US2817555A - Method and system of retrieving stuck pipe joints in well bores - Google Patents

Description

2 Sheets-Sheet 1 1N V EN TOR.

' FLLeBL/s, 5ft

` F.-L. LE BUS, SR

METHOD AND SYSTEM OF RETRIEVING STUCK PIPE Dec. 24, 1957 JOINTS IN WELL BORES Filed March l2, 1953 Il li Fig. Z

Qimw ATTORNEY Dec. 24, 1957 F. L. LE Bus, SR 2,817,555

METHOD AND SYSTEM OF RETRIEVING STCK PIPE JOINTS INWELL BORES 2 Sheets-Sheet 2 Filed March l2, 1955 INVENTOR.

if L Le Bus United States Patent* Wash Overshot and :Spear Engineers, Atlricorporated, Longview, Tex.; a corporation" of Texas` Application March 12, 1953, Serial"No.341,979 A 5 Claims.` (Cl. 294-436) 1() This invention relates to amethod'of retrieving-@studs drill collars from a well` bore, and .more particularly,- but not bywayof limitation,to a 'method .or system of Vreaming out key seats in the wellfborelwhile simultaneously 't` bit. ln rotary drilliiigrpractice of ldeep wells', thedrill 20 bit constantlytends to shift' laterally 'olrlthe.truetvertical' line of the bore, thereby providingwhat isknown-as'. crooked bores. A string of drill collars istusuallyinter#` posed between the drillingstring .andwthesdrill bit. A-r 5 drill collar is a tubular `'link of steel.havinga-substantialu thickness to impose additional weightzorrthe drill bit, and to lend rigidity or stiffness to` thevlowernportiontof` the drilling string for the transmission loffthe.torquey These t drill collar strings usually are of a length ofiapproximately f four hundred to siX-lnindredffeet long, and` with theH additional weight and rigidity provided thereby, ,willftendi to maintain a. straighter `bore during A`the :drilling :opera-H tion. The drill bit is larger intdiameter than-.the` drillf collar, consequently t leaving f, sufficient. clearance `or annulus between the string of drill,l collars and the welll-bored in order to receive a wash overapipe in `thefeventnthe bit and the drill collar are lostl or stuckfinta lkey-seat?? poition of the wellibore.

Key seatsare due lto the variance ofwthedrillvcollars` from a true vertical havingta tendency .todrill acrOOkedlA bore, caused bythe geologiealformation or'too`muchty weight applied-at' the surface ofitheJ/vell.'` Whenthem drilling collars vary from thel vertical,4 tl:1ey,rubA against the welll bore, thereby/providing anoffsetrecessrin-ther45 well bore which'connects with,` and is 4in alignment witha the well bore itself. These oil-set `recesses tare usually. of much lesser diameter Idue to the smallersizel of .the drill collars than that of- 'the drill `bit, and. arey knownu as `"key seats. i

50 The key seat normally doesnot interfere with-the drill ingguntila pulling job of the complete' `drilllstringfis t necessary, such as for example, `when it t-ist'desired to-` replace a worn drill bit'with a new one. In suchxinstances,`

the operator will raise the drill 'stringandthe.attendant 55 drill collars out ofthe well bore until` the .tdrillubitlt-isn pulled upwardly into a key-seat. Normally ,the drill bit is of a larger diameter than the key vseat causing the drills bit to hang up, or become stlick'therein. Unable-,tto see4 what the condition is, most drilling `operators have :a 60

of drill collars, and 'move downwardly"inthe annuls 70 between the collarfstring and the Swell' bore@ The .rotatinglwashover "pipe coming in contact with the-key.seat z ICC will ream out the5 strata there-around," and"n thereby free the drill bit and theadjacent drillcollarlstriiigg After the Ikey seat has "been cut away; the dr'ill` collars becomeloosened inthe well bore,^and will vdrop ,orrflll back to the bottom of the bore, which in most instances cause considerable damage "to the drill `bit, drill' collars and the drill pipe. Consequently; loosened `drill"collrs` are dropped back into the bore,` and anothershngtjob is usually necessaryto removethe broken bits andi-the like -out `of the bottom of the "well bore so"thedillihg `operation can continue.`V It is apparent sucheXtra 'fishing jobs are time consuming fand costly.'

