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Publication numberUS2046106 A
Publication typeGrant
Publication dateJun 30, 1936
Filing dateMar 5, 1936
Priority dateMar 5, 1936
Publication numberUS 2046106 A, US 2046106A, US-A-2046106, US2046106 A, US2046106A
InventorsBozeman John F
Original AssigneeBozeman John F
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Core drilling apparatus
US 2046106 A
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Description  (OCR text may contain errors)

June 30, 1936. B ZEMA 2,046,106

CORE DRILLING APPARATUS Filed March 5, 1956 4 Sheets-Sheet 1 g v /6 49 25 v /7 V 4? INVENTOR: uo/m E aazzzmxw;

ATTORNEY.

June 1936- J. F. BOZEMAN CORE DRILLING APPARATUS 4 Sheets-Sheet 2 Filed Mrch 5, 1936 ua/m/ E 5029mm l-IL I A Patented June 30, 1936 UNITED STATES CORE DRILLING APPARATUS John F. Bozeman, Houston, Tex.

Application March 5,

18 Claims.

This invention relates to improvements in core drilling apparatus.

The invention has more particularly to do with well drilling operations and more especially to means for taking out cored samples of the stratum or geological formation at different depths as the drilling operation. progresses in oil, gas and other relatively deep wells. The invention principally concerns rotary drills of the tubular stem or pipe string type, in which provision is made for the insertion therein of a core drill which operates, in its lowered position, through an axial bore in the main drill head or tool as provided at the bottom end of the tubular stem or string of piping to which rotation is imparted by the regular rotary driving machine provided on the base of the derrick just above the top of the well hole.

In core drilling operations of the character above described, the core drill is usually operated with its cutting end portion some distance in advance of the outer main drill bit or cutting tool, and, obviously, as the characters of the formations or strata, through which the cutting bits or tools pass, vary considerably in many respects, particularly as to the degree of hardness of the material being drilled through, there are times when the outer or main drill bit or cutting tool cuts relatively faster than the inner core drill element, resulting in serious damage to the latter as well as'an imperfect core or one that is not a true specimen of the stratum or formation.

To avoid damaging the core drill, provision has been made, in some cases, for yieldability endwise of the core drill when the latter meets with the resistance of relatively hard material during the drilling operation and the main drill cuts faster than said core drill, as just above pointed out; but, unless some provision is also made to give an indication at the top of or above the well hole, of such happening at the bottom of the well, so as to be readily observed by the operator; iii order that the speed of the feed androtation oi the drill stem may be reduced or operation thereof stopped entirely, and thereafter resuming operations with due care and proportionate speed in accordance with the then reasonably known conditions at the bottom of the well hole, the coring operation fails and the core that is obtained is not a true specimen of the stratum or formation.

The present invention has for one of its principal objects to provide for practical yieldability of the core drill and an automatic indication of such occurrence during the drilling operation.

1936, Serial No. 67,224

Another important object is to produce a simple, practical and eiiicient core drilling appliance or tool which is readily placed in the tubular drill stem or rotatable string of drill operating pipe, dropped or lowered into working relation to the 5 main drill bit or cutting tool, and releas'ably interlocked automatically in such working relation and being also under convenient control from above the well hole.

A further object is to provide simple yet practical means for lowering the core drill into the main drill stem and for readily withdrawing the core drill, at will. Y

A construction designed to carry out the invention willbe hereinafter described, together with other features of the invention.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings, in which an example of the invention is shown, and wherein: I

Figure 1 is a fragmentary view, in vertical section, of the lower end portion of the drill stem with a main drill bit or tool of the fishtail type applied and a core drill also applied and shown in partially extended but normal drilling position relative to the cutting end of the main drill bit or tool;

Figure 2 is a detailed sectional view of the stop ring element for the core drill, the vertical section of the ring being taken at substantially right angles to that shown in Figure 1;

Figure 3 is a vertical section, in fragmentary illustration, of the portion of the drill stem and contained parts just immediately above the parts shown in Figure 1;

Figure 4 is a view of the character of'Figures 1 and 3, showing parts and portions of the drill stem and contained parts next adjacent above the parts and portions shown in Figure 3;

Figure 5 is a view of the character of Figures 1, 3 and 4, showing the parts and portions completing the continuity of the structure above the parts and portions shown in Figure 4;

Figure 6 is a fragmentary longitudinal section of the lower portion of the core drill placing and withdrawing tool, showing the spring clutch element thereof engaged with the drawhead of the core drill;

Figure '7 is an elevatiqpal View of the spring 59 slip element of the core drill placing and with: drawing tool detached;

Figure 8 is a fragmentary longitudinal section of the upper portion of the core drill placing and withdrawing tool, and is a continuation of Figure 6, showing certain parts in an inoperative position for engaging the core drill;

Figure 9 is a longitudinal section of the core drill placing and withdrawing tool, with several intermediate portions broken away, but showing the correlation of certain parts operated to position for releasing the core drill and allowing the latter to remain placed in the main drill bit tubular drill stem, the end portion of which, as

shown, is tapered, as at 2, and screw threaded for attachment of the shank portion 3 of a drill bit or tool 4 which, as shown, is of the flshtail type.

" In the body portion 5 of the drill bit or tool 4 is an axial bore 6, the lower end portion 1 of which is reduced in diameter, aflording an annular shoulder 8, while extending diagonally downwardly and outwardly from the upper part of said bore 8 is a passageway 9 for supplyingdrilling fluid (termed "mud in the parlance of the oil fields and other well drilling activities) to the lower portion of one face (the forward face) of the drill 'wing'or blade 4, and similarly from the opposite side of the bore 6 is provided another passageway Ilifor supplying fluid to the corresponding face of the opposite wing or blade 4,

in accordance with the usual practice in well drilling operations.

Mounted loosely to slide endwise but held from rotation in the bore 6' of the drill bit or tool 4 'is a. stop ring or element l I, the lower part of the bore I! of which is of a diameter slightly larger than the external diameter of the tubular core drill cutter body member l3 (see Figure 1) to be later more fully described. The upper part of the bore of the element H is upwardly flared, as at M, and a tapered or bevelled annular seat portion I4 is provided where the parts I2 and I 4 of the bore merge, while diametrically opposite slots 9 and iii are provided in the upper wall portions 01' the element H to constantly register communicablywith said fluid passageways 9 and I0, respectively, of the main drill bit or tool 5. This stop ring or element It is yieldably held normally with its upper end in abutting contact with the lower end of the tapered lower portion 2 of the tubular drill stem section or joint 6, by a coiled spring element in interposed between the lower end of said element l i and said annular shoulder t of the bore ti.

