Drilling unit for rotary drilling of wells

[57] ABSTRACT

A drilling unit for rotary drilling of wells using casing as the drill string. The drilling unit is a self-contained assembly designed to be bodily inserted and withdrawn through the bore of a well casing string and comprises releasable latch means for non-rotatively locking the structure to the casing; a rotary power unit supported by the latch means and relatively connected to a bit assembly. The latter comprises a main or pilot bit and a plurality of radially extendible and retractable underreamers actuated by fluid pressure which may first be employed for driving the power unit.

Claims, 11 Drawing Figures

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PATENTEDMAY 91972 3,661,218

SHEET 1 OF 4

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A TTOf?N£F

PATENTED MAY 9 1972

SHEET 2 OF 4

3,661,218

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A TTOJENEY

PATENTEDmay 91972

3,661,218

SHEET 3 OF 4

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<img file="US3661218A_D0005.tif" />

A TTOR/V£y

PATENTEDmay 91972

3,661,218

SHEET 1+ OF 4

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ATTORNEY

3,661,218

DRILLING UNIT FOR ROTARY DRILLING OF WELLS

Rotary drilling of wells is commonly performed using a string of relatively small diameter drill pipe by which a larger diameter bit is rotated to drill a bore hole of the desired diameter. Casing to fit the large diameter bore hole is then inserted in the bore hole to line and support the wall thereof. Drilling in the uncased bore hole and the multiple operations involved in running separate drilling and casing strings necessarily increase the cost of the well and is subject to hazards of various types well known in the drilling industry.

Various systems have been proposed for drilling using the casing string as the drill pipe and such systems are disclosed in certain of my earlier copending applications, to wit: Ser. No. 778,509, filed Nov. 25, 1968 now U.S. Pat No. 3,552,507; Ser No. 803,911, filed Mar. 3, 1969 now U.S. Pat. No. 3,552,508; and Ser. No. 857,046, filed Sept. 11, 1969 now U.S. Pat. No. 3,552,509. These systems employ separate bit assemblies, which are designed to be bodily inserted and removed through the casing and locked to the lower end thereof for rotation by the casing. Such bit assemblies include combinations of main or pilot bit with a plurality of radially extensible and retractable underreamers.

As noted, the earlier systems contemplate arrangements in which the casing string itself is rotated to drive the bit section. This requires a rotary power apparatus at the surface to rotate or drive the casing string, and while such systems are found to be practical and reasonably successful, some problems occur which it is desirable to avoid to make the system even more successful from a practical standpoint. The principal problems include those arising form the need to provide an effective power apparatus for rotating the relatively large diameter casing particularly when the string has reached an extended length as the bore hole attains continuously increased depth.

The present invention contemplates an improved system which employs the separate form of drilling unit which is bodily inserted and withdrawn through the casing string, as in the earlier applications, but which includes as a part thereof a rotary power unit for driving the bit section while the casing string remains stationary and is merely fed into the bore hole behind the bit as the hole deepens. The power unit may be any of several known types of hydraulic motor or turbine units or may be an electrically powered motor of known design.

More specifically, the illustrative embodiment of the present invention contemplates a drilling unit which com- 45 prises an anchor or latch element for releasably securing the unit to the lower end of the casing; a bit section comprising a main or pilot bit and a set of radially extendible and retractable underreamers; and a rotary power drive member connecting the anchor element to the bit. The rotary drive member is 50 in the form of a hydraulic motor which is driven by pressure fluid, such as drilling mud pumped down through the casing. The underreamers are pivotally mounted to the body of the bit section and connected to an actuating plunger which is spring biased to urge the underreamers to their extended positions. 55 The underreamers are initially secured in reacted position by shear pins or the like which are breakable by fluid pressure applied to the plunger, the pressure fluid being the same as that employed to drive the power unit.

By the described system a well bore can be drilled to a desired depth while the hole is being continuously lined with casing without requiring rotation of the latter. The drilling unit can be inserted into and removed through the bore of the casing as required at any time during the drilling procedure.

