BACKGROUND OF THE INVENTION

In the drilling of oil and gas wells, downhole drilling motors may be connected to a drill string to rotate and steer a drill bit. Conventional drilling motors typically include a power assembly, a transmission assembly, and a bearing assembly. Rotation is provided by the power assembly. The transmission assembly transmits torque and speed from the power assembly to a drill bit disposed at a lower end of the drilling motor. The bearing assembly takes up the axial and radial loads imparted on the drill string during drilling. A releasable drilling stabilizer may be attached to a portion of a drill string or a drilling motor in order to stabilize the drill string or drilling motor within the wellbore. The releasable drilling stabilizer prevents unintentional key seating and reduces vibrations. Conventional releasable stabilizers include a central stiff stabilizing member having projections configured to engage an inner surface of the wellbore; slips, wedges, or flexible members disposed within the central stabilizing member for gripping an outer surface of the drill string; and end caps threadedly connected to the ends of the central stabilizing member. The end caps force the slips, wedges, or flexible members to grip the drill string as the end caps are threaded onto the central stabilizing member. Similar releasable stabilizers are disclosed in U.S. Patent No. 3,916,998 to Bass, Jr. et al. and U.S. Patent No. 4,258,804 to Richey et al. These conventional arrangements include at least two sets of contacting surfaces between the stabilizing member and the drill string, i.e., a first contact between the stabilizing member and the slip, wedge, or flexible member and a second contact between the slip, wedge, or flexible member and the outer surface of the drill string. Because the releasable stabilizer must transmit torque and axial load through frictional forces at the contact points, each set of contacting surfaces increases the chance of the releasable stabilizer not transmitting torque during use (i.e., failing, slipping, or otherwise becoming disconnected from the drill string).

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross-sectional view of a stabilizer assembly. Fig. 2 is a cross-sectional view of the stabilizer assembly taken from line A— A in

Fig. 1. Fig. 3 is a partial view of the stabilizer assembly taken from detail B in Fig. 1.

Fig. 4 is a cross-sectional view of an alternate embodiment of the stabilizer assembly including a grip section.

Fig. 5 is a partial view of the stabilizer assembly of Fig. 4 taken from detail B. Fig. 6 is a cross-sectional view of another alternate embodiment of the stabilizer assembly including a wedge member.

Fig. 7 is a partial view of the stabilizer assembly of Fig. 6 taken from detail B.

Fig. 8 is a cross-sectional view of a further alternate embodiment of the stabilizer assembly including the grip section and the wedge member. Fig. 9 is a partial view of the stabilizer assembly of Fig. 8 taken from detail B.

Fig. 10 is a partial cross-sectional view of an end of a stabilizing body of the stabilizer assembly with longitudinal grooves on the grip section.

Fig. 11 is a partial cross-sectional view of the end of the stabilizing body with circumferential grooves on the grip section. Fig. 12 is a partial cross-sectional view of the end of the stabilizing body with longitudinal grooves and circumferential grooves on the grip section.

Fig. 13 is a partial cross-sectional view of the end of the stabilizing body with a plurality of projections on the grip section.

Fig. 14 is a schematic view of the stabilizer assembly secured to a drilling motor within a wellbore.

DETAILED DESCRIPTION OF THE PREFERRED EMBODFMENTS

With reference to Fig. 1, stabilizer assembly 10 includes stabilizing body 12, first nut member 14, and second nut member 16. Stabilizing body 12 may be dimensioned to fit over a tubular member, such as a portion of a drill string or a drilling motor. Central portion 17 of stabilizing body 12 may include radial projection 18 extending from the outer surface of stabilizing body 12. Central portion 17 may have an increased diameter in relation to the remainder of stabilizing body 12. Radial projection 18 may be any projection extending in a radial direction beyond the outer surface of stabilizing body 12. In one embodiment, radial projection 18 may extend around the entire circumference of the outer surface of stabilizing body 12. In another embodiment, radial projection 18 may extend only partially around stabilizing body 12. As shown in Fig. 2, a set of radial projections 18 may be spaced apart around the outer surface of central portion 17 of stabilizing body 12.