To guide the endwise movement and prevent rotation of the element 9 within the bore of the drill bit or tool i, said element is provided with a relatively short longitudinal slot it in one side thereof, into which is projected the inner end portion ll of a screw-stud it inserted through a transverse screw-threaded opening provided therefor in the body portion 5 of the drill bit or tool i (see Figures 1 and 2).

The core drilling elements will now be de= scribed. As shown, the tubular lower body mem her it of the core drill is provided with an ordinary annular cutting bit or head it which is screw-threaded, as at 2b, to the lower end portion or said body member iii. The bit or head 89 is provided with an annular series of teeth 28 at up through proved type. The

ddiddidd its lower end, or, obviously, it may be provided with other cutting portions of any conventional or approved character. Above the cutting portions 26 of the bit or head 19 is formed an annular internal shoulder 22, between which and the adjacent end of the tubular body member I3 is loosely placed a ring member 23 having a series of upwardly extending and inwardly turned spring elements 24, through which the core cut by the bit or head I9 is forced upwardly into the tubular body member l3, or, rather, said member I3 is moved downwardly over the core during the drilling operation. As the formation of the core progresses it is taken into the upper drill body tube 25 which is screw-threaded on the upper end portion of said member i3.

Said ring member 23 and spring elements {I constitute a core retainer and being loosely mounted within the core drill, as shown, said retainer remains rotatively stationary with respect to the core but moves endwise downwardly over the core while the drill elements'are rotating and being simultaneously fed downwardly. In the region of the spring drill body tube I3 is preferably downwardly flared slightly, as at 24", to accommodate said spring elements and also aid in the entrance of the coreas it is forced into said tubular member ii, the latter being increased slightly in internal diameter some distance. above said flared portion 24', as at 24", which increased diameter continues body tubular member 25 may be of any desirable or ordinary length, depending upon the length of the core to be taken from the stratum or forma-- tion through which the well hole is being drilled and depending also upon the practice adopted in each particular locality of well drilling operations; and, as far as the cutting bit and core retainer are concerned, they may be of any appresent invention, however, comprehends radical improvements in the structure, mounting, operation and control of the core drill, which will now be described.

The drill cutter body member I3 is provided with an external annular bevelled shoulder 26 to engage the seat I l of the stop ring or element II when the core drill is dropped or lowered into the drill stem tubing and the main drill bit or tool I is in raised position, as it is well hole being drilled. The spring supported element ll afiords a cushion for the impact when the shouldered portion 26 of the core drill member l3 strikes said element, either when the core drill is dropped by gravity or when lowered by a lowering tool and cable into the main drill stem. In this connection, a special lowering and withdrawing or, as commonly termed a fishing tool, to be later more fully described, may be provided.

The tubular member 25 is screw-threaded, as at 2], at its upper end portion, to the lower nipple portion 28 of a valved coupling element 29 provided with a ball type check-valve member 3t normally closing the lower bore 36 of said coupling element (see Figure 3). The ball member 359 is limited in its upward unseating movement, by a cross bar 32, while transverse ports 33 are provid d just above the valve seat 34, affording communication between the upper bore 35 of the coupling element 29 and the fluid passage space between said core drill tube 25 and the main tubular drill stem i.

Threaded at its lower end portion, as at 31, to

the core drill tubing. The core drill the upper nipple portion 38 of the coupling element 29, is a tubular spring case or housing .39 having a reduced and externally screw-headed upper portion 40, provided with an axial bore 4! through which a piston rod or stem 42 is freely slidably fitted. As shown, said piston rod 42 has an integral head 43 at its upper end, said head 43 having a bifurcated or open-ended slotted upper portion 44 for a purpose to be presently more fully explained, while the lower end portion of said rod 42 is slightly reduced in diameter to afford an annular shoulder 45 and said reduced portion being externally screw-threaded to receive a detachable head 46 having a counterpart screw-threaded axial opening therein to fit the threads of said reduced end portion of the rod 42,

whereby said head 46 is attached to said rod 42 in a manner similar to an ordinary nut and tightened against said annular shoulder 45.

The upper portion of the piston rod 42 works within the lower end portion of an upper tubular casing or housing 4! which is screw-threaded, as at 48, and attached to the reduced externally screw-threaded portion 49 of the tubular casing or housing member 39, and containing a special latching and controlling means for the operation of the core drill when applied in working relation and in withdrawing it, as will be later more fully set forth.

Interposed in the tubular casing or housing member 39, between the piston head 45 and the end of the upper nipple portion 38 of the coupling element 29, is a coiled spring element 49, and a duplicate of said spring element, as at 50, is interposed in the casing or housing 41, between the upper piston head 43 and the end of the reduced upper end portion 40 of said tubular casing or housing member 39. These spring elements 49 and 50 are shown in their normal supporting condition in Figure 3 of the drawings.

Fitted slidably, with relative looseness, between the bifurcated end portions 44 of the upper piston head 43 is the lower hooked end portion of a latch element 5i having an inclined cam slot 52 through which a cross pin or bar 53 on the portions 44 is slidably fitted. The upper end portion of the latch element 5| is pivoted, as at 54, to the bifurcated lower end portion 55 of a link member 56 having an open-ended longitudinal slot 51 in which a reduced longitudinally elongated extension 58 of a fiuid flow controlling and core drill supporting bar 59 is loosely fitted to slide freely therein. The bar extension 58 is provided with an elongated longitudinal slot 60 through which a cross pin or bar ti on the link member 56 is slidably fitted.

The fiuid flow controlling and core drill supporting bar 59 is provided with an enlargement or piston type valve-head 52, the under shoulder portion 53 of which rests normally on the upper end of the tubular member ll (see Figure 5) while its upper shoulder portion 54 is tapered or bevelled, as at 55, and above which said bar extends, as at 55, for some distance, and being of substantially the same diameter as the main lower portion of the bar 59 below said enlargement or valve-head 52, while the above said portion 56, the bar is further reduced in diameter, as at 57, with a bevelled annular shoulder portion 68 at the base of said portion 5?. The extreme upper end portion of the reduced portion fill is tapered or pointed, as at 59, while just below said portion 59, an annular groove 15 is formed, thereby producing a draw-head 69 for the attachment of a special core drill placing and withdrawing or fishing tool to be presently described. Preferably, as shown, the top and bottom shoulders H, 12, respectively of the groove I0 are bevelled.

