US2572307A - Rotary drill stabilizer - Google Patents

Description

Oct. 23, 1951 c. c. BROWN ETAL ROTARY DRILL STABILIZER Filed Sept. 9, 1946 INVENTOR. rcera C Bmrwg Fred A M/rerm Irv ATTORNEY 'I l-1is invention relates Patented Oct. 23, 1951 UNITED STATES A'l ENT OFFlC A 2 07. ROTARY DRILL STABILIZER Cicero O.-Brown and Fred F..Waltermire, Houston, Tex.

Application September 9, 1946, Serial No. 695,638

sections joined together by threaded couplings,

commonly called tool joints, the outside diameters :of 'Whichare somewhat larger thanthat of thedrill pipe, but alsoof' substantially less'er' diameter than the bit and bitst m: andthe 'usual Kellyjoint and swivel attached to the upper end of the string, the kelly passing through'the'r'o tary table'and being rotated thereby in order to rotate the drilling stringand bit; Such "drilling strings are extremely flexible and elastic, particularly-when they have attained considerable length due to deepening of the well. Due tothi's flexibility and elasticity,-it-is gen rally necessary toadd' weight to the bit in order to keep the'bit in contact with the earth formation to enable it to drill ahead as'it-is rotated from the top of 1 the well:--- To increase-the weight'of the'bit. a section of pipe, commonly termed -a-'drill collar, isnormally interposed between the upper 'end of the bitstem andthe firstsectionofthe drill pipe. Such drill collars are generally of the same outsidadiameter as the bit stem and may vary in length -very considerably, depending primarily upon the depth ofthe well at a particulartime; These-drill collars may comprise asingle section of pi e or several-sections. depending upon the 1 length desired. For thepurnoses of this descriptionthe bit, bit stem and drill collars, together,

are sometimes herein-referred to as the bit section.

' Although the employment of drill collars helps to. stabilize the action of the drill bit; nevertheless, because its diameter must normally be less than the over-all diameter of the-bit and of the hole being drilled thereby, a substantial degree of clearance necessarily results between the out- 1 side of the drill collar and the wall of the well; with the result that some degree of-"eccentricity or gyration'of the upper end particularly of the drill. collar occurs-during drilling andfrequently results inthe drilling or crooked holesy-and cavi :1

tation -in th'e'sides of the bore hole where the upper end of the drill collar strikes the wall 2 Claims. (01. 255-28) under the eccentric or gyratory action mentioned. A further difficulty'which frequently. occurs, particularly in drilling deep wells with rotary drill" strings of the type described, .arises from the combination of the gyratory action of the. bit section, the varying hardness of the formations being drilled, the fiexibilityand e'lasticityof the drill string, the rotation thereof, and improper applicationof the weight on'thebit. This combination 'of conditions frequently'jcauses the bit .to change direction .andidep'art from the. true vertical; Often this'diversion in direction is con tinuous and the well bore will be drilled ata substantial angle to the vertical such that; when this condition is discovered, the drill string must be withdrawn to the point of departure of the orig.- inal bore hole from the vertical and 'by the use of suitable 'well known drilling tools,.the .well must he redrilled to straighten 'out'the hole. On the other hand, the deviation from the vertical may be only temporaryand the bit may, either by controlof the drilling operations or of its own accord, return to the original verticaldirection after a relativelyshort length of'hol'e has been drilled. i The common result 'of. such a temporary deviation is a lateral'bend in the bore hole to which, the flexible drill string will generally accommodate itself without undue difficulty. However, due to, the flexibility and elasticity of the drill string, the section of the drill string passing around such a curvedp'ortiori'of the hole, since it is normally under a substantial de ree of tension, will engage in a Whipping action laterally relative to the vertical axis of the bore holeand this action will cause the section of the drill pipe and any'tool joint thereon at this point to cut a vertical slot in theside of the formation along the curved portion of the bore hole until it attains a lateral depth at which the drill string may assume its substantially true vertical position throughout this section ofv the bore hole. The diameter of such a slot isnormally approximatelythat of the diameter'of any tool joints on the section of the drill pipe Which engages in this cutting action, and generally tapers outwardly towards its oppositeendsiwhere it merges with the straight sections of the bore hole. The slot thus'cut is commonly called in, the industry a key seat'and is a very common occurrence, particularly in the drilling of deep wells, and its presence is normally not. apparent to the driller until he attempts to Withdraw the. drill. string from the well.

