Claims
- 1. An apparatus positioned in the wall of a pipe for use in a wellbore to centralize the pipe in the wellbore wherein guide means in the wall of the pipe has an elongated piston mounted therein for movement from a retracted position within the outer profile of the pipe to an extended position wherein the piston extends outwardly from the wall of the pipe, and latch means are arranged for maintaining the piston in a retracted position while the pipe is being run into the wellbore, the latch means comprising;
- a substantially cylindrical guide surface formed transversely in the wall of the pipe;
- an annular guide groove formed in the wall of the pipe around the guide surface in a plane perpendicular to a longitudinal axis of the guide surface;
- an annular piston groove in an outer wall of the piston, said piston groove being in a plane perpendicular to the longitudinal axis of the piston;
- snap ring means mounted in said piston groove and arranged to expand outwardly over the outer surface of said piston into said guide groove when a force is applied to one end of said piston and thereby permit said piston to move from said retracted to said extended position for centralizing the pipe in the wellbore.
- 2. The apparatus of claim 1 wherein said annular piston groove is formed in the shape of a ring shaped channel having substantially straight side walls spaced from one another and extending inwardly into the outer surface of the piston and a stepped bottom surface extending between the side walls, which bottom surface is parallel to the outer cylindrical surface of the piston.
- 3. The apparatus of claim 2 wherein said snap ring is substantially circular in cross-section and the stepped bottom surface of the piston groove has a first wider portion that is no deeper into the surface of the piston than 0.5 times the diameter of the snap ring.
- 4. The apparatus of claim 3 wherein the first wider portion is sized to permit said snap ring to engage the bottom surface when said piston is in said retracted position.
- 5. The apparatus of claim 3 wherein said first wider portion is less wide than the diameter of the snap ring.
- 6. The apparatus of claim 3 wherein the stepped bottom surface has a second less wide portion that is no more wide than 0.33 times the total width of the stepped bottom surface.
- 7. The apparatus of claim 1 wherein said pipe is comprised of a casing pipe string and said piston when extended serves to move the casing pipe string toward the center of the wellbore.
- 8. The apparatus of claim 7 and further including an annular locking groove formed in the outer wall of the piston for receiving said snap ring when said piston has moved to said extended position and for fixedly holding said piston in said extended position.
- 9. The apparatus of claim 8 wherein said locking groove is configured to receive said snap ring so that continued forces applied to said piston will not permit further movement of said piston relative to said guide means.
- 10. Apparatus for spacing a casing pipe string from the walls of a borehole comprising;
- a plurality of annular side wall guide openings in the casing pipe string;
- a piston having a unitary piston body mounted for lateral sliding movement in the guide openings between a retained position and an outwardly extended locked position wherein the outer end of the piston is arranged to extend into contact with the wall of the borehole;
- latch means for holding said piston in said retained position including a first annular groove formed in the outer circumferential wall of said piston, a second annular groove formed in the inner circumferential wall of said side wall guide openings, and expandable ring means positioned in said first and second grooves when said piston is in said retained position.
- 11. The apparatus of claim 10 wherein the casing pipe string is made up of sections of casing pipe connected by collars greater in diameter than the casing pipe and providing a maximum exterior profile of the casing pipe string and wherein the outermost portion of said guide opening and the outer end of said piston present a profile that is less than the maximum exterior profile of the casing pipe string when said piston is in said retained position for running said casing pipe string into the borehole.
- 12. The apparatus of claim 10 wherein the inner end of said pistons is substantially clear of the inner bore of said casing pipe string when said piston is in said extended position.
- 13. Apparatus for spacing a casing pipe string from the walls of a borehole comprising;
- a plurality of annular side wall guide openings in the casing pipe string;
- a piston mounted for lateral sliding movement in the guide openings between a retained position and an outwardly extended locked position;
- latch means for holding said piston in said retained position including a first annular groove formed in the outer circumferential wall of said piston, a second annular groove formed in the inner circumferential wall of said side wall guide openings, and expandable ring means positioned in said first and second grooves when said piston is in said retained position, wherein said ring is expandable upon the application of predetermined force to one end of said piston for movement of said ring into said second annular groove to expand about the outer surface of said piston to permit said piston to move to said extended position.
- 14. The apparatus of claim 13 wherein said latch means is arranged to prevent movement of said piston in a direction opposite of its movement to said extended position.
- 15. The apparatus of claim 14 wherein said first groove has a stepped surface at the bottom of said groove, the depth of said stepped surface being determinative of the force necessary to expand said ring over the outer surface of said piston.
- 16. Apparatus for spacing a casing pipe string from the walls of a borehole comprising;
- a plurality of annular side wall guide openings in the casing pipe string;
- a piston mounted for lateral sliding movement in the guide openings between a retained position and an outwardly extended locked position, wherein said piston can move to only a single predetermined extended position to space the casing pipe string from the walls of the borehole; and
- latch means for holding said piston in said retained position including a first annular groove formed in the outer circumferential wall of said piston, a second annular groove formed in the inner circumferential wall of said side wall guide openings, and expandable ring means positioned in said first and second grooves when said piston is in said retained position.
- 17. The apparatus of claim 16 and further including a third annular groove which is formed in the outer wall of said piston for engaging said expandable ring when said piston is moved to said extended position to lock said piston in said extended position.
BACKGROUND AND SUMMARY OF THE INVENTION
This application is a continuation-in-part of U.S. patent application Ser. No. 761,210 filed Sep. 16, 1991, now U.S. Pat. No. 5,228,518 issued Jul. 20, 1993.
US Referenced Citations (22)
Continuation in Parts (1)
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Number |
Date |
Country |
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761210 |
Sep 1991 |
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