Wells – Processes – Perforating – weakening – bending or separating pipe at an...
Utility Patent
1998-05-05
2001-01-02
Lillis, Eileen D. (Department: 3673)
Wells
Processes
Perforating, weakening, bending or separating pipe at an...
C166S055200, C175S062000
Utility Patent
active
06167968
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to forming perforations in the casings of oil or gas wells. More specifically, the invention relates to apparatus and methods for cutting an opening in a well casing to permit subsequent drilling of a tunnel through surrounding earth for a substantial distance beyond the casing, for permitting the flow of liquid or gaseous hydrocarbons into the casing.
2. Related Art
In oil or gas wells, a contaminated zone is typically formed around the wellbore as a result of drilling fluids used during the drilling operation, and also as a result of the cement that is typically forced down into the bottom of a wellbore and up into the annular cavity between the well casing and the wellbore. This contaminated zone frequently presents a substantial barrier to the inflow of hydrocarbons to the well casing.
A number of expedients have been proposed and employed in an effort to provide flow passageways through the surrounding strata for permitting and increasing the flow of hydrocarbons into the well casing. For example, U.S. Pat. Nos. 4,790,384 and 5,107,943 show a method employing a cam drive cylinder means for driving a wedging cam to extend a radially moveable punch outwardly through the casing of a well.
Another common expedient for effecting casing and formation penetration is the use of explosive guns that fire projectiles or gas jets from a shaped charge through the well casing. These guns have limitations due to the compaction of the tunnels created by an explosion and on their limited penetration depth.
Other known systems involve separate mechanical cutting devices that are lowered to the bottom of the well. A first cutting device cuts a hole through the well casing and is subsequently removed from the well in order to permit the lowering and positioning of a nozzle jet-type cutter to cut into the surrounding formation. The positioning and removal of tools such as cutting devices to and from the well require time-consuming and expensive pulling and replacement of the pipe string extending above the tooling. With this known method, it can also be difficult to precisely locate the opening created by the mechanical cutting device at a deep well depth after the cutting device has been removed from the well. The foregoing problem is of substantial significance since the jet-type cutter must be accurately positioned adjacent the opening in order to function.
Other known systems involve radial drilling mechanisms that utilize a single drill bit mounted on a flexible drive shaft and are designed to drill through the well casing and radially outward into the surrounding strata for a short distance. These devices suffer from problems in successfully drilling repeatedly because the drill bit cannot effectively drill both the steel well casing and abrasive rock strata without excessive dulling.
Thus, there is a need in the art for a self-contained tool that can be run into an existing wellbore and repeatedly drill holes radially from the wellbore without the need for a turning radius outside the well casing. Applicants have recognized that this requires two drilling mechanisms: a first mechanism that is effective in drilling through steel well casing, and a second mechanism to effectively drill rock.
U.S. Pat. No. 5,392,858 (Peters et al.) describes a tool that mills a hole in the casing and then uses jetting to penetrate into the surrounding formation. A mill bit driven by a hydraulic motor mills a hole in well casing to allow passage of a high pressure fluid jet nozzle radially from the well casing into the surrounding formation. Although this apparatus enables both steps of the operation to be performed during a single trip into the well, it is limited by the fact that fluid jets are not efficient in deeply submerged environments even though high pumping pressures are employed at surface. The hydrostatic pressures encountered in downhole well operations greatly detract from the power of a fluid jet limiting its performance in many rock formation types. In addition, the high pumping pressures required increase the expense and danger of the operation, and it is difficult to convey the required pressures from surface to the tools in the bottom of the well.
Thus, there is a need in the art to provide a system for radially drilling through well casing that drills multiple holes through metal casing and multiple corresponding long tunnels through surrounding earth, without having to be raised and re-lowered between operations.
It is to fulfill the foregoing needs, among others, that the present invention is directed.
SUMMARY OF THE INVENTION
The invention provides an apparatus and method for drilling holes in the steel casing of an a oil or gas well, and for drilling into the surrounding earth. The apparatus includes a number of components that are preferably controlled by hydraulic fluid.
In a preferred embodiment, a first hydraulic motor drives a steel milling assembly and a second hydraulic motor drives a rock drilling assembly. All assemblies can be supported in a housing that is conveyed by conventional jointed pipe or coiled tubing down the well casing.
Control components cause a carriage carrying the milling assembly to be indexed up a predetermined distance relative to the well casing, and then extend a mill bit gradually into contact with the well casing while being rotated by a hydraulic motor. After the mill bit completes a hole through the well casing, the hydraulic components retract the mill bit and index the carriage back down to its starting position to align a rock drilling bit with the hole that was just drilled in the casing.
Preferably, the rock drilling bit is provided on the outer end of a flexible drillstem to enable the rock bit to extend while drilling radially from the wellbore, through the hole in the casing, as it is rotated by the second hydraulic motor.
The apparatus makes it possible to radially drill multiple holes through the metal casing and multiple corresponding long tunnels through surrounding earth, without having to be raised to the surface and re-lowered between operations.
Other objects, features and advantages of the invention will be apparent to those skilled in the art upon a reading of the following specification in accompaniment with the drawings.
REFERENCES:
patent: 2516421 (1950-07-01), Robertson
patent: 4185705 (1980-01-01), Bullard
patent: 4355685 (1982-10-01), Beck
patent: 4640362 (1987-02-01), Schellstede
patent: 5107943 (1992-04-01), McQueen et al.
patent: 5392858 (1995-02-01), Peters et al.
patent: 5687806 (1997-11-01), Sallwasser et al.
Allarie Michael M.
Marcin Robert
McQueen Grant D.
Peters Alan D.
Jacobson Price Holman & Stern PLLC
Kreck John
Lillis Eileen D.
Penetrators Canada, Inc.
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