Referring still to Fig. 1, stabilizing body 12 may also include first elastic members 20 at first end 22 and second elastic members 24 at second end 26. Elastic members 20 and 24 may be fingers formed by longitudinal slots 28 and 30, respectively. Longitudinal slots 28 and 30 may include rounded proximal ends 32 and 34, respectively. Rounded proximal ends 32 and 34 may prevent longitudinal slots 28 and 30 from propagating along the length of stabilizing body 12. As shown in Figs. 1 and 3, elastic members 20 and 24 may each include thinned section 36 and 38, respectively, between a proximal end and a distal end of each elastic member 20 or 24. In an alternate embodiment, elastic members 20 and 24 may be curved fingers formed by curved slots. Elastic members 20 and 24 may be integrally formed with stabilizing body 12. In one embodiment, elastic members 20 and 24 may be welded onto the remainder of stabilizing body 12.

Inner diameter 40 of central portion 17 of stabilizing body 12 may be dimensioned to fit over a tubular member, such as a portion of a drill string or a drill motor. Elastic members 20 and 24 on first and second ends 22 and 26, respectively, may be configured to be contracted or flexed to selectively provide first and second ends 22 and 26 with an inner diameter that is less than inner diameter 40 of central portion 17 in order to engage the tubular member over which it is positioned. Longitudinal slots 28 and 30 and thinned sections 36 and 38 may allow each elastic member 20 and 24 to flex relative to central portion 17 thus changing its radial position relative to the tubular member.

First end 22 of stabilizing body 12 may include threaded outer surface 42, and second end 26 may include threaded outer surface 44. Proximal end 46 of first nut member 14 may include threaded inner surface 48 configured to engage threaded outer surface 42 of first end 22 of stabilizing body 12. Proximal end 50 of second nut member 16 may include threaded inner surface 52 configured to engage threaded outer surface 44 of second end 26 of stabilizing body 12. First and second nut members 14 and 16 may be detachably connected to first and second ends 22 and 26 of stabilizing body 12 through these threaded connections. First nut member 14 may include tapered inner surface 54 configured to engage first elastic members 20. As first nut member 14 is threadedly connected to first end 22 of stabilizing body 12, first elastic members 20 may engage with and be contracted or flexed by tapered inner surface 54 of first nut member 14. Second nut member 16 may include tapered inner surface 56 configured to engage second elastic members 24. As second nut member 16 is threadedly connected to second end 26 of stabilizing body 12, second elastic members 24 may engage with and be contracted or flexed by tapered inner surface 56 of second nut member 16. In an alternate embodiment, first and second elastic members 20 and 24 may be contracted or flexed by clamping. Referring now to Figs. 1 and 3, when stabilizing body 12 is positioned over a tubular member, such as tubular member 58 shown in Fig. 3, threading first and second nut members 14 and 16 onto first and second ends 22 and 26 of stabilizing body 12 may force first and second elastic members 20 and 24 to engage with tapered inner surfaces 54 and 56. With further threading of first and second nut members 14 and 16 onto stabilizing body 12, tapered inner surfaces 54 and 56 may contract or flex first and second elastic members 20 and 24 such that contact surfaces 60 and 62 of first and second elastic members 20 and 24, respectively, contact and engage outer surface 64 of tubular member 58. With further threading of first and second nut members 14 and 16, contact surfaces 60 and 62 may grip outer surface 64 of tubular member 58 in order to detachably secure stabilizer assembly 10 onto tubular member 58.

In one embodiment, all threaded surfaces of stabilizer assembly 10 are oriented in the same direction (i.e., all right-hand threads or all left-hand threads). In this embodiment, if radial projections 18 are worn down and nut member 14 or 16 contacts an inner surface of a wellbore, one threaded connection will be loosened but the other threaded connection will be tightened. In other words, the threaded connection between nut member 14 and stabilizing body 12 may be loosened while the threaded connection between nut member 16 and stabilizing body 12 may be tightened. Alternatively, the threaded connection between nut member 16 and stabilizing body 12 may be loosened while the threaded connection between nut member 14 and stabilizing body 12 may be tightened. In this way, stabilizer assembly 10 will remain secured to the tubular member instead of both threaded connections being loosened. Figs. 4 and 5 illustrate an alternate embodiment of stabilizer assembly 10 in which contact surfaces 60 and 62 of first and second elastic members 20 and 24 include grip sections 70 and 72, respectively. Threading first and second nut members 14 and 16 onto stabilizing body 12 may contract or flex first and second elastic members 20 and 24 such that grip sections 70 and 72 engage outer surface 64 of tubular member 58. Further threading of first and second nut members 14 and 16 may cause grip sections 70 and 72 to grip outer surface 64 of tubular member 58 in order to detachably secure stabilizer assembly 10 onto tubular member 58. Grip sections 70 and 72 may provide a more secure connection between stabilizer assembly 10 and tubular member 58. In an alternate embodiment, stabilizing body 12 may include elastic members at only one end and stabilizer assembly 10 may include only one nut member.

