Claims
- 1. In a curve drilling assembly that is connectable to a rotary drill string for drilling a curved subterranean borehole having a bottom, having walls, having an inside radius and having an outside radius, the assembly comprising a flexible drill pipe section, a hole opener for enlarging the curved borehole comprising:
- a base disposed about a longitudinal bit axis for connecting to the downhole end of the flexible drill pipe section;
- a gauge portion that is disposed about said longitudinal bit axis, that extends from said base, that has an uphole end and that has a downhole end;
- a nose disposed about said longitudinal bit axis and extending from said gauge portion;
- a plurality of cutting elements that are carried by and extend from said gauge portion and that produce a lateral force on said hole opener at the downhole end of said hole opener in response to the rotation of the hole opener in the borehole;
- lower reaction pad means, carried by and extending from said gauge portion to trail said cutting elements by a maximum of 180 degrees and located generally below said plurality of cutting elements, for continuously contacting the borehole wall during rotation of the hole opener and for receiving a reactive force that is from said borehole, that is in response to said lateral force and that is directed adjacent to said downhole end of said gauge portion, said lower reaction pad means extending from said longitudinal bit axis by no more than the bore in which said hole opener is inserted; and
- upper reaction pad means, carried by and extending from said gauge portion to trail said cutting elements by a maximum of 180 degrees and located generally above said plurality of cutting elements, for continuously contacting the borehole wall during rotation of the hole opener and for receiving a reactive force that is from said borehole, that is in response to said lateral force and that is directed adjacent to said uphole end of said gauge portion of said hole opener, said upper reaction pad means extending from said longitudinal bit axis by approximately the same amount as said cutting elements, said lower reaction pad means and said upper reaction pad means having the effect of directing said longitudinal axis of said base portion to be tangent to the centerline of the curved portion of the borehole in which it is inserted.
- 2. The hole opener of claim 1, wherein said nose is sufficiently short relative to the length of said gauge portion and said base that said nose does not contact the outside of the curved borehole.
- 3. The hole opener of claim 1, wherein said cutting elements are sufficiently close to the downhole end of the flexible pipe section relative to the radius of curvature of said borehole that said downhole end of the flexible pipe section does not engage the curved borehole and cause said cutting elements to become inclined relative to the centerline of the curved borehole.
- 4. The hole opener of claim 3, wherein said gauge portion is located at a first distance Rg from said longitudinal axis, said cutting elements are located at a second distance Rc from said longitudinal axis, said borehole has a radius of curvature Rb at said cutting elements, and said cutting elements are located at a third distance L from the downhole end of the flexible drill pipe section, where said third distance L is a function of the product of said radius of curvature Rb and the difference (Rc-Rg) of said first distance and said second distance.
- 5. The hole opener of claim 4, wherein third distance L is on the order of the square root of said product.
- 6. The hole opener of claim 1, wherein said upper reaction pad means is positioned to trail behind said cutting elements by at least 90 degrees.
- 7. The hole opener of claim 1, wherein said lower reaction pad means is positioned to trail behind said cutting elements by at least 90 degrees.
- 8. The hole opener of claim 1, wherein said flexible section of drill pipe comprises wiggly pipe.
- 9. The hole opener of claim 1, wherein said flexible section of drill pipe comprises a plurality of articulated drill pipe segments.
- 10. The hole opener of claim 1, wherein said nose has an uphole end that is carried by said downhole end of said gauge portion and has a downhole end which is generally hemispheric in shape.
- 11. The hole opener of claim 1, wherein said gauge portion comprises a generally cylindrical section of pipe having a hollow interior and a plurality of longitudinally extending channels on its exterior surface.
- 12. In a curved subterranean borehole having an inside radius, having an outside radius, and having a predetermined borehole radius, a curve-opening tool comprising:
- a body that is disposed about a longitudinal bit axis, that has an uphole for connecting to the downhole end of a flexible pipe section, and that has a downhole end;
- a generally smooth nose extending from said downhole end of said body, said nose having a length that is sufficiently short relative to the length of said body that said nose does not substantially contact the outside of the curved borehole;
- cutting elements that are carried by and extend from said body intermediate said ends of said body, that cut along a line generally parallel to said longitudinal axis and that produce a lateral force on said body in response to rotation in the borehole;
- a lower reaction pad that is carried by and extends from said body to trail said cutting elements by a minimum of 90 degrees and a maximum of 180 degrees and that extends toward said downhole end of said body so as to contact the borehole wall during rotation in the borehole and receive a reactive force that is from said borehole, that is in response to said lateral force and that is directed adjacent to said downhole end of said body, said lower reaction pad extending from said longitudinal axis by no more than the radius of the wellbore in which said tool is inserted; and
- an upper reaction pad that is carried by and extends from said body to trail said cutting elements by a minimum of 90 degrees and a maximum of 180 degrees, that extends toward said uphole end of said body to contact the borehole wall during rotation in the borehole and receive a reactive force that is from said borehole, that is in response to said lateral force and that is directed adjacent to said uphole end of said body, said upper reaction pad extending from said longitudinal axis by about the same amount as said cutting elements, said lower reaction pad and said upper reaction pad having the effect of positioning said body such that said longitudinal axis is generally tangent to the centerline of the curved portion of the borehole in which it is inserted.
