BRIEF DESCRIPTION OF DRAWINGS
FIGS. 1A and 1B show a drilling stabilization system in accordance with embodiments disclosed herein.
FIG. 2 is a partial cross-sectional view of a drilling stabilization system in accordance with embodiments disclosed herein.
FIG. 3 shows a bearing housing in accordance with embodiments disclosed herein.
FIGS. 4A and 4B show a drilling stabilization system in accordance with embodiments disclosed herein.
FIG. 5 is a flowchart showing a method of drilling a formation in accordance with embodiments disclosed herein.
DETAILED DESCRIPTION
In one aspect, embodiments disclosed herein relate to a passive drilling stabilization system for maintaining a selected angle of drilling and avoiding dog legs. In another aspect, embodiments disclosed herein relate to a passive drilling stabilization system for maintaining a nominal gage of wellbore being drilled. In yet another aspect, embodiments disclosed herein relate to a method of drilling a concentric wellbore.
FIGS. 1A and 1B show an example of a BHA for drilling a wellbore in a formation in accordance with embodiments disclosed herein. As shown, a drilling stabilization system 100 in accordance with embodiments disclosed herein includes a motor 102, a bearing housing 106, and a drill bit 108. In one embodiment, motor 102 may be a positive displacement motor (PDM). Motor 102 may be suspended in the well from a threaded tubular, for example, drill string 110. Alternatively, motor 102 may be suspended in the well from coiled tubing (not shown). Motor 102 may include a motor drive sub 114, a power section 112, and a transmission housing 106. Power section 112 may include a conventional lobed rotor (not shown) for rotating a motor output shaft (not shown), and thereby rotating motor drive sub 114, in response to fluid being pumped through power section 112. In this embodiment, fluid flows through the motor stator (not shown) to rotate the axially curved or lobed rotor (not shown). Transmission housing 104 is disposed axially below power section 112. Transmission housing 104 houses a motor transmission including equipment, as known in the art, for converting eccentric motion of power section 112 to concentric motion for bearing assembly 106. As shown, transmission housing 104 has a substantially cylindrical outer surface and may be configured to couple with a lower end of power section 112 and an upper end of bearing assembly 106. Coupling of transmission housing 104, power section 112 and bearing assembly 106 may be performed by any method known in the art. For example, in one embodiment, transmission housing 104 may be integrally formed with power section 112 or, in an alternate embodiment, transmission housing 106 may be mechanically coupled to power section 112 and bearing assembly 106. For example, transmission housing 104 may be threadedly engaged with a lower end of power section 112 and threadedly engaged with an upper end of bearing housing 106. One of ordinary skill in the art will appreciate that bearing housing 106 may house a bearing package assembly (not shown) that comprises, for example, thrust bearings and radial bearings.
As shown in FIGS. 1A and 1B, bearing housing 106 may include at least two blades 116 radially outwardly extending from the otherwise uniform diameter cylindrical outer surface of bearing housing 106. One of ordinary skill in the art will appreciate that any number of radially outwardly extending blades 116 may be disposed on bearing housing 106, for example, three blades, four blades, or more. In contrast to conventional steering blade components, where the blades may be formed on a sleeve that is threaded over a bearing housing, in one embodiment disclosed herein, the at least two blades 116 may be integrally formed with bearing housing 106. Alternatively, the at least two blades 116 may be coupled to bearing housing 106 by any method know in the art, for example, welding or bolting. As shown, the at least two blades 116 may include a tapered surface 118 disposed on each axial end of each blade 116.
Referring now to FIG. 1B, in one embodiment, a plurality of stabilizing contact point elements 120 may be disposed on an outer surface of the at least two blades 116. Stabilizing contact point elements 120 may be configured to provide a plurality of contact points between the at least two blades 116 and a wall of the wellbore (not shown). Stabilizing contact point elements 120 may provide stabilization of transmission housing 104, and therefore motor 102, while minimizing damage to or cutting of the wall of the wellbore.
As shown in FIG. 2, in one embodiment, stabilizing contact point elements 120 may include a plurality of inserts. One of ordinary skill in the art will appreciate that the plurality of inserts may be attached to each blade 116 by any method know in the art, for example, brazing, press fitting, and welding. In one embodiment, the plurality of inserts may include diamond enhanced inserts (DEI). As shown, in some embodiments, stabilizing contact point elements 120 may include a plurality of inserts having a dome shape. In this embodiment, the plurality of dome-shaped inserts provide a series of relatively small contact points, indicated at A, between each blade 116 of bearing housing 106 and a wall 122 of the wellbore. Accordingly, the total surface area of contact between the plurality of stabilizing contact point elements 120 and wall 122 of the wellbore is relatively small, thereby reducing damage to the formation or wall 122 of the wellbore, while still providing sufficient stabilization of motor 102.
As shown in more detail in FIG. 3, bearing housing 106 has a substantially cylindrical outer surface and may be configured to couple with a lower end of transmission housing 104 (FIG. 1A), as described above. A lower end of bearing housing 106 may be configured to couple with an upper end of the motor drive sub 114 (FIG. 1A). As shown, at least two blades 116 are integrally formed on the outer surface of bearing housing 106. A plurality of holes 130 may be formed on outer surface 132 of the at least two blades 116 for receiving a plurality of stabilizing contact point elements (e.g., 120 of FIG. 1B).
