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Publication numberUS3825081 A
Publication typeGrant
Publication dateJul 23, 1974
Filing dateMar 8, 1973
Priority dateMar 8, 1973
Publication numberUS 3825081 A, US 3825081A, US-A-3825081, US3825081 A, US3825081A
InventorsMcmahon H
Original AssigneeMcmahon H
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Apparatus for slant hole directional drilling
US 3825081 A
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Description  (OCR text may contain errors)

United States Paten 11 1 McMahon I 111 3,825,081 [451 July 23,1974

[ APPARATUS FOR SLANT IIOLE DIRECTIONAL DRILLING [76] Inventor: Harvey S. McMahon, 4661 Rhapsody Dr., Huntington Beach,

Calif. 92649 t 122] Filed: Mar. 8, 1973 [21] Appl. No: 339,321

[52'] US. Cl. 175/73, 175/325 [51] Int. Cl E2lb 7/08 [581 Field of Search 175/61, 73, 76, 325, 343, 175/376 [56] References Cited UNITED STATES PATENTS 2,734,720 2/1956 Zublin 175/76 2,819,040 1/1958 James et al. 175/325 X 2,876,992 3/1959 Lindsay 175/73 3,045,767 7/1962 Klassen 175/325 X 3,081,829 3/1963. Williams 175/376' 3,092,188 6/1963 Farris et al 175/76 3,154,156 10/1964 Moore et al. 175/76 3,306,378 2/1967 Williams 175/325 11/1967 Livingston 175/73 2/1969 Bennett 175/343 ABSTRACT Method of slant hole directional drilling using a rotary drill wherein the drill collar carrying a plural cone bit v is nudged upwardly on each revolution by a radially projecting lobe being cam bearing on the surface at the low side of the hole, in conjunction with the action of one oversize cone in the bit which upon each upward nudging of the drill collar cuts in a predetermined laterally angular direction, whereby the direction of the well bore will be altered.

Theapparatus embodies a two cone or tricone bit in which the teeth of one cone are radially enlarged over e h of the he QUQPPQPUfi; he bitb mounted on a drill collar with the larger cone at an angular displacement from a radially projecting lobe .or cam mounted on the drill collar.

5 Claims, 7 Drawing Figures 21 LJ m E wr 25 g T j E 9 Z 4 f3 2:3 35% H f g {/i a 3 V n r. I" 7 APPARATUS FOR SLANT HOLE DIRECTIONAL DRILLING BACKGROUND on THE INVENTION reason or another is unsuitable for a continuation of straight drilling. Sometimes it is done as a relief well for uncappable blowouts, or to control fires. In some cases, it is highly desirable to control both the horizontal and vertical deviation within predetermined limits.

Various primary deflection tools have been employed for initiating and maintaining'the desired hole direction. Some are limited to the vertical angle only. Some such as whipstocks, and knuckle joints, are difficult to control. A more recent development comprises a fluid actuatedadjustable sub which suspends a bottomhole fluid-driven bit from a well string. Another known tool involves paddlesinterconnected by a shaft which is externally mounted in a groove on a drill collar.

These, and other systems known to applicant are unsatisfactory in many respects from the standpoint of malfunctions, added cost in equipment and in operation and maintenance, and lack of adequate control.

SUMMARY OF THE INVENTION The present invention is exemplified in both a method and an apparatus.

A principal object is to provide a method for slant hole directional drilling which is relatively simple to practice, and which lends itself to more accurate control than prior methods known to applicant.

One step is to impart an upward thrust of the bit end of the drill collar with sufficient frequency to produce the cumulative effect of pointing the bit somewhat upwardly. Concurrently with each upward thrust the bit is caused to attack an area laterally offset from the cylindrical plane of the hole immediately preceding the area of attack. The compositeresult is a bending of the hole to one side or the other, and/or to some extent upwardly. The attack of the bit can be arranged to proceed to either side, or upwardly without deviation to either side. The action can be made effective over a circular section described generally as extending from 8 a two cone) roller bit mounted at the lower end of a drill collar, the collar being'provided with a lobe or cam or other radial projection spaced upwardly from the bit, and one cone of the bit being formed with a buildup (extensions) of the teeth resulting in a larger cone diameter than that of the other cone or cones.

vIf the specially formed bit is disposed in a plane diametrically opposite the cam, only vertical deflection is achieved. By disposing such bit in a plane circumferentially (angularly) offset from the diametric plane of the cam, deflection is obtained primarily either to the right or left from the axis of the preceding section of the bore.

