Steering pad overextension prevention for rotary steerable system

Abstract

A steering head for steering a drill string may include a pad pusher including a steering pad and a piston. The steering pad may have a pivot axis, and be rotatable about the pivot axis between retracted and extended positions. The pad pusher may further include a motion restrictor to restrict rotation about the pivot axis. The steering head may further include a housing having a motion restrictor disposed at a position corresponding to the pad pusher motion restrictor. The pad pusher motion restrictor may be engageable with the housing motion restrictor to restrict motion of the steering pad relative to the housing.

Description

STEERING PAD OVEREXTENSION PREVENTION FOR ROTARY STEERABLESYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. § 119 to Provisional Application No.62 / 612,173 filed on December 29,2017, in the United States Patent and Trademark Office.TECHNICAL FIELDThe present disclosure generally relates to oilfield equipment and, in particular, to

[0002] downhole tools, drilling and related systems for steering a drill bit. More particularly still, thepresent disclosure relates to methods and systems for preventing overextension of the steeringpads of a downhole tool.BACKGROUND

[0003] Drilling wellbores in a subterranean formation usually reqmres controlling atrajectory of the drill bit as the wellbore is extended through the formation. The trajectory controlcan be used to steer the drill bit to drill vertical, inclined, horizontal, and lateral portions of awellbore. In general the trajectory control can direct the drill bit into and / or through productionzones to facilitate production of formation fluids, direct the drill bit to drill a portion of awellbore that is parallel to another wellbore for treatment or production assist, direct the drill bitto intersect an existing wellbore, as well as many other wellbore configurations.

[0004] Therefore, it will be readily appreciated that improvements in the arts of preventingagainst overextension of the steering pads, so as to prevent the steering pads from becomingloose or completely coming apart during drilling operations, are continually needed.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The following figures are induded to illustrate certain aspects of the presentdisclosure, and should not be viewed as exclusive embodiments. The subject matter disclosed iscapable of considerable modifications, alterations, combinations, and equivalents in form andfunction, without departing from the scope ofthis disclosure.1

[0006] Figure 1 illustrates a partial cross-sectional view of an onshore well system includinga downhole tool illustrated as part of a tubing string, according to some embodiments of thepresent disclosure.

[0007] Figure 2 illustrates a sectional view of the exemplary downhole tool of Figure 1,including a steering head, according to some embodiments of the present disclosure.

[0008] Figure 3 illustrates a perspective side view of the exemplary downhole tool of Figure2.[0009) Figure 4A illustrates a perspective sectional view of an exemplary embodiment of asteering head including a rotatable pad pusher, according to some embodiments.

[0010] Figure 4B illustrates a sectional view of the exemplary steering head of Figure 4A,including a pad pusher disposed in a fully retracted position, according to some embodiments.

[0011] Figure 4C is an exploded view of a steering pad of the exemplary steering head of Figure 4B, including motion-limiting protrusions and retaining recesses, according to someembodiments.Figure SA illustrates a perspective sectional view of an exemplary embodiment of a

[0012] steering head including a rotatable pad pusher, according to some embodiments.[0013) Figure SB illustrates a sectional view of the exemplary steering head of Figure SA,including a pad pusher disposed in a partially extended position, according to someembodiments.

[0014] Figure SC is an exploded view of a steering pad of the exemplary steering head ofFigure SB, including motion-limiting protrusions and retaining recesses, according to someembodiments.

[0015] Figure 6A illustrates a perspective sectional view of an exemplary embodiment of asteering head including a rotatable pad pusher, according to some embodiments.

[0016] Figure 6B illustrates a sectional view of the exemplary steering head of Figure 6A,including a pad pusher disposed in a fully retracted position, according to some embodiments.

