Claims
- 1. A rotary drill bit for drilling a bore hole comprising:
- a bit body having an upper end adapted to be connected to a drill string for rotating the bit and for delivering drill fluid to the bit, and having a plurality of legs extending from the lower end thereof, each leg including a journal on the extending end thereof having a longitudinal axis extending downwardly and generally radially inwardly of said leg;
- a roller cutter mounted for rotation about the longitudinal axis of each journal and having a plurality of rows of cutting elements including an outer gage row;
- said gage row of cutting elements adapted to cut the side wall of said well bore, the outer periphery of the bottom surface of said well bore, and the corner surface of said bore hole extending between said side wall and said outer periphery of said bottom surface; the remaining inner rows of cutting elements adapted to cut the remaining inner portion of said bottom surface; and
- a nozzle on said bit body positioned between a pair of adjacent roller cutters and having a nozzle orifice positioned closer to the bore hole side wall than to the axis of rotation of said bit at a height above the intersection of the longitudinal axes of said journals with said legs;
- said nozzle orifice being constructed and positioned to accelerate and direct a high velocity stream of drilling fluid downwardly and outwardly, the center of the volume of said stream being directed toward an impact point on the side wall above the center of said corner surface such that the majority of the fluid sweeps first across said corner surface and then across said bottom surface;
- said center of the volume of said stream being slanted for impacting said side wall at an impact angle greater than around fifteen (15) degrees away from a radial direction toward one of said adjacent cutters such that a substantial portion of the high velocity stream swirls around the corner surface toward said one cutter for scouring the formation at the lowermost cutting engagement contact location of the cutting elements in said gage row generally at said center of said corner surface.
- 2. A rotary drill bit as set forth in claim 1 wherein said high velocity fluid stream sweeps across a portion of said bottom surface to scour the formation at a majority of cutting engagement contact locations of said remaining inner rows of said adjacent cutter.
- 3. A rotary drill bit as set forth in claim 1 wherein said center of the volume of said high velocity stream sweeps across said center of said corner surface at a distance not greater than 0.42 inch per inch of bit diameter from the lowermost cutting engagement contact location of the cutting elements in said gage row at said center of said corner surface.
- 4. A rotary drill bit as set forth in claim 1 wherein said high velocity stream of drilling fluid is slanted against the direction of bit rotation toward the leading side of the trailing roller cutter of said pair of adjacent cutters with respect to the direction of rotation of said bit.
- 5. A rotary drill bit as set forth in claim 1 wherein said high velocity stream of drilling fluid is slanted in the direction of bit rotation toward the trailing side of the leading roller cutter of said pair of adjacent cutters with respect to the direction of rotation of said bit.
- 6. A rotary drill bit as set forth in claim 1 wherein said high velocity stream of drilling fluid is directed so that at least a side portion of said stream of drilling fluid contacts the cutting elements in said gage row prior to impacting said side wall.
- 7. A rotary drill bit for drilling a bore hole comprising:
- a bit body having an upper end adapted to be connected to a drill string for rotating the bit and for delivering drill fluid to the bit, and having a plurality of legs extending from the lower end thereof, each leg including a journal on the extending end thereof having a longitudinal axis extending downwardly and generally radially inwardly of said leg;
- a roller cutter mounted for rotation about the longitudinal axis of each journal and having a plurality of rows of cutting elements including an outer gage row;
- said gage row of cutting elements adapted to cut the side wall of said well bore, the outer periphery of the bottom surface of said well bore, and the corner surface of said bore hole extending between said side wall and said outer periphery of said bottom surface; and
- a nozzle on said bit body positioned between a pair of adjacent roller cutters and having a nozzle orifice positioned closer to the bore hole side wall than to the axis of rotation of said bit at a height above the intersection of the longitudinal axes of said journals with said legs;
- said nozzle orifice being constructed and positioned to direct a high velocity stream of drilling fluid downwardly and outwardly toward an impact point on the side wall above the center of said corner surface;
- said center of the volume of said stream being slanted for impacting said side wall at an impact angle away from a radial direction toward one of said adjacent cutters to sweep across said center of said corner surface at a distance not greater than 0.42 inch per inch of bit diameter from the lowermost cutting engagement contact location of the cutting elements in said gage row at said center of said corner surface, such that a substantial portion of said high velocity stream sweeps across said corner at said contact location.