As the drill collar is rotated, the bit makes an oversize" hole. Assuming that slant drilling is in process, with each revolution of the collar, the cam rides on the bottom'of the hole; This imparts an upward thrust which nudges the bit end of the collar upwardly, and, if the'oversize cone is circumferentially offset from the blade, the path it cuts deviates laterally or vertically,

that is, left or right, or upwardly, according to the angular offset of cam and oversize cone.

The degree of deviation is responsive to several factors: the axiallocation of the cam on the collar, the dimension of its radial projection, and the dimension of the oversize cone relative'to the other cone or cones.

' The arc of the bore is thus primarily determined; and

tors mentioned.

The cam'may be specifically designed, or it may be a blade or stabilizer of the type which conventionally is mounted in a series of three, equally spaced around the circumference of a drill collar to center the collar in drilling a straight hole. Eliminating all but one of these, in combination with the oversize cone, enables me to achieve the different and special function needed.

The roller bit may be a standard tricone or two cone type bit designed forwhatever formation is to be penetrated, with a buildup of the teeth on one cone, or in originally manufacturing the bit one larger cone may be installed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a somewhat diagrammatic section of a well the arc may be varied by changing one or all of the facbore with the tool shown working therein.

FIG. 2 is a vertical sectional view of a first form of the tool, shown in the well bore.

FIG. 3 is an enlarged section taken on the line 33 I FIG. 5, showing the oversize cone positioned relative to the cam or lobe for right hand deviation.

FIG. 7 is a view similar to FIG. 6 showing the oversize cone positioned for left hand deviation.

FIRST EMBODIMENT OF THE INVENTION In FIG. 1, the bracketed section S illustrates a straight slant well bore drilled down from the surface 15..The bracketed section T illustrates my special tool in the bore ready to start a deflection. The lower section D in broken lines indicates the angular deflection path to be followed in proceeding with operation of the tool.

. The drilling tool generally designated 20, is coupled steel hollow tube with threads at its upper end for connection with the drill string, and a threaded box 26 at its lower end which receives the shank 27 of a bit 28.

The mandrel is formed with a reduced diameter section 30 commencing at an annular shoulder 31 whereby a sleeve 32 may be fitted over the reduced section. The upper end 33 of the sleeve is adapted to abut the shoulder 31, and the lower end 35 is adapted to seat on an annular ledge 36 of the shank 27. v

The mandrel 23 and the sleeve 32, when assembled, comprise the drill collar 22.

Intermediate the ends of the drill collar'is fixedly mounted a cam or lobe 38. This may be similar to stabilizers which conventionally are spaced evenly around the periphery of a drill collar to maintain the collar concentrically within the bore for drilling straight holes. The omission of all but one such stabilizer is for an entirely'different purpose resulting in a different function, as previously mentioned and as will be-developed further in this description.

In the preferred form I use a true cam shape, as shown in FIG. 3', welded on the surface of the sleeve 32. The placement of the cam is determined by reference to the radial or angular disposition of an enlarged cone 40 on the bit 28 which will be further described. I

This bit 28 is conventional in some respects. .A tricone type is illustrated. It comprises the shank 27 already identified, formed with the annular ledge or shoulder 36, and bit legs 41. On these legs are rotation:- ally mounted cones 40, 46 and 47 embodying teeth 48, 49 and 50. The size and placement of teeth 49 and 50 are such as found in astandard tricone bit. Their extremities lie in a circular plane representing the approximate circumference of a bore which would be cut by a standard tricone bit of this type.

The departure from the conventional, which is an important part of my invention, lies in the buildup, or enlargement of the teeth 48 on the cone 40. As an example by way of illustration and not of limitation, if the teeth on the cones 46 and 47 are designed to cut a 9 5/8 inch bore, the teeth on cone 40 extend approximately 1/4 inch beyond. See FIG. 3.