[0017] Figure 6C is an exploded view of a steering pad of the exemplary steering head ofFigure 6B, including motion-limiting protrusions and retaining recesses, according to someembodiments.2DETAILED DESCRIPTION

[0018] The disclosure may repeat reference numerals and / or letters in the various examplesor Figures. This repetition is for the purpose of simplicity and clarity and does not in itself dictatea relationship between the some embodiments and / or configurations discussed.

[0019] The present disclosure further relates to methods and systems for preventing overextension of steering pads of a rotary steerable tool during drilling operations downhole.Generally, the present disclosure describes a rotary steerable tool for steering a drill stringincluding a steering head that can include a stop mechanism for preventing overextension of thesteering pads. This can be achieved by restricting a rotational motion of the steering about apivot axis of the steering pad. It is advantageous to restrict rotation of the steering pads aboutthe pivot axis to prevent the steering pads from pivoting too far past the fully extended position to a point where the piston is displaced out of the piston bore. The present disclosure providessystems and methods for restricting rotation of the steering pads, as discussed in further detailbelow.

[0020] In order to prevent the steering pads from extending to the point that the pistonbecomes displaced or separated from the piston liner, an extension-limiting mechanism can beprovided which acts as a stop to restrict rotation of the steering pads past a desired point. Theextension-limiting mechanism can prevent or minimize loss of various components of thesteering head downhole, which may not otherwise be retrievable.

[0021] According to some embodiments of the disclosure, the pad pusher includes first andsecond motion-limiting protrusions extending laterally from side faces of the steering pad. Thesteering pad may be rotationally coupled to a housing about a pivot axis of the steering pad. Thehousing may have a retaining recess extending through each of an uphole and a downhole sidethereof. In some embodiments, each retaining recess extends partially through a cross-section ofthe housing at the respective uphole and downhole sides. In other embodiments, each retainingrecess extends all the way through a cross-section of the housing at the respective uphole and downhole sides. The retaining recesses may be disposed at a position aligned with the respective first and second motion-limiting protrusions to receive the respective first and second motion-limiting protrusions therein. When the piston is actuated, a corresponding force is transferred tothe steering pad. In some embodiments the steering pad is integrally formed with the piston as asingle, continuous body or material. In other embodiments, the piston is otherwise coupled to3steering pad. Thus the steering pad and the piston can move together along the same curvedpath. Motion of the steering pad and the piston, i.e., the pad pusher, causes a correspondingmotion of the first and second motion-limiting protrusions within the respective retainingrecesses. Thus, rotation of the first and second motion-limiting protrusions is limited to a crosssectional area of the retaining recesses. Accordingly, rotation of the steering pads, which may beintegrally formed with the first and second motion-limiting protrusions, is restricted to the extentthe first and second motion-limiting protrusions rotate in the retaining recesses. As such, someembodiments of the present disclosure advantageously provide methods and apparatus forpreventing overextension of the steering pads by limiting rotation of the pads about the pivotaXIS.

[0022] Figure 1 shows a representative elevation view in partial cross-section of an onshorewell system 10 which can include a drilling rig (or derrick) 22 at the surface 16 used to extend atubing string 30 into and through portions of a subterranean earthen formation 14. The tubingstring 30 can carry a drill bit 102 at its end which can be rotated to drill through the formation14. A bottom hole assembly (BHA) 101 interconnected in the tubing string 30 proximate the drillbit 102 can include components and assemblies (not expressly illustrated in Figure 1), such as,but not limited to, logging while drilling (LWD) equipment, measure while drilling (MWD)equipment, a bent sub or housing, a mud motor, a near bit reamer, stabilizers, steering assembliessuch as a rotary steerable tool, a drill bit 102, and other downhole instruments. The BHA 101 canalso include a downhole tool 100 that can provide steering to the drill bit 102, mud-pulsetelemetry to support MWD / L WD activities, stabilizer actuation through fluid flow control, and near bit reamer control through fluid flow control. Steering of the drill bit 102 can be used tofacilitate deviations 44 as shown in FIGS. 1 and 2, and / or steering can be used to maintain asection in a wellbore 12 without deviations, since steering control can also be needed to preventdeviations in the wellbore 12.

