TORSIONAL ISOLATOR

Abstract

A torsional isolator (200, 300, 400) designed to reduce vibrations and shock experienced by electronics used during directional drilling is disclosed. The torsional isolator allows the drillstring electronics to oscillate at a slower rotational velocity than the data acquisition rate of associated sensors, such that the sensors record an average value of the azimuth heading thereby allowing for a higher accuracy measurement of the azimuth heading. The sample rate of the sensors is such that the sensors maximum error is reduced by the torsional isolator, as the output angular displacements are lower than the input angular displacements.

Description

BACKGROUND OF THE INVENTION

Rotational shock and vibratory input from the drillstring and the various components therein limits the accuracy of guidance, such as gyroscopic guidance, for the directional drilling. The existing shock/vibratory absorption equipment fails to substantially prevent degradation of the accuracy of the guidance equipment as the directional drilling tool is subjected to shock/vibratory inputs. Additionally, current isolation equipment is incapable of providing a return-to-zero point, thereby preventing accurate directional calculations for the gyroscope or directional sonde (i.e. measurement while drilling)

SUMMARY OF THE INVENTION

In many aspects, this invention provides for a torsional isolator for directional drilling operations.

In one aspect, the invention provides a torsional isolator for a drillstring, wherein the torsional isolator is positioned in the drillstring between electronics of the drillstring and a drillbit of the drillstring. The torsional isolator comprises a first assembly, the first assembly having a first end, a second end, at least one annular cavity, and a first spring mount, wherein the first end is joined to the interconnect opposite of the electronics housing and is proximate the drillstring electronics. The torsional isolator comprises a second assembly, the second assembly having a first end, a second end, and a second spring mount, wherein the second assembly is movably disposed within the first assembly and has the second end positioned proximate to the drillbit, wherein the second spring mount is interiorly positioned within one of the at least one annular cavities. The torsional isolator comprises at least one bearing, wherein the bearing is movably secured between an inner wall of the first assembly and the outer wall of the second assembly and provides for rotation therebetween. The torsional isolator comprises a torsional spring having a first end and a second end, wherein the first end is affixed to the first spring mount and the second end is affixed to the second spring mount. The torsional isolator comprises a stop-key having a first key element and a second key element, wherein the first key element is positioned on the first assembly and the second key element positioned on the second assembly, and wherein the first key element and the second key element are capable of preventing a rotation of the second assembly beyond a pre-defined limit from a static position The torsional isolator comprises a damper element affixed to the second assembly and positioned proximate the inner wall of the first assembly. The torsional isolator comprises a viscous fluid filling the annular cavity, wherein the viscous fluid provides viscous damping by having a thin film of viscous fluid adhering to the damper element as the first assembly and second assembly rotate relative to each other.

In another aspect, the invention provides a torsional isolator for a directional drilling tool. The directional drilling tool has at least a electronics housing, at least one interconnect and a drillbit. The electronics housing contains at least a drillstring electronics and is joined with the interconnect, wherein the drillbit is oppositely positioned from the drillstring electronics on the directional drilling tool. The torsional isolator comprises a first assembly, a second assembly, at least one bearing, a torsional spring, a stop-key, a damper element, and a viscous fluid. The first assembly has a first end, a second end, at least one annular cavity, and a first spring mount, wherein the first end is positioned proximate to the drillbit. The second assembly has a first end, a second end, and a second spring mount, wherein the second assembly is movably disposed within the first assembly and has the second end is joined to the interconnect opposite of the electronics housing and is proximate the drillstring electronics, wherein the second spring mount is interiorly positioned within one of the at least one annular cavities. The bearing is movably secured between an inner wall of the first assembly and the outer wall of the second assembly and provides for rotation therebetween. The torsional spring has a first end and a second end, wherein the first end is affixed to the first spring mount and the second end is affixed to the second spring mount. The stop-key has a first key element and a second key element, wherein the first key element is positioned on the first assembly and the second key element is positioned on the second assembly, and wherein the first key element and the second key element are capable of preventing a rotation of the second assembly beyond a pre-defined limit from a static position. The damper element is affixed to the second assembly and positioned proximate the inner wall of the first assembly. The viscous fluid fills the annular cavity, wherein the viscous fluid provides viscous damping by having a thin film of viscous fluid adhering to the damper element as the first assembly and second assembly rotate relative to each other.

Numerous objects and advantages of the invention will become apparent as the following detailed description of the preferred embodiments is read in conjunction with the drawings, which illustrate such embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic view of a hydrocarbon recovery system comprising a torsional isolator.

FIG. 2 illustrates an oblique view of the torsional isolator of the hydrocarbon recovery system of FIG. 1.

FIG. 3 illustrates an oblique partial view of the torsional isolator of FIG. 2 and primarily shows a drive shaft of the torsional isolator.

FIG. 4 illustrates an oblique partial view of the torsional isolator of FIG. 2 and primarily shows a torsional spring and a damper element assembled to the drive shaft.