This can be accomplished in the manufacture of the cone, or the teeth of a 9 5/8 inch cone may be built up an additional 1/4 inch by adding metal through a process comparable to welding. v

Provision is made to orient the cam relative to the oversize cone. This is achieved by lugs 52 welded to the external surface of the bit legs 41. A selected one of the lugs keys between a selected pair of stops 53 which are welded on the lower end of the sleeve. The lugs may be spaced 90 to 120 apart, and the pairs of stops similarly. It is preferable that the pairs of stops on the sleeve be circumferentially disposed approximately 90 to 120 from the peak of the cam..

In assembling the tool the bit may be placed on a table, the mandrel is suspended above it, and the sleeve is pushed up on the mandrel. The'operator then allows the sleeve to slide down and is rotated as desired so that the selected stops engage the selected lug on the bit. The mandrel is then turned totighten the threads on the shank and bring the assembly into a unitary relationship.

In its elementary form, the device needs only two pairs of stops, and two lugs. One is utilized for deviation left, and the other for deviation right. The string always turns clockwise (lookingdown). For'left hand deviation with the'peak of the cam at 6 o'clock, the oversize cone is advantageously located at approximately 9 oclock; and for right hand deviation the oversize cone would be at approximately 3 oclock. These spacings may be modified if desired.

Second Embodiment of the Invention an elongated shoe 139 preferably ,of aluminum or other relatively soft metal, capped by a sheath 140 of hard steel. These parts are made with arcuate cross sections sothat the assembly conforms to the outer surface of the drill collar; and they are secured to the collar by capscrews 141 threaded into-a selected line of a series of tapped sockets 142.

OPERATION The operation of both forms of. the invention is essentially the same.

Assuming a clockwise rotation of the drill string and the tool, as observed looking down, and working in a slant well bore, the cam during several degrees of rotary travel will contact the low side of the bore. For ex planation this will be referred to' generally as six oclock. Engagement with the low side of the bore causes a shifting of the axis of the tool upwardly.

Assume that the oversize or radially offset cone is disposed generally at nine oclock during the time the cam is at six oclock. During the upward shift of the axis of the tool the oversize cone attacks at the left side of the bore, while the minor size cone or cones advance in their own circular plane.

With continued rotation, and the cam itself rising from the low side, the tool settles by gravity and its axis lowers so that the major cone continues past 12 oclock, 3 oclock and 6 oclock without the extra radial thrust.

With each revolution the oversize cone continues its the oversize cone diametrically opposite. The latter action could be accomplished, although less efficiently,

by using a cam in association with a conventional bit (absent the oversize cone).

The angular attack of the oversize cone occurs with each revolution of the tool. Occurringwhen the blade is rotating through a relatively minor are at the low side, compared to cessation of the blade action when travelling through the relatively major are on the high side, the directional change in the bore is gradual. The cumulative effect of the cutting action is to produce a bore with a generally oval cross section, thus facilitating advance of the tool during the angular or curving operation.

While my primary purpose is to alter the direction of the well bore in accordance with a predetermined plan, the too] might be used, if desired, to correct for unwanted deviation in straight bore slant hole drilling.

Alternative Embodiments Of The Invention It shouldbe clear from the foregoing descriptions that for deviation an eccentric orbit of the cutting action is utilized. This is best accomplished by the combination of the oversize cone and the cam. It could also be achieved by offsetting a conventional bit in combination with the cam. An example would be to angle the axis of the thread couplingbetween the shank of the bit and the drill collar. Another example would be to offset the box from the axis of the collar. Still another would be to employ a bent sub between the bit and the cam.

Although I have herein shown and described my in-. vention in what I have conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention.

1 claim:

1. Apparatus for slant hole directionaldrilling comprising an annular elongated drill collar, a roller bit mounted at an end of the drill collar, the bit comprising a plurality of cones, the teeth of one cone projecting radially from the axis of the drill collar a greater distance than the teeth of the other cone or cones, a single radial projection on the drill collar spaced axially above the bit, the projection and the one cone of the bit being disposed in a predetermined angular offset relationship, whereby as the drill collar is revolved in a slant hole the projection rides on the low side of the hole with each revolution thus camming the bit end of the drill collar upwardly and the one cone simultaneously cuts laterally away from the circular plane of the hole immediately preceding such lateral cutting action.

