal 192 in the drill bit shank 110. Prior to attachment to the drill bit shank 110 the retainer bearings 150 are inserted into the raceway between the journal exterior surface and the lower cutter body 194 inner surface and cap head screw 151 inserted to hold them in place. Then the journal and cutter body assembly is attached to the bit shank 110. A wrench surface 193 is provided to allow the lower cutter body 194 and journal 192 assembly to be tightened to the shank 110. Thrust bearings 160 rotatably support the lower cutter body, along with roller bearings 170; which again, like those of the upper cutter body, are packed and protected from ingress of drilling fluid by O-rings 123 and 124. Upper cutter body 190 is populated with cutter elements 133 fabricated from tungsten carbide on those portions of the cutter body surface which come into crushing contact with the bore face BF and with rounded hardened buttons 132 and 131 for those portions of the cutter body which are merely contacting but not crushing the bore B.

Similarly, the lower cutter body 194 is populated is rounded or ovoid tungsten carbide elements 180 for merely contacting the lower bore hole face, larger conical tungsten carbide elements 181 for crushing engagement of the face and smaller conical elements 183 around the central axis of rotation of the lower cutting body 194 for crushing and grinding of the bore face BF. In larger bit sizes, a portion of the cutting elements 183 may be smaller than the cutting elements 181 around the center of rotation of the second cutter body to provide more cutting surface at the distal edge of the cutter body. Similarly, with smaller second cutter bodies, the smaller cutting elements may 183 may be used to populate all of the conical cutting elements to provide effective coverage of the cutter body exterior surface, without departing from the invention disclosed herein. As may be readily appreciated from Fig. 1 , the axis of rotation of both the upper cutter body and the lower cutter body, although independent are the same slightly skewed from the axis of rotation of the bit shank 1 10. The skew angle may vary with the geometry of the face of each cutter body but in the present case is about 10°. At all times the cutter elements are either in rolling engagement with the bore face or lifted by the skew angle from the bore face thereby offering no resistance or drag. Additionally, grooves or spaces (not shown) between the cutter elements can be provided on the exterior surfaces of each cutter to permit cuttings to be washed from the bore hole face (BHF) past the cutters up the annulus of the bore being drilled. The embodiment shown in Fig. 1 may be inserted through casing of smaller diameter than the drillable well diameter and therefore can be used for underreaming. The ability to both drill and underream is currently met with expensive polycrystalline diamond cutter (PDC) bi-center bits which are very expensive to operate and which cannot be operated under certain drilling conditions of increased WOB and high rotational speeds. Bi-center bits operated at great WOB or speed tend to deviate from the desired course. With the present embodiment, substantial WOB can be maintained to expedite the drilling while maintaining the desired directional control of the drill bit. Fig. 2 shows an alternative embodiment of the invention. The drill bit shank 210 connects to a drill string assembly or downhole steerable drilling motor similarly to the embodiment shown in Fig. 1. An annular passage 113 is again provided to allow fluid communication from the drill string to the jetting nozzle 214 and/or the jetting passage 216 through the second toroidal body 292 at the distal end of the drill bit shank 210. The second embodiment shown in Fig. 2 has the same large bearings provided in the embodiment shown in Fig. 1 and is assembled and used in much the same manner.

The embodiment shown in Fig. 2 differs in a significant respect from the apparatus shown in Fig. 1. The skew angle of the reaming first or upper cutter body 290 is offset from the lower or second toroidal cutter body 292. The skew angle could also be different for each body 290 and 292 without departing from the spirit of the invention disclose so long as the cutters on each toroidal body 290, 292, are lifted off the opposing bore face. The axis of rotation of the first toroidal or upper body need not be either parallel with or co-linearly aligned with the axis of rotation of the second toroidal or lower cutter body. As long as the geometry of the two cutter elements including the shape of the cutter bodies and the skew angle with the longitudinal angle of the drill shank are set to prevent the opposing cutter elements from dragging across the face of the bore thereby eliminating excessive torque and wear on the cutter elements, the spirit of the invention disclosed herein is satisfied. Fig. 3 discloses the stacked drill-bit and reamer combination providing a medial or intermediate cutter body 392. As in the prior embodiments, the drill shank 310 is adapted to be connected, such as by threading, to a drill string, a drill collar, or a mud motor in a manner well known in the drilling industry. The drill shank 310 provides a longitudinal passage 113 for fluid communication to lubricate and cool the cutter elements as they engage the surfaces to be cut and to carry away the cuttings from the bore hole face up the annulus of the bore. Multiple jetting ports 318, 314, and 316 can be provided to provide abundant fluid communication to the exterior of the drilling apparatus. A first or proximal cutter body 391 is rotatably supported on the drill bit shank 310 with a plurality of bearings 331 and 332. The proximal cutter body is retained on the drill bit shank 310 by retainer bearings 320. Similar to each of the prior embodiments, each bearing surface is sealed from the ingress of drilling fluid by O-ring seals and this cutter body is populated again by a multitude of cutter elements made from tungsten carbide, all as more fully described above.