For convenience in constructing and assembling the several correlated parts of the main drill stem tube or pipe joints with respect to the placing and operating of the core drill therein, the lowermost main drill stem section I preferably terminates with its upper end portion I in the region of the normally positioned link member 56 and it is, as customary in the practice, provided with an upwardly flared internally screw-threaded socket in which is received the correspondingly tapered screw-threaded reduced end portion l of an upper stem section or pipe joint I, which latter terminates with its upper end portion in the region of the draw-head of the core drill bar mem: ber 59 and is there provided with a screw-threaded socket I for the reception of the reduced screw-threaded end portion I of the next adjoining upper drill stem tube or pipe joint, indicated by the reference character I, and provided at its upper end portion with an attaching socket l similar to those hereinabove described, it being obvious that additional drill stem tubes or pipe joints are added to the string in the well hole in accordance with the usual practice as the drilling operation progresses.

Fitted as a packing gland in a bore 13 in the upper portion of the drill stem section I is a pair of abutting ring members l4, 15, the meeting end portions of which, as shown, are bevelled annularly for the reception of a rubber or other suitable packing ring 76 in the substantially V-shape annular groove thus provided, whereby to make a water-tight seal between the circumferences of said rings l4, l5 and the cylindrical face of the bore 13. As shown, said ring members 14, I5, are tightened between the annular shoulder H5 at the bottom of the bore 13 and the end of the reduced portion i of the drill stem section I The bore H of the ring members l4, 15. as thus jointly assembled in the bore 13, is substantially the same as the diameter of the valve-head 62, or in other words, the respective diameters of said parts are such that the valve-head 62 will work in the bore IT with an easy sliding fit and yet effectively seal the passageway through said bore ll when said valve-head is moved into it, so as to stop the fiow and circulation of the fluid, or

mud as it is more commonly termed in the well drilling operations, as will be later more fully described.

To afford an easy entrance of the valve-head 62 into the bore ll of the packing ring members 14, 75, the lower end portion of the bore in the lower ring member 75 is preferably bevelled, as at iii, to function with the bevelled shoulder 65 of said valve-head 52. In this connection it is preferable to correspondingly bevel the upper ring member 74, as at 78 so that said ring members l4 and 75 may be interchangeable.

Fitted in an enlargement of the main bore of the lower drill stem tube or pipe joint i, near the upper socket portion i thereof, is a longitudinally slotted latch anchor tube or cylindrical tubular cage-like element, designated generally by the numeral 79. The generally enlarged portion of the bore of the drill stem section l is shown more clearly in Figures 3 and 4 of the drawings and designated by the numeral Bil. As shown, said element "IQ is provided with a series of upper slots or openings 8i annularly thereof and a similar series of openings near the bottom thereof, as at 82;

Between said slots or openings SI, 82, are a is either lowered by a special tool orcable or multiplicity of larger longitudinally elongated slots or openings 83. In the core drill tubular member d'I there are also provided longitudinal slots 84, 85, the slot 84 being relatively longer than the slot 85 to permit considerable endwise move ment of the latch member 5i therein.

The slots or openings BI, 82, are provided in the latch anchor tube I9 primarily for the passage of the drilling fluid or mud while the slots 83 are provided primarily for the engagement of the hooked end portion of the latch member 5|, whereby to provide an interlocking eifeot, so that, under certain conditions and in relative positions of the correlated parts, the core drill is rotated by and with the main drill stem tube or string of piping, and at the same time the latch member 5| is interlocked against endwise movement in one direction with respect to said main drill stem but permitted limited movement endwise in the opposite direction.

The upper and lower portions of the main drill stem bore enlargement 80 are reduced in diameter, as at 56 and 87, respectively, to substantially the same diameter of the adjacent-end portions 88 and 89 of the latch anchor tube or element I9 which are fitted therein. The lower end portion 89 of said element I9, as shown, is provided with an open-ended slot 98 which fits over the protruding inner end portion of a stud 9| which is inserted in a transverse bore 92 provided therefor in the drill stem tube or pipe joint I (see Figure 3) and secured in place, preferably by a welding flux filling in a tapered recess at the outer end portion of said bore 92, as at 93.. This provision is to facilitate the placing of the anchoring element 19 and for holding it against rotation independently ol the drill stem section I." In order to also key the upper portion 88 of said element 'ISagainst rotation independently of said drill stem section I and further relieve said multi-slotted element I9 of torsion a longitudinal key pin or dowel-like pin 94 is placed in a longitudinal bore provided half and half in the contiguous portions of said drill stem section and the portion 88 of said element I9, as shown in Figure 4 of the drawlngs.

The latch anchor element I9 is held against endwise movement away from the shoulder 95 at the bottom of the portion 81 ofv the bore enlargement 80, by the'abutting end face 96 of the coupling portion I b of the upper drill stem section I which is inserted in the socket portion i of said drill stem section 5. This is clearly shown by reading the upper part of Figure 3 together with the lower part of Figure 4 as an upward continu= ation of Figure 3.

The core drill operationandcontrolwillrlow be described.

In accordance with the usual practice, when the core drill is to be applied, tne operation of the main drill is stopped for the time being and the drill stem tube or pipe string is raised to bring the drill bit or cutting tool up some distance from the bottom of the well hole thus far drilled, varying from several inches to a few feet, and the string of drill stein tubing or piping is held in such raised position in the rotary machine at the top of the well hole by the application or the usual slips or retaining elements generally employed for the purpose.

Afterthe driving section, or grief join or irelley as said section is more eoonly termed, is removed from the drill stem string, the core drilling appliance, with all of its parts assembled,

dropped by its own weight into'the drill stem tubing or piping, more generally in the latter way in many well drilling operations. In this connection it'may be here noted that in practically all deep well drilling operations the hereinbefore described fluid or "mud" is maintained in the well hole and kept in circulation during the time the drill is operating to clear the drill bit or cutter element of the detritus resulting from the operation of the tool and also to prevent caving of the well hole as well as settling and packing of the detritus at the bottom of the hole. It is, therefore. understood that this fluid or mud is in) the well hole and the main drill stem tubing when the core drill is lowered or dropped into said tubing, and that the circulation of the fluid or mud may or may not be stopped temporarily for the relatively short period during which the core drill is being initially placed in working relation to the main drill bit or cutting at the bottom of the tubular stem or pipe string.