- 13. The curve-opening tool of claim 12, wherein said body has an exterior surface that is located at a distance Rg from said longitudinal axis; wherein said cutting elements have an edge that is located at a distance Rc from said longitudinal axis; wherein said borehole has a radius of curvature Rb where said edge is located; and wherein said cutting elements are located at a distance L from the downhole end of said flexible section of drill pipe, where L has a magnitude on the order of the square root of the product of Rb and (Rc-Rg).
- 14. The curve-opening tool of claim 12, wherein said body comprises a section of pipe having at least two elongated drilling fluid channels on its exterior.
- 15. The curve-opening tool of claim 14, wherein said lower reaction pad and said upper reaction pad have portions extending between said channels.
- 16. A hole opener for enlarging a short radius curved subterranean borehole, having walls, having an inside radius and having an outside radius, comprising:
- a cylindrical section that has one end for connecting to the downhole end of a flexible section of drill pipe, said cylindrical section having a length that is sufficiently short that its opposite end does not engagingly contact the outside of the curved borehole;
- cutters that are carried intermediate ends of said section, that extend from said section, that have cutting edges generally aligned to the axis of said section and that produce a lateral force on said section in response to the rotation of the hole opener in the borehole;
- lower reaction pad means, carried by and extending radially from said section to trail said cutters by a minimum of 90 degrees and a maximum of 180 degrees and located generally towards said opposite end of said section, for engaging the borehole wall during rotation of the hole opener and for receiving a reactive force that is from said borehole, that is in response to said lateral force and that is directed towards said opposite end of said section, said lower reaction pad means extending from said axis by no more than the radius of the wellbore in which said hole opener is inserted; and
- upper reaction pad means, carried by and extending from said section to trail said cutters by a minimum of 90 degrees and a maximum of 180 degrees and located generally toward said one end of said section, for engaging the borehole wall during rotation of the hole opener and for receiving a reactive force that is from said borehole, that is in response to said lateral force and that is directed towards said one end of said section, said upper reaction pad means extending from said axis by approximately the same amount as said cutters, said lower reaction pad means and said upper reaction pad means having the effect of aligning the longitudinal axis of said cylindrical section to be tangent to the centerline of the curved portion of the borehole in which said hole opener is inserted.
- 17. A tool for enlarging a short radius curved subterranean borehole having a predetermined diameter, comprising:
- a base that has a longitudinal axis that has an uphole end for connecting to the downhole end of an articulated section of drill pipe, and that has a downhole end;
- a nose located at said downhole end of said base, said nose having a length that is sufficiently short relative to the length of said base and having a generally smooth exterior such that said nose does not engagingly contact the curved borehole;
- a plurality of cutting elements that are carried by and extend radially and longitudinally from said base and that produce lateral forces on said base in response to the rotation of the base in the borehole;
- reaction pad means, carried by and extending from said base to trail behind said cutting elements, for continuously contacting the borehole wall during rotation of the base and for receiving a reactive force that is from said borehole and that is in response to said lateral force, said reaction pad means comprising one radial member that extends towards said uphole end and from said longitudinal axis by an amount that is about the same as said cutting elements, and comprising another radial member that extends toward said nose and from said longitudinal axis by no more than the bore in which said tool is inserted, said radial members having the effect of aligning said axis of said base to be tangent to the centerline of the curved portion of the borehole.
- 18. The tool of claim 17, wherein said one radial member is positioned to trail behind said cutting elements by a minimum of 90 degrees and a maximum of 180 degrees; and wherein said another radial member is positioned to trail behind said cutting elements by a minimum of 90 degrees and a maximum of 180 degrees.
- 19. The tool of claim 17, wherein said reactive force is from said borehole and comprises components that are directed to locations adjacent to each of said radial members.
- 20. In a curve drilling assembly that is connectable to a rotary drill string for drilling a curved subterranean borehole having walls, having an inside radius and having an outside radius, a tool for enlarging the curved borehole, comprising:
- a base that disposed about a longitudinal axis for connecting to the downhole end of the drill string, said base having an uphole end that is connectable to the downhole end of a section of wiggly pipe and having a downhole end that is located at a predetermined distance from said uphole end of said base such that said downhole end of said base does not engagingly contact the walls of the wellbore;
- cutting elements that are located intermediate said ends of said base, that are carried by and extend radially and longitudinally from said base, and that produce a lateral force on said base in response to rotation of said cutting elements against the walls of the borehole;
- a lower reaction pad that is carried by said base, that is located generally towards said downhole end of said base, and that extends from said longitudinal axis by no more than the bore in which the tool is inserted; and
- an upper reaction pad that is carried by said base, that is located generally towards said uphole end of said base and that extends from said longitudinal axis by about the same amount as said cutting elements, said lower reaction pad and said upper reaction pad trailing behind said cutting elements and contacting the borehole wall during rotation of the base to receive a reactive force that is in response to said lateral force and to maintain said longitudinal axis generally tangent to the centerline of the curved portion of the wellbore.
RELATED PATENT APPLICATION
This is a continuation-in-part of a U.S. patent application filed on Jul. 13, 1994 and having a Ser. No. of 275,020 and abandoned following the filing of this patent application.
US Referenced Citations (7)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
275020 |
Jul 1994 |
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