- 8. A rotary drill bit as set forth in claim 7 wherein said center of the volume of said high velocity stream impacts said side wall at a slant impact angle greater than around fifteen (15) degrees away from a radial direction.
- 9. A rotary drill bit as set forth in claim 7 wherein said high velocity stream of drilling fluid is slanted against the direction of bit rotation toward the leading side of the trailing roller cutter of said pair of adjacent cutters with respect to the direction of rotation of said bit.
- 10. A rotary drill bit as set forth in claim 7 wherein said high velocity stream of drilling fluid is slanted in the direction of bit rotation toward the trailing side of the leading roller cutter of said pair of adjacent cutters with respect to the direction of rotation of said bit
- 11. A rotary drill bit as set forth in claim 7 wherein said high velocity stream of drilling fluid is directed so that at least a side portion of said stream of drilling fluid contacts the cutting elements in said gage row prior to impacting said side wall.
- 12. A rotary drill bit for drilling a bore hole comprising:
- a bit body having an upper end adapted to be connected to a drill string for rotating the bit and for delivering drill fluid to the bit, and having a plurality of legs extending from the lower end thereof, each leg including a journal on the extending end thereof having a longitudinal axis extending downwardly and generally radially inwardly of said leg;
- a roller cutter mounted for rotation about the longitudinal axis of each journal and having a plurality of rows of cutting elements including an outer gage row;
- said gage row of cutting elements adapted to cut the side wall of said well bore, the outer periphery of the bottom surface of said well bore, and the corner surface of said bore hole extending between said side wall and said outer periphery of said bottom surface; and
- a nozzle on said bit body positioned between a pair of adjacent roller cutters closer to the bore hole side wall than to the axis of rotation of said bit and having a nozzle orifice positioned at a height above the intersection of the longitudinal axes of said journals with said legs;
- said nozzle orifice being constructed and positioned to direct a high velocity stream of drilling fluid downwardly and outwardly toward an impact point on the side wall such that a majority of the fluid sweeps first across said corner surface and then across said bottom surface;
- said center of the volume of said stream being slanted toward one of said adjacent cutters to impact said side wall at a slant impact angle greater than around fifteen (15) degrees away from a radial direction such that a substantial portion of the high velocity stream swirls around the corner surface toward said one cutter for scouring the formation at the lowermost cutting engagement contact location of the cutting elements in said gage row at said center of said corner surface, said high velocity fluid stream further sweeping across a portion of said bottom surface to scour the formation at a majority of cutting engagement contact locations of rows other than said gage row of said one cutter.
- 13. A rotary drill bit as set forth in claim 12 wherein said high velocity stream of drilling fluid is slanted against the direction of bit rotation toward toward the leading side of the trailing roller cutter of said pair of adjacent cutters with respect to the direction of rotation of said bit.
- 14. A rotary drill bit as set forth in claim 12 wherein said high velocity stream of drilling fluid is slanted in the direction of bit rotation toward the trailing side of the leading roller cutter of said pair of adjacent cutters with respect to the direction of rotation of said bit.
- 15. A rotary drill bit as set forth in claim 12 wherein said high velocity stream of drilling fluid is directed so that at least a side portion of said stream of drilling fluid contacts the cutting elements in said gage row prior to impacting said side wall.