As the main drill bit (the bit 4 in the illustration in the accompanying drawings) is lifted from the bottom of the well hole, as hereinbefore stated, the lower cutting end portion of the core drill will be projected a distance substantially twice that of its normal cutting position ahead of the cutting end of the main drill bit, at which time the annular shoulder 26 of the lower core drill tubular member I3 is resting on the seat portion ll of the stop ring II, which latter, as hereinbefore described, is supported by the spring element I5 and thereby affords a cushion when the drill tube shoulder portion 26 strikes said seat portion ll of the stop ring II, as the spring element I5 yields and in which action the counter bevelling of the shoulder 26 and seat It function to centralize the tube I9 and stop element II so as to appreciably prevent and overcome any tendency for the element I I to become canted and bind in the bore 6 of the main drill bit body 5.

As the core drill is lowered or dropped into the main drill stem tubing or pipe string the hooked lower end portion of the latch member II, by

"the anchor tube or cage member I9 where the hooked end 5i of the latch member is below the horizontal plane of the upper ends of said slots or openings d3 of said anchor tube or cage member, whereupon the hook portion of said latch member is free to enter any one of said slots or openings 33 as said latch member SI, together with the connected parts above it, drop by their own combined weight and the pressure of the fluid or the mud in the drill stem tubing or pipe string of the main drill above them.

The parts being in the relative positions just above noted, if the drill stem l is rotated and the hooked end portion 5t of the latch member 5i is projected into the slot or opening 83, the core drill is, obviously, rotated therewith.

To start the drilling operation the main drill stem is lowered and after the core drill has begun ill socket, is a spring slip element M5, having a transverse open-ended slot ll 6 at its upper end through which is placed a transverse bar or cross member lli, riveted at its opposite ends in the tubular member ll l3, whereby said spring slip element l l5 is held against rotation in said mem-- ber llll, but permitted limited endwise movement.

As shown, the slip element lid, which is tubular, is provided with a multiplicity of longitudinal slots llll, thereby producing a series of spring tongue portions lid. The lower end portion of the bore l 28 of said slip element M5 is reduced in diameter, as at liil, and provided with internal screw-threads l22, the undersides oi which are bevelled and the upper sides of which are substantially horizontal or square, so as to receive, with endwise snap effect, the counterpart upper end portion l23 of a longitudinally movable bar or plunger member lil l, the extreme end portion of which is tapered or pointed, as at l25, to enter said threaded bore portion l22, and having external threads llld below said tapered or pointed end portion and extending to an adjacent bevelled shoulder l2ll at the base of said end portion 123 of the bar.

Some distance downward from the upper end of the bar or plunger member i2 3 it is provided with an annular external shoulder or collar portion l28, between the upper side of which and a screw-collar ltd threaded on the adjacent portion or" said bar l it is a packing ring lfilt of rubber or other suitable material compressible against the adjacent inner face of said tubular member 9? (see Figure 6).

Sleeved around said bar or plunger member l2 l and interposed between the end of the lower nipple extension lot of the coupling element lllb and said screw-collar lid is a coiled spring element lBl which normally acts to press said bar or plunger member l 23 downwardly.

The bar or plunger member lil l is externally screw-threaded, as at list, just below said annular collar portion l28 thereof, and to said threaded portion is attached the upper portion i335 of a spring slip element lilll. Said slip element ld l, which is shown in detail and detached in Figure 7, is tubular, as shown more clearly in Figure 6, and provided with a series of longitudinal slots ltd, thereby producing a series of spring tongue member lBt.

The lower end of said bar or plunger member lid is formed with a tapered recess or socket it? which is a substantial counterpart of the tapered end portion 69 of the draw-head 69 of the core drill, and the spring slip element l3 l has its lower end portion extended downwardly beyond said socketed end portion l3'l of said bar or plunger member ltd, and being externally bevelled annularly, as at llB, to engage said bevelled shoulder portion llll of the tubular member 9i and against which shoulder portion llll said end portion I38 of the slip element is normally pressed by said spring element ltl, the effect of which is to wedge the internal bevelled shoulder portions ldll into the annular groove ill and engaging relation to the under side of the shoulder portion ll of the draw-head ca of the core drill (see Figure 6).

In the socket l 3? of the bar or plunger member llll are transverse grooves l 40 communicating with an axial bore of relatively small diameter in said bar or plunger member, said axial bore, designated by the numeral l ll, communicating at its upper end with the bore of the aoaaioe tubular member Ell, at a point above said screwcollar member l2il through a transverse port l 'lfi. These grooves l lt, bore t lt, and port M2, are provided to relieve the compression of fluid in the bores of said tubular members 9i and l it between the screw-collar member i253 and the end l l l of the bore ll l oi the socket member lib when the fishing or withdrawing tool is dropped to engage the core drill; and, by contact of the lower end or" the bar or plunger member lil l with the draw-head 69 said bar or plunger is moved upwardly and thereby compresses said spring element lSl, which latter functions as a cushion and said cushioning effect is augmented by the displacement of the fluid in the bores of said tubular members ill and ll ll through said port M2, restricted bore l ll and said grooves l lll, thereby functioning with the effect of a shock-checking dash pot.

The spring slip element ltd, as before stated, is yieldably held by the spring element l ill in normal wedging contact with said shoulder portion ltl of the tubular member ill, and as the fish ing tool or withdrawing and core drill placing tool, as it may be termed, is lowered or dropped with momentum into the drill stem tubing or pipe string, and the socketed end portion lt'l of the bar or plunger member l2 i strikes the draw-head 69 of the core drill, the tubular member all continues on downwardly while the spring element l3l yields sufiiclently to permit such downward movement a distance so that the bevelled shoulder portion llll of said tubular member ll'l is far enough below the lower end of the spring slip element i3 3 to permit spreading of the internally shouldered portions lilll thereof over the drawhead til whereby they snap into the annular groove lil. Then, as the spring element lBl reacts to lift said tubular member ill, the lower end portion of said spring slip member ltd comes in contact with said bevelled shoulder llll and the internal shoulder portions of the slip element l3 are wedged in interlocking relation under said shoulder portion ll of the draw-head 69 of the core drill.