Other and more specific objects and advantages of this in- 65 when the sleeve is moved downwardly sufficiently to move envention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawing which illustrates a useful embodiment in accordance with this invention.

FIGS. 2A and 2B, together, comprise a view similar to

FIGS. 1A and IB showing the anchor element locked to the casing and the underreamers in their extended relation;

FIG. 3 is a view similar to FIGS. 1A and 2A, showing the running tool in process of being released from the anchor element;

FIG. 4 is a partial view of the tool portion illustrated in FIG. 3 showing a fishing tool in engagement with the anchor element preparatory to effecting release thereof to permit withdrawal of the drilling unit from the casing;

FIGS. 5 and 6 are cross-sectional views taken respectively on lines 5—5 and 6—6 of FIG. 1 A;

FIG. 7 is a cross-sectional view taken in line 7—7 of FIG.

, 2B; and,

FIGS. 8A and 8B, together, comprise a longitudinal sectional view of the hydraulic power unit employed for rotating the bit section.

Referring to the drawing, there is shown the lower end of a string of pipe P, conventionally referred to as casing, to which is threadedly connected a landing shoe 10 having a bore 11 matching the bore ofthe casing, and flared at its lower end 12. A plurality of angularly spaced splines or landing pins 13 project into bore 11 and an annular latching or anchor recess 14 is provided in the wall of bore Ila short distance above landing pins 13.

The drilling unit, designated generally by the letter U comprises an anchor sub-assembly A, a power drive assembly B connected to the anchor sub-assembly, and a bit section C connected to drive assembly B for rotation thereby. The overall dimensions of the drilling unit as a whole are made such that the unit may be bodily inserted and withdrawn through the bore of casing P.

anchor sub-assembly A includes a tubular body 16 having an axial bore 18 and terminating at its lower end in an externally threaded pin 20 by which it is connected to the housing 22 of the power drive assembly B. The upper end portion of body 16 is enlarged in internal diameter to define the enlarged bore 24 enclosed by a tubular cage 26. The latter has a plurality of angularly spaced, rectangularly shaped, radial openings 28 in which correspondingly shaped anchor dogs 30 are mounted for radial movement into and out of anchoring engagement with recess 14. The extension of body 16 is provided with a plurality of angularly spaced, longitudinally extending spline slots 32 open at their lower ends to receive landing pins 13 and closed at their upper ends to form landing shoulders 34 to be engaged by pins 13 for landing the drilling unit in the landing shoe 10 and forming a non-rotative connection between the anchor sub-assembly and the landing shoe. The spacing between shoulders 34 and openings 28 is made such that when the anchor assembly is landed on pins 13, dogs 30 will be in registration with recess 14. An annular seal element 36 is circumferentially mounted in the exterior of body 16 between shoulders 34 and openings 28 to seal off bore 11 below anchor recess 14. The upper end of cage 26 is connected to a running collar 38 which has an annular seal 40 circumferentially mounted in the exterior thereof to seal off bore 11 above recess 14.

The anchor sub-assembly includes a tubular setting sleeve 42 mounted for axial sliding movement in bore 24 of the anchor cage. Sleeve 42 carries an annular external enlargement 44 intermediate its ends adapted to project anchor dogs 30 radially outwardly into anchoring engagement in recess 14 largement 44 behind the dogs (FIG.2A) and to release the dogs for retraction from recess 14 when the sleeve is subsequently moved upwardly to raise enlargement 44 above the dogs (FIG. 1 A).

In the drawing: 70

FIGS. 1A and IB, together, comprise a longitudinal sectional view of the drilling tool inserted in the casing string on a running string immediately prior to being locked to the casing; the underreamers of the bit section being shown in their retracted positions;

The external diameter of the portion of setting sleeve 42 above enlargement 44 is made sufficiently less than the internal diameter of collar 38 to provide an annular space 46 of sufficient width to receive therebetween a shear sleeve 48.

