US3635295A

US3635295A - Apparatus for drilling a small borehole downwardly from the bottom of a large borehole

Info

Publication number: US3635295A
Application number: US881394A
Authority: US
Inventors: James H Cobbs
Original assignee: Fenix and Scisson Inc
Current assignee: Fenix and Scisson Inc
Priority date: 1969-12-02
Filing date: 1969-12-02
Publication date: 1972-01-18
Anticipated expiration: 1989-01-18

Abstract

A small borehole drilling tool, lowered into a large borehole tubular drilling bit, includes a drill shaft interconnected to the large borehole drilling bit through driving drums for common rotation therewith. The small borehole drilling tool further includes upwardly of the drill shaft a coaxial neck, and an annular seal interposed between the neck and the inner wall of the large borehole drilling bit to form a drilling fluid chamber which receives and retains drilling fluid which in turn produces a downward thrust force on the upper surface of the annular seal to force the small borehole drill shaft downwardly into the earth during rotation thereof.

Description

United States Patent Cobbs [451 Jan. 18,1972

[54] APPARATUS FOR DRILLING A SMALL BOREHOLE DOWNWARDLY FROM THE BOTTOM OF A LARGE BOREHOLE James H. Cobbs, Tulsa, Okla.

[ 73] Assignee: Fenix 8: Scisson, Inc., Tulsa, Okla.

[22] Filed: Dec. 2, 1969 [21] Appl. No.: 881,394

[72] Inventor:

840,744 l/l907 Boof ..175/258 Primary Examiner-James A. Leppink Attorneyl-lead & Johnson 571 ABSTRACT A small borehole drilling tool, lowered into a large borehole tubular drilling bit, includes a drill shaft interconnected to the large borehole drilling bit through driving drums for common rotation therewith. The small borehole drilling tool further includes upwardly of the drill shaft a coaxial neck, and an annular seal interposed between the neck and the inner wall of the large borehole drilling bit to form a drilling fluid chamber which receives and retains drilling fluid which in turn produces a downward thrust force on the upper surface of the annular seal to force the small borehole drill shaft downwardly into the earth during rotation thereof.

PATENTEUJAN18 $972 IV/,IIIIIMV/AII /9 71L p i1 I 4 fl] I I TNT 7 3 i /H I I lm BIL i I/VVE/VTOR JAMES H. COBBS WfM ATTORNEYS DOWNWARDLY FROM THE BOTTOM OF A LARGE BOREI'IOLE BACKGROUND OF THE INVENTION Often it is desirable to drill a small borehole into the earth downwardly from the bottom of a large borehole. For example, the need for a small borehole extension downwardly of a large borehole is illustrated in my pending U.S. application, Ser. No. 837,477 entitled Method and apparatus For Measuring In situ The Earth Stress At A Preselected Subterranean Area.

Presently, the drilling of such a small borehole is accomplished by first drilling the large borehole to a depth immediately above that desired for the small borehole. Then the largeborehole drill is raised out of the hole, and the small borehole drill is lowered to the bottom of the borehole for the drilling of the small borehole. Removing the drill string by which the large borehole drill is suspended and rotated required a substantial amount of time and energy.

In addition, in small borehole drilling methods presently being used, the small borehole drill string must be of a length at least equal to the depth of the large borehole, which often is 200 feet or more. Because of the required long length and relative small diameter thereof, a small borehole drill shaft rotating within the large diameter borehole, has a tendency to bow during the drilling operation.

It is therefore an object of this invention to provide an apparatus for drilling a small diameter borehole extension to a large diameter borehole.

More particularly, an object of this invention is to provide an apparatus wherein a small borehole can be drilled downwardly from the bottom of a large borehole without requiring removal of the large borehole drill string.

SUMMARY OF THE INVENTION Generally, the apparatus comprises a hollow splined drill shaft which terminates on the lower end thereof with a bit. Coaxially connected to the upper end of the drill shaft is a drive drum having on the outer periphery thereof driving lugs which engage flutes on the inner wall of a tubular large borehole drilling or coring tool affixed to the lower end of a rotatable drill string in a large borehole. Rotation of the large borehole drilling tool causes rotation of the small borehole drilling tool. Extending upwardly from the drive drum is a hollow neck having an annular sealing means which forms in cooperation with the neck and the inner wall of the large borehole drill string a fluid chamber such that fluid pumped into the interior of the large borehole drilling tool creates a downwardly acting hydraulic thrust force to cause the rotating small borehole drilling tool to penetrate the earth.