With the several parts in the correlated positions and engaging relation as shown in Figures 6 and 8, if the cable H3 is pulled upwardly the core drill is thereby withdrawn, because, in the meantime, the main drill stem tubing or pipe string has been raised preparatory to the application of the fishing or withdrawing tool. When the bar 59, at the upper end of which the drawhead 69 is provided, is lifted, the lower end 60 of the slotted portion till of the bar extension 58 first engages the cross bar tl, whereupon the link member 55 is lifted, thereby lifting the latch member bl; and the shoulder at the upper end of the slot 83 in the latch anchor tube orcagelike member '09 being then raised to a position somewhat above the hook of said latch member, the slotted portion 52 of the latch member rides on the cross-bar 55 on the bifurcated portions 44 of the piston head l3, whereby the latch member is cammed and swung back to clear said shouldered upper portion of the slot 83 and is then free to be further lifted through the instrumentality of the connected elements above it; and, by reason of the lower end of the slot 52 coming in contact with said cross-bar 53, the piston stem or rod l2 is pulled up with the latch member 5i and, of course, the entire core drilling tool structure is withdrawn.

In the event the core drill should stick from any cause, or become frozen, as it is commonly further lowered to the cutting position; that is to say, after the core drill cutter portion I9 has cut a 'suflicient length of the core for said cutter portion to be in its normal cutting position ahead 5 of the main drill bit 4 as shown in Figure 1 of the drawings. Then, as long as the core cutter and the main drill bit cutting ends remain in this working relation, the drilling operation'may continue unlnterruptedly until the length of the 10 core is completed. However, should the main drill bit out faster than the core drill bit or cutter portion, the core drilltubing will yield upwardly,

or, rather, with the same effect, it will be that the main drill stem moves downwardly with respect to said core drill tubing, and by reason of the hooked portion 5I of the latch member 5| being engaged under the upper end of the slot or opening 83 of the anchor tube or cage member I9, and the slot 85 of the tube member 41 of the core drill assembly being entirely above the lower end of said latch member SI, and also that the upper end of the slot 52 is in engagement with the cross bar 53 of the bifurcated portion 44 of the piston head 43, said head 43 and the lower head 46 connected thereto by the stem or rod 42, are obviously moved downwardly with the main drill stem I, or, putting it the other way around, the core drill tubing 41 moves upwardly with respect to said elements, 43, 42 and 46, whereupon said upper spring element 50 is compressed between'said upper head 43 and-the opposed end portion 40 of the tubular casing or housing member 39, and simultaneously therewith the lower spring element 49 is compressed between said lower head 46 and the end of the opposed nipple extension 38 of the check-valved coupling element 29.

It is here noted that the compound springs 49, 50, are a very important feature of the inven- 40 tion, as such are provided in order to attain the requisite normal spring pressure and re-active effect within limited longitudinal range or dimensions. In this connection the compounding of the spring elements may be further multiplied. The above noted relative movement of the parts is also permitted because of the provision of the longitudinal slot 60 in the reduced lower end portion 56 of the fluid valve controlling and core drill supporting bar 59 with which the cross bar 6| of the slotted portion of the link member 56 cooperates. This provision permits of the upper end of the tubular member 41 bearing normally against thebiittom shoulder 63 of the valve-head 62, whereby to push said valve-head 62 up into the bore 11 of the packing gland rings I4, I 5 of the main drill stem section I.

As soon as the valve head 62 enters, even slightly, into said bore 11 of the ring members 14, 15, the flow of the drilling fluid or mud through said 60 bore 4.! .isstopped and thereby the back pressure.

in the drill stem tubing or pipe string above said valve-head 62 retards the action of the drilling fluid or mud pump, and possibly stopping the operation of the pump entirely, depending upon 65 the type of pump used; and, anyway, giving an appreciable indication to the operator that core drill has yielded and caused the cessation in the .flow and circulation of the drilling fluid or mud; or, in some cases, such occurrence may be obvi ously indicated by a pressure gage as is sometimes used in the fluid or mud circulating system.

Obviously, as soon as the operator notices that the core drill has yielded, with the effect as above indicated, it is only necessary to raise the main drill stem tubing or pipe string to lift the main drill bit from the bottom of the well hole or retard the downward feed of said main drill stem until the core drill again is in its normal drilling position with respect to the cutting end of the 5 main drill bit, to which position the core drill is moved by the re-action of said spring elements 49, 50, whereupon the valve-head 62 is either withdrawn from said bore 11 of the ring members I4, I5, by the weight of the parts attached above 10 said valve-head and the bar member 59 below it, or augmented by the fluid or mud pressure from above.

To release the fluid or mud from the tubular members I3 and 25 as the formed core is moved 15 up into said members, the hereinbefore described ball check-valve. 30 is provided, so that when unseated, the fluid or mud passes out through the ports 33 in the coupling element 29 into the annular space 36 between the core drill tubing 20 and the main drill stem tube I. In this connection it may be here noted that said ball check valve 30 has a further important function in normally preventing entrance of the circulating fluid or mud downwardly into the tubes 25 and I3 and 25 washing away the. formed core therein.

After the core is completed the core drill is removed from the main drill stem by means of a special fishing or coredrill withdrawing tool to be now described, which tool is also adapted 30 for lowering the core drill into the main drill stem, in some operations, instead of dropping the core drill by its own weight, as hereinbefore stated.

Said fishing or withdrawing and core drill 35 lowering tool is illustrated in Figures 6, 'I, 8 and 9 of the drawings, the lower core drill engaging portions of the tool being shown in Figure 6 and the upper portions in Figure 8. As shown, said tool comprises a lower main tubular member 91, 40 the lowermost bore portion 98 of which is of a. diameter to fit slidably over the stem portion 65 of the core drill. At the top of the bore portion 98 is an internal annular shoulder 99, having a bevelled underface of the bevelled shoulder 68 at the upper end of the stem portion 66 of the core drill, and a bevelled upper face IOI above which the bore I02 is enlarged to a diameter somewhat larger than the bore 98.

The 'bore I02 is reduced slightly in diameter, as at I03, beginning with an annular internal shoulder I04 and extending up to a coupling element I05, said coupling element having a screw-threaded lower nipple portion I06 to which the upper 55 end portion of said tubular member is attached, as at I01. The upper nipple extension I09 of said coupling element I65 is externally screwthreaded, as at I09, for the attachment of the tubular lower end portion draw-bar or rod I I I, commonly termed a "sinker bar because it is utilized as a weight in lowering the tool into the drill stem tubing or pipe string, 1 and varying in length in actual practice from approximately four to six feet. However, said bar 35 is not of any restricted length except, of course, within certain limits for convenience in handling the tool in placing it in the drill stem tubing and withdrawing it therefrom.