Figs. 6 and 7 illustrate stabilizer assembly 100, which may include stabilizing body 12, first nut member 102, and second nut member 104. Stabilizing body 12 of stabilizer assembly 100 may be identical to stabilizing body 12 of stabilizer assembly 10. Proximal end 106 of first nut member 102 may include threaded inner surface 108 configured to engage threaded outer surface 42 of first end 22 of stabilizing body 12. Proximal end 110 of second nut member 104 may include threaded inner surface 112 configured to engage threaded outer surface 44 of second end 26 of stabilizing body 12. First and second nut members 102 and 104 may be detachably connected to stabilizing body 12 with these threaded connections. Referring still to Figs. 6 and 7, first nut member 102 may include distal internal shoulder (or radial shoulder) 114, and second nut member 104 may include distal internal shoulder (or radial shoulder) 116. First wedge member 118 may be disposed within first nut member 102, and may engage distal internal shoulder 114 thereof. Second wedge member 120 may be disposed within second nut member 104, and may engage distal internal shoulder 116 thereof. First wedge member 118 may include tapered inner surface 122 configured to engage first elastic members 20. Second wedge member 120 may include tapered inner surface 124 configured to engage second elastic members 24. When stabilizing body 12 is positioned over tubular member 58, threading first and second nut members 102 and 104 onto first and second ends 22 and 26 of stabilizing body 12 may force first and second elastic members 20 and 24 to engage with tapered inner surfaces 122 and 124 of first and second wedge members 118 and 120, respectively. With further threading of first and second nut members 102 and 104 onto stabilizing body 12, tapered inner surfaces 122 and 124 may contract or flex first and second elastic members 20 and 24 such that contact surfaces 60 and 62 of first and second elastic members 20 and 24 contact and grip outer surface 64 of tubular member 58. In this way, stabilizer assembly 100 may be detachably secured to tubular member 58. In one embodiment, first and second wedge members 118 and 120 may be formed of a different material than the remainder of stabilizer assembly 100. For example, first and second wedge members 118 and 120 may be formed of a harder material than the remainder of stabilizer assembly 100 in order to provide stronger tapered inner surfaces 122 and 124 and to provide a stronger grip between contact surfaces 60 and 62 and outer surface 64 of tubular member 58.

In another embodiment, all threaded surfaces of stabilizer assembly 100 are oriented in the same direction (i.e., all right-hand threads or all left-hand threads). In this embodiment, if radial projections 18 are worn down and nut member 102 or 104 contacts an inner surface of a wellbore, one threaded connection will be loosened but the other threaded connection will be tightened. In other words, the threaded connection between nut member 102 and stabilizing body 12 may be loosened while the threaded connection between nut member 104 and stabilizing body 12 may be tightened. Alternatively, the threaded connection between nut member 104 and stabilizing body 12 may be loosened while the threaded connection between nut member 102 and stabilizing body 12 may be tightened. In this way, stabilizer assembly 100 will remain secured to the tubular member instead of both threaded connections being loosened.

In an alternate embodiment, stabilizing body 12 may include elastic members at only one end and stabilizer assembly 100 may include only one nut member.

Figs. 8 and 9 illustrate an alternate embodiment of stabilizer assembly 100 in which contact surfaces 60 and 62 of first and second elastic members 20 and 24 include grip sections 70 and 72, respectively. Threading first and second nut members 102 and 104 onto stabilizing body 12 may cause first and second elastic members 20 and 24 to engage tapered inner surfaces 122 and 124 of first and second wedge members 118 and 120. First and second elastic members 20 and 24 may, in turn, be contracted or flexed such that grip sections 70 and 72 may engage and grip outer surface 64 of tubular member 58. Grip sections 70 and 72 may include any combination of grooves and/or projections to improve the resistance to movement of stabilizer assembly 10 or 100 on a tubular member. For example, grip sections 70 and 72 may include longitudinal grooves 130 as shown in Fig. 10. Longitudinal grooves 130 may provide improved prevention of relative rotation between stabilizing body 12 and the tubular member to which it is detachably secured. In another embodiment, grip sections 70 and 72 may include circumferential grooves 132 as shown in Fig. 11. Circumferential grooves 132 may provide improved prevention of sliding by stabilizing body 12 along the tubular member to which it is detachably secured. In a further embodiment, each of grip sections 70 and 72 may include a combination of longitudinal grooves 130 and circumferential grooves 132 as shown in Fig. 12. The combination of longitudinal grooves 130 and circumferential grooves 132 may provide improved prevention of relative rotation and improved prevention of sliding of stabilizing body 12 relative to the tubular member to which it is detachably secured. In yet another embodiment, grip sections 70 and 72 may include a plurality of projections 134 as shown in Fig. 13. Projections 134 may be formed by overlapping longitudinal grooves and circumferential grooves.