To facilitate rotation of the small borehole drilling tool a second or alignment drum can be utilized for interconnecting the small borehole drilling tool with the large borehole drilling tool at a lower point.

DESCRIPTION OF THE DRAWINGS is an element of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the lower portion of a large diameter borehole which extends to the earths surface. A small diameter borehole 12 is to be drilled from the bottom of large borehole 1,0. The words large' and small" as describing

boreholes

10 and 12 are not intended to mean specific dimensions but are employed to distinguish boreholes l0 and 12 from each other. Typically, borehole 10 will be of a size to accommodate standard drilling tools and equipment such as presently utilized in the oil industry.

Positioned in large borehole 10 is a tubular large borehole drilling or coring tool 14 which terminates, on the lower end thereof, with a tubular coring bit 16. Coring bit 16 may typically include the use of diamonds or other abrasive drilling devices well known in the art. Square walled flutes 18 in the inner wall of tubular drilling tool 14 extend from the coring bit 16 part way up the inner wall of tool 14, and have a longitudinal length substantially equal to the desired depth of small borehole 12. Flutes 18 are paralleled to each other and equally spaced, as shown in FIG. 2. Large drilling tool 14 is affixed to the lower end of a drill string 19 which extends to the earth's surface. Drill string 19 provides means of rotation of the large drilling tool andalso forms a conduit or supplying drilling fluids to the large drill.

Coaxially disposed within the hollow interior of large borehole drilling tool 14 is a small borehole drilling tool tool generally indicated by the numeral 20 which includes; a small diameter externally splined drill shaft 22; an upper driving drum 24; a lower alignment drum 26; and an upstanding neck portion 28.

The small borehole drill shaft 22 is tubular in shape and terminates, on the lower end thereof with a coring bit 30. Bit 30 may also be of the noncoring type. Longitudinal splines 32 on the outer periphery of shaft 22 are at equally spaced interval as shown in FIG. 2.

An inner core barrel 34 is coaxially disposed in the hollow interior of drill shaft 22. Inner core barrel 34 has a length substantially equal to that of shaft 22 and has an outer diameter less than the inner diameter of shaft 22 so as to provide an an-' nular fluid passageway 36 therebetween.

Looking now at the upper end of shaft 22, rigidly and coaxially secured thereto is a cylindrical upper drive drum 24 having neck portion 28 affixed to and extending upwardly therefrom.

Below upper drive drum 24 is lower alignment drum 26 which rests on the bottom of large borehole 10. The lower alignment drum 26 has an axial opening 38 therethrough having equally spaced grooves 39 therein (see FIG. 2) to match and slidably receive splines 32 such that the drum is rotationally locked to shaft 22. The lower alignment drum 26 is permitted to travel longitudinally relative to shaft 22 and rides on the bottom of large diameter hole 10.

Attached to each of

drums

24 and 26 on the outer periphery thereof are a plurality of equally spaced driving lugs 40 which project outwardly therefrom to engage flutes 18 in the inner wall of large borehole drilling tool 14, thereby rotationally interconnecting shaft 22 and drilling tool 14. As shown in FIG. 3, driving lugs 40 are comprised of

flat plate portions

42A, 42B, 42C, 42D, 42 E, sequentially pivoted to each other to form a unitary linkage.

Plate portions

42A and 42E have attached to the upper and lower edges respectively one end of expansion springs 44A and 448. The opposite ends of

springs

44A and 44B are suitably secured to notches 46 in

drums

22 and 24 so as to longitudinally and inwardly

bias plate portions

42A and 42B which in turn through the pivotal linkage of portions 44B and 44D outwardly bias portion 42C to assure tight engagement thereof in flutes l8.

Coaxially affixed to the upper end of driving drum 24 over the central aperture 24A thereof is the annular hollow upstanding neck 28. Communication with fluid passageway 36 in shaft 22 is provided through the central opening 24A in drum 24 with the interior of neck 28 and through apertures 28A with the interior of large diameter drilling tool 14.