2. Apparatus as defined in claim 1 in which the drill collar comprises a mandrel and a sleeve thereon, the radial projection is mountedon the sleeve of the drill collar, stops mounted at the lower end of the sleeve, lugs provided on the bit adapted selectively to key with a stop for fixing circumferential relation of sleeve and bit, whereby offset angular relation of the one cone and the radial projection may be adjustably fixed.

3. Apparatus for slant hole drilling comprising a rotary drill collar, a cutting element mounted on the drill collar, and means on the drill collar engageable with the bottom of the hole to impart an eccentric motion to the cutting element during its rotation, the means to impart the eccentric motion comprising a cam on the drill collar,the cutting element comprising a roller bit, the roller bit including a plurality of cones, one cone being oversized relative to the other cone or cones, and the oversized cone being disposed circumferentially offset relative to the position of the cam.

4. Apparatus for slant hole directional drilling comprising a rotary drill collar, a roller bit mounted on the drill collar, nudging means fixedly mountedon the drill collar protruding radially therefrom at one circumferential location only engageable with the bottom of the hole on each revolution to impart a deviation in the direction of attack of the roller bit duringthe engagement of said means with the bottom of the hole, said roller bit comprising teeth which at a circumferential spacing from said nudging means extend a greater radial distance from the axis of the drill collar than they extend at the circumferential location of said means.