This invention is primarily coneerne'dwitlifar Inet'hdy or system of reaming drill collars and 'bits that-ae-stuck holdingth Stuck drilycouars hreinp 15 in an 'oil well borekey seat "insu'ch a manner that the drill collar and attendantdri'll'y bit'are 'simultneouslyl' secured to` the wash l-overfpipe to prevent the Iloosenedt drill collar string from falling down 'to the bottom. of the bore after becoming unstuckby'the reamingoperation.-

An importanrobjectof this invention is to retriever stuckidrill collars and the attendant rockbit from .a =kyseatedrecess ofA an 'oil well bore' inamanner to prevent dropping of'the drill collarto the bottomof'lthe bore upon becoming loosened lfromv the ikey seated recess.-`

And still afurther object Vofthis invention` is totpro-fvide a method 'of continuous 'rearn'ing for loosenirigstuckdrill collars from a key seated "recessof an` oil well'bore while simultaneouslyassuringthat the drillcollar mayr be-held in position when loosened from. the KyseatedM recess, and thereby prevent droppingtdthe bottormof.` thef'well bore:

And still another "object 'of this" invention is" to "retriever stuck -drill collars from a key seated recess of fa.we1l" bore', and catchingand holding ithe drillicollars substant-i: tially in positionas 'theyare loosened during the reaming., operation.`

And'still another "object of this .invention is to provide4 a system of retrieving-a drill collar string :stuckinfatkeyf seated recess of* a well bore by a continuous reamingiopz.` eration around thedrill collars while simultaneously-imm terconnecting the stuck drillcollar vwith the reamingf apparatus, yet permitting downward movement around-the# collar string.`

And stilly a further'object vof'thi's invention is .to Vdrilli-Y -out a'key seated recess inwhi'ch'is: wedged (a drill'collarf-i and `immediatelycatching 'the loosened Ldrill-collar uponL `completing the drillingof the key 'seat in order. to preventm dropping of the drll'collar backtinto'the hole.

And stillvanother object of vthe invention is torretrievef stuck drill collars from a'key seated fret-:essof-'awwelly bore by a fishing string providing.v a continuous reaming operation which contemplates an addition of extratjoints of drill pipe to theis'hing stringwithout` interruptionof the Areaming operation; and immediately catchingsand-l holding `a loosened drillcollarwith the iishingstring.

An additional object of this invention-is to maintaina connection between a drill: collar wedged in a key seat of-` a well bore during a reaming operation-by a iishingstrings: in 'sucha manner to catch and hold thetloosened collarf'` and prevent dropping to the bottom ofV the wellf bora-but permitting lowering of the held drill collar to the bottomof. the well bore where the iishing string maybe released from:A thecollar and removed fromI-the bore.

`Other objects and advantages ofthe inventiomwillfbe evident from the `following*detailed descriptionread'tinlf conjunction with the accompanyingdrawings?whichile' lustrate my invention.

In. the drawings:

Figure .1 is a:broken `elevational Aviewof. 'the wellbrtrelf depicting a crookedbore drillingoperation. i.

Figure 3 is a view similar to Fig. 1 depicting a drill bit moved upwardly into stuck relation with a key seat recess, and the wash over pipe disposed over the drill string wit certain parts broken away for clarity.

Figure 4 is a view taken on lines 4-4 of Fig. 3.

Figure 5 is a view similar to Fig. 3 depicting downward movement of the wash over pipe over the stuck drill collar string.

Figure 6 is a view similar to Fig. 5 showing the wash over pipe substantially adjacent the drill bit and key seat.

Figure 7 is a view taken on lines '7-7 of Fig. 6.