When a drill string has out such a key seat along a bore hole, it will be seen that its smallthe well is normally done at relatively high speed,

the string may thus become stuck in the key seat and cause the attendant difficulties resulting from such an accident. It is possible, however,

that the presence of such a key seat may become known to the driller through the actions of the drill and by carefully withdrawing the drill string, while rotating it, it may be possible to work the drill string around through the curved portion of the drill hole and avoid sticking the drill string in the manner described. However, this is a relatively fortuitous circumstance, since the more common situation is that the presence of a key seat is not initially discovered until the drill collar has become stuck.

Whenever the bit section becomes stuck in a key seat or for other reasons, various expedients may be employed in an effort to release them. For example, a quantity of oil may be pumped down the drill string and up around the outside of the bit section in an effort to provide a degree of lubrication which will efiect its release. These expedients generally take time to efiectuate, even if they prove successful. During such time mud circulation is generally continued in order to prevent settling of cuttings and sloughing of the material lining the bore hole which would otherwise aggravate the difliculty. However, rotation of the drill during this period cannot generally be continued due to the danger of twist-offs and the inability to rotate the drill string may aggravate the conditions causing sticking despite the continuation of mud circulation.

Once it becomes evident that the bit section cannot be released by way of the conventional expedients, it then becomes necessary to break the drill stem, preferably at a point as close as possible to the point at which the drill is stuck, so that the greatest possible length of drill string may be withdrawn from the well, leaving a minimum amount of equipment to be recovered by conventional fishing operations. This breaking of the drill string may be accomplished by reversing the direction of rotation of the rotary table to unscrew the drill stem or by shooting off the drill stem with explosives placed as near as possible to the point of sticking. However, although some degree of control may be exercised as to the point at which the drill string will unscrew or the shot may be placed, the results are uncertain, at best, particularly since such operations are generally a matter of last resort after all other expedients designed to release the drill have been tried without success. During the time required to exhaust all other expedients, the bore hole above the original point of sticking may be damaged or otherwise so affected that it may no longer be possible to get close to the sticking point with the final breaking operations and much greater portions of the drill string must then be left in the hole for removal by fishing or other operations conventionally employed to clear the bore hole.

It is a principal object of this invention, therefore, to provide a tool for rotary drilling which will obviate or eliminate one or more of the difficulties, such as those described above, which are commonly encountered in rotary drilling.

Other important objects of this invention are to provide a tool for stabilizing the drill collar to reduce the eccentric or gyratory motion thereof to a minimum; to aid in releasing the drill string when it has become stuck in a key seat or other obstruction in the bore hole; and in cases where permanent sticking of the bit section has occured, to effect a break in the drill string so as to recover the maximum length of the drill string leaving a relatively minor portion to be recovered by subsequent fishing operations.

Other objects of this invention are to provide a rotary drilling tool which is adapted to be inserted in the drilling string adjacent a drill collar and which is provided with a longitudinally slidable and rotatable section which functions as a stabilizer for the drill collar while, at the same time, permitting a degree of longitudinal and rotational movement of the drill string relative thereto; and which is provided with a clutch mechanism by means of which a controlled breaking of the drill string may be effected if desired.

Other and more specific objects of this invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings which illustrate useful embodiments in accordance with this invention.

In the drawings:

Fig. 1 is a partly diagrammatic view of a portion of a bore hole illustrating the position and form of a key seat in such a bore hole and showing the position of the drill string, including a tool in accordance with this invention, in position in the bore hole;

Fig. 2 is a cross-section taken along line 22 of Fig. 1;

Fig. 3 is an elevational view, partly in section, of a tool in accordance with one embodiment of this invention;

Fig. 4 is a cross-section taken along the line 44 of Fig. 3;

Fig. 5 is a view of a portion of the tool in accordance with another embodiment of this invention.

Fig. 6 is a view of a portion of the tool in accordance with still another embodiment of this invention.