5. Apparatus for slant hole directional drilling comprising an annular elongated drill collar, a roller bit mounted at an end of the drill collar, the bit comprising teeth extending radially from the axis of the drill collar a greater distance in one direction than in the diametrically opposite direction, a single radial projection on the drill collar spaced axially above the bit, the single projection and the extending teeth of the bit being disposed in 'a predetermined angular offset relationship, whereby as the drill collar is revolved in a slant hole the projection rides on the low side of the hole with each revolution thus camming the bit end of the drill collar upwardly and the extending teeth simultaneously cut laterally away from the circular plane of the hole immediately preceding such lateral cutting action.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4262758 *Dec 10, 1979Apr 21, 1981Evans Robert FBorehole angle control by gage corner removal from mechanical devices associated with drill bit and drill string
US4307786 *Dec 10, 1979Dec 29, 1981Evans Robert FBorehole angle control by gage corner removal effects from hydraulic fluid jet
US4638873 *May 23, 1984Jan 27, 1987Welborn Austin EDirection and angle maintenance tool and method for adjusting and maintaining the angle of deviation of a directionally drilled borehole
US4886130 *Jul 26, 1988Dec 12, 1989Evans Robert FNutational technique for limiting well bore deviation
US4982802 *Nov 22, 1989Jan 8, 1991Amoco CorporationMethod for stabilizing a rotary drill string and drill bit
US5058689 *Oct 19, 1990Oct 22, 1991Collinsworth Stephen MWear protective means for a drilling tool
US5095981 *Nov 8, 1990Mar 17, 1992Mikolajczyk Raymond FCasing centralizer
US5234063 *May 28, 1992Aug 10, 1993Collinsworth Stephen MRemovable wear protective means for a drilling tool
US5350028 *Jun 24, 1992Sep 27, 1994Institut Francais Du PetroleDevice for adjusting the path of a rotary drilling tool
US5803194 *Nov 19, 1996Sep 8, 1998Kennametal Inc.Wear protector for a drilling tool
US6116356 *Jun 15, 1998Sep 12, 2000Baker Hughes IncorporatedReaming apparatus and method with enhanced stability and transition from pilot hole to enlarged bore diameter
US6173797 *Aug 24, 1998Jan 16, 2001Baker Hughes IncorporatedRotary drill bits for directional drilling employing movable cutters and tandem gage pad arrangement with active cutting elements and having up-drill capability
US6290007Jan 2, 2001Sep 18, 2001Baker Hughes IncorporatedRotary drill bits for directional drilling employing tandem gage pad arrangement with cutting elements and up-drill capability
US6321858 *Jan 28, 2000Nov 27, 2001Earth Tool Company, L.L.C.Bit for directional drilling
US6321862Aug 5, 1998Nov 27, 2001Baker Hughes IncorporatedRotary drill bits for directional drilling employing tandem gage pad arrangement with cutting elements and up-drill capability
US6425448Jan 30, 2001Jul 30, 2002Cdx Gas, L.L.P.Method and system for accessing subterranean zones from a limited surface area
US6439320Feb 20, 2001Aug 27, 2002Cdx Gas, LlcWellbore pattern for uniform access to subterranean deposits
US6478085Feb 20, 2001Nov 12, 2002Cdx Gas, LlpSystem for accessing subterranean deposits from the surface
US6484819 *Oct 4, 2000Nov 26, 2002William H. HarrisonDirectional borehole drilling system and method
US6561288Jun 20, 2001May 13, 2003Cdx Gas, LlcMethod and system for accessing subterranean deposits from the surface
US6575235Apr 15, 2002Jun 10, 2003Cdx Gas, LlcSubterranean drainage pattern
US6598686Jan 24, 2001Jul 29, 2003Cdx Gas, LlcMethod and system for enhanced access to a subterranean zone
US6604580Apr 15, 2002Aug 12, 2003Cdx Gas, LlcMethod and system for accessing subterranean zones from a limited surface area
US6622803Jun 29, 2001Sep 23, 2003Rotary Drilling Technology, LlcStabilizer for use in a drill string
US6662870Jan 30, 2001Dec 16, 2003Cdx Gas, L.L.C.Method and system for accessing subterranean deposits from a limited surface area
US6668918Jun 7, 2002Dec 30, 2003Cdx Gas, L.L.C.Method and system for accessing subterranean deposit from the surface
US6679322Sep 26, 2002Jan 20, 2004Cdx Gas, LlcMethod and system for accessing subterranean deposits from the surface
US6681855Oct 19, 2001Jan 27, 2004Cdx Gas, L.L.C.Method and system for management of by-products from subterranean zones
US6688388Jun 7, 2002Feb 10, 2004Cdx Gas, LlcMethod for accessing subterranean deposits from the surface
US6708764Jul 12, 2002Mar 23, 2004Cdx Gas, L.L.C.Undulating well bore
US6725922Jul 12, 2002Apr 27, 2004Cdx Gas, LlcRamping well bores
US6732792Feb 20, 2001May 11, 2004Cdx Gas, LlcMulti-well structure for accessing subterranean deposits
US6848508Dec 31, 2003Feb 1, 2005Cdx Gas, LlcSlant entry well system and method
US6942030Feb 11, 2004Sep 13, 2005Cdx Gas, LlcThree-dimensional well system for accessing subterranean zones