[0023] At the surface location 16, the drilling rig 22 can be provided to facilitate drilling thewellbore 12. The drilling rig 22 can include a turntable 26 that rotates the tubing string 30 and the drill bit 102 together about the longitudinal axis XI. The turntable 26 can be selectivelydriven by an engine 27, and selectively locked to prohibit rotation of the tubing string 30. Ahoisting device 28 and swivel 34 can be used to manipulate the tubing string 30 into and out ofthe wellbore 12. To rotate the drill bit 102 with the tubing string 30, the turntable 26 can rotate4the tubing string 30, and mud can be circulated downhole by mud pump 23. The mud may be a calcium chloride brine mud, for example, which can be pumped through the tubing string 30 andpassed through the downhole tool100. In some embodiments, the downhole tool 100 can includea steering head, and a rotary valve that selectively applies pressure to at least one output flowpath to hydraulically actuate the steering head. Additionally, the mud, if used above the rotarysteerable tool and drill bit, can be pumped through a mud motor (not expressly illustrated inFigure 1) in the BHA 101 to turn the rotary steerable tool and the drill bit 102 without having torotate the tubing string 30 via the turntable 26.

[0024] Figure 2 illustrates a sectional view of the exemplary downhole tool of Figure 1,having a drill string steering system including a steering head, according to some embodimentsof the present disclosure. Figure 3 illustrates a perspective side view of the exemplary downholetool of Figure 2. According to various embodiments of the present inventions, the drill stringsystem 200 includes a steering head 218 including one or more pad pushers 223. AlthoughFigure 2 depicts one pad pusher 223, the disclosed embodiments are not limited to thisconfiguration. In some embodiments, as shall be later described, the steering head includes twopad pushers 223 (as illustrated in Figure 3), and in other embodiments, three or more pad pushers223. Each of the pad pushers 223 includes a steering pad 220 and a piston 224. As depicted, thesteering pad 220 and the piston 224 may be coupled to each other using any suitable couplingmechanism. In some embodiments, the steering pad 220 and the piston 224 may be integrallyformed as a single continuous body or material. In yet other embodiments, however, the piston224 and the steering pad 220 may be separate components, with the piston 224 being actuatableto contact and move the steering pad 220 to push against the earth 102 to provide the desireddrilling vector. As depicted in Figures 2 and 3, hydraulic fluid 203, e.g. mudflow flows into thedrill string steering system 200 from the uphole end and passes through the central bore 212 to arotary valve 230 and a flow manifold 240 to control mud flow to actuate the piston 224 whichthen operates to extend the steering pad 220.

[0025] As depicted, the steering head 218 is configured with a channel or bore 226 in whichthe piston 224 reciprocates upon being hydraulically or otherwise actuated. In someembodiments, the piston channel or bore 226 may be a linear channel or bore. In yet otherembodiments, the piston channel or bore 226 in which the piston 224 reciprocates may be acurved channel or bore.5As the mud flows through the central bore 212, the mud can flow through a turbine

[0026] 250 and past an electric generator, steering controller and motor assembly 260 used to control theangular position of the rotary valve 230. In the depicted example, mudflow 203 can pass througha filter screen 280 prior to passing through the rotary valve 230 and the flow manifold 240. Thefilter screen 280 can include apertures or openings sized to allow the flow of mud whilepreventing debris from passing through the flow manifold 240 and to components downstream ofthe flow manifold 240 to prevent obstruction and damage to the downstream components. Thefilter screen 280 can be formed from a metallic or ceramic perforated cylinder or mesh or anyother suitable filter material.

