US3276824A

US3276824A - Drill string stabilizer

Info

Publication number: US3276824A
Application number: US308825A
Authority: US
Inventors: George T Carter
Original assignee: Grant Oil Tool Co
Current assignee: Grant Oil Tool Co
Priority date: 1963-09-13
Filing date: 1963-09-13
Publication date: 1966-10-04
Anticipated expiration: 1983-10-04

Description

Oct. 4, 1966 G. T. CARTER 3,276,824

DRILL STRING YSTABILIZER Filed sept. 13, 196s 2 sheets-sheet 1 p5?? MS @rra/@Vga G. T. CARTER DRILL STRING STAB ILIZER Oct. 4, 1966 2 Sheets-Sheet 2 Filed Sept. 13, 1963 United States Patent O 3,276,824 DRILL STRING STABILIZER George T. Carter, Houston, Tex., assignor to Grant Oil Tool Company, Los Angeles, Calif., a corporation ol California Filed Sept. 13, 1963, Ser. No. 308,825 4 Claims. (Cl. 308-4) This invention relates to drill string stabilizers, and more particularly to a drill string stabilizer assembly adapted to be removably aixed to the drill collar portion of the drill string.

Drill string stabilizers are well known as tools for cushioning lateral shock loads and lateral movements of the drill collar or drill string in rotary drilling operations. One common type is that which acts as a bearing in which the drill string rotates. Deflection under the weight supplied by the drill string to the bit makes it very diflicult to drill a hole which does not deviate from the vertical. To supply as much weight as possible directly above the bit, more drill collar sections have been used in recent years. Such drill collars are thick-walled sections of heavy pipe with flush heavy joints or couplings which increase the rigidity of the drill string and reduce the Wobbling of the drill bit. Additionally, drill collars are of suicient weight thatl the compressive force necessary on the bit is exerted by the collar section while the drill pipe portion of the string remains in tension. Various studies have been made which dictate the use of stabilizers at specied distances above the bit for various drilling parameters. For example, when the hole becomes inclined or crooked, the drill string makes contact with one side of the hole, causing the bit to make uneven contact with the bottom of the hole, thereby increasing the crookedness or deviation. These studies, of which the Woods-Lubinsky report is an example, indicate the exact footage above the drill bit at which stabilizers should be positioned to minimize deviation. Thus, stabilizers function toY center the drill string relative to the walls of the hole being drilled to thereby cause even contact of the bit with the bottom of the hole and provide for straighter and faster drilling.

In the prior state of the art, such stabilizers of the bearing type include a tool body adapted to be inserted between sections of the drill collar portion of the drill string, and a rotatable portion termed the boot or bushing which is rotatably mounted upon the tool body in order that the body may rotate within the bushing while the bushing remains stationary relative to the hole. The tool body in turn includes a cylindrical journal or mandrel section having an outside diameter matable with the inside diameter of the boot, and a length greater than the length of the boot such that when the boot is in place thereon, the boot can freely rotate;

At the upper end of the mandrel section there is conneeted a top collar having a diameter sufiicient to provide a transverse shoulder to limit the upward travel of the boot along the mandrel. A lower transverse shoulder is provided by the tool body to limit the downward travel of the boot along the mandrel. The top colla-r and mandrel section have suitable ush threaded joints for connection into the drill string between adjacent sections of drill collar.

In nomal operation, the drill string moves downwardly with respect to the boot such that the boot rotates in bearing contact with the upper shoulder. Means are usually provided for locking the boot into nonrotating engagement with the lower shoulder to allow for washover operations. Thus, a series of indentations are typically provided in the bearing surface of the lower shoulder. These indentations are matable with ratchet-like indentations in 3,276,824 Patented Oct. 4, 1966 the lower end surface of the boot. When the boot is forced into contact with the lower shoulder it cannot rotate in one direction and a washover tool can be utilized to remove the boot from the tool body.

From the foregoing it can be seen that prior art stabilizers are adapted only to be inserted between sections of drill collar, which sections are of standard length. The positioning of the stabilizer is thus limited to points above the drill bit where a joint occurs between sections oi drill collar.

Accordingly, it is a primary object of the present invention to provide a drill string stabilizer which is adapted to be positioned at any point along the length of the drill collar.

It is another object of the present invention to provide an improved drill string stabilizer assembly which can be inserted on the drill collar without causing another tool joint or connection therein.