FIGS. 4A and 4B show a drilling stabilization system 400 coupled to a drill string 440 in accordance with an embodiment disclosed herein. As discussed above, drilling stabilization system 400 may include a motor (not shown), a power section 412, a transmission housing 404, a bearing housing 406, and a drill bit 408. As shown, transmission housing 404 is threadedly coupled with a lower end of power section 412 and bearing housing 406 is threadedly coupled with a lower end of transmission housing 404.
Referring now to FIG. 4B, bearing housing 406 may include at least two blades 416 radially outwardly extending from the otherwise uniform diameter cylindrical outer surface of bearing housing 406. One of ordinary skill in the art will appreciate that any number of radially outwardly extending blades 416 may be disposed on bearing housing 406, for example, three blades, four blades, or more. In contrast to conventional steering blade components, where the blades may be formed on a sleeve that is threaded over the bearing housing, in the embodiment shown, the at least two blades 416 are integrally formed with bearing housing 406. Alternatively, the at least two blades 416 may be coupled to bearing housing 406 by any method know in the art, for example, welding or bolting. As shown, the at least two blades 416 may include a tapered surface 418 disposed on each axial end of each blade 416 that helps guide the BHA into the wellbore when inserting it at the surface.
In one embodiment, transmission housing 404 may include at least two blades 426 radially outwardly extending from the otherwise uniform diameter cylindrical outer surface of transmission housing 404. One of ordinary skill in the art will appreciate that any number of radially outwardly extending blades 426 may be disposed on transmission housing 404, for example, three blades, four blades, or more. In the embodiment shown, the at least two blades 426 are integrally formed with transmission housing 404. Alternatively, the at least two blades 426 may be coupled to transmission housing 404 by any method know in the art, for example, welding or bolting. As shown, the at least two blades 426 may include a tapered surface 428 disposed on each axial end of each blade 426 that helps guide the BHA into the wellbore when inserting it at the surface.
In some embodiments, a plurality of stabilizing contact point elements 420 may be disposed on an outer surface of blades 416, 426 of the bearing housing 406 and the transmission housing 404, respectively. Stabilizing contact point elements 420 may be configured to provide a plurality of contact points between the at least two blades 416 of bearing housing 406 and the at least two blades 426 of transmission housing 404, and a wall of the wellbore (not shown). Stabilizing contact point elements 420 may provide stabilization of a motor while minimizing damage to the wall of the wellbore.
Furthermore, stabilizing contact point elements 420 may include a plurality of inserts disposed in a plurality of holes formed on the outer surface of the at least two blades 416 of bearing housing 406 and the at least two blades 426 of transmission housing 404. One of ordinary skill in the art will appreciate that inserts may be attached to each blade 416, 426 by any method know in the art, for example, brazing, press fitting, and welding. In one embodiment, the plurality of inserts may include diamond enhanced inserts (DEI). In some embodiments, stabilizing contact point elements 420 may include a plurality of inserts having a dome shape (see FIG. 2). In this embodiment, the plurality of dome-shaped inserts may provide a series of relatively small contact points between each blade 416, 426 and a wall of the wellbore (not shown). Accordingly, the total surface area of contact between the plurality of stabilizing contact point elements 420 and wall of the wellbore (not shown) is relatively small, thereby reducing damage to the formation or wall of the wellbore (not shown), while still providing sufficient stabilization of the BHA.
In the embodiment shown in FIGS. 4A and 4B, the blades 416, 426 of bearing housing 406 and transmission housing 404, respectively, are located in a critical lower end 432 of drill string 440. Stabilization of the critical lower end 432 of drill string 440 may provide directional stability of the drill string 440 as the bit 408 drills the formation. The critical lower end 432 of drill string 440 may be defined as the downhole end of a drill sting, including portions of the BHA, that are disposed below the power section 412 of a motor. In particular, stabilizers such as the blades 416, 426 of bearing housing 406 and transmission housing 404, respectively, disposed proximate to drill bit 408 may provide enhanced stabilization of the BHA. Accordingly, in this embodiment, the critical lower end 432 of drill string 440 includes transmission housing 404, bearing housing 406, a motor drive sub 414, and bit 408.
The blades 416, 426 of bearing housing 406 and transmission housing 404, respectively, may provide stability of the critical lower end 432 by reducing or minimizing the amount of flex of critical lower end 432 as it moves downward through the formation. In one example, on a drill string configured to drill an approximately 8½ inch hole, the axial distance from the tip of drill bit 408 to a top of the at least two blades 426 disposed on transmission housing 404 may be approximately 5 to 6 feet. In another example, on a drill string configured to drill an approximately 12¼ inch hole, the axial distance from the tip of drill bit 408 to the top of the at least two blades 426 disposed on transmission housing 404 may be approximately 6 to 7 feet. Thus, minimization of flex of the critical lower end 432 minimizes deviation of bit 408 from a planned trajectory. Accordingly, a BHA with a drilling stabilization system in accordance with embodiments disclosed herein may follow a substantially vertical trajectory regardless of variations in the formation. Further, a drilling stabilization system in accordance with embodiments disclosed herein may enable a BHA to maintain a directional trajectory, that is, a trajectory that is angled from the vertical line of the wellbore, with less deviation than a traditional BHA.
