US3893523A

US3893523A - Curvable pipe section

Info

Publication number: US3893523A
Application number: US416086A
Authority: US
Inventors: John Doise Jeter
Original assignee: TEXAS DYNAMATICS Inc
Current assignee: TEXAS DYNAMATICS Inc
Priority date: 1973-11-15
Filing date: 1973-11-15
Publication date: 1975-07-08
Anticipated expiration: 1992-07-08

Abstract

A drill string section which may be used with its longitudinal axis straight or curved is made up of two or more coaxial tubular members, each bent in a continuous curve over part of its length, one rotatable within the other between selected rotational relative positions so that each member may strain the other toward straightness when their independent centers of curvature are on opposite sides of their mutual centerline with means to induce such relative rotation upon command. Alternately, two coaxial equally curved tubular members, as an assembly, inside a normally straight drill string section, or housing, is caused to tend to curve to impart a strained curvature to the housing. The inner assembly may be held stationary relative to earth while the housing is rotated, the result when the inner assembly is curved being a curved drill string section with its longitudinal axis lying in a stationary plane while the drill string is rotated about its longitudinal axis. Used in either configuration, the drill pipe section may be inserted into a well bore straight and used straight with the ability to induce the curve as needed for laterally deflecting the well bore as it is being drilled.

Description

United States Patent 1 J eter July 8,1975

[75] Inventor:

[52] US. Cl 175/74; 175/75 [51] Int. Cl E21b 7/08 [58] Field of Search 175/73, 74, 75, 76, 61; 285/118, 184; 138/140, 148

[56] References Cited UNITED STATES PATENTS 2,621,894 12/1952 Zublin 175/75 X 2,631,820 3/1953 Zublin 175/75 3,637,032 l/l972 .leter 175/73 3,743,034 7/1973 Bradley 175/61 3,767,836 10/1973 Gels et a1. 175/61 X Primary ExaminerDavid H. Brown [57] ABSTRACT A drill string section which may be used with its longitudinal axis straight or curved is made up of two or more coaxial tubular members, each bent in a continuous curve over part of its length, one rotatable within the other between selected rotational relative positions so that each member may strain the other toward straightness when their independent centers of curvature are on opposite sides of their mutual centerline with means to induce such relative rotation upon command. Altemately, two coaxial equally curved tubular members, as an assembly, inside a normally straight drill string section, or housing, is caused to tend to curve to impart a strained curvature to the housing. The inner assembly may be held stationary relative to earth while the housing is rotated, the result when the inner assembly is curved being a curved drill string section with its longitudinal axis lying in a stationary plane while the drill string is rotated about its longitudinal axis. Used in either configuration, the drill pipe section may be inserted into a well bore straight and used straight with the ability to induce the curve as needed for laterally deflecting the well bore as it is being drilled.

5 Claims, 6 Drawing Figures P'A'TEF ITEH JUL 8 ms SHEET 10F 2 FIG.1

was

SHEET 20F 2 3333,523

MFHTEHJUL 8 ms FIGS FIG5 CURVABLE PIPE SECTION In the drilling of holes, it is often desirable or necessary to control the direction in which the bore is progressing as it is being drilled. In well drilling it is customary to use a bent section in the drill string just above a drilling motor driving the drilling bit to encourage it to move laterally, deflecting the bore as drilling progresses. Normally there is an abrupt bend inserted between straight sections. This places an abnormal strain on drilling equipment both in action and when being placed in the well bore. Some devices are being used which are inserted into the well bore straight and subsequently bent by a hinging action. Such devices cannot be rotated when bent. The US. Pat. No. 3,637,032, issued Jan. 25, 1972, has a hinged joint that can be rotated, but a considerable amount of machinery is involved and the bend is a point bend rather than a curve.

The term curvable as used herein is defined as bendable with bending occurring normally, but not exclusively, within the elastic limit of the material being bent in a reasonably uniform amount per unit of length over the length being bent.

The device of this invention may be inserted into a bore hole straight and caused to curve when needed. The device may also be used non-rotative above a drilling motor or it may be used in an alternate embodiment with the curved centerline being a line in a stationary plane relative to earth while the drill string rotates in normal drilling practice. The device may be used end-to-end making up a series of curvable sections, each being curved in turn as the point of departure is reached as drilling progresses resulting in a long continuous curve comprising any desired degree of total curvature.