Another object of the present invention is to provide a drill string stabilizer which can be changed in location on the drill collar section of a drill string without disassembly of the drill collar sections.

Yet another object of the present invention is to provide an improved stabilizer which is removably ailixed at any point along the length of the drill collar without damage to the collar.

The present invention comprises a drill string stabilizer assembly having a bushing section adapted to be rotatably mounted upon the exterior surface of a drill collar section. An upper shoulder assembly is removably affixed to the exterior surface of the drill collar and provides a transverse shoulder which limits the longitudinal movement of the bushing along the drill colla-1 in one direction and a lower shoulder spaced from the upper shoulder by -a distance greater than the length of the bushing. y

Such a stabilizer allows the drill collar to rotate within the bushing section which is attached directly to the drill collar without weldments of any kind and which is limited in vertical travel on the drill collar by means of these special shoulder assemblies. In this manner the stabilizer may be randomly spaced along the drill string, as desired, and does not need extra connections or the insertion of bodies within the drill string. By use of the present invention better prediction and control of hole direction and deviation can be obtained, and since no stabilizer body is required the freight-handling problem is reduced.

The novel features which are believed to be characteristic of t-he invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connect-ion with the accompanying drawing in which a presently preferred embodiment of the invention is illustrated by way of eX- ample. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only, and is not intended as a deiinition of the limits of the invention.

In the drawings:

FIGURE l is a view in elevation of a drill string with a stabilizer assembly, in accordance with the present invention, in place on the drill collar;

FIGURE 2 is a partial sectional view in elevation of the lower shoulder assembly in position on the drill collar;

FIGURE 3 is a sectional view, taken along the line 3 3 of FIGURE 2;

FIGURE 4 is a partial sectional View of a first alternative shoulder assembly;

FlGURE 5 is a View in elevation of a second alternative shoulder assembly; and

FIGURE 6 is a partial view, taken along the line 6-6 of FIGURE 5.

Various types of stabilizer lbushings, sometimes termed boots, bearings or bushings are well known to the art and are formed from various materials and in various configurations. For example, such bushings are commonly formed of rubberor elastomeric material molded about a metal cylindrical sleeve such that the inner cylindrical surface and outer cylindrical surface are rubberbearing surfaces. Some rubber configurations use strips of aluminum or other metal at the exterior wear surfaces.

The present invention is equally applicable to all such stabilizer bushings mentioned above so long as the bushing `is of the type which remains in a substantially nonrotating condition relative to the walls of the hole while the drill string rotates within the bushing. kFor pur-poses of illustration, a bushing formed as a steel cylinder 10 with radially extending ribs 11 is shown. The ribs 11 are spirally formed about the outer surface of the steel cylinder 10 and extend to the maximum diameter of the bushing which is approximately equal to the diameter 14 of the hole being drilled. The drill collar section 15 of the drill string extends upwardly from the bit 16 and is formed of drill collars threadably interconnected and joined to the drill pipe 17 which extends upwardly therefrom. The drill collar section 15 is of substantially uniform diameter throughout its entire lengt-h.

The bushing 10 has an inside diameter substantially equal to but greater than the outside diameter of the drill collar such that when placed on the drill collar it is freely rotatable with respect thereto. In accordance with the present invention, the bushing 10 is positioned on the surface of the drill collar between spaced-

apart shoulders

20 and 21 defined by lremovably aflixed upper and

lower shoulder members

23 and 24, respectively.

Each of the

shoulder members

23 and 24 is adapted to `frictionally engage the surface of the drill collar section 15. The upper and

lower members

23, 24 are identical except that the lower member 24 is shown as defining a series of indentations 27 in its shoulder 21 to provide a means for moving the bushing 10 into nonrotating engagement with the drill string. This is done by moving the bushing 10 downwardly, until indentations on `the lower edge 28 of the bushing engage the indentations 27 in the shoulder. Washover operations can then be carried out if necessary.