Referring now to FIG. 4B, in one embodiment, a longitudinal, cylindrical, reaming stabilizer 460 may be coupled to a lower end of motor drive sub 414 and an upper end of drill bit 408. The stabilizer 460 has longitudinal flutes 462 and lands 464. The flutes 462 are configured to allow fluid flow back past the stabilizer 460 (for this reason the flutes 462 may be referred to as “junk slots”). The lands 464 define an outer transverse diameter of reaming stabilizer 460. In some embodiment, the lands 464 and flutes 462 may be spirally arranged. One of ordinary skill in the art will appreciate that any number of flutes and lands may be used, for example, in one embodiment, there may be six lands 464 and six flutes 462.
Furthermore, lands 464 on the stabilizer 460 may be provided with a plurality of hardened inserts 466 extending outwardly from lands 464. In this embodiment, outer edges of the inserts 466 may define the transverse diameter of reaming stabilizer 460. The hardened inserts 466 may include a hardened surface, such as a polycrystaline diamond or tungsten carbide, for engaging a formation. In one embodiment, hardened inserts 466 may be removably mounted in reaming stabilizer 460 by brazing, for example by silver brazing the inserts 466 into a hole formed on lands 464. Alternatively, inserts 466 may be tight fit in reaming stabilizer 460 in holes formed on lands 464. In one embodiment, the transverse diameter of drill bit 408 is larger than the transverse diameter of reaming stabilizer 460. Alternatively, the transverse diameter of drill bit 408 is substantially the same as the transverse diameter of reaming stabilizer 460. Accordingly, when the drill bit 408 wears down to less than gage diameter, the reaming stabilizer 460 will engage the formation and function as a reamer. One example of a reaming stabilizer 460 is disclosed in U.S. Pat. No. 6,213,229, assigned to the assignee of the present disclosure, and is incorporated by reference in its entirety.
In one embodiment, drilling stabilization system 400 may be coupled to a drill string and lowered into a wellbore. As the bit drills the formation, the plurality of stabilizing contact point elements 420 disposed on blades 416, 426 of bearing housing 406 and transmission housing 404, respsectively, may contact the wall of the wellbore (not shown), thereby reducing vibrations of the drill string. The dome-like shape of the plurality of contact point elements 420, in accordance with embodiments disclosed herein, in combination with the stiffness or rigidity of the BHA provided by two sets of at least two blades 416, 426 disposed proximate the drill bit 408, allow the BHA to drill the formation with reduced drag while maintaining concentricity of the planned trajectory.
FIG. 5 shows a method of drilling a wellbore in accordance with embodiments disclosed herein. In one embodiment, a formation may be drilled with a directional drilling BHA 550 that may include one or more of a drill bit, a drill collar, a stabilizer, a reamer, a mud motor, a rotary steering tool, measurement-while-drilling sensors, and any other device useful in subterranean drilling. The directional drilling BHA may be any BHA known in the art, for example, a rotary steering system or an automated drilling system, as described above. The directional drilling BHA may then be used to deviate the trajectory of the planned wellbore by, for example, actuating a hydraulic rib on a stabilizer sleeve to move the BHA in an angled direction. Accordingly, the direction of drilling the formation may be changed 552. Next, the drill string may be pulled to the surface and the directional drilling BHA removed from the drill string 554 once the wellbore has been deviated from an original trajectory, for example, from a vertical trajectory.
Next, a drilling stabilization system in accordance with embodiments disclosed herein may be coupled to the drill string 556 and lowered into the wellbore. The drilling stabilization system coupled to the drill string may be lowered into the deviated wellbore and the formation may be drilled with the drilling stabilization system 558. Accordingly, the drilling stabilization system may drill the formation and maintain the deviated trajectory of the wellbore initiated by the directional drilling BHA. Because a drilling stabilization system in accordance with embodiments disclosed herein is a passive system, that is, stabilization of the system does not require automated or actuated parts, the cost of operating the system may be significantly less than an active system.
Advantageously, embodiments disclosed herein may provide a drilling stabilization system for drilling substantially concentric vertical wellbores with reduced deviations from a planned vertical trajectory. In addition, embodiments described herein may provide a more efficient and economical drilling stabilization system for drilling a concentric wellbore. Embodiments disclosed herein may also advantageously provide a drilling stabilization system for drilling a formation that maintains a deviated trajectory. Further, embodiments described herein may provide a method for drilling a formation along a deviated trajectory while maintaining the deviated trajectory. Still further, a drilling stabilization system in accordance with embodiments described herein may provide a stable and stiff BHA with reduced friction and a higher rate of penetration. Yet further, a drilling stabilization system in accordance with embodiments described herein may provide stabilizing contact point elements that provide stabilization of the BHA with reduced damage to or cutting of the formation.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
Patent Application
20080047754