Figure 8 is a view taken onlines 8 8 of Fig. 6.

Figure 9 is a view taken on lines 9-9 of Fig. 6.

Figure 10 is a view taken on lines 11d-lll thereof.

Figure 11 is an elevational view partly in section of the slip joint interposed in the drill pipe string.

Referring to the drawings in detail, and more particularly Figs. 1 to 4, inclusive,reference character 2 designates a well bore in which is disposed a string of drill pipe 4 connected at 6 to a string ofheavier drill collars 8. It will be understood that the drill collars usually about thirty feet in length and are connected in vertical tandem relation in a suitable manner (not shown.) ln Fig. 1, the upper portion 1t) thereof shows a tendency of the drill collars to vary in one direction from the vertical, thereby providing acrooked bore 2. Theintermediate portion 12 of Fig. 1 shows a substantial variation in a slightly ditferent direction from the vertical of theWell bore 2, and that the abrasive rubbing of thedrill collars 8 have formed a key seat recess 14 (Fig. 2). At the lower end of thedrill collars 8 is secured theusual drill bit 16. The lowermost portions of Fig. 1 show still a further exaggerated variance from the vertical in that the variation providing the crooked bore may be formed in an opposite direction from the variation upward therefrom.

When a key seat condition occurs in a crooked well bore, thedrill bit 16 usually becomes stuck (Fig. 4) upon pulling the drill string upward. In such a situation it is then necessary to ream out the well bore 2 and thekey seat 14. As is clearly shown in Figs. 3, 5 and 6, the drill string 4 is unjointed from thedrill collars 8 at the connecting point 6, thereby permitting removal of the drill string to the surface of the well.

A wash overpipe 18 having a reamer Ztl withteeth 21 at the lower-most end thereof is interposed between the drill string 4 and thestuck drill collars 8. It will be apparent that the diameter of the wash over pipe is greater than that of the drill string, or that of the drill collars in order to be disposed in theannulus 23 between thedrill collars 8 and thewell bore 2. A slip joint 22 for a purpose as will be hereinafter set forth is interconnected between the upper-most portion of the wash overpipe 18 and the bottom of the drill pipe string 4.

The lower-most interior portion of the wash overpipe 18 is adapted to receive a wall hanger overshot 24 carrying a plurality of circumferentially spacedslip members 26 for a purpose as will be hereinafter set forth. A plurality of circumferentially spaced friction dogs 28 are carried by thewall hanger 24 and with theslips 26 support thewall hanger 24 in the wash overpipe 18 during the lowering operation to the top of thecollar string 8. Thewall hanger 24 and cooperatingslip members 26, as well as the friction dogs 28, are old and well known in the art and constructed generally in the manner shown in the prior patents to Costello, No. 2,190,442, issued February 14, 1940, or Lowry, No. 2,487,456 issued May 8, 1949. Ajoint spear 30 is removably connected with theWall hanger 24 in a manner not shown, and extends downwardly therefrom as shown in Figs. 3, 5 and 6. Thespear 30 is provided with a taperedpin member 32 for threaded connection with the taperedbox 34 at the top of theupper-most drill collar 8 from which the drill string 4- has been unjointed. The taperedpin members 32 andspear 30 are contractible and expandable and of the type old and well known in the art and constructed generally in the manner shown in the two prior patents to Wilson, No. 1,418,766, issued June 6, 1922, and Hindlerliter, No. 2,105,885, issued January 18, 1938.

