Boring or penetrating the earth – Tool shaft advanced relative to guide insertable in... – With anchor for guide engaging hole side wall
Reexamination Certificate
1997-12-04
2001-04-24
Bagnell, David (Department: 3673)
Boring or penetrating the earth
Tool shaft advanced relative to guide insertable in...
With anchor for guide engaging hole side wall
C175S079000, C175S320000, C175S323000, C166S117500, C464S052000, C464S058000
Reexamination Certificate
active
06220372
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to apparatus for drilling lateral drainholes from a wellbore. More particularly, drainholes are drilled using a bit driven by a flexible shaft formed of two or more concentric coil springs, having opposite pitch, guided through a short radius turning elbow anchored within the wellbore.
BACKGROUND OF THE INVENTION
After a well, completed into a formation, has been producing oil or gas over an extended period of time, the rate of production generally diminishes, often due to depletion of the reservoir or due to near-wellbore effects. Methods of alleviating diminished production can include treating the near-wellbore effects and increasing the drainage area or wellbore access. Treatment of near-wellbore effects include hot oil flushing to melt paraffins, high pressure fracturing, chemical treatments, or re-perforation of the casing and acidizing to open up additional flow passages. Each of these treatments are subject to restrictive use or success of short duration.
A more progressive solution is to increase the drainage area. This is generally accomplished by drilling holes laterally outwardly from the wellbore so as to increase communication with the formation. These holes are known as drainholes.
Typically, the hydrocarbon bearing portion of the formation is rather shallow. This delimits where the lateral drainholes are placed, requiring significant precision in vertical placement. Additionally, the drainholes must first pass through the existing casing and then extend into the formation.
Whipstock diversion or horizontal drilling techniques using mud motors account for most of the re-entry drilling techniques. Generally a full drilling rig is required and is used in combination with a whipstock to deviate the drill string. A portion of the casing is milled out and a rotary drilling string or mud motor essentially drills a new wellbore. This requires a large radius of turn which complicates targetting of the payzone. The process is expensive and results in a single new hole.
Lance-type penetrators, such as that disclosed in U.S. Pat. No. 5,392,858 to Peters, introduce apparatus to first mill through the casing and then provide a flexible conduit which supplies high pressure fluid to a nozzle. The nozzle jets forward while advancing, hydraulically cutting into the formation. Small radii (12″) can successfully be achieved. Unfortunately, the high pressure fluid can erode the casing cement and re-establish undesirable cross-communication with vertically adjacent layers.
A lesser known technique is to provide a section of highly flexible drill shaft at the downhole end of a rotary shaft. These techniques use a single coiled spring as the power transmitting member with an internal or external elastomer sheath or hose to contain drilling fluids. These systems, as disclosed in U.S. Pat. Nos. 3,838,736 and 4,051,908 to Driver, have the following features in common: a tubing string is lowered into the casing, the string having a 90 degree elbow at its lower end; a flexible hollow shaft is connected to the lower end of drill pipe and is lowered down into the tubing string; the drill string is rotated, the flexible shaft is directed laterally by the elbow and proceeds to drill through the casing and into the formation. These and similar systems are limited to low drilling rotational speeds and low axial loading to avoid premature failure of the coil spring flexible shaft.
In the context of stabilizing the roofs of mines, a flexible drill shaft is used to drill holes upwardly into the roofs. By providing a flexible shaft, shaft lengths and thus hole depths greater than the height of the mine corridor can be achieved. As disclosed in U.S. Pat. No. 4,057,115 to Blanz, contra-wound bands or springs are used for the shaft. An outer band is helically wound about a coil spring having an opposite pitch. A drill bit is secured to the shaft's upper end. A rotary drive clamps onto the circumference of the outer band and applies torque. The drive and shaft are advanced axially upwardly, driving the bit into the mine's roof. When the rotary drive approaches the roof, it is unclamped, lowered axially and is re-clamped onto the shaft. During drilling, the outer band tends to contract, and the inner coil tends to expand, lending axial stability to the shaft.