As shown in FIGURES 2 and 3, shoulder member 24 includes a sleeve 30 and socket 31. The sleeve 30 is cylindrical in configuration with an inside surface 32 matable with the exterior surface of the drill collar section 15. The sleeve has an outside surface 33 of a iirst diameter extending from the bearing shoulder 21 and a second portion 34 of second outside diameter with a transverse stop surface 35 between. The second portion 34 has male threads 36 throughout its length. Extending longitudinally from the male threads 36 on second portion 34 is a tapered portion y38 having a maximum Wall thickness adjacent the threaded portion which results in an outside surface 40 of maximum diameter less than the root diameter of the male threads 36 on second portion 34. The tapered portion 38 tapers to a minimum Wall thickness at the lower end 42 of the sleeve 30. In its normal or relaxed condition, the diameter of the inside surface 32 of sleeve 30 is substantially uniform throughout its length but the inside surface 44 of the tapered portion 38 is preferably serrated, knurled or rubber lined to provide maximum Y frictional engagement with drill collar element 15.1V A

eter approximately equal to the diameter of the lirst outside surface 33 of sleeve 30. The socket has female threads 48 along the inner surface 50 and this threaded section is matable with the male threads 36 of the sleeve 33. The threads are engageable to the point at which the upper end 52 of the socket 31 engages the stop surface 35 on sleeve 33. Extending longitudinally from the threaded portion is a female tapered surface 54 matable in interfering engagement with the outside `surface of tapered portion 38: That is, the maximum inside diameter of the inside tapered surface 54 is adjacent the threads 4S and is less than the maximum diameter` of the male taper 38 in the relaxed condition by an amount suflicient to cause the male taper to be forced inwardly. Similarly, the inside diameter at the minimum point of the female taper section 56 is less than the minimum outside diameter of the male taper section 38. Thus, yif'the threads are fully engaged, the male taper section 38 is forced inwardly by the amount of interference in the taper 'diameters` A series of suitable Spanner wrench openings 50, or other means for threading the sleeve and socket into engagement, are provided.

As an illustration of the relative sizes of the various parts, la 6% drill collar in one embodiment of the present invention utilizes a shoulder assembly which is 5 in overall length, of which a 1 section is of the first diameter of the sleeve, a 2" length is of the engaged threads, and a 2 length is of the tapered port-ions. The taper utilized i-s from 1 to 2 inches per foot of length.

Thus in utilizing the present invention, the lower shoulder assembly 24 is slipped over the upper` end of the drill collar at a convenient point and is lowered to the position at which the shoulder 21 is yat the lowermost point of travel desired for the bushing 10. The sleeve and socket of shoulder element 24 are then threaded `into engagement suiiiciently to cause the inside surface 44 ofthe male tapered portion 38 of the sleeve to be forced into engagement with `the drill collar to a suiicient extent to bind the shoulder assembly 24 in longitudinal non-rotational engagement with the drill collar. When suicient frictional engagement is achieved, a set screw 51 0r other similar means is used to lock the sleeve vand socket in the engaged position. The bushing 10 is then slipped onto the drill collar an-d allowed to come to rest on the lower shoulder 21. The upper shoulder member 23 `is thereafter slipped onto the drill collar with the bearing shoulder 20 downward in the orientation of the drill string shown in FIGURE 1. The shoulder 20 is spaced from the shoulder 21 by ra suitable distance to allow the desired travel of the bushing l10 between the shoulders. The sleeve and socket of the upper shoulder member 2-3 are then threaded into engagement until the surface` 44 of the tapered portion 38 of the sleeve againcomes into frictional engagement with the drill collar to an extent suliicient to prevent movement of the drill collar. The socket and sleeve of the upper shoulder member 23 are then locked in such engagement by the set screw or other suit-` table means 51.

Thus, it can be seen that the stabilizer `assembly in accordance with the present invention -is placed on the drill collar at any point along the length thereof and is so positioned Without uncoupling 'any portion of the drill collar at an undesired point. By means of the presentinvention, the drill collar stabilizer is located upon the drill collar without the .necessity of an additional tool'body being `inserted between sections of the drill string.` The means for retaining the stabilizer in position in accordance n with the present invention is such as to not cause damage above. In the embodiment of FIGURE 4, however, the sleeve member is formed into separate parts with an inner sleeve portion defining the bearing shoulder 60 and first diameter portion 61 with a stop surface 62 between the outer diameter and a male threaded portion 63. The tapered portion 64 of the sleeve is separable from the inner portion thereof and is adapted to be in abutting relationship at its upper surface or end 65 with the lower end surface 66 of the inner sleeve portion. The tapered portion 64 has an outer tapered surface 65A and an inner friction engaging surface 67 which is shown in the relaxed condition, and when in such relaxed condition has an inside diameter substantially equal to the diameter of the drill collar so that it may be easily positioned thereon. The socket 68 has a female threaded portion 69 extending from the inner end surface 70 thereof and is threadable to the point at which the end surface 7l) engages the transverse surface 62. A female tapered surface 71 is provided in the socket with a taper which is matable with the outside tapered surface 65A of the sleeve, but with interfering dimensions such that when it is moved longitudinally along the sleeve it causes the sleeve to be moved radially inwardly. Radially inward movement of the tapered portions 64 of the sleeve is allowed by a longitudinal slot 73 provided through the wall of the sleeve to allow its diameter to be reduced. A skir-t portion 75 of -the socket extends downwardly below the tapered portions thereof and includes means, such as -spanner wrench openings 76, for engaging the socket and sleeve into threaded connection.