Operation With the upper drill string 4 removed, and thedrill collars 8 andbit 16 stuck in thekey seat recess 14, a fishing drill string including the wash overpipe 18 provided with thewall hanger 24 andjoint spear 30 are lowered into the well bore. Thewall hanger 24 and the removable connectingspear 30 are disposed in the lower-most portion of the wash overpipe 18 and are lowered therewith. Thejoint spear 30 and its taperedpin portion 32 are provided with a plurality ofthreads 38 for engagement with the threaded box of the upper drill collar 8 (Fig. 6). During the lowering operation of the wash over unit into the well bore, thewall hanger 24 is supported in thewash pipe 18 by engagement of the slips with the inner wall of the wash pipe simultaneous with the friction dogs 28. As soon as thejoint spear 30 and its movable threadeddogs 32 make up in thedrill collar box 34, the wall hanger is prevented from further downward movement due to the stuck condition of thefish 8. Continued rotation and downward movement of thewash pipe 18 after the make up connection will be against the friction hold of thedogs 28 with the inner wall of the wash pipe, yet providing suii'icient friction therebetween, whereas the slips will be moved downwardly into a released or non-engaging position with the wash pipe 1S. After the stuck fish or drill collar is loosened, it immediately starts to move downwardly and consequently will pull the freely movableinner stem portion 25 of thewall hanger 24 downwardly. The slips cooperate with a tapered body portion (not shown) connected with the inner stem portion, such as that shown in the patents to Costello, No. 2,190,442 and Lowry, No. 2,487,456. Such downward movement of the wall hanger will cause expansion of the slips outwardly into engagement with thewash pipe 18, Thedogs 28 are supported loosely on the inner stem of the wall hanger by a helical spring 27 and have any suitable connecting means, such as links carrying the slips thereabove. Consequently, when the lish is loosened, the friction hold of the dogs is suiiicient to support the slips in position until the freely movableinner stem 25 carrying the tapered portion (not shown) is moved into a. position to cause outward expansion of the slips against the inner wall of thewall pipe 8 and thereby automatically engaging tl e loosened fish with thewall pipe 18 and thereby precluding any further downward movement thereof.

As soon as thejoint spear 30 is threadedly engaged in thebox 34 of theupper drill collar 8, the wash overpipe 18 continues its movement downward around the stuckdrill collar string 8. lt will be apparent that the joint spear provides a connection between thewall hanger 24 and thecollar box 34, and yet the disengaged position of theslips 26 relative to the inside of the wash over pipe, until engagement is desired, permits movement of the wash overpipe 18 and thereamer 20 downwardly around thedrill collar string 8 to provide a reaming action of the well bore and particularly, thekey seat recess 14. The downward rotative movement of the wash overpipe 18 is sufficient to overcome the friction of thedogs 28 of thewall hanger 24 during the teaming operation. Furthermore, the vertical friction between the friction dogs 28 and the inside of the wash overpipe 18 is the only wear accountable during the lowering and rotating of the wash over pipe in thewell bore 2.

During the continuous reaming operation of thc downwardly movingreamer 20, thewall hanger 24 through the connectingjoint spear 30 maintains a simultaneous engagement with the top of thedrill collar string 8 at all times. A swivel connection (not shown) is provided be-` tween thewall hanger 24 and the spear joint ,30 to permit rotation of the Wall hanger after the threaded connection of the spear with the drill collar. It will be apparent that with the joint'spearinterconnecting"betweenth'e wall hanger 24 "and the drill collar `string8, any engagements" of the slip Z6 with the inside of the wash overpipe'lS would immediately provide an interconnectionbetween"drill collar string 8 andbit 16 are loosened,'and thus free to drop to the bottom ofthe well bore. However,thc Wall hanger 24 is so constructed andarranged in a manner not shown, that any downward movement ofVthe Iconnecting string 8 will cause actuation of the slips .l6`out` Wardly into biting engagement withthe inside of the wash overpipe 18. In like "manner any substantial upward movement of the Wash overpipe 18 will cause an outward i biting engagement of theslips 26 with'the inside of thepipe 18.

It vwill thus be seenas depicted in Figs. 6 to 10, inclu sive, that as the `reamer 20 andthe wash over pipe 18' move downwardly over thecollar string 8," anew bore 40"(Fig.` 7) is provided in order to substantially straighten otthe crookedness of the old well bore 2`.` Figure 8 depicts the reaming `of thenew bore 40`in one direction of the oldcrooked bore 2 from the verticaL'while Fig. 9 discloses a similar situation for an opposite direction of variance for theold bore 2 with the vertical. The complete reaming of thekey seat 14 by thereamer 20"to provide an enlarged bore`42 'is set forth in Fig. 10.