Setting sleeve 42 is initially secured in its upper inactive posi75 tion with respect to dogs 30 by one or more shear screws 50

3,661 3 which extend transversely through collar 38, shear sleeve 48 and into setting sleeve 42. When thus shear-pinned together, the lower end of shear sleeve 48 rests on the upper end of cage 26. The upper end of shear sleeve 48 is provided with an inwardly extending lip 52 adapted to overhang an external shoulder 54 on the running collar 56 carried by the lower end of a conventional running tool string S, the details of which do not form a part of this invention.

Power drive unit B may be of any suitable and known form capable of rotating the bit section, the details of which do not form a part of this invention. However, for purposes of this description, there is illustrated in FIGS. 7A and 7B, more or less diagrammatically, a form of power unit, commercially known as a “Dyna-Drill,” manufactured by Dyna-Drill Company of Long Beach, California, which is essentially a hydraulic motor of the Mayno screw type, comprising a single thread rotor 60 running in a rubber lined spiral passageway 61 and adapted to be rotated by hydraulic fluid pumped down through casing P. Rotor 60 is suitably connected to a drive shaft 62 the lower end of which carries a threaded pin 63 by which the drive shaft is operatively connected to the bit section C by means of a tubular coupling 64 having a threaded box 65 at its upper end for receiving pin 63 and an externally threaded pin 66 at its lower end.

Bit section C includes a tubular body 70 having a bore 71 and an internally threaded box 69 at its upper end for receiving coupling pin 66. The lower end of body 70 carries a tubular collar 72 having an axial bore 73 and terminating in an internally threaded box 74 adapted to receive the hollow shank 75 of a conventional bit 76 which may be a roller-type bit as shown or may be a drag-type or other known form of bit adapted to serve as the main or pilot bit in boring the drill hole.

The wall of body 70 above collar 72 is provided with a plurality of angularly spaced, longitudinal slots 68 in each of which is pivotally mounted an underreamer, designated generally by the letter R.

An annular piston 77 is slidably reciprocable in bore 71 above slots 68 and forms the head of a downwardly extending tubular plunger 78 having a bore 79 which opens through the center of piston 77. The lower end of plunger 78 extends slidably through the central opening 80 of a conical cap 81 closing the upper end of bore 73 of collar 72. Plunger 78 is resiliently biased downwardly by a strong coil spring 82 mounted in compression between piston 77 and the inner end of coupling 64.

Each of the underreamers R comprises a cutter arm 83 and a crank arm 84 extending at an angle to the butter arm. A pivot pin 85 extends transversely through the crank arm adjacent its juncture with the cutter arm and is journaled in the walls of slot 68 (FIG. 7). The free end of the cutter arm carries an inwardly extending cutter shaft 86 on which is rotatably mounted a frustoconical cutter 87 of a generally conventional design. Crank arm 84 is formed with an extension 88, the free end of which carries an inwardly projecting crosshead pin 89 positioned in a crosshead slot 90 provided in a related side portion of plunger 78 (FIG. 7). With this arrangement, it will be seen that movement of plunger 78 downwardly will act on crosshead pins 89 and thence through extensions 88 and crank arms 84 to rotate the underreamers outwardly while reverse movement of the plunger will act to retract the underreamers. Since coil spring 82 normally tends to urge plunger 78 downwardly and thereby bias the underreamers to their extended positions, the underreamers are initially secured in the retracted position (FIG. IB) by means of shear pins 91 which extend transversely through the cutter arm into the walls of the related slots 68. Breaking of shear pins 9Ϊ, as will be described hereinafter, will release the underreamers for movement to their extended positions.

A plurality of jets 92 are mounted in the walls of cap 81 and directed so as to discharge fluid upwardly and outwardly at an angle selected to cause the fluid to strike the teeth of the extended cutters 87 to wash cuttings therefrom, as well as to ,218 impinge on the wall of the well bore at points immediately in advance of the cutters to apply a softening or erosive action thereon which will improve the cutting efficiency of the underreamers.