Drill bit shank 310 is also adapted for coupling to an intermediate or medial annular body 390 which provides exterior bearing surfaces or races for supporting another medial cutter body 392 similarly to those embodiments previously disclosed. The medial annular body provides as previously described an additional jetting port 314 made in a manner well known to those skilled in the art. Coupled at the distal end of the medial annular body is the distal cutter journal 393 which rotatably supports cutter body 394 on bearings cooperatively placed between the journal 393 and the cutter body 394.

Similar to the prior embodiment shown in Fig. 1, since the diameter of the largest or proximal element is substantially less than the full bore diameter which can be drilled by this embodiment, the configuration shown in Fig. 3, can be used for underreaming by inserting the assembly in the smaller casing then after leaving the casing rotating the assembly on bottom to create an enlarged bore.

Fig. 4 shows an alternative embodiment of the invention wherein the toroidal reamer is combined with a standard drill bit, such as a 9 7/8 inch tri-cone or a diamond drill bit, for example. Similar to the other embodiments, the drill bit shank 410 is adapted with external threads 412 for connection to a drill string or a drill motor in a manner well known to this industry. Drill bit shank 410 likewise provides a longitudinal passage 413 to allow fluid communication through the shank to the drill bit at the proximal end of the assembly. Drill bit shank 410 can also provide a jetting nozzle and passage to allow fluid communication to the well bore to lubricate the cutters and assist in carrying away cuttings made by the cutters. As may be further appreciated from the side cross-sectional view of Fig. 4, the drill bit shank 410 has a distal connection formed by threads on an extension 512 for connection to a journal body 500 which is off the main longitudinal axis of the drill string and skewed from said longitudinal axis. The journal 500 also provides a fluid passage 415 which allows the fluid from passage 413 to communicate to a drill bit 700, which may be a standard tri-cone drill bit or a polycrystalline diamond drill bit as may be desired. The drill bit 700 of the present view is shown only schematically. The present embodiment shown in Fig. 4 also discloses the additional feature of mounting the journal extension with cross-over sub 600 which allows the male threaded standard drill bit 700 to be used. Journal 500 may also be appreciated to be skewed with the extension which connects to the drill bit is skewed back to be collinear with the main longitudinal axis of the drill string.

Journal 500 provides a bearing race on its external surface to support a plurality of bearings, which in this view are balls 420. Toroidal cutter body 490 is mounted on the journal 500 through a passage 417 which is then closed by a pin 419 which is retained in said passage 417 by a locking pin 423. Alternative means of inserting the balls in the races may be used without departing from the scope or intent of the present invention. Pin 423 also provides an internal passage 411 to allow a floating grease seal so that the lubrication so that pressure on the exterior and interior between the seals 421 and 422 of the ball bearings is balanced, all in a manner well known in this industry. Cutter body 490 is populated with cutter elements 501 which may be tungsten carborundum or other materials well known in this industry.

Again, as previously described above, each of the cutter elements of the stacked bit- toroidal reamer combination can be populated to permit grooves (either longitudinal or spiral) about the exterior surface between the cutting elements to permit the movement of cuttings past the cutter body in a manner well known in the industry. Further, as previously described, each bearing surface can be provided with a pressure-compensated grease reservoir to continuously lubricate each bearing surface during the operation of the stacked assembly.

Fig. 5 shows another embodiment of the present invention having a single drill bit shank 510 threaded at its proximal and distal ends. The proximal end connects to the drill string DS and its distal end connects to a stabilizer 650. Each of the other elements found in the drill bit shank 510 are similar to those previously described herein. For example, the drill bit shank 510 can provide a passage and jetting nozzle to allow fluid communication from the interior longitudinal passage to the area adjacent the reamer to lubricate and clear cuttings up the bore B. Insertion of the bearings is accomplished in Fig. 5 in a manner similar to those described in Fig. 1. Other methods of inserting the bearings can be adopted without departing from the scope of this invention. Fig. 5 shows the bearing system at 720 and may be a combination of ball and roller bearings to permit the cutter body 602 to roll around its axis of rotation which is both skewed and offset from the main longitudinal axis of the drill string and the drill bit 700 at the distal end of the assembly. This skewed and offset body allows the reamer and drill bit assembly to be inserted in a restricted drill string to underream below the restriction in a bore B in a manner well known to those familiar with the bi-center bit drilling activities. A stablilizer 650 is placed at the distal end of the drill bit shank 510 to centralize the reamer in the bore to allow underreaming. Such stabilizer 650 may be three or four bladed having hard facing on each distal arm to hold the connected members in the center of a previously drilled bore hole BH. Although described as a schematic drawing of a drill bit 700, an operator could connect the reamer combination 510 of the present invention to a bull nose or to other drill string members (not shown) without departing from the spirit or intent of the present disclosed invention. These bottom hole assemblies would then provide the guide for reamer above them as it underreams the bore.

It may also be recognized that each of the bearings of the present invention could be formed from any number of well-known alternatives in the trade such as friction bearings made from alloys of berrylium and copper which may be used in high tension loading of the bearings without departing from the spirit or intent of this disclosure. Thrust roller bearings could also be used at the distal edge of the journal to absorb the longitudinal loading of the reamer. Each of these alternatives may be substituted into the description of the present invention and are well known to those skilled in this industry.