At the upper end of the bar III is provided an 70 ordinary socket member II2 to which the lower I end of the cable H3 is attached securely in any usual or approved manner.

Fitted loosely in the tubular member III), the bore II4 of which constitutes, 'in effect, a slip 75 I00 which is a counterpart 45 H0 of an elongated eo termed, in the main, drill stem, so as not to be drawn out by the cable and fishing tool as just above described, provision is made for the release of the fishing tool from the draw-head of the core drill. To this end, in practice, the cable H3 is passed through a suitable or approved stufiing box or packing element, not shown, but obvious, placed on or in the upper end portion of the main drill stem tube or pipe string ,at the top of or 'above the well hole and provision is made for pumping the fluid or mud, hereinbefore described in connection with the drilling operation, in which event hydraulic pressure is set up in the drill stem above the fishing tool, whereupon, if the cable I I3 is let down or slackened with respect to the engaged fishing tool which it would otherwise be tending to lift up, the pressure of the fluid or mud on the top shoulder I I0 of the tubular portion III) of the sinker bar II2, as well as upon the shoulder I I2 at the top of the cable attaching socket H2 and the outer surface of the tubular member 91, will force the fishing tool downwardly until the lower end 9'! of said tubular member 91 comes in contact with the annular shoulder 64 at the top of the valve-head 62, which latter is resting with its bottom shoulder 63 on the upper end of the tubular member 41 of the core drill.

As the fishing tool moves downwardly under the pressure of the fluid or mud, as just above described, the spring slip element II5 comes in contact with the upper end portion I25 of the plunger member I24 and by reason of the provision of the cross bar II! and the slot-ted portion II6 of said slip element I I5, said element is raised in the bore II4 of the socket member IIO until the upper end of said slip element is arrested against the end II4 of the bore I I4, immediately upon the happening of which, the pointed and externally screw-threaded end portion I25, I26, of the plunger member I24 is forced into the screw-threaded reduced lower end bore portion I22 of said spring slipmember or element II5 with a sudden snap eifect because the bevelled internal annular shoulder portion I08 of the upper extension I08 of the coupling member I05 is at the time located a sufiicient distance below the externally bevelled lower end portion ii of the spring slip element I I5, so that the tongue members H0 are free to spread as the counterpart screw-threaded portions I22 and I26 ride into engagement with each other and become interlocked against endwise separation until released in a manner to be presently described.

With the several parts positioned and interlocked as just above described, and as shown in Figure 9 of the drawinga the internal annular shoulder IOI of the tubular member 91 is positioned a considerable distance below the bevelled end portion I38 of the spring slip element I34. Now, if the cable H3 is pulled upwardly under power, the tubular member 431 is lifted with the sinker bar II2 through the connection of the coupling element I05 and the slip socket tubular member H0, and the bevelled lower end Ill-i of the spring slip element II5 becomes seated and wedged in the counterpart seat afiorded by the bevelled shoulder portion I08 of the nipple portion I08 of said coupling element I05, whereby said tongue portions II9 of the spring slip element II5-are securely held against release from the screw-threaded end portion I23 of the plunger member I24. Then, as the tongue members I36 of the spring slip element I34 are unrestrained from outward movement, the internal shoulder portions I39 thereof are spread out of engagement from under the shoulder II of the drawhead and the fishing or withdrawing tool is withdrawn, leaving the core drill in the main drill stem tubing or pipe string.

When the fishing or withdrawing tool is withdrawn, the plunger member I24 is released from the spring slip element II5 by unscrewing the engaged end portion I23 from the screw-threaded end portion I2I of the spring slip element by applying a key-tool with a blade similar to a screw-driver to the grooved portions I40 in the tapered end socket I3'I of the plunger member I24, which is readily accomplished by inserting the key-tool in through the lower end portion of the tubular member 91.

In cases where the core drill is lowered into the main drill stem tubing or pipe string by the withdrawing and lowering tool of the invention herein described, the lower end portion of the tool (the tubular portion 91 thereof) is placed over the upper end portions 61, 66, of the core drill, with the spring slip element I34 engaged with the draw-head 69; and, after the core drill is lowered into its working relation to the main drill bit or cutter element 4, the lowering tool is released by the same process as that followed in releasing the tool from the stuck or frozen core drill, as hereinabove described. That is to say, the hydraulic pressure is set up in the drill stem tubing to effect the engagement of the 0 plunger member I24 with the spring slip element II5, after which the cable is pulled upwardly,

withdrawing the lowering tool from the core drill, whereby said core drill by its own weight and the fluid pressure in the lower portion of the surrounding drill stem tubing is held with sufiicient resistance for the release of the spring slip tongue members I36 from the draw-head 69.

Obviously, the general structure and arrangements of the assembled apparatus, as well as the details of the several component parts thereof, may be changed or modified in many respects within the spirit and scope of the invention as defined in the appended claims. The invention, therefore, is not limited to the specific construction and arrangements shown in the accompanying illustrative drawings.

What I claim and desire to secure by Letters Patent, is:

1. In combination with a main tubular drill stem having a drill bit or cutting tool at the lower end thereof, said bit or cutting tool having an axial bore therethrough, a core drill insertable in said drill stem and movable operably in and through the bore of said main drill bit or cutting tool, means for releasably interlocking said core drill to said main tubular drill stem to be rotated by and with said stem and having provision for limited endwise movement of the core drill in the region of its rotatably interlocked working position in said main tubular drill stem and bit or cutting tool, means for yieldably pressing the core drill in normal cutting position with its'cutting end portion in ad- Vance of the main bit or cutting tool, and means for indicating to the operator the yielding of the core drill from its normally advanced drilling position.

2. In combination with a main tubular drill stem having a drill bit or cutting tool at its lower end, said bit or tool having an axial bore therethrough, a core drill insertable in said drill stem and movable operably in and through the bore of said main drill bit or cutting tool, means for drill bit or cutting tool, means for" yieldably' pressing said core driii endwise into normal cutting position with its cutting ,end in advance of said main drill bit or tool, and means on said core drill for closing the bore of said main drill stem and stopping the how of the fluid in said stem upon the yielding of the coredrill from its normally advanced drilling position with respect to said plain drill bit or cuttingtool.

