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United States Patent   Patent Number: 5,271,472
Leturno  Date of Patent: Dec. 21,1993
 DRILLING WITH CASING AND RETRIEVABLE DRILL BIT
 Inventor: Richard E. Leturno, Piano, Tex.
 Assignee: Atlantic Richfield Company, Los Angeles, Calif.
 Appl. No.: 960,667
 Filed: Oct. 14,1992
Related U.S. Application Data
 Division of Ser. No. 744,859, Aug. 14, 1991, Pat. No. 5,197,553.
 Int. CI.' E21B4/00
 U.S. Q 175/107; 175/267
 Field of Search 175/62, 69, 73, 76,
175/85, 94, 93, 99, 230, 320, 107, 267
 References Cited
U.S. PATENT DOCUMENTS
1,833,134 11/1931 Stokes 175/259
3,603,412 9/1971 Kammerer 175/260
4,153,121 5/1979 Allan 175/266 X
4,470,470 9/1984 Takano 175/261 X
4,550,392 10/1985 Mumby 175/45 X
4,616,719 10/1986 Dismukes 175/94
4,646,856 3/1987 Dismukes 175/107
4,651,837 3/1987 Mayfield 175/260
5,064,006 11/1991 Waters et al 175/61 X
Primary Examiner—Ramon S. Britts
Assistant Examiner—Roger J. Schoeppel
Attorney, Agent, or Firm—Michael E. Martin
Wellbores are formed in the earth with elongated, tubular drillstems which include retrievable bit assemblies. The retrievable bit assembly includes a body having locking dogs engageable with cooperating recesses formed in a sub at the bottom of the drillstem. The bit assembly includes radially extendable and retractable arms with cutters thereon for forming the wellbore to a diameter greater than the drillstem, but whereby the arms may be retracted to withdraw the bit assembly through the drillstem with wireline retrieval apparatus or the like. The wellbore may be drilled with a tubular drillstem comprising wellbore casing with a bit connected to the lower end of the drillstem and retrievable through the drillstem by the wireline retrieval apparatus whereby the casing may be left in the wellbore upon completion of drilling operations.
4 Claims, 2 Drawing Sheets
DRILLING WITH CASING AND RETRIEVABLE
This is a division, of application Ser. No. 07/744,859, 5 filed Aug. 14, 1991 now U.S. Pat. No. 5,197,553, issued Mar. 30, 1993.
BACKGROUND OF THE INVENTION
1. Field of the Invention 10 The present invention pertains to a drilling assembly
and method wherein the drill bit, a bit-drive motor and measurement-while-drilling or logging-while-drilling instruments are retrievable through the drillstem and the drillstem itself may be left in the wellbore to serve as 15 the casing or wellbore liner.
Conventional rotary drilling operations require relatively frequent withdrawal of the elongated sectionalized drillstem or "drillstring" from the wellbore to in- 20 spect or replace the drill bit or portions of the drillstem, to perform well logging operations and to install permanent well casing. This insertion and withdrawal process is time-consuming, hazardous to operating personnel and increases the possibility of damaging the well due to 25 inadvertent dropping of the drillstring into the wellbore or encountering the influx of formation fluids into the wellbore due to the swabbing effect encountered during the drillstring insertion and removal process.
To overcome these problems and hazards, certain 30 techniques have been proposed for drilling with retrievable bits and with drillstring arrangements wherein a liner or casing is inserted into the wellbore coextensively with the drillstem and drilling bit. British Published Patent Application 2,216,926A to Jumblefierce 35 Limited describes a lining or casing assembly which is advanced through the wellbore which is being formed independently by a drill bit connected to a drillstem which extends through the casing and is advanced simultaneously with the casing. U.S. Pat. No. 4,651,837 to 40 W. G. Mayfield describes a retrievable drill bit which may be inserted in and retrieved through a drillstem. However, the simultaneous advance of both the casing and drillstem has certain shortcomings with respect to complications in making up the joints between the drill- 45 stem sections and the casing sections, the added weight of the double stem and other complications of using double-stem components. Accordingly, the objective remains to significantly reduce the cost of drilling and installing casing when using any one of known drilling 50 fluid mediums for drill cutting removal and the like, which is at least one of the objectives met by the present invention.
SUMMARY OF THE INVENTION 55
The present invention provides an improved method of drilling a well by utilizing a liner or casing as the drillstem in combination with a retrievable bit or a retrievable bit and downhole bit-drive motor assembly and retrievable measurement-while-drilling (MWD) 60 and/or logging-while-drilling (LWD) devices.
In accordance with one important aspect of the present invention, a method of drilling a well is provided wherein the drillstem is advanced through the formation being drilled by a retrievable bit which has radially- 65 movable cutter means to provide a borehole sufficiently larger than the maximum diameter of the drillstem so as to provide a suitable cuttings evacuation annulus and
sufficient space for receiving cement to isolate formation regions and to fix the combined drillstem/casing in place when drilling operations are complete. By utilizing the well casing as the drillstem, expensive and hazardous insertion and retrieval operations are minimized.
In accordance with another important aspect of the present invention, there is provided a unique retrievable bit and retrievable bit and motor assembly for use in well drilling operations wherein retrieval of the drillstem for bit repair or replacement is eliminated and wherein the drillstem may be left in the wellbore to function as a wellbore casing or liner.
The present invention still further provides a unique retrievable bit drive motor and bit assembly which may be inserted in and retrieved from a wellbore through the drillstem which may or may not be left in the wellbore and utilized as the wellbore casing or liner. Thanks to the arrangement of the present invention, expensive and hazardous "tripping" in and out of the drillstring may be eliminated during bit and drive motor maintenance and replacement operations. Wellbore washouts, fluid influxes due to drillstem swabbing effects and drillstring failures may be minimized. The drilling, formation evaluation and casing installation processes may be combined into essentially one operation and the chances of stuck drillstrings, failed fishing operations or abandonment of a wellbore are all eliminated. The invention significantly reduces the cost of drilling a wellbore in operations such as oil and gas reservoir development.
Those skilled in the art will recognize the abovedescribed features and advantages of the present invention together with other superior aspects thereof upon reading the detailed description which follows in conjunction with the drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a vertical section view in somewhat schematic form of a wellbore being drilled by the method and apparatus of the present invention;
FIG. 2 is a detail view showing one embodiment of a retrievable bit assembly in accordance with the present invention;
FIG. 3 is a section view taken along the line 3—3 of FIG. 2;
FIG. 4 is a view similar to FIG. 1 showing a well being drilled in accordance with an alternate embodiment of the present invention; and
FIG. 5 is a detail view of a retrievable bit and motor assembly used in the embodiment of FIG. 4.
DESCRIPTION OF PREFERRED
In the description which follows, like parts are marked throughout the specification and drawing with the same reference numerals, respectively. The drawing figures are not necessarily to scale and certain features are shown in generalized or schematic form in the interest of clarity and conciseness.
Referring to FIG. 1, there is illustrated an earth formation 10 into which a wellbore 12 is being formed by a drilling assembly and method in accordance with the present invention. The wellbore 12 is being formed utilizing a conventional drilling rig 14, partially shown in FIG. 1, including a rotary drive mechanism comprising so-called rotary table 16 which is adapted to rotatably drive a drillstem, generally designated by the numeral 18. The wellbore 12 is shown already partially cased by a surface casing 20.