[0027] In the depicted example, the rotary valve 230 and the flow manifold 240 regulate orcontrol the flow of the mud there through to control the extension of the steering pads 220. Insome embodiments, the rotation of the rotary valve 230 abutted against the flow manifold 240controls the flow of mud through the flow manifold 240. The rotary valve 230 is rotated by amotor 264 within an electric generator, steering controller and electric motor assembly 260.

[0028] In the depicted example, as mud flow is permitted by the rotary valve 230, the mudflow can continue in a piston flow channel242 of the flow manifold 240. In some embodiments,a piston flow channel 242 can pass through the flow manifold 240 and the tool body 210 toprovide mud flow to the piston channel or bore 226. In the depicted example, the tool bodyincludes one piston bore 226. However, as shall be illustrated and described in the variousembodiments of the present disclosure, the tool body 210 can include one or more piston bores226 formed in the tool body 210. In some embodiments, the piston bores 226 are disposedwithin a pad retention housing 221 formed within the tool body 210. In the depicted example,mud flow from the piston flow channel 242 is received by the piston bore 226 and the pistonseals 228 to actuate and extend the piston 224. As illustrated, the steering pad 220 is integrallyformed with the piston 224. However, as previously discussed, the steering pad 220 and thepiston 224 may be separately formed and otherwise coupled. As described herein, thecombination of the steering pad 220 and the piston 224, whether being formed as separate partsthat are coupled together, or being formed as a part of a single, continuous body, shall be referredto as a pad pusher 223. The pad pusher 223 may be actuated by the mud flow provided throughthe piston flow channel 242, to extend the steering pad 220 radially outward against the wall ofthe wellbore 12.6

[0029] Pressure against the piston 224 can be relieved by a relief flow channel 222 formedthrough the pad pusher 223. Mud flow can pass through the relief channel 222 to allow formaintaining or reducing pressure upon the piston 224 to facilitate the retraction of the piston 224when the rotary valve 230 has closed mud flow to that piston.

[0030] In some embodiments, the mud flow can bypass the filter screen 280 and the flowmanifold 240 to continue through the central bore 212 as a bypass flow 214. The bypass flow214 can continue through the downhole end 204 of the drill string steering system 200 and canbe directed to the bit nozzles 113 of the drill bit 102 to be circulated into an annulus of thewellbore 12.In the depicted example, the motor 264 is an electrical motor that can be controlled to

[0031] rotate the rotary valve 230 as desired to provide a desired drilling vector. In the depictedexample, the motor 264 is contained within a motor housing 262 and rotates the rotary valve 230via a motor shaft 270. In some embodiments, the motor 264 maintains the rotary valve 230 in ageostationary position as needed.

[0032] In the depicted example, components of the electric generator, steering controller and electric motor assembly 260 can be disposed, surrounded, bathed, lubricated, or otherwiseexposed to a lubricant 265 within the motor housing 262 while many of the controller electroniccomponents are protected in a pressure barrier cavity (not shown). In some embodiments thelubricant 265 is oil that is isolated from the mud within the wellbore. In the depicted example,the pressure of the lubricant 265 can be balanced with the downhole pressure of the mud. Insome embodiments, a compensation piston 266 can pressurize the lubricant 265 to the samepressure as the surround mud without allowing fluid communication or mixing of the mud andthe lubricant 265. In some embodiments, a biasing spring 268 can act upon the compensationpiston 266 to further provide additional pressure to the lubricant 265 within the motor housing262 relative to the pressure of the mud. The biasing spring 268 can impart around 25 psi ofadditional pressure, over the mud pressure, to the lubricant 265 within the motor housing 262. Insome embodiments, electrical energy for the motor 264 is generated by mud flow passingthrough the turbine 250. In some embodiments, the turbine 250 can rotate about a turbine shaft252 and power an electric generator.