- 16. A rotary drill bit for drilling a bore hole comprising:
- a bit body having an upper end adapted to be connected to a drill string for rotating the bit and for delivering drill fluid to the bit, and having three integrally connected legs extending from the lower end thereof, each leg including a generally cylindrical journal on the extending end thereof having a longitudinally axis extending downwardly and generally radially inwardly of said leg;
- a roller cutter mounted for rotation about the longitudinal axis of each journal and having a plurality of rows of cutting elements including an outer gage row;
- said gage row of cutting elements adapted to cut the side wall of said well bore, the outer periphery of the bottom surface of said well bore, and the corner surface of said bore hole extending between said side wall and said outer periphery of said bottom surface; and
- a nozzle on said bit body positioned between each pair of adjacent roller cutters, each nozzle having a nozzle orifice positioned closer to the bore hole side wall than to the axis of rotation of said bit at a height above the intersection of the longitudinal axis of said journal with said leg;
- said nozzle orifice being positioned to direct a high velocity stream of drilling fluid downwardly and outwardly, the center of the volume of said stream being directed toward an impact point on the side wall above the center of said corner surface such that the majority of the fluid sweeps first across said corner surface and then across said bottom surface;
- said center of the volume of said stream being slanted away from a radial direction at a slant impact angle of at least around fifteen (15) degrees against the direction of bit rotation toward the leading side of the trailing cutter of said pair of cutters for impacting said side wall so that a substantial portion of the high velocity stream swirls around the corner surface toward said trailing cutter for scouring the formation at the lowermost cutting engagement contact location of the cutting elements in said gage row generally at said center of said corner surface.
- 17. A rotary drill bit as set forth in claim 16 wherein the center of volume of said high velocity stream is slanted toward said trailing cutter away from a radial direction to impact said side wall at a slant impact angle between around 20 degrees and 50 degrees.
- 18. A rotary drill bit as set forth in claim 16 wherein said center of the volume of said high velocity stream sweeps across said center of said corner surface at a distance not greater than 0.42 inch per inch of bit diameter from the lowermost cutting engagement contact location of the cutting elements in said gage row at said center of said corner surface.
- 19. A rotary drill bit as set forth in claim 16 wherein the center of the volume of said high velocity stream is directed toward an impact point on said side wall between around 1/4 inch and 3 inches above the lowermost cutting elements in said gage row.
- 20. A rotary drill bit for drilling a bore hole comprising:
- a bit body having an upper end adapted to be connected to a drill string for rotating the bit and for delivering drill fluid to the bit, and having three integrally connected legs extending from the lower end thereof, each leg including a generally cylindrical journal on the extending end thereof having a longitudinal axis extending downwardly and generally radially inwardly of said leg;
- a roller cutter mounted for rotation about the longitudinal axis of each journal and having a plurality of rows of cutting elements including an outer gage row;
- said gage row of cutting elements adapted to cut the side wall of said well bore, the outer periphery of the bottom surface of said well bore, and the corner surface of said bore hole extending between said side wall and said outer periphery of said bottom surface; and
- a nozzle on said bit body positioned between each pair of adjacent roller cutters, each nozzle having a nozzle orifice positioned closer to the bore hole side wall than to the axis of rotation of said bit at a height above the intersection of the longitudinal axis of said journal with said leg;
- said nozzle orifice positioned to direct a stream of drilling fluid downwardly and outwardly toward one of said pair of adjacent roller cutters, the center of the volume of said stream being slanted at a substantial angle away from a radial direction toward an impact point on the side wall above the center of said corner surface such that the majority of the fluid sweeps first across said corner surface toward said one cutter for scouring the formation thereat;
- said center of the volume of said stream prior to impact against said side wall being spaced from the cutting elements in the gage row a distance not greater than 0.070 inch with more hydraulic energy being directed by said high velocity stream against the cutting elements in said gage row than against the cutting elements in any other row prior to impact of said stream against said side wall.
- 21. A rotary drill bit as set forth in claim 20 wherein the center of volume of said high velocity stream is slanted away from a radial direction to impact said side wall at a slant impact angle of at least around 15 degrees.
- 22. A rotary drill bit as set forth in claim 20 wherein the center of volume of said high velocity stream is slanted away from a radial direction to impact said side wall at a slant impact angle between around 20 degrees and 50 degrees.
- 23. A rotary drill bit as set forth in claim 20 wherein said center of the volume of said high velocity stream impacts said side wall at a height between around 1/4 inch and 5 inches above the lowermost cutting elements in said gage row.
- 24. A rotary drill bit as set forth in claim 20 wherein said nozzle orifice is positioned at a location below the upper surface of said trailing roller cutter.
- 25. A rotary drill bit as set forth in claim 20 wherein said nozzle orifice is positioned generally centrally between said pair of adjacent cutters.
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of pending application Ser. No. 502,046 filed Mar. 30, 1990, now the U.S. Pat. No. 5,029,656, which is a continuation-in-part of pending application Ser. No. 381,040 filed July 17, 1989, now the U.S. Pat. No. 4,989,680.