FIG. 5 illustrates an oblique partial view of the torsional isolator of FIG. 2 and primarily shows a first connector of the torsional isolator as configured for connection to the torsional isolator components of FIG. 4.

FIG. 6 illustrates an orthogonal bottom end view of the torsional isolator.

FIG. 7 illustrates a section view of the torsional isolator of FIG. 6 taken along section A-A.

FIG. 8 illustrates an enlarged view of an upper portion of the section view of FIG. 7.

FIG. 9 illustrates an enlarged view of a lower portion of the section view of FIG. 7.

FIG. 10 illustrates an orthogonal upper end view of the torsional isolator.

FIG. 11 illustrates a section view of the torsional isolator of FIG. 10 taken along section B-B.

FIG. 12 illustrates an enlarged view of an upper portion of the section view of FIG. 11.

FIG. 13 illustrates an enlarged view of a lower portion of the section view of FIG. 11.

FIG. 14 illustrates a section view of the torsional isolator from FIGS. 11 and 13 taken along section C-C.

FIG. 15 illustrates a section view of the torsional isolator from FIGS. 7 and 9 taken along section D-D.

FIG. 16 illustrates an oblique view of another torsional isolator.

FIG. 17 illustrates a section view of the torsional isolator of FIG. 16.

FIG. 18 illustrates an oblique view of yet another torsional isolator.

FIG. 19 illustrates an orthogonal side view of the torsional isolator of FIG. 18.

FIG. 20 illustrates an orthogonal upper end view of the torsional isolator of FIG. 18.

FIG. 21 illustrates a section view of the torsional isolator from FIG. 20 taken along section E-E.

FIG. 22 illustrates an enlarged view of an upper portion of the section view of FIG. 21.

FIG. 23 illustrates an enlarged view of a lower portion of the section view of FIG. 21.

FIG. 24 illustrates a section view of the torsional isolator from FIG. 19 taken along section F-F.

FIG. 25 illustrates an enlarged view of an upper portion of the section view of FIG. 24.

FIG. 26 illustrates an enlarged view of a lower portion of the section view of FIG. 24.

FIG. 27 illustrates a partial cutaway view of the torsional isolator of 18.

FIG. 28 illustrates a root mean square performance graph of a torsional isolator such as the torsional isolator of FIG. 2.

FIG. 29 illustrates a return-to-zero performance graph of a torsional isolator such as the torsional isolator of FIG. 2.

DETAILED DESCRIPTION

The torsional isolator is shaped to operate in a drillstring associated with drilling wells. The torsional isolator has a cylindrical form. In one embodiment, the torsional isolator is used in directional drilling operations such as measurement while drilling (MWD).

Referring now to FIG. 1, a schematic view of a hydrocarbon recovery system 100 is shown. The hydrocarbon recovery system 100 may be onshore or offshore. The hydrocarbon recovery system 100 generally comprises a drillstring 102 suspended within a borehole 104. The drillstring 102 comprises a drillbit 106 at the lower end of the drillstring 102, a muleshoe or universal bottom hole orienting (UBHO) sub 108 connected above the drillbit 106, a bent housing mud motor 110 or other rotary steerable tool connected between the UBHO sub 108 and the drillbit 106, and a electronics housing 111 or housing that carries electronic components 112. In this embodiment, the hydrocarbon recovery system 100 further comprises a torsional isolator 200 configured to provide torsional vibration and/or shock damping as well as torsional and/or angular biasing functionality that tends to maintain and/or return components above and below the isolator to known and/or preset angular orientations relative to each other. The torsional isolator 200 is connected to the electronics housing 111 via a suitable interconnect 113. The torsional isolator 200 is connected to a mule shoe 115 via a suitable interconnect 117. Because the mule shoe 115 and the UBHO sub 108 are generally connected via a locating slot and tab configuration and/or some other suitable connection selected to provide a known orientation between the mule shoe 115 and the UBHO sub 108, the UBHO sub 108 and the components connected below the UBHO sub 108 are provided a known angular orientation relative to the electronics housing 111. The hydrocarbon recovery system 100 comprises a platform and derrick assembly 114 positioned over the borehole 104 at the surface. The derrick assembly 114 comprises a rotary table 116 which engages a kelly 118 at an upper end of the drillstring 102 to impart rotation to the drillstring 102. The drillstring 102 is suspended from a hook 120 that is attached to a traveling block. The drillstring 102 is positioned through the kelly 118 and the rotary swivel 122 which permits rotation of the drillstring 102 relative to the hook 120. Additionally or alternatively, a top drive system may be used to impart rotation to the drillstring 102.

In some cases, the hydrocarbon recovery system 100 further comprises drilling fluid 124 which may comprise a water-based mud, an oil-based mud, a gaseous drilling fluid, water, gas and/or any other suitable fluid for maintaining bore pressure and/or removing cuttings from the area surrounding the drillbit 106. Some drilling fluid 124 may be stored in a pit 126 and a pumping system 127 may deliver the drilling fluid 124 to the interior of the drillstring 102 via a port in the rotary swivel 122, causing the drilling fluid 124 to flow downwardly through the drillstring 102 as indicated by directional arrow 128. The drilling fluid 124 may exit the drillstring 102 via ports in the drillbit 106 and circulate upwardly through the annulus region between the outside of the drillstring 102 and the wall of the borehole 104 as indicated by directional arrows 130. The drilling fluid 124 lubricates the drillbit 106, carries cuttings from the formation up to the surface as it is returned to the pit 126 for recirculation, and creates a mudcake layer (e.g., filter cake) on the walls of the borehole 104.