A second alternative embodiment is shown in FIG- URES and 6 which differs from the shoulder members previously described. The -shoulder member of this embodiment is of one piece `only without interfering tapers a-s in the previously described embodiments. Thus, as shown in FIGURIES 5 and 6, the shoulder providing member 80 `of this embodiment is generally cylindrical in configuration with an inside diameter -81 substantially equal to but greater than the outside diameter of the drill collar such that it is matable therewith. The cylinder is split longitudinally at one point in its circumference by a slot 82 which extends the full length of the cylinder.

'Ihe inside diameter 81 and outside diameter 83 of the member 80 are substantially constant, and the decrease in diameter in this embodiment is provided by forcing the

surfaces

85 and 86 of the slot 82 toward one another by fastening means, such as bolts or screws. Thus, as shown in FIGURES 5 and 6, a series of longitudinally spaced tangential indentations 87 are provided at opposite sides of the slot 82 in a staggered arrangement throughout the length of the slot; that is, the indentation 87A is at one side of the slot 82 and is formed to provide a bearing surface 88 with a female` threaded opening 89 extending therefrom to the slot and into the wall of the cylinder at the opposite edge of the slot. A screw can then be threaded into the female threaded opening 89 at both sides of the slot, brought into engagement with the bearing surface 88, and tightened further to draw the

surfaces

85 and 86 of the slot together. rIlhe indentation 87B is longitudinally spaced therefrom at the opposite side of the slot 82 and so forth throughout the length of the slot.

The shoulder member 80 of FIGURES 5 and 6 is brought into engagement with the drill collar, to provide a bea-ring shoulder 90 comparable to the bearing shoulders and 21 previously described, by placing it upon the ydrill collar in its relaxed condition, inserting the screws into each of the indentations 87, and then tightening the screws until the slot 82 is closed to thereby tightly engage the shoulder member 80 upon the drill collar.

From the foregoing it will be apparent to one skilled in the art that various modifications in the construction and arrangement of parts of the present invention can be made. For example, the tapered surfaces in embodiments suoh as shown in FIGURE l can be incorf5 ponated into the threaded portion by forming a split, tapered, threaded male section. In connection with the present invention it has also been found that a steel bushingrhaving `an inner surface of rubber is particularly suitable.

Thus, the present invention discloses an improved drill collar stabilizer apparatus in which two shoulder forming means are removably aiiixed to the exterior surface of the drill collar with the shoulders spaced Iapart Ialong the length of the drill collar and with a stabilizer bushing positioned therebetween.

What is claimed is:

1. A drill string stabilizer assembly comprising in combination:

a drill string section having a cylindrical exterior wall;

a Ycylindrical bushing `rotatably positioned upon the cylindrical surface of the drill string section; a first shoulder defining means, means for releasably securing said shoulder defining means to said cylindrical surface, said shoulder defining means being juxtaposed to one end of said bushing and havin-g a diameter greater `than the inside diameter of said tbushing to limit the longitudinal travel of said bushing in one direction; and a second shoulder defining means, means for releasably securing said shoulder defining means to said cylindrical surface, said second shoulder defining means being juxtaposed but spaced from the opposite end of said bushing to limit the longitudinal travel thereof in the direction opposite said one direction.