This invention relates to rotary drill bits for drilling oil wells and the like, and more particularly to an improved hydraulic action of drilling fluid against the roller cutters of the drill bit and the earth formation being drilled.
While conventional drill bits have been satisfactory for drilling relatively brittle formations, they do not provide satisfactory rates of penetration when drilling relatively plastically deformable formations. Many commonly encountered formations such as salts, shales, limestones, cemented sandstones, and chalks become plastically deformable under differential pressure conditions when the hydrostatic pressure of the column of drilling fluid bearing on the bottom and corner of the well bore exceeds the pressure in the pores of the formation surrounding the bore.
In addition to compressive strengthening of plastic formations, high drilling fluid pressure causes the well known "chip hold down" phenomenon, where rock cuttings formed by the bit teeth are held in place by the pressure on the bore hole surface resulting in regrinding of the cuttings and decreased penetration rates. Weighting particles and drilled formation particles entrained in the mud increase the severity of chip hold down by blocking the flow of drilling fluid into the formation fractures and pore spaces, thereby restricting equalization of the bore hole and formation pore pressures and preventing chip release. In many impermeable formations such as shale, only a relatively small amount of fine particles is sufficient to seal off the formation fracture openings and severely limit chip removal.
Under these conditions "bit balling" often occurs where the reground cuttings and solid particles remaining on the hole bottom tend to adhere to the roller cutter, particularly in "sticky" formations such as shales, limestones, and chalks. The cuttings and fine solids are trapped between the well bore surfaces and the teeth and body of the rolling cutter, thereby being compressed by the drilling weight applied to the cutter as it is engaged to cut the formation. Compression of the solids onto the cutter surface builds a hard coating between and around the cutting teeth, often of sufficient thickness to reduce the effective protrusion of the cutting elements and limit their drilling effectiveness.
Numerous attempts have been made to overcome chip hold down and bit balling tendencies by modifying the configuration of the hydraulic nozzles to improve the cleaning efficiency and distribution of the drilling fluid energy. In U.S. Pat. No. 2,192,693, Payne describes a rolling cutter bit with an open hydraulic passage near the center of the bit body which flushes drilling fluid over an outer gage row of teeth. The hydraulic passage directs a relatively low velocity stream of drilling fluid directly toward the uppermost portion of the cutter to achieve a flushing action normal to the body of the rotating cutter.
Bennett in U.S. Pat. No. 3,618,682 dated Nov. 9, 1971 provides an extended enclosed passageway for the drilling fluid to a point adjacent the teeth at the bottom of the hole. The flow channel for the drilling fluid after striking the side wall is directed downwardly while enclosed by the leg and the adjacent side wall until exiting closely adjacent the corner of the bore hole. Bennett is used with a low pressure fluid and thereby can not take advantage of the high velocity cleaning power available from jet nozzles. The change in direction of a high velocity drilling fluid by the flow channel in the leg of the bit would result in substantial erosion with a high velocity drilling fluid.
Feenstra in British Patent No. 1,104,310 dated Feb. 21, 1965 utilizes an angled jet nozzle at the end of an extended tube to direct a fluid stream underneath the roller cutter at the outer row of teeth in cutting engagement on the bottom of the hole. The abrasive action resulting from a substantial change in direction of the drilling fluid causes erosion as well as reducing the flow velocity. In addition, requirements for the flow area and wall thickness of the flow channel give rise to compromises between design space and structural integrity. For these reasons, curved high velocity flow channels directing fluid under the cutting teeth have had limited success in rolling cutter bit applications.
A method to improve hole cleaning without extended flow channels is shown by Lopatin, et al in Russian Patent No. 258,972 published Dec. 12, 1969 where a rolling cutter drill bit has nozzle passages directed downwardly and radially outwardly against the side wall of the bore hole to strike above the bottom corner, providing an inwardly sweeping fluid stream having a high velocity across the corner and bottom of the well bore tangential to the formation surface. This design serves to clean solids away from the fracture openings at the surface of the formation, reduce the hold-down pressure on the fractured cuttings, and facilitate removal of dislodged cuttings by the high velocity fluid stream.