It is an object of this invention to provide a device to curve and uncurve a drill string section in a long, reasonably uniform curve after it is inserted in a well bore.

It is another object of this invention to provide a device to curve and uncurve a length of drill pipe through a command sent down from the surface of the earth.

It is another object of this invention to provide a curve inducing device that may be held stationary relative to earth even though the drill string in which it is installed may rotate or oscillate independently of the curve inducing device.

It is a further object of this invention to provide a device to induce relative rotation of the curve inducing members to control the end-to-end direction change in the centerline of the curve inducing section.

It is another object of this invention to provide a drill string section that can be used with other similar sections in series to form a long, continuous curve in the well bore and follow through such curvature with minimal strain.

It is yet another object of this invention to provide a device to control the amount of curvature induced into the drill string in response to needs as determined by a programmed instrument package in the vicinity of the drill bit.

It is still a further object of this invention to provide a device capable of inducing the elected amount and orientation of curvature in a drill string upon commands transmitted from the surface through communication means contained in the drill string.

These and other objects, advantages and features of this invention will be apparent to those skilled in the art from a consideration of this specification, including the attached drawings and appended claims.

FIG. 1 is an elevation of an uncurved assembly device of this invention inserted between the lower end of a drill string and a downhole motor driving a drill bit typical of normal earth boring operations.

FIG. 2 is the same as FIG. 1 except that the curvable section of this invention is shown in the curved configuration and has caused the advancing drill bit to deflect laterally, changing the direction in which the well bore is being drilled.

FIG. 3 is a longitudinal section of the curvable section shown in the uncurved configuration.

FIG. 4 is a longitudinal section of the curvable section shown in the curved configuration.

FIG. 5 is a longitudinal section of a curvable device that can be used in rotary drilling with or without a downhole motor.

FIG. 6 is the same as FIG. 5 but shown in the curved configuration.

In the anticipated down hole operation, as shown in FIG. 1, the device of this invention 2 is attached to drill string 1 at the top and to downhole motor 3 at the bottom. A down hole drilling motor has an output shaft 4 rotating a drilling bit 5. Although the downhole motor output shaft rotates relative to the drill string, in most cases it is desirable to rotate drill string 1 while drilling to avoid stuck drill string and to condition the hole. With device 2 in the straight configuration drill string rotation is practical.

To change the direction of the bore hole as it is being drilled, device 2 is caused to curve along its longitudinal axis by processes to be described later so that the drill bit will be urged to deflect laterally as shown in FIG. 2. During this activity, The drill string is normally oriented relative to earth by one of a variety of currently used means so that the lateral deflection will be in a preferred direction and, of course, the drill string will not be rotated.

In accordance with the device of this invention the basic act of changing the curvature of the longitudinal axis of a drill string section requires only two structural load bearing members. As shown in FIG. 4 an outer member 12 is part of the drill string, being attached above by means not shown to the upwardly extending drill string and being attached below by means not shown to the downwardly extending drill string. The midsection of member 12 is tubular and has an inherent curve in its longitudinal axis. Inner member 11 is axially supported for rotation within the bore of member 12 and has generally the same axial curvature and flexure characteristics as member 12 in the length of member 12 that its occupies. Actuator 6 can rotate member 11 for relative rotational positioning within member 12 about their mutual longitudinal axis. In this embodiment, the outside diameter of member 11 is only slightly smaller than the midsection bore diameter of member 12 so that the longitudinal axis of both members generally coincide. Rotation of degrees will change the radius of curvature of the device between opposite extremes. Intermediate curvature changes require less relative motion. It is preferable that at one extreme of the range of possible axial curvatures the device approaches straightness, as shown in FIG. 3. In referring to FIG. 4, assume that inner member 11 can be inserted into the bore of outer member 12 since both have approximately the same curvature and the bore of member 12 clears the major diameter of member 11. Bearing balls are inserted through a plug (not shown) to axially retain member 11 in position within member 12. FIG. 4 then shows

members

11 and 12 in the unstrained condition. The curvature of the assembly then approximates the individual axial curvature of member 11 and member 12.

