Boring or penetrating the earth – Cutter element laterally shiftable below ground – Cutter element shifted by fluid pressure
Reexamination Certificate
1999-10-28
2002-04-30
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Cutter element laterally shiftable below ground
Cutter element shifted by fluid pressure
C175S289000, C175S291000
Reexamination Certificate
active
06378632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to underreamers used to open a hole below a restriction so that the opened hole is larger than the restriction itself. More particularly, this invention relates to a hydraulically actuated underreamer in cooperation with an actuator associated therewith to remotely actuate the underreamer when fluid is circulating in a borehole. The cutter arms of the underreamer retract when fluid circulation ceases through a cutter arm retractor contained within the underreamer housing.
2. Description of the Related Art
Underreamers are used in the petroleum industry to enlarge boreholes. Such tools can be used in drilling oil, gas or water wells and in mining operations. An underreamer has basically two operative states, a closed or collapsed state where the diameter of the tool is sufficiently small to allow movement of the tool in the narrowest part of the borehole, and an open or partly expanded state where one or more arms with cutters on the ends thereof, pivot out from the body of the tool. In this latter position the borehole is enlarged as the tool is rotated and lowered in the borehole.
A drilling type underreamer is typically used in conjunction with a drill bit positioned below or downstream of the underreamer. The drill bit can drill the borehole to be underreamed at the same time as the underreamer enlarges the borehole formed by the bit. Circulation of drilling fluid to the drill bit is required to remove detritus from the bottom of the borehole and to cool and clean the bit as it drills the borehole.
Underreamers of this type usually have hinged arms with cutters attached thereto. These pivoted arms tend to break during the drilling operation and must be removed or “fished” out of the borehole before the drilling operation can continue. The tool typically has rotary cutter pocket recesses formed in the body where the arms are retracted when the tool is in a closed state. These pockets have a tendency to fill with debris from the drilling operation which makes collapsing of the arms difficult. If the arms do not fully collapse, the drill string may easily hang up in the borehole when an attempt is made to remove the string from the borehole. Most of the prior art underreamers utilize swing out cutter arms that are pivoted at an end opposite the cutting end of the reamer and are actuated by mechanical or hydraulic forces acting on the arms to extend or retract them. Typical examples of these types of underreamers are found in U.S. Pat. Nos. 3,224,507; 3,425,500 and 4,055,226.
An early example of a mechanically actuated expandable drill bit that does not use pivoting cutter arms to ream a borehole is taught in U.S. Pat. No. 3,365,010. This drill bit utilizes a pair of blade type cutters that ride in opposed, axially oriented channels. The channels are angled with respect to the axis of the bit such that when the blades impact the bottom of the borehole, shear pins retaining the blades are broken allowing the blades to move up the channels thereby expanding out against the borehole wall for subsequent borehole enlargement. A large pin for each blade retains the expanded blades in a desired position thus controlling the gage of the borehole. When the expandable drill bit is tripped out of the borehole, the blades fall down the angled tracks through frictional and gravitational forces thus diminishing the gage diameter of the expandable drill bit so that the drill string may be removed from the borehole. Once the shear pins are sheared, the expandable drill bit can only be used as a hole opener and only when the expandable drill bit is in contact with the borehole bottom.
U.S. Pat. No. 3,433,313 teaches an under-reaming tool having a tubular body with a sleeve movably positioned therein and adapted, when moved in one direction responsive to the pressure of drilling fluid, to move cutters to their opposite direction. Also responsive to the pressure of drilling fluid, the cutters are allowed to retract from their cutting position. A drilling fluid passage is formed in the tubular body to increase the flow area for drilling fluid when the cutters are in their cutting position and a means of positively moving the sleeve in the opposite direction with a wireline tool. The wireline tool is used to stop the flow of drilling fluid thus allowing the cutters to retract. This patent is disadvantaged in that a wireline device must be used to retract the cutters so that the tool may be tripped out of the borehole or to render the under-reamer inoperative downhole.
U.S. Pat. No. 5,368,114 teaches an under-reaming tool for use in preferably horizontal and extended reach boreholes. The tool includes a succession of stabilizers, underreamers and expandable stabilizers. A drilling mud activator is provided for the expandable elements of the underreamers and expandable stabilizers. The underreaming device comprises a main body with a number of guiding surfaces distributed over the circumference thereof which have a pitch angle that increases radially in an axial direction. A ring collar formed as a piston in a surrounding cylinder housing forms a small and a large radial annular surface. The piston further forms reaming pads/wings and/or stabilizer pads/wings in sliding contact with a respective guiding surface, the pads being taken up in ports in a jacket surrounding the main body in such a way that the pads can only be moved radially relative to the jacket, the jacket being attached to or formed as a part of the cylindrical housing. This patent is disadvantaged in that, in order to position the pad/wings associated with the reamer and stabilizer function, the pressure differential across the manipulating piston must be controlled and monitored by a microprocessor device positioned downhole; the information being electronically relayed to the rig platform.
Other related underreamer type patents include U.S. Pat. Nos. 4,141,421 and 4,889,197.
In general, prior art underreamers are disadvantaged in that those having cutting structures located at the end or near the end of a pivotable arm are inherently vulnerable to breakage of the pivot pins which retain the arms on the mandrel. Also, the mandrel recesses into which the cutters retract when they are collapsed tend to become easily fouled with debris during the cutting operation when the arms are extended. As a result, the arms are difficult to retract into the mandrel recesses.
Moreover, if the prior art tools are capable of transmitting fluid therethrough, it is typically accomplished using a centrally located hole or cylindrical tube. Most often, three cutters are used to dress each tool. A majority of these type tools do not positively collapse. Rather, a cutter retraction spring forces a piston to retract. The cutters however are not generally connected to the piston retraction spring and must retract through release of engagement with the borehole wall or retract through gravitational forces. The piston is usually in such a position that it is not possible to isolate fluid pressure from acting on it without preventing circulation of the drilling fluid. In other words, the tool cannot be enabled or disabled without stopping fluid circulation.
Another disadvantage of the prior art is that the cutter size and positioning are not optimized for the full range of hole opening sizes. In order to adjust the expanded diameter of a conventional underreamer, it is necessary to replace the cutting arms with larger or smaller arms or to adjust the location of their pivot points inwardly or outwardly with respect to the axis of the tool. It may even be necessary to replace the underreamer altogether with one which will provide a different expanded diameter.
Yet another disadvantage of the prior art is that the hydraulic capability is not optimized for the high fluid flow rates required.
The present invention overcomes the deficiencies of the prior art.
SUMMARY OF THE INVENTION
An expandable underreamer is disclosed which consists of an underreamer body forming at least a pair of opp
Dewey Charles H.
Saylor James E.
Bagnell David
Conley & Rose & Tayon P.C.
Gay Jennifer H
Smith International Inc.
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