US6964298Jan 20, 2004Nov 15, 2005Cdx Gas, LlcMethod and system for accessing subterranean deposits from the surface
US6964308Oct 8, 2002Nov 15, 2005Cdx Gas, LlcMethod of drilling lateral wellbores from a slant well without utilizing a whipstock
US6976533Aug 15, 2003Dec 20, 2005Cdx Gas, LlcMethod and system for accessing subterranean deposits from the surface
US6986388Apr 2, 2003Jan 17, 2006Cdx Gas, LlcMethod and system for accessing a subterranean zone from a limited surface area
US6988548Oct 3, 2002Jan 24, 2006Cdx Gas, LlcMethod and system for removing fluid from a subterranean zone using an enlarged cavity
US6991047Jul 12, 2002Jan 31, 2006Cdx Gas, LlcWellbore sealing system and method
US6991048Jul 12, 2002Jan 31, 2006Cdx Gas, LlcWellbore plug system and method
US7025137Sep 12, 2002Apr 11, 2006Cdx Gas, LlcThree-dimensional well system for accessing subterranean zones
US7025154Dec 18, 2002Apr 11, 2006Cdx Gas, LlcMethod and system for circulating fluid in a well system
US7036584Jul 1, 2002May 2, 2006Cdx Gas, L.L.C.Method and system for accessing a subterranean zone from a limited surface area
US7048049Oct 30, 2001May 23, 2006Cdx Gas, LlcSlant entry well system and method
US7073595Sep 12, 2002Jul 11, 2006Cdx Gas, LlcMethod and system for controlling pressure in a dual well system
US7090009Feb 14, 2005Aug 15, 2006Cdx Gas, LlcThree-dimensional well system for accessing subterranean zones
US7100687Nov 17, 2003Sep 5, 2006Cdx Gas, LlcMulti-purpose well bores and method for accessing a subterranean zone from the surface
US7134494Jun 5, 2003Nov 14, 2006Cdx Gas, LlcMethod and system for recirculating fluid in a well system
US7163063Nov 26, 2003Jan 16, 2007Cdx Gas, LlcMethod and system for extraction of resources from a subterranean well bore
US7207390Feb 5, 2004Apr 24, 2007Cdx Gas, LlcMethod and system for lining multilateral wells
US7207395Jan 30, 2004Apr 24, 2007Cdx Gas, LlcMethod and system for testing a partially formed hydrocarbon well for evaluation and well planning refinement
US7222670Feb 27, 2004May 29, 2007Cdx Gas, LlcSystem and method for multiple wells from a common surface location
US7264048Apr 21, 2003Sep 4, 2007Cdx Gas, LlcSlot cavity
US7299864Dec 22, 2004Nov 27, 2007Cdx Gas, LlcAdjustable window liner
US7353877Dec 21, 2004Apr 8, 2008Cdx Gas, LlcAccessing subterranean resources by formation collapse
US7360595May 8, 2002Apr 22, 2008Cdx Gas, LlcMethod and system for underground treatment of materials
US7373984Dec 22, 2004May 20, 2008Cdx Gas, LlcLining well bore junctions
US7419223Jan 14, 2005Sep 2, 2008Cdx Gas, LlcSystem and method for enhancing permeability of a subterranean zone at a horizontal well bore
US7571771May 31, 2005Aug 11, 2009Cdx Gas, LlcCavity well system
US8291974Oct 31, 2007Oct 23, 2012Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface and tools therefor
US8297350Oct 31, 2007Oct 30, 2012Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface
US8297377Jul 29, 2003Oct 30, 2012Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface and tools therefor
US8316966Oct 31, 2007Nov 27, 2012Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface and tools therefor
US8333245Sep 17, 2002Dec 18, 2012Vitruvian Exploration, LlcAccelerated production of gas from a subterranean zone
US8371399Oct 31, 2007Feb 12, 2013Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface and tools therefor
US8376039Nov 21, 2008Feb 19, 2013Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface and tools therefor
US8376052Nov 1, 2001Feb 19, 2013Vitruvian Exploration, LlcMethod and system for surface production of gas from a subterranean zone
US8434568Jul 22, 2005May 7, 2013Vitruvian Exploration, LlcMethod and system for circulating fluid in a well system
US8464784Oct 31, 2007Jun 18, 2013Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface and tools therefor
US8469119Oct 31, 2007Jun 25, 2013Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface and tools therefor
US8479812Oct 31, 2007Jul 9, 2013Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface and tools therefor
US8505620Oct 31, 2007Aug 13, 2013Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface and tools therefor
US8511372Oct 31, 2007Aug 20, 2013Vitruvian Exploration, LlcMethod and system for accessing subterranean deposits from the surface
WO1993001390A1 *Jun 24, 1992Jan 21, 1993Inst Francais Du PetroleDevice for adjusting the path azimuth of a rotary drilling tool
WO1998015710A1 *Oct 8, 1997Apr 16, 1998Baker Hughes IncReaming apparatus with enhanced stability and transition from pilot hole to enlarged bore diameter
WO2002059447A1Jan 23, 2002Aug 1, 2002Andergauge LtdDirectional drilling apparatus
Classifications
U.S. Classification175/73, 175/325.2
International ClassificationE21B7/04, E21B7/08, E21B17/00, E21B7/06, E21B17/10
Cooperative ClassificationE21B7/064, E21B17/1078
European ClassificationE21B17/10T, E21B7/06D