FIG. 3 shows the assembly after actuator 6 has rotated member 11 about 180 within member 12. Assume equal curvature of member 11 and member 12 as produced and equal stiffness of member 11 and member 12. The 180 rotation places the center of curvature of member 11 and member 12 on opposite sides of their mutual centerline. Both members tend to curve in opposite directions and each places a bending load on the other and having the same stiffness characteristics, the imposed bending loads are equal. Having the same flexure qualities, member 11 and member 12 strain the same amount resulting in forcing both tubes to be strained to and constrained in a straight configuration. Radial loading between member 11 and member 12 is shown to be carried by full length bearing surfaces 13 being the outside of member 11 and the inside of member 12.

In straight or curved application, drilling fluid flows down the drill string bore, around actuator 6, between actuator support spider ribs 7 and into throat areas 9, into the bore 14 and on through lower terminus 15 to which the lower drill string apparatus is attached. Actuator 6 receives instructions and power from other devices such as the Directional Drilling Apparatus No. 3,637,032, issued Jan. 25, 1972, or perhaps the Steerable Drill String, No. 3,743,034, issued July 3, 1973.

Referring to FIG. 5, the threaded devices necessary to assemble the parts shown have been omitted to simplify the description of the function of invented features. Assume that inner member 30 can be installed in outer member 29 along with actuator 25, and assume further that outer member 29 can be installed in housing along with orienting motor 21.

Housing 20 is part of a drill string being attached at the top by means not shown to the upwardly extending drill string and being attached at the bottom by means not shown to the downwardly extending drill string.

Motor 21 is any suitable continuously rotatable motor capable of rotating shaft 23 continuously in either direction at any needed speed and can orient and hold shaft 23 relative to a set of coordinates not necessarily related to housing 20. The motor 21 may be controlled by the aforesaid patents.

Actuator 25 may be the same as actuator 6 of FIG. 3 and FIG. 4. Actuator 25 may receive control and power through shaft 23 of motor 21 from the same means controlling motor 21.

As manufactured, housing 20 will be straight as shown in FIG. 5 and member 29 and member 30 will be equally curved as shown in FIG. 6. After member 30 is inserted into member 29 they will be rotated about 180 relative to each other and then will be straight as described above relative to FIG. 3 and FIG. 4. The straight assembly will then be inserted into the bore of housing 20. Axial relationship between member 29 and member 30 is controlled by thrust bearings in actuator 25 by way of shaft 27. Axial position of member 29 within housing 20 is controlled by thrust bearings (not shown) in motor 21 by way of shaft 23.

In normal straight rotary drilling, the straight configuration of FIG. 5 would be appropriate. Member 29 and member 30 are strained to straightness and held in that condition. Motor 21 is inactive and all shown are stationary relative to housing 20.

When being used to urge the drill bit to move laterally to change the well bore direction actuator 25 rotates member 30 about within member 29. The inner

assembly comprising members

29 and 30 will then tend to curve within housing 20. The normally straight housing 20 will resist the curving forces of the inner assembly and they will not fully reach their unstrained inherent curvature, but housing 20 will be curved to some extent by such forces. Motor 21 is then activated to orient the inner assembly so that the resulting curve lies in a selected plane relative to earth. This plane is selected by one of the aforementioned patents or other means.

The curvature relationships and the relative rotation of the curved elements are mentioned herein for discription convenience and are not to be regarded in a limiting sense. There are many possible combinations of radius of curvature, angle of relative rotation and flexure relationships.

Housing 20 may rotate or oscillate relative to earth without changing the plane of curvature of the assembly relative to earth because motor 21 rotates member 29 within the bearing surfaces 32. Bearing 32 may comprise the outer surface of member 29 and the inner surface of housing 20.

Drilling fluid is delivered down the bore of the drill string, flows around motor 21, between spiders 22, through 26, through 28, down bore 31 and out bore 34.