The hydrocarbon recovery system 100 further comprises a communications relay 132 and a logging and control processor 134. The communications relay 132 receives information and/or data from sensors, transmitters, and/or receivers located within the electronic components 112 and/or other communicating devices. The information is received by the communications relay 132 via a wired communication path through the drillstring 102 and/or via a wireless communication path. The communications relay 132 transmits the received information and/or data to the logging and control processor 134 and the communications relay 132 receives data and/or information from the logging and control processor 134. Upon receiving the data and/or information, the communications relay 132 forwards the data and/or information to the appropriate sensor(s), transmitter(s), and/or receiver(s) of the electronic components 112 and/or other communicating devices. The electronic components 112 comprise measuring while drilling (MWD) and/or logging while drilling (LWD) devices and the electronic components 112 may be provided in multiple tools or subs and/or a single tool and/or sub. In alternative embodiments, different conveyance types including, for example, coiled tubing, wireline, wired drill pipe, and/or any other suitable conveyance type may be utilized. In some embodiments, the above-described communications comprise mud pulse telemetry in which the drilling fluid 124 is used as a communication medium.

Referring now to FIG. 2, the torsional isolator 200 of hydrocarbon recovery system 100 is shown in greater detail. Specifically referring to FIGS. 2-5, the torsional isolator 200 includes a barrel 202 longitudinally connected between a first connector 204 and a second connector 206. The first connector 204 includes a female receptacle for receiving and connecting to other drillstring 102 components. The second connector 206 includes a male portion for insertion to and connecting to other drillstring 102 components. The torsional isolator 200 is configured so that the first connector 204 is an upper or higher located connector as compared to the second connector 206 that is located relatively lower in the drillstring 102. The torsional isolator 200 is configured to damp angular rotational energy transmitted between the first connector 204 and the second connector 206. The torsional isolator 200 is also configured to provide rotational and/or angular biasing forces between the first connector 204 and the second connector 206 so that the torsional isolator 200 tends to maintain or return the first connector 204 to a preset and/or known relative angular orientation the second connector 206 is maintained when rotational forces of hydrocarbon recovery system 100 permit. The torsional isolator 200 has a central longitudinal axis 208. The above-described rotational and/or angular biasing forces and relative rotational and/or angular orientations are relative to rotation about the central longitudinal axis 208. The angular damping functionality of the torsional isolator 200 is accomplished by shearing fluids 210 within the torsional isolator 200. The angular biasing force and/or angular orientation return functionality of the torsional isolator 200 is accomplished in part by transmitting angular forces through a torsional spring 212 configured to allow loading of the spring in both rotational directions about the central longitudinal axis 208.

Referring now to FIGS. 2-15, the torsional isolator 200 includes a first assembly 214 that is generally torsionally rigid and a second assembly 216 that is also generally torsionally rigid. Rotation of the first assembly 214 relative to the second assembly 216 is damped by shearing the fluids 210. Relative angular displacements of the first assembly 214 relative to the second assembly 216 are resisted and/or decreased by the torsional spring 212. The first assembly 214 includes the barrel 202, the first connector 204, a thrust insert 218, and a centering insert 220. The first connector 204 is partially received within the barrel 202 and is joined to the barrel 202 via a sealed and threaded connection. The thrust insert 218 is received within and joined to the lower end of the barrel 202 via a sealed and threaded connection. The centering insert 220 is received within and joined to the lower end of the thrust insert 218 via a sealed and threaded connection. The second assembly 216 includes the second connector 206, a drive shaft 222, and a damper element 224. The drive shaft 222 is connected to the second connector 206 via a threaded connection and is further captured relative to the second connector 206 using slotted spring pins 226 inserted into holes of the second connector 206 and concavities of the drive shaft 222. The damper element 224 is connected to the upper end of the drive shaft 222 via a Woodruff key 228 captured between a recess 230 of the drive shaft 222 and channel 232 of the damper element 224.

The drive shaft 222 is received through central passages of the centering insert 220, the thrust insert 218, and the torsional spring 212. The upper end of the drive shaft 222 is received within a lower cavity 234 of the first connector 204. Needle bearings 236 are disposed in the lower central cavity 234 between the first connector 204 and the drive shaft 222. The needle bearings 236 serve to maintain a coaxial alignment between the first assembly 214 and the second assembly 216. Radial bearings 238 or ball bearings are captured between the thrust insert 218, the centering insert 220, and the drive shaft 222 to maintain a coaxial alignment between the first assembly 214 and the second assembly 216. Thrust bearings 240 are provided between a shoulder 242 of the drive shaft 222 and adjacent portions of the thrust insert 218 and the thrust bearings 240 are captured by connecting a bearing nut 244 to an upper interior portion of the thrust insert 218. The thrust bearings 240 provide a strong axial load transfer path so that large compressive or tensile loads are fully transmitted through the torsional isolator 200 even while the torsional isolator 200 serves to reduce system energy associated with twisting the torsional isolator 200 about the central longitudinal axis 208. The thrust bearings 240 are particularly useful in transferring axial forces associated with drilling and fishing out drillstring 102 components.