2. A drill string stabilizer comprising in combination:

a drill collar having a cylindrical exterior surface;

ya cylindrical bushing rotatably positioned upon the cylindrical surface of said drill collar 'and having radially extending ribs extending from the outer surface thereof;

a first shoulder defining means removably afi'ixed to said cylindrical surface for limiting longitudinal travel of said bushing in one direction;

a second shoulder defining means removably aixed to said cylindrical surface and spaced from the opposite end of said bushing to limit longitudinal travel thereof in the opposite direction;

.at least one of said shoulder defining means including a sleeve having an inside surface engageable with said cylindrical surface of said drill coll-ar, said sleeve having a portion of its outer surface having male threads thereon, a male tapered portion extending from said portion having male threads, said male tapered portion having an outside surface having its greatest diameter nearer said portion having male threads and having its outside surface having its least diameter at the end thereof remote from said portion having male threads, slots extending longitudinally through said male tapered portion, said male tapered portion having a friction inner surface engaging said cylindrical surface of said drill collar; and

a socket having female threads on the inner surface thereof engageable with the male threads of said sleeve, said socket having a female tapered portion engageable with said male tapered portion, whereby when said sleeve and said socket are threadedly engaged said friction inner surface of said male tapered portion frictionally engages said drill collar.

3. A drill string stabilizer comprising:

a drill collar having a cylindrical exterior surface;

a cylindrical bushing rotatably positioned upon the cylindrical surface of the drill collar;

a first shoulder defining means removably affixed to said cylindrical surface to limit longitudinal travel of said bushing in one direction; and

a second shoulder defining means removably affixed to said cylindrical surface and spaced from the opposite end of said bushing to limit the longitudinal travel thereof in an opposite direction;

said shoulder dening means comprising `cylindrical sleeves positioned -over said drill collar and having an inner surface portion frictionally engageable with said drill coll-ar and releasable means for exerting an inwardly directed force upon the frictional portion to thereby removably position said shoulder deining means against longitudinal movement.

A drill string stabilizer comprising:

drill collar having a cylindrical exterior surface; cylindrical bushing rotatably positioned upon the cylindrical surface of said drill collar;

rst shoulder defining means removably axed to said cylindrical surface to limit the longitudinal travel of said bushing in one direction; A

second shoulder defining means removably aHiXed to said cylindrical surface to limit the longitudinal travel of said bushing in the opposite direction,

said shoulder defining means including a sleeve with -a male tapered portion having an inside surface in engagement with the outer surface of said drill collar, a socket having a female tapered portion engaging said male tapered portion of said sleeve, said socket and sleeve -having threaded connections whereby longitudinal -movement of said socket in one direction causes greater inward gripping force by said male sleeve.

References Cited by the Examiner UNITED STATES PATENTS Mack 308-4 Putman 308-4 Hoffman 30S-237 Nelson 285-323 X Lane 30S-4 Kamerer 30S-4 snub 285-323 X Wright. t

Hanes 287-5204 Wright 308-4 Parky 166-243 X` Lee 285-323 kDAVID I. WILLIAMOWSKY, Primary Examiner.

FRANK SUSKO, Examiner .L. L. JOHNSON, Assistant Examiner.

Claims

4. A DRILL STRING STABILIZER COMPRISING: A DRILL COLLAR HAVING A CYLINDRICAL EXTERIOR SURFACE; A CYLINDRICAL BUSHING ROTATABLY POSITIONED UPON THE CYLINDRICAL SURFACE OF SAID DRILL COLLAR; A FIRST SHOULDER DEFINING MEANS REMOVABLY AFFIXED TO SAID CYLINDRICAL SURFACE TO LIMIT THE LONGITUDINAL TRAVEL OF SAID BUSHING IN ONE DIRECTION; A SECOND SHOULDER DEFINING MEANS REMOVABLY AFFIXED TO SAID CYLINDRICAL SURFACE TO LIMIT THE LONGITUDINAL TRAVEL OF SAID BUSHING IN THE OPPOSITE DIRECTION, SAID SHOULDER DEFINING MEANS INCLUDING A SLEEVE WITH A MALE TAPERED PORTION HAVING AN INSIDE SURFACE IN ENGAGEMENT WITH THE OUTER SURFACE OF SAID DRILL COLLAR, A SOCKET HAVING A FEMALE TAPERED PORTION ENGAGING SAID MALE TAPERED PORTION OF SAID SLEEVE, SAID SOCKET AND SLEEVE HAVING THREADED CONNECTIONS WHEREBY LONGITUDINAL MOVEMENT OF SAID SOCKET IN ONE DIRECTION CAUSES GREATER INWARD GRIPPING FORCE BY SAID MALE TAPERED PORTION AND LONGITUDINAL MOVEMENT OF SAID SOCKET IN THE OPPOSITE DIRECTION CAUSES A RELEASE OF THE MALE TAPERED PORTION TO PERMIT REMOVAL OF SAID SLEEVE.