Received on the upper end of the upstanding neck 46 is a conical-shaped attachment cap having a base of a greater diameter than that of the neck to provide means for receiving and retaining a wireline tool, such as commonly used in the art, utilized in lowering or raising the small borehole drilling tool 20 into or from the interior of the large borehole drilling tool 14.

An annular resilient seal 48 is interposed between the inner wall of the large borehole drilling tool 14 and the outer wall of neck 28. Seal 48 fits firmly against the walls of neck 46 and drilling tool 14 to form in cooperation therewith a drilling fluid chamber 50 for receiving drilling fluid pumped thereinto from the earths surface. Chamber 50 serves two purposes; first, it causes the drilling fluid to impose a hydraulic downward thrust force on the small borehole drilling tool 20 to force small drill bit 30 into drilling engagement with the earth, and second it causes drilling fluid to flow through ports 28A for eventual entrance into fluid passageway 36 to thereby carry away the cutting from small drill 30.

In operation, the large borehole is drilled in the standard manner and terminates directly above the desired location of the small borehole. Tubular drilling tool 14 is positioned in borehole 10 as illustrated in FIG. 1. Next small borehole drilling tool is coaxially introduced into the interior of drill string 19 and lowered into drilling tool 14 by means of a wireline tool which grasps cap 47. As the small borehole drilling tool 20 enters the large diameter tubular drilling tool 14 driving lugs 40 on

drums

24 and 26 engage flutes 18 to rotationally interconnect small borehole drilling tool 20 to tubular drilling tool 14. Annular seal 48 forms drilling fluid reservoir chamber 50. The wireline tool is removed by means well known in the petroleum industry.

With small borehole drilling tool 20 properly positioned at the bottom of borehole 10, drilling fluid is pumped from the earth s surface into chamber 50 and bears against annular seal 48. As the fluid builds up in the chamber, a portion thereof continuously flows through ports 28A to the interior of neck 28 and down into passageway 36, within shaft 22. The fluid flows out of shaft 22 and past the lower end of drill 30, carrying cuttings with it and then upwardly in the annular area exterior of large diameter drill tool 14, carrying cutting from drill 30 to the earth's surface.

Simultaneously with the pumping of the drilling fluid, tubular drill tool 14 is rotated by means of drill string 19 extending to the earth's surface in the same manner as rotary drilling is normally accomplished. The rotation of large diameter drilling tool 14 is transferred by lugs 40 to upper and

lower drums

24 and 26 and by the drums to shaft 22. The rotation of shaft 22 coupled with the downward thrust force exerted thereon by the drilling fluid on annular seal 48 causes core bit 30 to penetrate the earth while drilling fluid flowing through passageway 36 carries away the core cuttings. This rotary drilling action causes a small diameter core 52 to be cut as shaft 22 with drill 30 downwardly advances. The core barrel 34 receives the core 52 to help keep it intact and to facilitate subsequent removal of the core in the same manner as core barrels are typically used in coring operations. Downward movement of drill shaft 22 may be continued until upper drive drum 24 contacts lower alignment drum 26.

During the operation utilizing small diameter drilling tool 20 to provide small borehole 12 the large diameter drilling tool 19 is rotated but no weight or downward thrust is applied to the tool 14 so that large diameter hole 10 is not extended. This is accomplished utilizing standard rotary drilling techniques used in the petroleum industry by which the weight of the drilling string 19 and tool 14 is cancelled by upward lifting forces applied at the earth's surface while the drill string 19 is rotated.

Lower drive drum 26 serves to assist the upper drive drum 24 in transmitting torque from large drilling tool 14 to shaft 22 and at the same time helps stabilize and align the lower end of shaft 22, especially when the drilling of small diameter hole 12 is first begun.

After the small diameter borehole is drilled to the desired depth a wire-line tool may be lowered within the drill string to grasp the cap 47 and remove the small diameter drilling tool 20 from the interior of the drill string 19 and drilling tool 14. The interior of the drilling string 19 and tool 14 is then clear for further operations as desired. Following such further operation large borehole 10 may be extended by the rotation of the drill string 19 and lar e drill tool 14 in the conventional manner. It can be seen that y the apparatus of this invention a small diameter borehole 12 followed by a coaxial large diameter borehole 10 may be achieved without the time consuming necessity of removing the drill string 19 and large diameter tool 14 from the hole.