Referring to the drawings and to Figs. 3 and 4 in particular, which illustrate one useful embodiment in accordance with this invention, the device consists of a generally tubular body member ll having a bore H and provided with an internally threaded box l2, adapted for connection to the threaded pin 13 of a tool joint l4, which is a part of a conventional drill stem l5 (Fig. l), the bore H of the device being in general alignment with the bore of the tool joint and its connected drill stem. The diameter of body In is preferably made equal to or slightly greater than that of tool joint M, the upper end of body It! being tapered at Ifia to the diameter of the tool joint. Beginning at a point spaced from the upper end of body Ii), the exterior of the body is reduced in diameter throughout the remainder of its length, forming a shoulder It at an intermediate point along body H]. The portion of reduced diameter of the body, termed the mandrel, is designated by the numeral I1, and at its lower end is provided with a tapered threaded pin l8 for attachment thereto *of a tubular sub 1 9 having= a complementary thread'edboX 25 for reception of pin 1-8. The lower end or sub 9 is provided-with athreaded'pin 2 l, which isadapted for connection into a box 22 of a conventional d-rill collar 23. "The outsidediameter of sub l9is" generally made the-same as that of drill collar23- and bothare therefore, substantially larger indiameter than tool joint M and body In. Slidably mounted on mandrel I1 is a generally-cylindrical' sleeve, termed a stabilizer 24, constructed' of" Duprene, rubber,-or other resilient plastic" material which 'is preferably .resistant to the actiono'f oil and other w'elYfluids. -Stabilizer '24 is preferably'molded about a'met'al reinforcing sleeve-25', which forms a core for "the stabilizer,-an'd-is provided-with a plurality of perforations 26 for assistance in' anchoring-the plastic material thereto. Reinforcing-sleeve is; provided at itsupper and lower-ends,-which extend beyond the ends of the body'of plastic material attachedthereto, with outwardlyextending generally annular flanges'fland *28, respectively, the outer diameters of which are substantially equal to that'of sub l9. W-ith this reinforcing arrangement, stabilizer 24' becomes a relatively rigid member so far as resistance to longitudinal pressure is concerned. "The exterior surface of stabilizer Mus-preferably formed in molding toprovide "a series'o'f uniformly spaced longitudinalribs" 29- thereonwhichextend radially outwardlyfrom the periphery of the stabilizer; "The'radial' length of ribs" 29*"is preferably such that the diameter of a circle en'- compassing the outer-edges thereof which='wil1 begreater than that of thedr'ill' collar and 'sub "l9, and which'will be almost equal to "the diameter of thebore h01e,so*that the stabilizer will offer no appreciable resistance to themov'e- -ment of the drill stringin 'the'bore-hole-under in contact, the teeth will becomeengaged only J when sub 19 andthe drill stem, to which itis attached, are rotated in the counter-clockwise direction, that is counter to 'thedirection of rotation for "normal drilling. The over-all length of stabilizer 24, including teeth 32 =and flange 2-1. is" made less than the length ofmandr'el :1 between shoulder 16' and the upper edges of teeth-33' of the sub, whereby adeg-ree of-'longitudinal movement of stabilizer 24 on mandrel H may occur. A suitable degree of clearance 'isalso provided between the inner surface'of stabilizer Mrand the outer surface of mandrel l! to provide free relative rotational and longitudinal movement between these members.

Shoulder IS and theupper edge of sub llf'form stop: means to' limit thelongitudinal movement of: stabilizer 24 relative to the drill string.

The device of this invention is employed in rotary drilling in the following manner:

The tool of this invention is inserted'in a' .drill'string between the lower end'of-drill stem and the upper endof drill collar" 23, 'theLlatterhaving' a conventional bit 34 I attached to the lower end thereof-I .As drillin'g'proceeds, cutting .theibore': hole; 35n'with2a diameter;substantially the same asthat of the cutting-edges "o'fthe bit, the tool will move downwardly through-the bore hole following'the" bit. Stabilizer 24 will act to stabilize the bit section,--since the ribs' 29- -th'ereon-will bridge-the" annular space between the wali' Of'the bore hole and the outside of the; drill collar and" forma type of sleeve bearing for theupper end or the drill collar which will, thereforepreduceithe tendency of -the upperend of the drill-collar to engage in any eccentric-or gyratory*movement. When made of resilient materialgas described, stabilizer 2 willalso' absorb-the-shock of" any such'movementagainst the wall of -'-the-= well bore; the ribbed configuration affording a degree of resilient flexing undersuch-=movement,=and this will further aid in preven'ting-the drilF-collar' from digging into I -drill"string is being" rotated inthe-normal or clockwise'di-rection. In this event; the -teeth 33 on sub-"lw'ill merely roll under and past teeth 32. I-nter-locking-of the teeth"- will be effected -i-n-"the manner I described hereinafter.

