Boring or penetrating the earth – Cutter element laterally shiftable below ground – Cutter element shifted by fluid pressure
Patent
1997-07-22
1998-12-29
Schoeppel, Roger
Boring or penetrating the earth
Cutter element laterally shiftable below ground
Cutter element shifted by fluid pressure
175279, 175285, 175286, 175406, 175434, 175435, E21B 728
Patent
active
058530541
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a 2-stage underreamer, that is to say a reaming tool for use in a subterranean well bore, the tool having axially spaced apart first and second reaming stages. 2-stage underreamers have been proposed in which the bodies of the upper and lower stages are releasably secured to each other by way of a threaded interconnection. Whilst such an arrangement considerably assists the manufacture of the tools it suffers from the disadvantage that very close manufacturing tolerances are necessary if, when the upper and lower body parts are screwed together, the blades on the upper and lower parts are to end up at exactly the correct angular position relative to each other. Further, the presence of a screw-threaded joint between the upper and lower stages of the tool reduces the strength of the body as compared with the strength of a unitary body.
SUMMARY OF THE INVENTION
Accordingly, a first aspect of the present invention provides a 2-stage underreamer comprising an upper pair of reaming blades mounted in a slot or pocket in a body and a lower pair of reaming blades mounted in a slot or pocket in the body, wherein the body is unitary.
In the preferred embodiment of the present invention the blades of the upper stage are hingedly mounted on the body and are movable from a retracted storage position to an extended use position by movement in respective first and second mutually parallel planes. Similarly, the lower blades are hingedly mounted on the body and are movable from a retracted storage position to an extended use position in third and fourth respective mutually parallel planes. In the preferred embodiment the third and fourth planes are perpendicular to the first and second planes.
In the preferred embodiment of the invention power means are provided for moving the blades from their respective retracted to their respective extended positions. Such power means preferably comprises a hydraulically actuated piston which exerts a force on a cam surface of its associated blade to cam the blades from the retracted to the extended positions. Preferably, spring biasing means are provided for biasing the blades from their extended towards their retracted position so that if the power means ceases to act on the cam surfaces of the blades the blades will be retracted under the influence of the spring biasing means.
Preferably, a single upper blade power means is provided for acting simultaneously on both upper blades and a single lower blade power means is provided for acting simultaneously on the lower blades.
In a particularly preferred embodiment of the invention the power means comprises a piston having a first piston portion having a circular face on which hydraulic fluid acts to generate a force and a second piston portion which is annular and upon which hydraulic fluid acts to create force reinforcing that produced by the hydraulic fluid acting on the first piston portion. To this end, in the preferred embodiment of the invention the first piston portion is connected to the second piston portion by a rod which passes through an annular member which sealingly engages the rod and a bore provided in the body and separates a fluid chamber which is bounded on one side by the second piston portion from a zone of the bore of the body which is vented to the exterior of the body.
Whilst the above described power means is particularly suitable for use in the 2-stage reamer of the present invention, the power means may be more generally applicable and may be utilized in other apparatus requiring generation of a force by application of a hydraulic pressure.
Preferably, means are provided for indicating when at least one of the sets of blades has moved from its retracted to its extended position. Such means preferably comprises a flow passage through the tool for hydraulic fluid the cross-sectional area of which changes when one of the sets of blades moves from its retracted to its extended position, thereby providing an indication by way of the fluid flow rate through
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Armell Richard Alvin
McGarian Bruce
Schoeppel Roger
Smith International Inc.
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