During the detailed description of the preferred embodiments, specific language has been used for the sake of clarity. However, it is to be understood that such words are not meant as words of limitation and include all equivalent which operate in a similar manner to accomplish a similar purpose.

What is claimed:

1. An apparatus for drilling a small borehole downwardly from the bottom of a large borehole comprising:

a tubular large borehole drilling tool having internal longitudinal flutes in the lower portion thereof;

means for rotating said large borehole drilling tool from the earths surface;

a tubular drill shaft coaxially received within the large borehole drilling tool and having a bit secured to the lower end thereof;

a drive drum rigidly secured to the upper end of said drill shaft and having a longitudinal opening therethrough communicating with the opening in said drill shaft whereby drilling fluid introduced in the upper end of said large drilling tool flows downwardly through said drive drum, said drill shaft, and out through said bit;

at least one drive lug secured to the outer periphery of said drive drum and extending outwardly therefrom to engage said flutes to cause rotation of the drive drum and drill shaft as said large drilling tool is rotated and permitting longitudinal movement of said drill shaft and drive drum relative to said large borehole drilling tool; and

seal cup means affixed to the upper end of said tubular drill shaft, the seal cup means sealably and slidably engaging the interior of said tubular large borehole drilling tool providing a fluid chamber responding to fluid pressure to force said drill shaft downwardly.

2. An apparatus according to claim 1 including:

an alignment drum slidably and nonrotatably received on said drill shaft below said first drive drum, said alignment drum having at least one drive lug secured to the outer periphery thereof to slidably engage the flutes on the interior surface of the large borehole drilling tool.

3. An apparatus as in claim 1 wherein said drive lug on said first drum comprises:

a plurality of plate portions pivotally secured together to form a unitary outwardly expandable linkage; and

spring means biasing said linkage outwardly from said drive drum.

4. An apparatus according to claim 1 including:

wire-line attachment means secured to said drive drum.

5. An apparatus according to claim 1 including:

an upstanding tubular neck portion projecting from the upper end of said drive drum, the tubular interior being in communication with drive drum opening, said neck portion having a fluid passageway aperture therein.

6. An apparatus as in claim 5 including:

wire-line tool attachment means at the upper end of said neck portion.

7. An apparatus as in claim 5 wherein said seal cup means is interposed between the outer periphery of said neck portion and the inner periphery of large borehole drill tool providing a fluid chamber receiving drilling fluid thereabove.

Claims

1. An apparatus for drilling a small borehole downwardly from the bottom of a large borehole comprising: a tubular large borehole drilling tool having internal longitudinal flutes in the lower portion thereof; means for rotating said large borehole drilling tool from the earth''s surface; a tubular drill shaft coaxially received within the large borehole drilling tool and having a bit secured to the lower end thereof; a drive drum rigidly secured to the upper end of said drill shaft and having a longitudinal opening therethrough communicating with the opening in said drill shaft whereby drilling fluid introduced in the upper end of said large drilling tool flows downwardly through said drive drum, said drill shaft, and out through said bit; at least one drive lug secured to the outer periphery of said drive drum and extending outwardly therefrom to engage said flutes to cause rotation of the drive drum and drill shaft as said large drilling tool is rotated and permitting longitudinal movement of said drill shaft and drive drum relative to said large borehole drilling tool; and seal cup means affixed to the upper end of said tubular drill shaft, the seal cup means sealably and slidably engaging the interior of said tubular large borehole drilling tool providing a fluid chamber responding to fluid pressure to force said drill shaft downwardly.

2. An apparatus according to claim 1 including: an alignment drum slidably and nonrotatably received on said drill shaft below said first drive drum, said alignment drum having at least one drive lug secured to the outer periphery thereof to slidably engage the flutes on the interior surface of the large borehole drilling tool.

3. An apparatus as in claim 1 wherein said drive lug on said first drum comprises: a plurality of plate portions pivotally secured together to form a unitary outwardly expandable linkage; and spring means biasing said linkage ouTwardly from said drive drum.

4. An apparatus according to claim 1 including: wire-line attachment means secured to said drive drum.

5. An apparatus according to claim 1 including: an upstanding tubular neck portion projecting from the upper end of said drive drum, the tubular interior being in communication with drive drum opening, said neck portion having a fluid passageway aperture therein.

6. An apparatus as in claim 5 including: wire-line tool attachment means at the upper end of said neck portion.