Referring now to Fig. 14, stabilizer assembly 10 may be detachably secured to a portion of drill string 140. For example, stabilizer assembly 10 may be detachably secured to bearing section 142 of drilling motor 144. To secure stabilizer assembly 10 to bearing section 142, a user may slide first nut member 14, then stabilizing body 12, then second nut member 16 over bearing section 142. First and second nut members 14 and 16 may be threaded onto first and second ends 22 and 26 of stabilizing body 12, which in turn may contract or flex first and second elastic members 20 and 24 to grip bearing section 142 with contact surfaces 60 and 62 of first and second elastic members 20 and 24. Where contact surfaces 60 and 62 include grip sections 70 and 72, first and second elastic members 20 and 24 may grip bearing section 142 with grip sections 70 and 72. In one embodiment, stabilizing body 12 and first and second nut members 14 and 16 may be placed over a tubular member in another order, such as by first sliding on stabilizing body 12, then sliding on first and second nut members 14 and 16.

Drilling motor 144 may be lowered from well surface 146 into wellbore 148 with stabilizer assembly 10 secured to the outer surface of bearing section 142. Drill string 140 and drilling motor 144 may be rotated in order rotate drill bit 150. Radial projections 18 of stabilizer assembly 10 may contact the inner surface of wellbore 148 in order to stabilizing drill string 140 and drilling motor 144 within wellbore 148 as the components are rotated.

When drilling motor 144 is removed from wellbore 148, stabilizer assembly 10 may be detached from bearing section 142. Unthreading first and second nut members 14 and 16 from first and second ends 22 and 26 of stabilizing body 12 allows first and second elastic members 20 and 24 to expand, thereby releasing contact surfaces 60 and 62 (or grip sections 70 and 72) from the outer surface of bearing section 142. Finally, a user may slide first and second nut members 14 and 16, along with stabilizing body 12, off of bearing section 142.

In the same way, stabilizer assembly 100 may also be detachably secured to drill string 140 in order to stabilize drill string 140 within wellbore 148. Threading first and second nut members 102 and 104 onto first and second ends 22 and 26 of stabilizing body 12 contracts or flexes first and second elastic members 20 and 24 to grip drill string 140 with contact surfaces 60 and 62 (or grip sections 70 and 72) of first and second elastic members 20 and 24. Unthreading first and second nut members 102 and 104 from first and second ends 22 and 26 of stabilizing body 12 allows first and second elastic members 20 and 24 to expand, thereby releasing contact surfaces 60 and 62 (or grip sections 70 and 72) from the outer surface of drill string 140.

Stabilizer assemblies 10 and 100 both include stabilizing body 12 that directly contacts and grips a tubular member over which it is positioned; neither stabilizer assembly includes a separate member (such as a slip or a wedge) for gripping the tubular member. Because the stabilizing body 12 directly contacts both the tubular member and the inner surface of the wellbore, stabilizing body 12 is capable of transmitting torque and axial load to prevent rotation and sliding of stabilizing body 12 relative to the tubular member.

Because stabilizing body 12 includes integral elastic members, stabilizing body 12 includes only one set of contacting surfaces between stabilizing body 12 and the tubular member. The single contacting surface arrangement of stabilizing body 12 reduces the chance of failure due to not transmitting torque during use over conventional stabilizers including at least two contacting surfaces between the stabilizing member and the tubular member. While preferred embodiments have been described, it is to be understood that the embodiments are illustrative only and that the scope of the invention is to be defined solely by the appended claims when accorded a full range of equivalents, many variations and modifications naturally occurring to those skilled in the art from a review hereof.