Should the "bitsection-become stuck in the borehole; asmayoften occur, so that-it cannot be withdrawn" from the well without placing-undue strainon the drill string, the" sl-idable a!- rangement or stabilizer 24 on-mand-rel l 'Imay be utilizedto employ the tool as a setof jars-to free the bit" section: '-"I-his= may-be accomplished by applyingan upward pull" on the drill" stemby -mean's-*of-'the' conventional draw works (not shown), at the' top 'of the well until the drill stem;"-because'--of its naturarelasticity, is" in'increasd-tvAhsidn. Then the" drill string "is quickly released and then caught after ashort-interval.

"These actions will transmit an energy wave down the drill stem and produce'a'sharp impact between shoulder -|6*o'f body I0 and the upperedge of flange" 2T. This will produce a jarring efiect 'on"=' the'bit section, particularly since itis relativel'y closeto' th-pcintof 'impact; and willloosen the bit' section. This jarring action may be re- --peated= as often as necessary to free the bit.

When conditions *in the bore hole become-such as will normally cause 1 the bit to become stuck, whetherit-bean unusual degree of settling of cuttings,- sloughing of material'from' the wall of the bore holeythe presence of key seats or other obstructionss'stabilizer 24-;since it is the portion-of "the drill string, other than the. bit itself," having the" largest diameter, will'normallybecome stuck -first in any obstruction whichwould not pass the-bit se'ctiomand this will occur generallybefore the bit sectionitself becomes stuck too tightly -to -respor'id to'rotationof t-he drillstem. Rotation of the bit section may, therefore-, be continued by means of' this' tool =Whi1e operations are G'OhdlIGtQd'tU ffIBG CHG drill string; as by'efiec'tin'g the jarring action described above.

' Wham-a key seat form's the principal: obstruc= ztion to' the" removal. of. thef-d rill string, stabilizer 24 will be the portion which will first become stuck therein as the drilling string is drawn upwardly therethrough. When this occurs, the tools may often be jarred loose in the manner previously described and the presence of a key seat being thus disclosed, it then becomes possible for the driller, by carefully controlling the rate of withdrawal of the drill string and by continuing its rotation, to work the string around the key seat through the bore hole proper and thus withdraw the tools. Here again the presence of the stabilizer 24 in the drill string, which permits the driller to maintain relatively free rotation of the string, is of great assistance in these removal operations.

In a case, however, where stabilizer 24 becomes so stuck in the bore hole that the tools cannot be released by any of the previously mentioned expedients and it then becomes necessary to break the drill string, the tool in accordance with this invention may be employed to effect the break in the following manner:

An upward pull will be applied through the draw works to the upper end of the drill string which will draw the lower end thereof, comprising mandrel ll, sub l9, drill collar 23 and bit 34, upwardly through stabilizer 24 until teeth 33 on sub l9 engage teeth 32 On the lower end of stabilizer 24. lhe rotary table is then rotated in the counter-clockwise direction to similarly rodrilling art, the drill stem can generally be caused i to back-oil at a point very close to the portion thus held stationary, with the result that maximum lengths of the drill string can thus be readily recovered without serious damage, generally leaving only the stabilizing tool and bit section to be removed by the subsequent fishing or other well known operation employed to clear the hole.

Such fishing operations will also be substantially aided by the form of the stabilizer 24. Where the latter is constructed of relatively soft plastic material, whether or not the rib-type configuration is employed, it becomes relatively easy, when a conventional reaming cutter is run into the well, to ream olf the relatively soft material composing the stabilizer to the point where conventional hollow fishing tools may easily pass over the outside of the remainder of stabilizer 24 to reach and grasp the drill collar.