In this embodiment, the torsional spring 212 is joined between the first assembly 214 and the second assembly 216. The torsional spring 212 includes a first spring mount 246 and a second spring mount 248 joined together by a helical winding 250 that wraps around the drive shaft 222. The first spring mount 246 is connected to the second assembly 216. Referring to FIGS. 4 and 14, the first spring mount 246 includes a portion of a cylindrical half ring shape and a lower end of the damper element 224 includes a generally complementary cylindrical half ring shape. The half ring shapes are joined together around the drive shaft 222 by threaded bolts received in bolt holes 252. In this way, the first spring mount 246 of the torsion spring 212 is rotationally locked with the second assembly 216. The second spring mount 248 is connected to the first assembly 214. The second spring mount 248 includes a cylindrical ring shape that is received within and adjacent to the inner wall of the barrel 202. The cylindrical ring shape and the barrel 202 are joined together by threaded bolts received in bolt holes 254. In this way, the second spring mount 248 of the torsion spring 212 is rotationally locked with the first assembly 214. Accordingly, differentials in angular rotation between the first assembly 214 and the second assembly 216 result in winding or unwinding the torsional spring 212 from a default, zero, and/or resting position. When the external rotational forces are sufficiently reduced, the torsional spring 212 will return the first connector 204 and the second connector 206 to the initial, default, zero, and/or resting relative positions that is selected to additionally return the rotationally sensitive electronics 212 to a known angular location and/or aziumuth. This behavior is also referred to as a return-to-zero behavior or functionality.

In this embodiment, the damper element 224 includes a thin tube 256 at the upper end of the damper element 224 and the first connector 204 includes a cylindrical protrusion 258 at the lower end of the first connector 204. When the torsional isolator 200 is assembled, the damper element 224 is radially captured between the cylindrical protrusion 258 and the interior wall of the barrel 202. In this embodiment, fluid 210 is provided to the annular spaces between the thin tube 256 and the cylindrical protrusion 258. Fluid 210 is also provided to the annular spaces between the thin tube 256 and the barrel 202. Accordingly, differentials in angular rotation between the first assembly 214 and the second assembly 216 result in shearing of the fluid 212, a process that consumes rotational energy and thereby dampens the torsional isolator 200 response. This behavior is also referred to as angular or torsional damping. In this embodiment, the fluid 210 is introduced into the isolator 200 via a fill port 260 that extends centrally and longitudinally from the first connector 204 to spaces in fluid communication with the annular spaces adjacent the thin tube 256. A seal screw 262 is used to seal the fill port 260.

During operations of the hydrocarbon recovery system 100 and the torsional isolator 200, the second assembly 216 is subjected to substantial vibration and shock as the vibration and shock are transmitted from the drillbit 106 and/or other drillstring 102 components. The amplitude of angular or torsional vibration, shock, and/or displacement transmitted from the first assembly to the drillstring 102 is reduced as a function of the resistance of the torsional spring 212 and/or the damper element 224 shearing the fluid 210. In an alternative embodiment (not shown), the positioning of the first assembly 214 and the second assembly 216 on the drillstring 102 may be flipped such that the first assembly 214 is positioned nearer the drillbit 106 than the second assembly 216.

Described another way, the torsional isolator 200 has at least three types and/or sets of interfaces between the first assembly 214 and the second assembly 216. A first set of interfaces are the above-described bearing interfaces. While the types of bearings are described above as including radial bearings, thrust bearings, and needle bearings, any type of bearing capable of being movably secured between an inner cylindrical wall and an outer cylindrical wall and providing for rotation between the first assembly 214 and the second assembly 216 are contemplated by this disclosure. Preferably, the bearings minimize friction between the first assembly 214 and the second assembly 216. The value of reducing the friction is to transmit as little of the shock and vibration as possible from the input side of the damper to an output side, namely, the lower end of the second assembly 216 to the upper end of the first assembly 214. Lower friction also allows the torsional isolator to return the upper and lower ends of the torsional isolator 200 to zero or neutral positions, which are associated with a true azimuth heading of a component of the electronics 212, namely, a directional assembly.

The second type of interface is the torsional spring 222. The torsional isolator has a static position when the tool is at rest. The positioning of the torsional spring 222 creates a centering force for counteracting the rotational forces of second assembly 216. The result is that the first assembly 214 returns to an original position associated with the static position so that as the second assembly 216 is rotated, the first assembly 214 will eventually return to its original static position relative to the second assembly 216. The torsional spring 222 ensures the first assembly 214 returns to the same static position, also referred to as the neutral or zero point rotationally with respect to the second assembly 216. This requirement provides for the electronics 212 to be able to measure a tool face. The tool face is defined as the true azimuth heading of a directional drilling assembly.