3. The combination as set forth in claim 2, and the fluidf flow-stopping means on the core drill comprisgig a valve-head portion movable slidably endwise into a portion of the main drill stem bore thereabove of a diameter substantially the same as the diameter of the valve-head. V

4. In combination with a rotary drilling tube and fixed cutting bit at the lower end thereof; a core c-Zutting tube fitted with a core retainer and so constructed that it will travel from the surface down through the rotary drilling tube, to an automatic anchorage in its core cutting position and being removable upwardly through the rotary drilling tube to the surface, *rneans for projecting said core cutting tube with its cutting end portion ahead of the driii bit of the rotary drilling tube, means for circulating drilling fluid down through said rotary drilling tube and around the core cutting tube, means operable between the core cutting tube and rotary drilling tube to block circulation of the drilling fluid when the core cutting tube yields upwardly from normally projected core cutting position, whereby to indicate such occurrence to the operator.

5. In combination with a tubular rotary drill stem through which a core drill may be dropped or lowered and also: removed upwardly there through by means oij a cable tool, a fixed drill bit carried by the drill stem and having an axial bore of largeif diameter than the lower end portion of the core drill butsmaller than the upper portion of the core drill, providing an upper facing shoulder on which rests a spring supporting a stop ring, said stop. ring'having side fluid ope nings f'communicably registering with fluid pessagesjin the main drill bit, said stop ring having a reduced lowerbore portion below said side fluid openings aifording an internal annular stop shoulder for the core drill, said stop ring locked to rotate with said main drill bit'but movable endwise therein, said annular shoulder of the stop ring receiving in'contact an external annular shoulder on the core drill and the stop ring yielding downward and acting as a shock absorber by compressing'the supporting spring therebelow when the core drill is dropped or lowered into working position with relation to themain drill bit.

6. In combination with a tubular rotary drill stem, a core drill capable of being dropped or lowered, either by itsjown weight or-by means of a cable tool and also jremoved'upwardly through the drill stem, said core drill'in operative position being projected through an axial bore in the main drill bit or cutting tool at the lower end of said drill stem, the core drill having a shouldered externalportion above its cutting end portion, the axial bore of the main drill bit having an upper enlarged} portion aifording an internal annular shoulder, a stop ring slidable endwise in said enlargement of the bore of the main drill bit to receive by supporting contact therewith said .7 aotaroe r l external shouldered portion of the core drill when the latter is dropped or lowered in the tubular main drill stem, and a spring element interposed between said stop ring and said internal annular shoulder of the bore of the main drill bit whereby to yieldably support said stop ring and function with said ring to cushion the impact when the core drill is dropped 'or lowered in said main drill stem.;

7.The combination set forth in claim 6, and further describing ,the main drill bit or cutting tool as provided I with fluid passages and said stop ring as provided with constantly communicab-1e openings maintained in registering relation to said fluid passages of the main drill bit or cutting tool whereby to circulate fluid from the main drill stem through said fluid passages of the drill bit or cutting tool, and the axial :bore of the drill bit or cutting tool and also the'bore of the stop ring being of a diameter suillciently larger than the diameter of the care drill portions working therethrough, whereby to circulate fluid in the space therebetween 8, The combination set forth in claim 6, and further describing the core drill as having an interlocking engagement with the main drill stem whereby to be rotated by and with the latter but permitted endwise movementwith respect to said main drill stein, means for yieldably pressing the core drill downwardly into normal working position with its cutting end portion projected in advance of the main drill bit or cutting tool, and means on said core drill for closing the bore of the main drill stem and stopping circulation of the fluid therein upon the yielding endwise movement pf the 'core drill upwardly with respect to the main drill bit or cutting tool or the relative downward movement of the main drill stem and its drill bit or cutting tool whereby to lessen the projection of the core drill cutting end portion from its normal working position with respect to the main drill bit. i;

The combination of a tubular main drill stern and a core drill inserted in said main drill stem, means for releasably interlockingsaidcore drill to said main drill stem so as to be rotated by and with the latter but being permitted endwise movement relative to the main drill stem, yieldable means for holding said core drill in normally positioned working relation in said main drill stem, said core drill having a cylindrical valve-head at its upper portion, and the bore of said main drill stem having a replaceable valvering into the bore of which said valve head of the core drill slides to close fluid circulation through said main drill stem upon'the yielding upwardly'of the core drill'with respect to the main drill stem or the movement of the main drill stem downwardly with respect to said core drill.

.10. The combination set forth in claim 9, and the valve-ring consisting of relatively hardened metal and having packing means for providing a seal against passage of fluid between the ring and the boi e of the main drill stem.

11. In combination with arotary drill stem, a

, fixed drill bit having a central bore, a core barrel of the fixed drill bit with the core cutting head extended beyond said fixed drill bit, said fcore barrel being detachably latched tosaid rptary drill stem, the latching means comprising a latch member pivotally secured at its upper portion to an upper inner longitudinally movable member,

- bar extended upwardly beyond the upper end of the core barrel and having a longitudinally slidable connection with said first mentioned longitudinally movable member to which the latch member is pivotally attached, the lower end portion of said latch member having a longitudinally operable cam connection with a plunger member, compound spring elements acting upon said plunger member whereby to normally hold said latch member in interlocked engagement with the rotary drill stem and functioning to yieldably hold said core barrel with its core cutting head portion in the normally extended working relation of said head with respect to the fixed drill bit.

12. In a core drill, the combination of ,a main tubular drill stem having a fixed bit at its lower end, a tubular core drill body inserted in said main drill stem and means for releasably interlocking said core drill tubular body member to rotate with said main drill stem but with relative longitudinal movement between said main drill stein aindesaid core drill tubular body member, said means comprising a latch member having a hooked lower portion engageable'with a slotted shoulder portion of the main drill stem; said hooked lower portion of the latch member having a cam slot therein, a plunger member yieldably supported and normally urged upwardly in said tubular core drill body by compound spring elements, said plunger member having a transverse bar member extended through the cam slot ofsaid latch member and cooperating with said cam slot to normally hold said latch member in "engagement with said slotted shoulder portion of the main drill stem, a longitudinally movable link member within said core drill tubular body member, the lower end portion of said link member being pivotally attached to the upper end portion of said latch member, and a supporting bar slidable longitudinally in said tubular core drill body and having a longitudinally slotted connection with the upper portion of said link member, said bar extending above said core drill tubular body memberand having at its upper end provision'for engagement with a lowering and lifting cable tool.