Instead of constructing stabilizer 24 of resilient or plastic material, as described, stabilizer 24 may be constructed of steel or other metal having ribbed configuration similar to that described. In

"this case, the stabilizer will retain the stabilizing I a Fig. illustrates another formof stabilizer which may be successfully employed with the tool of this invention in place of stabilizer 24. In this embodiment a stabilizer 3B, which may be zconstrueted of resil or p sticma ri lsio the type previously described or of steel or other metals, as may be desired, is slidably mounted on mandrel l'l. Instead of an external ribbed configuration, as in the previously described embodiment, stabilizer 3B is provided with a smooth exterior and a plurality of circumferentially spaced longitudinal passageways 39, which extend through the body of the material between the inner and outer surfaces thereof for passage of drilling fluid therethrough. Since much of the material forming the body of stabilizer 38 will be removed in providing passageways 39, this embodiment, even when constructed of metal, can be ground or reamed off when necessary without undue difliculty. In substantially all other respects, this embodiment will function just as that previously described and will retain the advantageous features thereof.

Fig. 6 illustrates still another embodiment in accordance with this invention in which flange 28 and the upper end of sub i9 are provided with teeth elements 40 and 4|, respectively, which are of substantially square shape or of other suitable configuration such that, when brought into interengagement by an upward pull on the drill string, clutching engagement of stabilizer 24 with the drill string will be effected, irrespective of the direction of rotation of the drill string. Such an embodiment is particularly useful in connection with the milling operation described above. In this operation by clutching the parts together while rotating slowly in the normal or clockwise direction, a rotational component may be imparted to the reciprocatory movement of stabilizer 24 which w ll aid the millin p nhis embodiment may also be employed for the unscrewing or backing-off operation previously described, when necessary or desirable, by rotating the drilling string in the counter-clockwise or anti-normal direction While the teeth are held in inter-engagement by an upward pull applied to the drill string.

It will be understood that the dimensions of the parts of the device in accordance with this invention may be varied depending primarily on the size of the drill bit and drill collars employed. The degree of longitudinal movement of the stabilizer on mandrel I7 is likewise variable but, in general, only a few inches of such movement is all that is necessary. Merely by way of illustration, in the case of a 12-inch stabilizer, the degree of longitudinal movement may be about eighteen to twenty-four inches to enable the device to successfully accomplish its several functions.

It will be understood that while the device in accordance with this invention is preferably employed by inserting it in a drill string immediately adjacent the upper end of the bit section, it may be employed successfully by inserting it between sections of a drill collar, and in some cases may be spaced above the end of the uppermost drill collar.

Various alterations and changes may be made in the details of the device in accordance with this invention within the spirit of this invention and without departing from the scope of the appended claims.

What we claim and desire to secure by Letters Patent is:

1. A drill collar stabilizer comprising, a tubular body member adapted to be inserted in a drill string adjacent a drill collar, said body member having a portion of reduced diameter intermediate its endsgto form an upper stop member on said body member, a tubular sub connected to the lower end of said body forming a lower stop member, a tubular sleeve member rotatably mounted on said portion of reduced diameter and slidable thereon between said stop members, cooperating clutch means arranged between the lower end of said sleeve member and the lower one of said stop members engageable only upon upward movement of said tubular body relative to said sleeve member to effect clutching engagement thereof, a

plurality of angularly spaced vertically extending ribs on the exterior of said sleeve member, the external diameter of said sleeve member including said ribs being greater than that of said drill collar, said tubular sleeve member including said ribs comprising a generally tubular body constructed of resilient rubber-like material mounted upon a tubular metallic core, the ends of which extend beyond the ends of said body of resilient material, laterally extending flanges on the opposite ends of said core, the upper one of said flanges cooperating with the upper one of said stop members for efiecting jarring impact therebetween, and the lower one of said flanges carrying one of said clutch members.

2. A rotary drill stabilizer comprising, a tubular body insertible in a drill string, a first stop member mounted at an intermediate point on said body, an enlargement forming a second stop member connected to said body below said first stop member, a tubular sleeve member rotatably and slidably mounted on said body between said stop members, said sleeve member comprising a tubular metallic core, laterally extending flanges on the opposite ends of said core, a generally tubular member constructed of resilient rubberlike material mounted on said core between said flanges and having a plurality of angularly spaced longitudinal ribs projecting radially from the exterior surface thereof, and cooperating clutch elements mounted on the lower one of said flanges and the adjacent stop member engageable upon upward movement of said tubular body relative to said sleeve member.

CICERO C. BROWN. FRED F. WALTERMIRE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,072,320 Thomas Mar. 2, 1937 2,166,937 Bettis July 25, 1939 2,177,300 Kellegrew Oct. 24, 1939 2,323,027 Gerstenkorn June 29. 1943

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