Referring now to FIG. 15, a stop-key 262 is comprised of a first key element 264 and a second key element 266. As shown in FIG. 15, the first key element 264 is positioned on the first assembly 214 and the second key element 266 is positioned on the second assembly 216. The first key element 264 and the second key element 266 are capable of preventing a rotation of the second assembly 216 beyond a pre-defined angular limit from a static position. The stop-key 262 and/or the placement of the torsional spring 212 at the first spring 246 mount prevents angular motions of the second assembly 216 beyond a predefined limit. In one embodiment, a tab (not shown) and stop-key 262 are used with the torsional spring 212 to prevent motion beyond the predefined limit. In one embodiment, the predefined limit is about ±120 degrees. In one embodiment, when the second assembly 216 rotates up to about ±120 degrees, the second spring mount 248 functions as a hard stop and contacts a stop-key mounted to the second assembly, thereby preventing any additional rotation. Elastomeric bumpers 268 are provided to soften the contact between the first key element 264 and the second key element 266.

The third type of interface is the damper element 224 which is configured to rotate relative to adjacent components in a manner that shears fluid 210. Each annular cavity, as well as the other cavities, within the torsional isolator is preferably filled with a viscous fluid such as silicone. The viscous fluid is selected for a particular application based upon the viscosity and the desired damping properties. By way of a non-limiting example, the viscosity of the vicious fluid is between about 2,000 centistokes (cSt) to about 60,000 cSt. In the embodiment using silicone fluid, the viscous fluid has a viscosity of about 20,000 cSt. As the first assembly 214 and the second assembly 216 rotate relative to each other, a thin film of viscous fluid adheres to the opposing sides of the damper element 224. The viscous fluid 210 is subjected to shear forces that result in viscous damping of rotational forces. This viscous damping facilitates the return of the torsional isolator 200 to a zero position by using the torsional spring 222.

In this embodiment, the torsional spring 222 is a wire wound spring or a machined spring. The torsional spring 222 works in torsionally and/or angularly alternating directions and allows for plus/minus motion with a single component. This plus/minus motion biases the torsional isolator to the zero position. This is similar to the embodiment discussed herein. In an alternate embodiment, the torsional spring 222 is a wire-coil spring (not shown). In another alternate embodiment, the torsional spring 222 is a two-wire-coil spring (not shown) working in opposing directions, thereby enabling a positive preload to the zero position. In yet another alternate embodiment, a rubber tubeform configuration (not shown) functions as the torsional spring 222 and is combined with one or more of the previously identified embodiments.

In addition to the foregoing embodiments, the torsional isolator 200 allows the electronics 212 to angularly oscillate at a slower rotational velocity than the data acquisition rate of associated sensors, such that the sensors are recording an average value of the azimuth heading. As a result, the average value of the azimuth heading is more accurate than taking an instantaneous reading at the wrong heading as would be the case when electronics and/or sensors are more rigidly coupled to the source of vibration and/or oscillation of the drillstring 102, such as, in a case where no torsional isolator 200 is utilized.

Referring now to FIGS. 16 and 17, another embodiment of a torsional isolator 300 is shown. The torsional isolator 300 is substantially similar to the torsional isolator 200 but the torsional isolator 300 includes no stop-key substantially similar to stop-key 262. Otherwise, the components and features referenced by 304, 314, 302, 354, 318, 320, 316, 306, 308, 362, 360, 310, 334, 336, 324, 346, 312, 348, 350, 322, 344, 340, 342, 328, 320, 356, and 338 represent components and features substantially similar to the components and features of torsional isolator 200 referenced by referenced by 204, 214, 202, 254, 218, 220, 216, 206, 208, 262, 260, 210, 234, 236, 224, 246, 212, 248, 250, 222, 244, 240, 242, 228, 220, 256, and 238, respectively.

Referring now to FIGS. 18-27, the torsional isolator 400 includes a first assembly 414 that is generally torsionally rigid and a second assembly 416 that is also generally torsionally rigid. Rotation of the first assembly 414 relative to the second assembly 416 is damped by shearing the fluids 410. Relative angular displacements of the first assembly 414 relative to the second assembly 416 are resisted and/or decreased by the torsional spring 412. The first assembly 414 includes the barrel 402, the first connector 404, a thrust insert 418, and a centering insert 420. The first connector 404 is partially received within the barrel 402 and is joined to the barrel 402 via a sealed and threaded connection. The thrust insert 418 is received within and joined to the lower end of the barrel 402 via a sealed and threaded connection. The centering insert 420 is received within and joined to the lower end of the thrust insert 418 via a sealed and threaded connection. The second assembly 416 includes the second connector 406, a drive shaft 422, and a damper element 424. The drive shaft 422 is connected to the second connector 406 via a threaded connection and is further captured relative to the second connector 406 using slotted spring pins 426 inserted into holes of the second connector 406 and concavities of the drive shaft 422. The damper element 424 is connected to the upper end of the drive shaft 422 via a Woodruff key 428 captured between a recess 430 of the drive shaft 422 and channel 432 of the damper element 424.