[0033] In the depicted embodiments, the steering pad 220 and the piston 224 are integrallyformed. However, as previously discussed, the steering pad 220 and the piston 224 may be7separately formed and otherwise coupled. The term "integrally f ormed" can refer to aconfiguration in which the steering pad 220 and the piston 224 are formed as a single, continuousbody or material. Thus, the steering pad 220 and the piston 224 move together along the samepath. In some embodiments the path is a curved path which is defined by a curved piston linerdefining the piston bore 226. In other embodiments, the piston channel or bore 226 may be alinear channel or bore. Thus, as depicted in Figure 2, the piston 224 is actuated by the hydraulicfluid 203, e.g., pressurized mud flow, thereby causing the piston 224 and the steering pad 220which move as an integral part, to move along the path defined by the piston liner. In someembodiments, the steering pad 220 can have a semi-circular cross-sectional profile.

[0034] In the example illustrated in Figure 2, the pad pusher 223 is actuated by receivingmudflow 203 in the piston bore 226 from the piston flow channel 242. A piston seal 228 preventsthe migration of fluid out of the piston bore 226. As the pad pusher 223 extends, the steering pad220 can pivot about pivot coupling 227 relative to the tool collar 211.

[0035] Figure 4A illustrates a perspective sectional view of an exemplary embodiment of asteering head 218 including a rotatable pad pusher 223, according to some embodiments. In thedepicted embodiments, the steering head 218 includes a plurality of pad pushers 223 mountedonto or about the collar 211. Although two pad pushers are depicted in Figure 4A, the steeringhead 218 is not limited to this configuration and may include only one pad pusher 223, or morethan two pad pushers 223. In some embodiments, the steering head 218 includes one or morepad retention housings 221. Although two pad retention housings 221 are depicted in Figure 4A,the steering head 218 is not limited to this configuration and may include only one pad retentionhousing 221 or more than two pad retention housings 221. As illustrated in Figure 4A, each pad retention housing 221 may be mounted onto the collar 211 using fasteners 318. The fasteners 318may be positioned through each of the pad retention housings 221 to couple the pad retentionhousings 221 to each other around and / or through the collar 211. As also illustrated in Figure4A, each of the pad pushers 223 can be mounted to the collar 211 via a respective pad retentionhousing 211. That is, since each of the pad pushers 223 are directly, pivotally coupled to arespective housing 221, each pad pusher 223 is thus indirectly coupled to the collar 211 throughthe pad retention housings 221.

[0036] Figure 4B illustrates a sectional view of the exemplary steering head 218 of Figure4A, including a pad pusher 223 disposed in a fully retracted position, according to some8embodiments. As illustrated, the pad pusher 223 includes a steering pad 220 and a piston 224.The steering pad 220 has an uphole side 402, a downhole side 404, and a pivot axis. The pivotaxis can extend through a rotational center of the pivot coupling 227. The pad pusher 223 maythus be rotatable about the pivot axis between retracted and extended positions, and includes a motion restrictor 408 to restrict rotation about the pivot axis. As depicted the steering head 218further includes a housing 221 having a motion restrictor 410 disposed at a positioncorresponding to the pad pusher motion restrictor 408. Thus, the pad pusher motion restrictor408 may be engageable with the housing motion restrictor 410 to restrict motion of the steeringpad 220 relative to the housing 221.[0037) In the depicted embodiments, the pad pusher motion restrictor 408 includes a firstmotion restrictor 408A at an uphole side, and a second motion restrictor 408B at a downhole sideof the pad pusher 223. The housing motion restrictor 410 similarly includes a first motionrestrictor 41OA at an uphole side 21OA, and a second motion restrictor 41OB at a downhole side210B of the housing 210. Thus, the first motion restrictor 408A of the pad pusher 223 mayengage the first motion restrictor 41OA of the housing 210, and the second motion restrictor408B of the pad pusher may engage the second motion restrictor 41OB of the second housing torestrict the motion of the steering pad 220 relative to the housing 221.