In operation, drilling unit U will be suspended from running string S by the connection between running collar 56 and shear sleeve 48, all of the several parts being in their inactive or retracted positions as seen in FIGS. 1A and IB. Running string S will usually be a conventional wire line string including conventional jars (not shown) by which jarring impacts can be directed through the running string to the tools suspended thereon. The thus suspended drilling unit will be lowered through the bore of casing P until the anchor sub-assembly is landed on pins 13 in the landing shoe. Thereupon, downward jarring blows applied through the running string will serve to break the inner portions of shear pins 50 which secure setting sleeve 42 to shear sleeve 48, the latter being held stationary by its seating on the upper end of cage 26. Thereupon, the downward jarring will drive setting sleeve 42 downwardly sufficiently to move enlargement 44 behind dogs 30 projecting them outwardly into recess 14 (FIG. 2A) and thereby anchoring the unit to the landing shoe.

With the drilling unit thus anchored to the lower end of the casing, upward pull, accompanied by upward jarring, if necessary, will be applied through the running string and running collar 56 to shear sleeve 48 to thereby apply sufficient upward force to break the portions of shear pins 50 connecting shear sleeve 48 to collar 38 (FIG. 3). This releases the running string from the drilling unit allowing the running string to be withdrawn from the casing and leaving the drilling unit anchored to the lower end of casing.

Fluid, such as water or drilling mud will now be pumped down the casing and through the several connecting bores in the drilling unit. The fluid will pass through passageway 61 actuating rotor 60 and shaft 62 to rotate the bit section. The pressure fluid discharging from passageway 61 will flow into bore 71 of the bit section applying pressure to piston 77 by reason of the flow restriction formed by the reduced diameter flow passages defined by bore 79 of the plunger and the still smaller diameter jets and wash ports through which the fluid finally discharges from the bit section. The fluid pressure thus applied to the plunger will supplement the force of spring 82 sufficiently to break shear pins 91, thereby releasing the underreamers for movement to their extended positions and being held extended by the combination of the forces exerted by spring 82 and the fluid pressure while the bit section is being rotated by the power drive unit. As the drilling progresses, sections of casing will be added to the upper end of the casing string similarly to the procedures employed in conventional rotary drilling using ordinary drill pipe.

When necessary to withdraw the drilling unit from the casing in order to repair or replace the pilot bit, underreamers or any other part of the unit, then, as seen in FIG. 4, a fishing tool, designated generally by the letter T, of any generally conventional form, the details of which do not form a part of this invention, will be run into the casing bore on a wire line or tubing string, as desired, and will be latched beneath a downwardly facing shoulder 93 in the bore of setting sleeve 42. On application of upward pull to the fishing string, the setting sleeve will be drawn upwardly moving enlargement 44 above dogs 30, to the position shown in FIG. 1A, thereby releasing the dogs for retraction from recess 14. Continued upward pull will then draw the underreamers inside landing shoe 10, the flared lower end 12 of the latter acting on the underreamer arms to collapse the underreamers against the opposition of spring 82 in response to the upward pull being applied to the drilling unit and thus allow the entire drilling unit to be withdrawn through the casing bore to the surface.

When drilling is to be resumed, the drilling unit, with the parts in the original retracted positions, will be returned through the bore of the casing to its lodgment in shoe 10, reanchored therein and fluid pressure reapplied to rotate the bit section and thereby resume the drilling operation.

3,661,218

From the foregoing it will be evident that a drilling system is provided in which the casing itself, which is ordinarily required to line the previously drilled bore hole, will be continuously, non-rotatively fed into the bore hole as the drilling proceeds, thereby obviating all of the additional operations conventionally required in rotary drilling and for casing the well. The hazards accompanying the conventional drilling and casing operations, including those arising from “round trips” of the drill string, will be obviated, drilling operations greatly facilitated, and time of operation substantially reduced.

While the illustrative embodiment discloses the use of a fluid pressure-type power drive, it will be evident that drive unit B may be a fluid operated turbine, or an electric motor. Various other modifications and variations may be made in the details of the illustrative embodiment within the scope of the appended claims but without departing from the spirit of this invention.