The drive shaft 422 is received through central passages of the centering insert 420, the thrust insert 418, and the torsional spring 412. The upper end of the drive shaft 422 is received within a lower cavity 434 of the first connector 404. Needle bearings 436 are disposed in the lower central cavity 434 between the first connector 404 and the drive shaft 422. The needle bearings 436 serve to maintain a coaxial alignment between the first assembly 414 and the second assembly 416. Radial bearings 438 or ball bearings are captured between the thrust insert 418, the centering insert 420, and the drive shaft 422 to maintain a coaxial alignment between the first assembly 414 and the second assembly 416. Thrust bearings 440 are provided between a shoulder 442 of the drive shaft 422 and adjacent portions of the thrust insert 418 and the thrust bearings 440 are captured by connecting a bearing nut 444 to an upper interior portion of the thrust insert 418. The thrust bearings 440 provide a strong axial load transfer path so that large compressive or tensile loads are fully transmitted through the torsional isolator 400 even while the torsional isolator 400 serves to reduce system energy associated with twisting the torsional isolator 400 about the central longitudinal axis 408. The thrust bearings 440 are particularly useful in transferring axial forces associated with drilling and fishing out drillstring 102 components.

In this embodiment, the torsional spring 412 is joined between the first assembly 414 and the second assembly 416. The torsional spring 412 includes a first spring mount 446 and a second spring mount 448 joined together by a helical winding 450 that wraps around the drive shaft 422. The first spring mount 446 is connected to the second assembly 416 by threaded bolts. In this way, the first spring mount 446 of the torsion spring 412 is rotationally locked with the second assembly 416. The second spring mount 448 is connected to the first assembly 414. The second spring mount 448 includes a cylindrical ring shape that is received within and adjacent to the inner wall of the barrel 402. The cylindrical ring shape and the barrel 402 are joined together by threaded bolts received in bolt holes 454. In this way, the second spring mount 448 of the torsion spring 412 is rotationally locked with the first assembly 414. Accordingly, differentials in angular rotation between the first assembly 414 and the second assembly 416 result in winding or unwinding the torsional spring 412 from a default, zero, and/or resting position. When the external rotational forces are sufficiently reduced, the torsional spring 412 will return the first connector 404 and the second connector 406 to the initial, default, zero, and/or resting relative positions that is selected to additionally return the rotationally sensitive electronics 412 to a known angular location and/or aziumuth. This behavior is also referred to as a return-to-zero behavior or functionality.

In this embodiment, the damper element 424 includes a thin tube 256 at the upper end of the damper element 424 and the first connector 404 includes a cylindrical protrusion 458 at the lower end of the first connector 404. When the torsional isolator 400 is assembled, the damper element 424 is radially captured between the cylindrical protrusion 458 and the interior wall of the barrel 402. In this embodiment, fluid 410 is provided to the annular spaces between the thin tube 456 and the cylindrical protrusion 458. Fluid 410 is also provided to the annular spaces between the thin tube 456 and the barrel 402. Accordingly, differentials in angular rotation between the first assembly 414 and the second assembly 416 result in shearing of the fluid 410, a process that consumes rotational energy and thereby dampens the torsional isolator 400 response. This behavior is also referred to as angular or torsional damping. In this embodiment, the fluid 410 is introduced into the isolator 400 via a fill port 460 that extends centrally and longitudinally from the first connector 404 to spaces in fluid communication with the annular spaces adjacent the thin tube 456. A seal screw 462 is used to seal the fill port 460.

During operations of the hydrocarbon recovery system 100 and the torsional isolator 400, the second assembly 416 is subjected to substantial vibration and shock as the vibration and shock are transmitted from the drillbit 106 and/or other drillstring 102 components. The amplitude of angular or torsional vibration, shock, and/or displacement transmitted from the first assembly to the drillstring 102 is reduced as a function of the resistance of the torsional spring 412 and/or the damper element 424 shearing the fluid 410. In an alternative embodiment (not shown), the positioning of the first assembly 414 and the second assembly 416 on the drillstring 102 may be flipped such that the first assembly 414 is positioned nearer the drillbit 106 than the second assembly 416.

Described another way, the torsional isolator 400 has at least three types and/or sets of interfaces between the first assembly 414 and the second assembly 416. A first set of interfaces are the above-described bearing interfaces. While the types of bearings are described above as including radial bearings, thrust bearings, and needle bearings, any type of bearing capable of being movably secured between an inner cylindrical wall and an outer cylindrical wall and providing for rotation between the first assembly 414 and the second assembly 416 are contemplated by this disclosure. Preferably, the bearings minimize friction between the first assembly 414 and the second assembly 416. The value of reducing the friction is to transmit as little of the shock and vibration as possible from the input side of the damper to an output side, namely, the lower end of the second assembly 416 to the upper end of the first assembly 414. Lower friction also allows the torsional isolator to return the upper and lower ends of the torsional isolator 400 to zero or neutral positions, which are associated with a true azimuth heading of a component of the electronics 412, namely, a directional assembly.