It may also be readily appreciated that alternative cutter arrangements, such as hardened steel surfaces or mill tooth cutter bodies, could be substituted for the cutter bodies providing carbide inserts for some drilling applications without departing from the spirit or purpose of this invention. Such cutter tooth arrangements come within the scope of the present invention.

Since the present system allows free movement of each toroidal cutter body, bit whirl is minimized. Bit whirl is experienced when excessive WOB causes the bit to stick against the face of the bore as torque builds up in the drill string assembly. When the bit is freed, it whirls to relieve the built-up torque causing damage to the drill string and related assemblies. Bit steering is enhanced because the system does not have a tendency to drift as additional weight is placed on the bit. Since embodiments of the invention can be used that provide a diameter of bore greater than the diameter of the bit and reamer combination, each embodiment may be used to replace PDC bi-center bits.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and it can be readily appreciated by those skilled in the art that various changes in the size, shape and materials, as well as in the details of the illustrated construction or combinations of the elements described herein may be made without departing from the spirit of the invention.

Claims

CLAIMS What is claimed is: 1. An drilling apparatus comprising: an annular body adapted to be coupled at a proximal end to a drill string assembly and providing a plurality of bearing races on an exterior surface; a first toroidal cutter body providing a plurality of bearing races on an inner surface of the first cutter body; a first plurality of bearings cooperating with said bearing races and rotatably supporting the first toroidal cutter body on said annular body; a journal attached to a distal end of the annular body; a second cutter body providing a plurality of bearing races on an inner surface of said second cutter body; and, a second plurality of bearings rotatably supporting the second cutter body on said journal.

2. The apparatus of claim 1 wherein the first and second cutter bodies have an axis of rotation skewed from the longitudinal axis of the annular body.

3. The apparatus of claim 2 wherein the first and second cutter bodies are each non-coaxial.

4. The apparatus of claim 1 wherein the annular body provides fluid communication between the drill string assembly and a passage through the first toroidal cutter body.

5. The apparatus of claim 1 wherein the second cutter body is toroidal.

6. The apparatus of claim 5 wherein the fluid communication is between the first toroidal cutter body and through a passage in the second toroidal cutter body.

7. A stacked drilling apparatus comprising: an first annular body adapted to be coupled at a proximal end to a drill string assembly and providing a plurality of bearing races on an exterior surface; a proximal toroidal cutter body providing a plurality of bearing races on an inner surface of the proximal cutter body; a first plurality of bearings cooperating with said bearing races and rotatably supporting the proximal toroidal cutter body on said annular body; a medial annular body adapted to be coupled at a distal end of the said first annular body and providing a plurality of bearing races on an exterior surface; a medial toroidal cutter body providing a plurality of bearing races on an inner surface of the medial cutter body; a second plurality of bearings cooperating with said bearing races and rotatably supporting the medial toroidal cutter body on said medial annular body; a journal attached to a distal end of the medial annular body; a distal cutter body providing a plurality of bearing races on an inner surface of said distal cutter body; and, a third plurality of bearings rotatably supporting the distal cutter body on said journal.

8. A stacked drilling apparatus comprising: a drill bit shank; a offset journal body connected to said drill bit shank providing a longitudinal passage to permit fluid communication, threads for connection to the drill bit shank, and to connect to a drill bit; a toroidal reamer rotatably secured to said offset journal body providing a sealed bearing race on an internal surface, a lubrication passage to provide lubrication to the sealed bearing race, which lubrication passage is hydraulically balanced, and a plurality of cutting elements on its exterior surface for rolling and crushing engagement of a bore hole face; and. a lower extension on said journal body providing threaded connections for a drill bit which is colinear with the longitudinal axis of the drill string whereby the drill bit is axially aligned with the drill string thereby permitting the drill bit and toroidal reamer to be inserted through a restricted bore to widen the bore at its distal end.

9. The apparatus of claim 8 wherein the drill bit is a standard tri-cone drill bit.

10. The apparatus of claim 8 wherein the drill bit is a polycrystalline diamond drill bit.

11. The apparatus of claim 8 wherein the drill bit is a single cone skewed drill bit.

12. A method of drilling a bore comprising: coupling the apparatus of any one of claim 1 , 7 or 8 to a drill string; inserting the coupled apparatus in a bore; rotating the drill string and coupled apparatus to drill and enlarge the bore.

13. A method of drilling a bore comprising: coupling the apparatus of any one of claim 1 , 7 or 8 to a fluid driven downhole motor; inserting the coupled motor and said apparatus into a bore; and, circulating fluid to drive the downhole motor and operate said apparatus to drill and enlarge a bore.

14. A method of underreaming a bore comprising: connecting an apparatus having a skewed and offset toroidal reamer to a drill string; connecting said skewed and offset toroidal reamer to a stabilizer; connecting said stabilizer to a bottom hole assembly; inserting said skewed and offset toroidal reamer into said bore to underream and enlarge the bore.