Childers, et al, in U.S. Pat. Nos. 4,516,642 and 4,546,837 employ a high velocity flow stream or fluid jet to first clean the cutting elements on a rolling cutter bit and then clean the formation at the bottom of the hole. The fluid jet trajectory passes the cutter tangential to its outer periphery with a portion of the jet volume impinging on the cutting elements and the remainder of the jet volume striking downwardly on the hole bottom underneath the cutter body slightly forward of cutting elements engaging the formation. The cleaning of both the cutter and the well bore bottom in separate and sequential actions provides improved penetration rates by attacking both bit balling and chip hold down. Deane, et al in U.S. Pat. No. 4,741,406, add a modification to this concept in which the fluid jet cleans both the rolling cutter teeth and the formation with an improved flow pattern. High velocity fluid flows radially outwardly and downwardly to impinge upon the hole bottom, then turns upwardly while moving toward the outer periphery of the hole, and next returns upwardly alongside the original nozzle exit in a spaced outer return channel for enhanced transport of cuttings away from the hole bottom.
The primary object of this invention is to maximize the penetration rate of rolling cutter drill bits by providing a hydraulic nozzle configuration for delivering a high velocity flow of drilling fluid on the cutting elements and the formation at the contact engagement area of the cutting elements with the formation with minimal erosion of the nozzle flow passageways.
The invention utilizes the geometry or geometrical configuration of the roller cutters and the cutting paths of the teeth at various positions on the cutter to insure intimate contact of the high velocity flow with cutting engagement areas. Special consideration is given to the outermost or gage row of cutting elements or teeth for cutting the corner surface where the formation is difficult to cut and balling of the teeth is prevalent. The gage row of cutting elements or teeth cut the side wall and diameter of the well bore, the outer periphery of the well bore bottom surface, and the corner surface between the side wall and bottom surfaces. The remaining rows of cutting elements cut the remaining bottom surface. The nozzle discharge orifice is positioned between and above the roller cutters without any nozzle extension being required. Such a nozzle orifice position accelerates and directs a high velocity drilling fluid downwardly and outwardly with the center of the volume of the stream being directed toward an impact point on the side wall at or above the corner surface so that a majority of the fluid sweeps first across the corner surface and then across the bottom surface. The center of the volume of the fluid stream is slanted toward one of the adjacent roller cutters so that a substantial portion of the high velocity stream swirls around the corner surface to scour the formation at the cutting engagement contact location of the gage row with the formation. While much of the prior art has provided some increase in penetration rates, it has been found that certain aspects of the nozzle position and direction of the fluid flow path therefrom are more important than expected.
The outermost or gage row of cutting elements for each roller cutter is the row that most affects the rate of penetration of the rotary drill bit. The formation is stronger at the annular corner of the bore hole formed at the juncture of the horizontal bottom surface and the vertically extending cylindrical side surface of the bore hole formation. Thus, the outermost or gage row of cutting elements is the critical row in determining the rate of penetration. It is important that maximum cleaning action by the pressurized drilling fluid be provided particularly for the cutting elements in the outermost or gage row at the cutting engagement of such cutting elements with the formation, and preferably at the cutting engagement of other rows of cutting elements.
Application Ser. No. 381,040, now U.S. Pat. No. 4,989,680, relates to a roller cutter drill bit in which a high velocity stream of drilling fluid is directed against the cutting elements in the gage row to provide an increased hydraulic action first against the cutting elements in the gage row and then sequentially against the bore hole bottom generally adjacent the corner of the bore hole.
The present invention likewise is directed to an improved hydraulic action for the cutting elements in the gage row. However, the drilling fluid is discharged in a direction toward an adjacent roller cutter with the center of the volume of drilling fluid first impacting the side wall of the bore hole at an impact point on the side wall at or above the corner surface so that a substantial portion of the fluid scours the corner surface at the cutting engagement contact location of the gage row with the formation, and sweeps across the bottom surface at the cutting engagement contact location of the cutters. The stream of drilling fluid is directed against the side wall and slanted toward an adjacent roller cutter in such a manner that the velocity of the drilling fluid sweeping across the corner surface and under the cutting elements is not substantially reduced after impacting the side wall of the bore hole so that adequate velocity is retained for the subsequent sweeping action. The high velocity stream after impacting the side wall sweeps with a thin high velocity swirling action along the side wall and around the corner surface, and then beneath the cutter across the bottom hole surface to scour and clean the corner and bottom surfaces at the cutting engagement contact locations of the cutting elements.