The second type of interface is the torsional spring 422. The torsional isolator has a static position when the tool is at rest. The positioning of the torsional spring 422 creates a centering force for counteracting the rotational forces of second assembly 416. The result is that the first assembly 414 returns to an original position associated with the static position so that as the second assembly 416 is rotated, the first assembly 414 will eventually return to its original static position relative to the second assembly 416. The torsional spring 422 ensures the first assembly 414 returns to the same static position, also referred to as the neutral or zero point rotationally with respect to the second assembly 416. This requirement provides for the electronics 412 to be able to measure a tool face. The tool face is defined as the true azimuth heading of a directional drilling assembly. A stop-key 462 substantially similar to stop-key 262 is provided. The stop-key 462 and/or the placement of the torsional spring 412 at the first spring mount 446 prevents angular motions of the second assembly 416 beyond a predefined limit. In one embodiment, a tab (not shown) and stop-key 462 are used with the torsional spring 412 to prevent motion beyond the predefined limit In one embodiment, the predefined limit is about ±120 degrees. In one embodiment, when the second assembly 416 rotates up to about ±120 degrees, the second spring mount 448 functions as a hard stop and contacts a stop-key mounted to the second assembly, thereby preventing any additional rotation.

Referring now to FIG. 27, a first difference between torsional isolator 400 and torsional isolators 200,300 is that the lower end of the damper element 424 is located relatively higher and is bolted to a longitudinal spacer 425 by threaded bolts. Referring now to FIGS. 21-26 Another difference between torsional isolator 400 and torsional isolators 200,300 is that the longitudinal length of the thrust insert 418 is significantly longer, thereby lengthening an annular space within the thrust insert 418 as well as lengthening the overall longitudinal length of the torsional isolator 400.

One or more of the torsional isolators 200, 300, 400 and/or alternative embodiments disclosed herein may comprise a spring rate (K) of 0.6 in*lb/degrees and a damping coefficient (C) of 0.05 in*lb*sec/degrees at a design frequency of about 5-7 Hz and a design amplitude of about 10-15 degrees for hydrocarbon recovery systems utilizing a single torsional isolator. One or more of the torsional isolators 200, 300, 400 and/or alternative embodiments disclosed herein comprise a spring rate (K) of 0.3 in*lb/degrees and a damping coefficient (C) of 0.03 in*lb*sec/degrees at a design frequency of about 5-7 Hz and a design amplitude of about 10-15 degrees for hydrocarbon recovery systems utilizing two torsional isolators. One or more of the torsional isolators 200, 300, 400 and/or alternative embodiments disclosed herein may alternatively comprise a spring rate (K) of 0.7 in*lb/degrees (static) and 0.4+/−0.1 in*lb/degrees (dynamic) and a damping coefficient (C) of 0.06+/−0.01 in*lb*sec/degrees at a design frequency of about 0.1-10 Hz and a design amplitude of about 0.5-14.7 degrees for hydrocarbon recovery systems utilizing a single torsional isolator.

Referring now to FIG. 28, a graph of degrees of rotation versus time is provided that compares a larger input angular drive envelope to a smaller output angular driven envelope. The graphed data is useful for calculating a root mean square (RMS) input value of 0.70 degrees and a RMS output value of 0.47 degrees which is approximately a 33% reduction in angular rotation. In some embodiments, an RMS reduction of up to about 50%.

In some embodiments, peak amplitude angular displacement reductions of about 20-60% are contemplated. In some embodiments, the general operating conditions of a torsional isolator disclosed herein include operating pressures of about 20,000 psi, temperatures of about 350 degrees Fahrenheit, and fishing loads of about 20,000 lb.

Referring now to FIG. 29, a graph of degrees of rotation versus time is provided that demonstrates that the angular location of the torsional isolators disclosed herein may, as viewed on the graph, remain centered on the vibratory input while drilling is taking place. Once drilling and/or vibratory input ceases, the torsional isolators angularly return to zero locations and/or orientations.

In some embodiments, fluids such as fluid 210 may leak from the torsional isolators disclosed herein as a result of the fluid expanding to due increased operation temperatures as compared to the temperatures at which the fluid was inserted into the torsional isolators. In some embodiments, it is contemplated that the torsional isolators disclosed herein be refilled with fluid after being fished out and/or after a set number of hours of operation, such as 250 hours.

In some embodiments, the phrase “an upper end” refers to a first end and the phrase “a lower end” refers to as a second end. It will be appreciated that any of the torsional isolators 300, 400, and/or alternative embodiments of torsional isolators disclosed herein may be utilized in place of and/or in addition to the torsional isolator 200 of the hydrocarbon recovery system 100. Further, multiple torsional isolators of the same or different type may be utilized in a hydrocarbon recovery system 100 or other drilling and/or directional drilling system.