It will be apparent that as soon as the key seat aperture orrecess 14 is reamed sufficiently by the tool '20 to provide the new recess 42, the string ofdrill collars 8 will become loosened, and under ordinary circumstances would fall to the bottom of thewell bore 2 causing considerablel damage to therotary rock bit 16 and the drill collar string` itself.` Insuch instances the cones of the bit usually break ott, and thereby necessitate an extra shing job of these broken parts from the well bore before the drilling operations can continue.

The present method precludes any such dropping or falling ofthedrill collar string 8 upon becoming loosened from thekey seat formation 14. The connection provided by the joint spear 313 between the topofthe drill collar 8 and thewall hanger 24 is such that when either a slight (only an inch or two) movement downward oi thecollars 8,w or a slight movement upward on the surface hoisting equipment for the wash' overpipe 18,` the slips 26 -are moved to biting engagement with the inside of the wash overpipe 18, thereby firmly holding the looseneddrill collar string 8 in suspension in the well bore and preventing it from falling to the`bottom thereof. Thewash overl pipe 18 and the loosened drill 'collar string -8 andbit 16 may then be pulled from the well bore 2 Ato the surface, particularly if thebore 2 has been reamed clean.

Slip joz'nt operation f It becomes apparent that during thereaming operation that thekey seat recess 14 may be at a considerable distance" downwardly from the top of thedrill collar string 8,`lconsequently the length of thewash overpipe 18 rotatingdownwardly thereover is not suic'ient toreach the key seat, thus it may become necessary to add additional joints of drill pipe in order to continue the'downward movement oftheWash pipe 18; As is well known,` in a rotary rig (not shown) the usual square kelly and rotary table (not facetof the well is movedupward, andi this movement lis" permittedfbyrthe slipjoint 222i- It becomestappare'nt/that ifA'thefslipjoint 22 was not interposedli-the drillvstring* 51"iloosely threaded to thethreads 52 of the safety jointI pin 545 The pin and `box are separatedAat 56` provid-5 ing engaging shouldersSSLto prevent tightening of the' threads `51 and 521during` the wash` over operation of t thepipe 18 and the reamer20i Aninner mandrel 60 "is secured at thetop of thebox `50 and extends downwardly through the joint 22 into Vconnection at the bottomwith1` apiston member 62. Rubber packer membersare prof vided at`63, 64` and 66 Vto sealvoif the circulation and1 mud 'pressure from `seep'ing `through-and contactingthe The mud circulation'` passes" inner i threaded walls. through themandrel 60, wash over pipe18 andto the reaming tool `20"in aiwell known manner.

The lower end ofthe slip joint 22 is provided-withta' tapered threadedportion68 for engagementwith thel pipe 182 The' slip l and piston 62 i are provided with clutch dogsn'72-and 70;,respectively, which" areiadapted to be moved into engaging position (not" shown) `when the upper safety joint box 50'is unthreaded? from thepin 54- and moved verticallyupward into spacedi top\(not shown) of the wash over joint 22, `and particularly -the 'pin 54 relation to the safety joint pin'54, thereby assnringthat the 'washt` `over 'pipey `18fandlthe reamer 20`1will lstill 'con'= tinuel toy rotate,` if necessary.

WhenV it is desired `to add an additional 'joint of-pipei to the drill `string to provide for continuous Teaming; it` is not necessary `to disengage thesafetyspear 30frornthef drill collar 8, thereby creatingthe possibility that thel heavy `drill collar may become loosened `and drop tot the bottom of 'the well `bore string. 8J The `rotary kelly (not shown) l at the` surface" of -thewell `is raised out of the well threads `51 and 52, and since al1 other piper are tightly threaded, the slip joint body 22fwill` sep-v arateordisjoint at 56 to permitvertical fmovement upi'A ward of the box member Stimovingthelower fclutch dog 70 into engagement with the upperclutch dog 72. The upward movement of the is inserted `therein and the rotary drillingloperationlis continued until the vertical spaced condition of thesep* arated slip joint 22 is consumed, when it may benecesLIV saryto add another joint ofdrill pipe for continuing the reammg operation.