The stream of drilling fluid from the nozzle is slanted toward an adjacent roller cutter at a sufficient angle to provide a swirling action first around the corner surface at the cutting engagement area of the gage row, and then a sweeping action across the hole bottom at the cutting engagement areas of other cutting elements of the associated cutter for the effective cleaning of the formation at the specific location where there is engagement of the cutting elements. With discharge nozzles positioned generally centrally between the cutters, the high velocity stream of drilling fluid is slanted toward an adjacent cutter and directed against the side wall at a slant impact angle away from a radial direction at least around fifteen (15) degrees and preferably between thirty (30) and fifty (50) degrees for normal three cutter bits. It is difficult to achieve slant impact angles of greater than fifty (50) degrees on normal three cutter bits due to geometry restrictions. Other bit designs such as two cutter bits might achieve improved results with larger slant impact angles than fifty (50) degrees depending on the nozzle exit position. Such a slant impact angle for the high velocity stream has been found to be desirable for directing sufficient high velocity fluid flow around the corner surface at the cutting engagement contact locations, and then underneath the roller cutter and across the hole bottom.
The outwardly directed high velocity stream impacts the side wall above the center of the corner surface and causes a substantial portion of the stream to swirl circumferentially around the corner surface toward the associated cutter for scouring the corner surface where it is being cut by the cutting elements in the gage row. As the direction of the high velocity fluid is slanted further away from a radial direction, the more the swirling action of the stream sweeping along the corner surface is brought into contact with the formation at the cutting engagement locations of the gage row and across the hole bottom at the cutting engagement locations. An optimum penetration rate can be achieved by selecting a specific nozzle direction for a given nozzle exit position and roller cutter geometry to facilitate access of the high velocity flow to a maximum number of cutting engagement locations. It is also important to optimize contact of the high velocity stream with the associated cutter prior to impacting the side wall so that effective tooth cleaning action is obtained without excessive hydraulic energy loss in the high velocity stream before it strikes the side wall and sweeps across the cutting engagement locations of the gage row.
It is an object of this invention to demonstrate that removing cuttings and fine solid particles away from the cutting engagement locations for a rotary drill bit provides substantial improvements and that scouring the formation at the cutting engagement locations of the teeth in the gage row is particularly important, particularly at the corner surface which is the most difficult area of the bore hole to drill.
It is another object of the present invention to provide a rotary drill bit in which the center of a drilling fluid stream is directed from a nozzle orifice toward an impact point on the bore hole side wall at or above the corner surface between the side wall and the bottom surface for sweeping first across the corner surface and then across the bottom surface.
An additional object of the present invention is to provide a nozzle for the stream of drilling fluid positioned on the drill bit between a pair of roller cutters and directing the drilling fluid outwardly against the side wall of the bore hole and slanted toward an adjacent roller cutter to provide a swirling action to scour the formation specifically at the cutting engagement locations on the corner and bottom surfaces of the hole.
A further object is to provide an improved hydraulic cleaning action during cutting engagement employing a conventional hydraulic jet nozzle to direct a high velocity flow toward specific tooth engagement areas and without the requirement of a special passage for nozzle extension or high velocity flow redirection.
Other objects, features, and advantages of this invention will become more apparent after referring to the following specification and drawings.
US Referenced Citations (22)
Foreign Referenced Citations (5)
| Number |
Date |
Country |
| 36772 |
Sep 1981 |
EPX |
| WO9005830 |
Mar 1990 |
WOX |
| 258972 |
Apr 1970 |
SUX |
| 344099 |
Aug 1972 |
SUX |
| 1104310 |
Feb 1968 |
GBX |
Continuation in Parts (2)
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Number |
Date |
Country |
| Parent |
502046 |
Mar 1990 |
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| Parent |
381040 |
Jul 1989 |
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Patent Grant
5096005