Other embodiments of the current invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. Thus, the foregoing specification is considered merely exemplary of the current invention with the true scope thereof being defined by the following claims.

Claims

1. A torsional isolator for a drillstring, wherein the torsional isolator is positioned in the drillstring between electronics of the drillstring and a drillbit of the drillstring, the torsional isolator comprising: a first assembly, the first assembly having a first end, a second end, at least one annular cavity, and a first spring mount, wherein the first end is joined to the interconnect opposite of the electronics housing and is proximate the drillstring electronics;a second assembly, the second assembly having a first end, a second end, and a second spring mount, wherein the second assembly is movably disposed within the first assembly and has the second end positioned proximate to the drillbit, wherein the second spring mount is interiorly positioned within one of the at least one annular cavities;at least one bearing, wherein the bearing is movably secured between an inner wall of the first assembly and an outer wall of the second assembly and provides for rotation therebetween;a torsional spring having a first end and a second end, wherein the first end is affixed to the first spring mount and the second end is affixed to the second spring mount;a stop-key having a first key element and a second key element, wherein the first key element is positioned on the first assembly and the second key element positioned on the second assembly, and wherein the first key element and the second key element are capable of preventing a rotation of the second assembly beyond a pre-defined limit from a static position;a damper element affixed to the second assembly and positioned proximate the inner wall of the first assembly; anda viscous fluid filling the annular cavity, wherein the viscous fluid provides viscous damping by having a thin film of viscous fluid adhering to the damper element as the first assembly and second assembly rotate relative to each other.

2. The torsional isolator of claim 1, wherein the predefined limit is ±120 degrees.

3. The torsional isolator of claim 1, further comprising at least three bearings.

4. The torsional isolator of claim 3, wherein at least one of the bearings is a radial bearing.

5. The torsional isolator of claim 3, wherein at least one of the bearings is a thrust bearing.

6. The torsional isolator of claim 3, wherein at least one of the bearings is a needle bearing.

7. A torsional isolator for a directional drilling tool having at least a electronics housing, at least one interconnect and a drillbit, the electronics housing contains at least a drillstring electronics and is joined with the interconnect, wherein the drillbit is oppositely positioned from the drillstring electronics on the directional drilling tool, the torsional isolator comprising: a first assembly, the first assembly having a first end, a second end, at least one annular cavity, and a first spring mount, wherein the first end is positioned proximate to the drillbit;a second assembly, the second assembly having a first end, a second end, and a second spring mount, wherein the second assembly is movably disposed within the first assembly and the second end is joined to the interconnect opposite of the electronics housing and is proximate the drillstring electronics, wherein the second spring mount is interiorly positioned within one of the at least one annular cavities;at least one bearing, wherein the bearing is movably secured between an inner wall of the first assembly and an outer wall of the second assembly and provides for rotation therebetween;a torsional spring having a first end and a second end, wherein the first end is affixed to the first spring mount and the second end is affixed to the second spring mount;a stop-key having a first key element and a second key element, wherein the first key element is positioned on the first assembly and the second key element positioned on the second assembly, and wherein the first key element and the second key element are capable of preventing a rotation of the second assembly beyond a pre-defined limit from a static position;a damper element affixed to the second assembly and positioned proximate the inner wall of the first assembly; anda viscous fluid filling the annular cavity, wherein the viscous fluid provides viscous damping by having a thin film of viscous fluid adhering to the damper element as the first assembly and second assembly rotate relative to each other.

8. The torsional isolator of claim 7, wherein the predefined limit is ±120 degrees.

9. The torsional isolator of claim 7, further comprising at least three bearings.

10. The torsional isolator of claim 9, wherein at least one of the bearings is a radial bearing.

11. The torsional isolator of claim 9, wherein at least one of the bearings is a thrust bearing.

12. The torsional isolator of claim 9, wherein at least one of the bearings is a needle bearing.

13. A torsional isolator for a drillstring, wherein the torsional isolator is positioned in the drillstring between electronics of the drillstring and a drillbit of the drillstring, the torsional isolator comprising: a first assembly, the first assembly having a first end, a second end, at least one annular cavity, and a first spring mount, wherein the first end is joined to the interconnect opposite of the electronics housing and is proximate the drillstring electronics;a second assembly, the second assembly having a first end, a second end, and a second spring mount, wherein the second assembly is movably disposed within the first assembly and has the second end positioned proximate to the drillbit, wherein the second spring mount is interiorly positioned within one of the at least one annular cavities;at least one bearing, wherein the bearing is movably secured between an inner wall of the first assembly and an outer wall of the second assembly and provides for rotation therebetween;a torsional spring having a first end and a second end, wherein the first end is affixed to the first spring mount and the second end is affixed to the second spring mount;a damper element affixed to the second assembly and positioned proximate the inner wall of the first assembly; anda viscous fluid filling the annular cavity, wherein the viscous fluid provides viscous damping by having a thin film of viscous fluid adhering to the damper element as the first assembly and second assembly rotate relative to each other.