The invention having been described, what is claimed 1. A curvable drill pipe section carried by a pipe string extending into a well bore that can be actuated to change the radius of curvatures of the longitudinal centerline of the section comprising; an inherently curved tubular outer member, an inherently curved cylindrical inner member axially supported and radially constrained within the bore of said tubular outer member such that the longitudinal centerline of the inner member is generally coincident with the longitudinal centerline of said outer member for relative rotation and relative rotational positioning within said outer member, means to rotate said inner member relative to said outer member, means to lock said inner member in selected rotational position relative to said outer member, so that by changing the rotational position of said inner member relative to said outer member said inner member will strain said outer member to change the curvature of the longitudinal centerline of the section.

2. The device of claim 1 in which said inherently curved tubular outer member and said inherently curved cylindrical inner member have such inherent radius of curvature of their longitudinal centerlines and such flexure characteristics that in at least one relative rotational position their mutual centerline is generally straight.

3. A curvable drill string section carried by a pipe string extending into a well bore that can be actuated to change the radius of curvature of the longitudinal centerline of the section comprising; a housing having a generally cylindrical longitudinal opening, means at each end to attach said housing to pipe string components in end-to-end relationship, an inherently curved outer tubular member axially and radially supported within the opening of said housing such that the longitudinal centerline of said outer member generally coincides with the longitudinal centerline of said housing for rotation within said opening, an inherently curved cylindrical inner member axially and radially supported within the bore of said outer tubular member such that its longitudinal centerline generally coincides with the longitudinal centerline of said outer member for rotational movement and rotational positioning relative thereto, means to rotationally move and rotationally position said inner member relative to said outer member, means to rotate said inner and outer members as an assembly relative to said housing, whereby said inner member can be selectively rotationally positioned within said outer member to urge the centerline of said outer member to a selected curvature and said assembly can be rotated relative to said housing so that as said housing is rotated by the pipe string relative to earth the centerline of said assembly can be caused to lie in a plane independent of said housing so that said housing is urged by said assembly to curve along a centerline in said plane as said housing is rotated about said centerline to cause a drill bit attached thereto to tend to deflect laterally as drilling takes place.

4. The device of claim 3 in which said outer inherently curved member and said inherently curved inner member have such intrinsic axial curvatures and flexure characteristics that in at least one relative rotational position therebetween their mutual centerline will be strained to approximate straightness.

5. A curvable drill string section carried by a pipe string extending into a well bore that can be actuated to change the radius of curvature of the longitudinal centerline of the section comprising; a housing having a generally cylindrical central longitudinal opening, means at each end to attach said housing to pipe string components in end-to-end relationship, an inherently curved outer tubular member axially and radially supported within the opening of said housing such that the longitudinal centerline of said outer member generally coincides with the longitudinal centerline of said housing for rotation within said opening, an inherently curved cylindrical inner member axially and radially supported within the bore of said outer tubular member such that its longitudinal centerline generally coincides with the longitudinal centerline of said outer member for rotational movement and rotational positioning relative thereto, means to rotationally move and rotationally position said inner member relative to said outer member, means to rotate said inner and outer members as an assembly relative to said housing and to rotationally position and assembly relative to an earth related coordinate system, whereby said inner member can be selectively rotationally positioned within said outer member to urge the centerline of said outer member and said housing to a selected curvature and said assembly can be rotated relative to said housing so that as said housing is rotated by the pipe string relative to earth the centerline of said assembly can be caused to lie in a selected plane independent of said housing so that said housing is urged by said assembly to curve along a centerline in said plane as said housing is rotated about said centerline to cause a drill bit attached thereto to tend to deflect laterally in a selected direction as drilling takes place.

Claims

1. A curvable drill pipe section carried by a pipe string extending into a well bore that can be actuated to change the radius of curvatures of the longitudinal centerline of the section comprising; an inherently curved tubular outer member, an inherently curved cylindrical inner member axially supported and radially constrained within the bore of said tubular outer member such that the longitudinal centerline of the inner member is generally coincident with the longitudinal centerline of said outer member for relative rotation and relative rotational positioning within said outer member, means to rotate said inner member relative to said outer member, means to lock said inner member in selected rotational position relative to said outer member, so that by changing the rotational position of said inner member relative to said outer member said inner member will strain said outer member to change the curvature of the longitudinal centerline of the section.