In most instances `after the drill collar `string S-"has4 been loosened and theslips 26 are set into engagement either by` a pull upward -on thewash pipe 18, or the downward movement of the loosenedcollars 8`, the wash`overpipe 18 and theattendant drill pipestringvvill ish" orvpull the loosened drill collarsiSand bit 16-from the" well.` Thilsis particularly true since the previous ream mg operation has straightened many of the crookedor vertical variations of thewell bore 2. In such instances i merely pulled to the top of'the wellA along with the drill collars 8for replacementof` the Washpipe string is thedrill bit 16 or the like.`

In some instances the bore maynot be cleanV enoughto Warrant retrieving, collars from the well bore by the wash over`pipestring.. The present invention contemplates removal of l the loosened drill collars`8 by other'suitable 1m'eans,l,such" asja `releasing overshot (notlshown). This `is;accorn- Intiadding the pipevjoint; the"spear 30 `and its attendantwall `hanger 24 inthe wash` overpipe 18 `remain in engagement with `1the` drill `collar bore and the slip joint 22 is unthreaded at theloosely threaded right hand joints in `the dri1l` slip` joint 22 permits the inser'V tion of the extra joint of drill pipe, after which the kelly" or fishing of the'loosened drill' collar string S to 1the extreme bottom of the well bore by thewash pipe 18, after which the removablejoint spear 30 is disengaged by a suitable plug means in a .manner not shown to release the wash over pipe 1S,

and theWall hanger 24 from any engagement with thejoint spear 30 connected with thedrill collar string 8. With thedrill collars 8 resting on well bottom, and the wall hanger overshot 24 released therefrom, the wash string 1S is removed from the well bore, after which a suitable releasing overshot (not shown) provided on a drill pipe string may be inserted in thewell bore 2 for engaging the top of thespear 30, thereby removing thedrill collar string 8 from the well bore.

It will be apparent that the slip joint permits insertion of an eXtra section of pipe without vertical movement of the reaming tool on the end of thewash pipe 18, thereby eliminating any possibility of cave-ins or loosened debris falling into the Well bore which would be motivated by the vertical movement of the reamer.

It will thus be seen that the wall hanger changes its relationship respecting the Wash pipe during the various cycles of the operation. In the lowering of the wash pipe, the wall hanger is in a floating or semi-rigid disposition in the lower end of the wash pipe. As soon as the joint spear connects with the upper end of the drill collar string, the wall hanger then is positively attached to the drill collar string With its attachment to the wash pipe remaining in the floating or semi-rigid condition in order to permit the downward and rotating movement of the wash pipe for the reaming operation. As soon as the key seat recess is removed sufficiently to unloosen the stuck drill collar, the slips of the wall hanger are moved to an engaging position to then provide a positive connection between the wall hanger and the wash over pipe, thereby eliminating the oating or semi-rigid condition previously set forth.

From the foregoing, it will be apparent that the present invention contemplates a method or system of reaming out stuck drill collars from key seat recesses in crooked well bores yof oil wells. Simultaneous with the reaming operation, the disjointed and stuck drill collar is connected with the fishing tool providing the reaming operation so that upon loosening of the drill collar, the collar is immediately gripped or caught by the fishing string to prevent dropping of the collar to the bottom of the well bore, thereby creating considerable damage to the drilling tools and the like. Furthermore, the invention contemplates adding an extra joint of drill pipe during the fishing operation without disconnecting the `connection between the fishing string and the stuck drill collar.

Changes may be made in the combination and arrangement of parts as heretofore set forth in the specification and shown in the drawings, it being understood that any modification in the precise embodiment of the invention may be made within the scope of the following claims without departing from the spirit of the invention.

