Boring or penetrating the earth – With expansible bore wall anchor
Patent
1995-06-14
1996-07-02
Schoeppel, Roger J.
Boring or penetrating the earth
With expansible bore wall anchor
E21B 418
Patent
active
055312802
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an anchor for use in a drill string.
Drill strings are subjected to variations in the fluid pressure in the well bore. These variations in pressure can cause any tool mounted on the string to move axially within the bore, and this axial movement can affect the accurate operation of the tool. In particular, if a drill string carrying a cutting tool is caused to expand or contract by changes in fluid pressure, the accuracy of the cutting operation will be impaired. Any unscheduled axial movement of the tool would cause the cutters to trace a spiral path in the well bore. One cause of undesirable tool movement is pulsations in the fluid pressure within the drill string resulting from operation of the mud pumps.
It would therefore be desirable to be able to anchor the drill string at a particular location to prevent axial movement of the tool in the well bore.
Axial movement caused by well bore pressure changes is particularly noticeable on small diameter work strings and coiled tubing. In general, the smaller the diameter of the string, the greater the effect becomes. In order to ensure that a cutting tool will cut successfully and accurately it is clearly necessary to hold the tool against axial movement.
The anchor of the present invention has been developed to endeavour to prevent any axial movement of a drill string at the location of the anchor as fluid pressure in the drill string or annulus is varied. The anchor may be used with any other tool which requires location at a specific depth within a tubing or casing of a well bore.
According to the present invention there is provided a drill string anchor for use in a well bore, the anchor having a body, a through bore and a plurality of anchor assemblies, each assembly comprising an anchor member, a piston supported within the body and a biassing means, the piston being radially movable in response to fluid pressure in the through bore between a first retracted position and a second extended position in which the piston drives the anchor member into contact with the wall of the well bore, and the biassing means acting to provide a force biassing the piston towards the first retracted position.
Preferably the inner face of the piston is exposed to the fluid pressure in the through bore, and the outer face of the piston is toothed to constitute the anchor member. The biassing force may be provided by any suitable means such as a coil spring or belville washers, and in the particularly preferred embodiment is provided by a leaf spring. The leaf spring may be fixed to the body at one end, the other end of the leaf spring engaging the piston.
Preferably, each anchor assembly additionally comprises a stop means for limiting radial extension of the piston. Each anchor assembly may also comprise a bleed passage between the inner and outer faces of the piston and a check valve may fitted to the bleed passage.
In a particularly preferred embodiment of the present invention the anchor has two axially separated sets of anchor assemblies, each set comprising three equiangularly spaced anchor assemblies, the two sets being circumferentially offset by sixty degrees with respect to each other.
The present invention will now be described in more detail with reference to the accompanying drawings, in which:
FIG. 1 is a quarter cross-section of an anchor of the present invention showing details of one embodiment of anchor assembly;
FIG. 2 is a diagrammatic longitudinal view of a preferred embodiment of the anchor: and
FIG. 3 is a quarter cross-section of an anchor showing details of an alternative embodiment of an anchor assembly.
Referring first to FIG. 1, an anchor 1 has a body 11, a central through bore 12, and a plurality of anchor assemblies 13. Only one such anchor assembly 13 is shown in FIG. 1. Each anchor assembly comprises a piston 2 movable in a chamber 16, a return spring 3 and a stop 4. A passage 5 allows communication between the through bore 12 and the inner face 14 of the piston. A seat member 6 is provided on the inner face
REFERENCES:
patent: 2546950 (1951-03-01), Nixon
patent: 2612346 (1952-09-01), Nelson
patent: 2792063 (1957-05-01), Jones
patent: 3062303 (1962-11-01), Schultz
patent: 3138214 (1964-06-01), Bridwell
patent: 3512592 (1970-05-01), Kellner
Lau Werner
McGarian Bruce
Steinkamp Manfred
LandOfFree
Drill string anchor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Drill string anchor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Drill string anchor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1499565