13. In combination, a tubular main drill stein having a centrally bored main bit at its lower end, a tubular core drill body member inserted in said main drill stem and movable longitudinally therein, a core cutting head at the lower end of said core drill tubular body. member, a supporting bar movable longitudinally in said tubular body member and projected normally above the upper end of said tubular body member, a link member in said tubular body member having a limited end-wise movable connection between its upper portion and the lower end portion of said supporting bar, a latch member having a hooked lower portion working through a longitudinal slot provided therefor in said tubular body member and being pivotally attached at its upper end portion to the lower portion of said link member, a plunger member having limited end-wise movement in said tubular body member, compound spring elements normally urging said plunger upwardly to its uppermost limit, a sliding cam connection between the upper portion of said plunger member, the main drill stem having an internal shoulder portion under which the hooked portion of the latch member engages by the action of the sliding cam connection with the plunger member and the action of said compound spring elements whereby to yieldably hold the core drill tubular body member in normal position in the main drill stem with the core cutting head projected to work in advance of the main drillbit.

14. In combination, a main tubular drill stem having a main bit at its lower end, a core drill tubular body member inserted in said tubular drill stem and having a cutting head projected through an axial bore in said main bit to a normal working position in advance of said main bit, a longitudinally slotted anchor tube fitted in said main drill stem in fixed relation thereto as to both rotative and end-wise movement, a supporting bar slidable both longitudinally and rotatively in said core drill tubular body member, the upper portion or said supporting bar being projected normally above said core drill tubular body member, a link member in said core drill tubular body member, the upper portion or said link member having a slot and pin connection with the lower end portion of said supporting bar whereby said link and bar are movable endwise relative to each other but are keyed against independent rotation, a latch member having its upper portion pivotally attached to the lower portion of said link member, the lower portion of said latch member having a transverse hook extension to enter the longitudinally slotted portions of said anchor tube in said main drill stem, said core drill tubular body member being longitudinally slotted for the movement of the latch member, a plunger member having limited endwise movement in said core drill tubular body member, a sliding cam connection between the upper portion of said plunger member and the lower portion of said latch member whereby when said plunger member is at the limit of its upward movement said latch member is projected to cooperative engaging relation with said longitudinally slotted anchor tube of said main drill stem, and movement downwardly of said plunger member retracts said latch member from such cooperative relation to said anchor tube, and compound spring elements arranged to normally press said plunger member upwardly to its uppermost limit and effect the actuation of said latch member to its cooperative engaging relation with said anchor tube of the main drill stem, in which relation of the parts the core drill tubular body member is yieldably held in its normal position in said main drill stem.

15. In combination with a tubular main drill stem having a main bit at its lower end, a core drill inserted in said main drill stem, releasable latching means for holding said core drill in its working position in said main drill stem, said core drill having a core cutting head at its lower end projected ahead of the main cutting bit of said main drill stem in the normal position oi. the parts, said core drill having a supporting bar extending upwardly therefrom and provided with an attached head, a cable supported and actuated lowering and raising tool having a tubular body member, the lower end portion of which is adapted to be fitted-over the upper end portion of said supporting bar of the core drill, and a spring slip member in said tubular body member of said raising'and lowering tool adapted to engage the head portion of said supporting bar of said core drill, said spring slip element having an upwardly extending plunger bar, and a second spring slip element having limited end-wise movement in said cable supported and actuated tubular member, said second described spring plunger member of the lower spring slip element having counterpart screw-threads for interlocking engagement when said second mentioned slip element and said plunger extension are moved in relation to each other as by the upward movement of the plunger member or the downward movement of said tubular body portion of the cable tool.

16. In combination with a tubular main drill stem and a core drill inserted in said main drill shoulder, a spring slip element in said tubular body member having tongue members bevelled at their lower ends to engage the bevelled annular seat of said tubular body member of the supporting and actuating body tube, said spring slip element having a depending central extension having an axial bore therethrough, the lower portion of said bore terminating in transverse grooves in a tapered socket at the end thereof for the reception of the tapered headed portion ofthe supporting bar of the core drill, the upper end portion of said axial bore communicating with the space in said tubular body member ofthe raising and lowering toolthrough a transverse port in an upward extension of said spring slip element, the; upper portion of said upper extension of said spring slip element having provision for releasable snap engagement with an upper springslip element provided therefor in said tubular body member of the raising and lowering 2,04%,108 slip elementv and the upper end portion of said tool, whereby said tool may be lowered into the main drill stem with the core drill attached and being releasable from the core drill when lowered into working position in the main drill stem.

17. In combination with a tubular main drill stem, a core drill operable and removable through its entire length by meansof a cable lowering and lifting tool, a characteristic cable tool having means for engaging the core drill and having spring and hydraulic shock absorbing means to stop said tool in downward travel and prevent automatic release of tool when lowered into engagement with the core drill, and means for forcing said tool farther down after engagement with I the core drill by hydraulic pressure supplied through said tubular main drill stem from above whereby to effect release of said tool.

18. In combination with a detachable rotary core drill insertable in a tubular rotary drill stem and removable by means of a cable tool, the core drill having latch means to hold core drill down and rotate it with the main drill stem when in coring position within rotary drill stem, core drill anchor tube in the main drill stem, means adapted to rigidly secure said core drill anchor tube at each end in the main drill stem at working position of latch on core drill to hold down and rotate the core drill and by-pass a portion of the drilling fluid from around core drill latch through ports in the upper end of anchor tube and down between anchor tube and main drill stem through cavity formed in main drill stem, said fluidreturning through ports in anchor tube back around of cavity in main drill stem, and means for blocking circulation of fluid above said herein described circulating provision automatically upon the yielding of the core drill from normal drilling position.

JOHN F. BOZEMAN.

' core drill at lower end of anchor tube and bottom

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2582361 *Apr 4, 1949Jan 15, 1952Reed Roller Bit CoCore taking apparatus
US2890022 *Sep 3, 1957Jun 9, 1959Brown Jr Lothrop LReplaceable drill bit
US3123160 *Sep 21, 1959Mar 3, 1964 Retrievable subsurface well bore apparatus
US4852672 *Aug 15, 1988Aug 1, 1989Behrens Robert NDrill apparatus having a primary drill and a pilot drill
US8286731Oct 21, 2009Oct 16, 2012Ressi Di Cervia Arturo LMethod and apparatus for constructing deep vertical boreholes and underground cut-off walls
Classifications
U.S. Classification175/248, 175/249, 175/257, 175/317
International ClassificationE21B25/04, E21B25/00
Cooperative ClassificationE21B25/04
European ClassificationE21B25/04