I claim:

l. The method of retrieving a stuck drill collar of a drilling string from a key seated recess of an oil well bore which consists of unjointing the drilling string from the drill collars at a point above the key seat, lowering a fishing string into the well bore and providing a reaming action for enlarging the key seat to release the stuck collar, supporting a tool in the fishing string for connection between the tool and the stuck drill collar prior to the reaming action, releasing the tool from the fishing string after connection thereof with the stuck collar to permit lowering of the reaming string in the well bore to a point substantially below the key seated recess, rotating the reaming string with simultaneous movement downwardly through the key seated recess after connection of the tool with the stuck pipe for loosening the collars, preventing the loosened collar from a substantial dropping in the well bore by automatically engaging the connected tool with the fishing string.

2. In a method of retrieving stuck drill collars of a drill string from a well bore which consists of disjointing the drilling string from the collars at a point above the stuck position thereof, lowering a reaming string into the well bore, supporting a retrieving tool in the reaming string for connection with the stuck collars, releasing the tool after connection with the stuck collars to permit lowering of the reaming string in the well bore to a point substantially below the point of the drill collar connection, rotating the reaming string with simultaneous lowering thereof for reaming the well bore around the stuck position of the collars for loosening the collars therein, preventing the loosened collars from dropping a substantial distance in the Well bore by automatically engaging the released tool with the reaming string.

3. ln a method of releasing stuck pipe from cave-ins in a well vbore which consists of lowering a reaming string and providing a reaming action around the cave-ins adjacent the stuck portion of the pipe, supporting a tool in the reaming string during the lowering thereof for connection with the stuck pipe, releasing the supported tool from the string after connection with the stuck pipe to permit lowering of the reaming string substantially below the connected position of the stuck pipe7 rotating the reaming string with simultaneous movement downwardly through the cave-ins for loosening the collars, engaging the tool with the roaming string substantially instantaneous upon the pipe being loosened in the bore to prevent dropping of the pipe to the bottom of the well.

4. The method of retrieving a stuck drill collar of a drilling string from a key seated recess of an oil well bore which consists in unjointing the drilling string from the drill collars at a point above the key seat, lowering a fishing string into the well bore and providing a reaming action for enlarging the key seat to release the stuck collar, supporting a gripping tool in the fishing string for establishing a connection with the stuck drill collar, releasing the gripping tool from the fishing string to permit lowering of the fishing string in the well bore to a point substantially below the key seat recess, lowering the reaming string after the connection of the tool with the stuck collar for loosening the collars, automatically engaging the tool with the fishing string substantially instantaneous with a loosening of the drill collar in the well bore, providing an expansion drilling string above the stuck collars permitting telescoping of the drill string for addition of an extra joint of pipe during the reaming operation without breaking the connection with the drill collars.

5. In a system for retrieving stuck drill collars of a drilling string from a key seat recess of a well bore comprising unjointing the drilling string from the stuck collars at a point above the key seat, lowering a wash over pipe into the well bore above the stuck collars, 'supporting a retrieving tool in a substantially fixed position in the wash over pipe for positive engagement with the collars, releasing the fixed position of the retrieving tool in the wash pipe after connection with the collars to permit a continued downward movement of the wash pipe for loosening the stuck collars in the well bore, automatically re-engaging the retrieving tool into a fixed position in the wash pipe substantially instantaneous with the loosening of the stuck collar to prevent dropping of the collars a substantial distance in the well bore.

References Cited in the file of this patent UNITED STATES PATENTS 1,767,286 Hinderliter June 24, 1930 2,122,602 Beck July 5, 1938 2,281,389 Shaiier Apr. 28, 1942 2,416,613 Costin Feb. 25, 1947 2,449,841 Claypool et al Sept. 21, 1948 2,647,008 Stewart et al. July 28, 1953 2,762,438 Naylor Sept. 11, 1956

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