This apparatus does not address the difficulties of downhole operation, including the ability and the need to introduce an axial load into the flexible shaft yet still make small radius turns, wherein the axial load originates before the turn is made.
SUMMARY OF THE INVENTION
Apparatus is provided or drilling drainholes laterally outwards from even very small diameter casings, enabling accurate and economical access to the hydrocarbon producing formation.
More particularly, apparatus is lowered down within the well's casing. The apparatus comprises a flexible shaft having a bit at the lower end and a shaft guide conduit. The “L” shaped guide conduit re-directs the shaft from a path parallel to the casing, to one substantially perpendicular to the casing. The shaft guide conduit is rigidly anchored within the casing. Accordingly, the bit is directed towards the casing, enabling cutting through the casing and into the formation. The flexible shaft has upper and lower ends and is formed of a helically wound outer coil spring and one or more helically wound and smaller inner coil springs residing concentrically therein. Each successively smaller inner coil spring has an outer diameter substantially the same as the inner diameter of the adjacent larger coil spring. Each coil spring is wound opposite in direction to that of the next adjacent coil spring. Each coil spring is held in rigid relation to each other coil spring at the shaft's upper and lower ends. The direction of the bit's rotation is coordinated with the direction of winding of the outer coil spring so that the diameter of the outer coil spring tightens upon the expanding diameter of the next adjacent inner coil spring. The “L” shaped shaft guide conduit has an upper straight portion and a lower elbow portion, the combined length of which is at least as long as the length of the shaft. Bushings are located within the lower elbow portion of the shaft guide conduit for causing the shaft to flex and turn while permitting rotation and axial movement therethrough. A motor is drivably connected to the top of the shaft and is movable up and down within the casing. Accordingly, when the motor is rotating the bit, and the shaft is lowered, the shaft guide conduit supports the shaft, guides it through the elbow portion and directs the bit against the casing for cutting through the casing and then into the formation.
Preferably, a driveshaft positioned between the motor and the shaft permits the shaft to pass through the shaft guide conduit without interference between the shaft guide conduit and the motor.
REFERENCES:
patent: 1429146 (1922-09-01), Karge
patent: 1481078 (1924-01-01), Albertson
patent: 1804819 (1931-05-01), Spencer, Jr. et al.
patent: 2198016 (1940-04-01), Rogers et al.
patent: 2390646 (1945-12-01), Hays
patent: 2441881 (1948-05-01), Hays
patent: 2709070 (1955-05-01), Bielstein
patent: 2852230 (1958-09-01), Garrison
patent: 2906499 (1959-09-01), Travis
patent: 3011568 (1961-12-01), Grimm
patent: 3234723 (1966-02-01), Brown
patent: 3838736 (1974-10-01), Driver
patent: 4007797 (1977-02-01), Jeter
patent: 4051908 (1977-10-01), Driver
patent: 4057115 (1977-11-01), Blanz
patent: 4058176 (1977-11-01), Fischer
patent: 4266619 (1981-05-01), Bodine
patent: 4290494 (1981-09-01), Blanz
patent: 4424045 (1984-01-01), Kulischenko et al.
patent: 4476945 (1984-10-01), Hearn
patent: 4497381 (1985-02-01), Dickinson, III et al.
patent: 4658916 (1987-04-01), Bond
patent: 4762186 (1988-08-01), Dech
patent: 4964474 (1990-10-01), Poesch
patent: 5052404 (1991-10-01), Hodgson
patent: 5085283 (1992-02-01), Seabourn et al.
patent: 5148877 (1992-09-01), MacGregor
patent: 5165421 (1992-11-01), Fleischhacker et al.
patent: 5197783
Bagnell David
Millen White Zelano & Branigan P.C.
Singh Sunil
Wenzel Downhole Tools Ltd.
LandOfFree
Apparatus for drilling lateral drainholes from a wellbore does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for drilling lateral drainholes from a wellbore, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for drilling lateral drainholes from a wellbore will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2504025