[0038] The first motion restrictor 408A of the pad pusher 223 may either be a first motion-limiting protrusion or a first retaining recess. Accordingly, the first motion restrictor 41OA of thehousing may either be a first retaining recess corresponding to the first motion-limitingprotrusion of the pad pusher 223, or a first motion-limiting protrusion corresponding to the firstretaining recess of the pad pusher 223. Similarly, the second motion restrictor 408B of the padpusher 223 may either be a second motion-limiting protrusion or a second retaining recess.Accordingly, the second motion restrictor 41OB of the housing 221 may either be a secondretaining recess corresponding to the second motion-limiting protrusion of the pad pusher 223, ora second motion-limiting protrusion corresponding to the second retaining recess of the padpusher 223. In some embodiments, the first and second motion restrictors of the housing maybe first and second motion-limiting protrusions respectively, extending laterally from therespective uphole and downhole sides 221A and 221B ofthe housing 221. Accordingly, the firstand second motion restrictors of the pad pusher 223 may be first and second retaining recessesextending laterally through the respective uphole and downhole sides 221A and 221B of the9housing 221. Thus, the first and second retaining recesses are configured to receive therespective first and second motion-limiting protrusions therein.

[0039] In other embodiments, as depicted in Figures 4A-4C, the first and second motionrestrictors of the pad pusher 223 are first and second motion-limiting protrusions 408A and408B, extending laterally from the respective uphole and downhole sides of the pad pusher.Accordingly, the first and second motion restrictors of the housing are first and second retainingrecesses 41OA and 41OB respectively, configured to r eceive the respective first and secondmotion-limiting protrusions 408A and 408B therein. As depicted, the first motion-limitingprotrusion 408A extends laterally from the steering pad uphole side 402. Further, a second motion-limiting protrusion 408B extends laterally from the steering pad downhole side 404. The first andsecond motion-limiting protrusions 408A, and 408B may be formed at positions mirroring eachother, on opposite faces or sides of the steering pad 220. That is, the first and second motion-limiting protrusions 408A, and 408B may be disposed on either side of a plane which extendsthrough a center of the steering pad 220 in in a direction orthogonal to an uphole- downholedirection. In the depicted embodiments, each of the first and second motion-limiting protrusions408A and 408B are integrally fanned with the pad pusher 223. That is, the pad pusher 223 andthe first and second motion-limiting protrusions 408A, and 408B are formed as a single,continuous body or material. However, the various embodiments described herein are not limitedto the aforementioned configuration. In other embodiments, each of the first and second motion-limiting protrusions 408A and 408B may each be fixedly coupled or fastened to the pad pusher223.

[0040] In the illustrated embodiments, cross-section of each of the first and second motion-limiting protrusions 408A, and 408B tapers in size along a plane orthogonal to an uphole-downhole direction of the steering pad 220. In particular, as illustrated for example, in Figure4C, a cross-sectional height h of each of the first and second motion-limiting protrusions 408A,and 408B diminishes in size along the plane orthogonal to an uphole-downhole direction of thesteering pad 220. Referring to Figure 4C, for example, each of the first and second motion-limiting protrusions 408A, and 408B have a first edge 416, and a second edge 418 positionedparallel to the first edge. In the depicted examples, the second edge is positioned below the firstedge 416, however, the various embodiments described herein are not limited to theaforementioned configuration. Each of the first and second motion-limiting protrusions 408A,10and 408B may further include and a third angularly oriented edge 420 coupled to at least one ofthe first and second edges. In the depicted examples, the third edge 420 is angularly orientedwith respect to the first and second edges, however, the various embodiments described hereinare not limited to the aforementioned configuration. The tapering shape of the first and secondmotion-limiting protrusions 408A, and 408B is defined by the angular orientation of the thirdedge 420 with respect to the first and second parallel edges 416, and 418.

[0041] As illustrated in Figure 4B, the housing 221 couples the steering pad 220 of the padpusher 223 to the tool collar 211. The housing 221 has a first retaining recess 41OA extendingthrough a cross-section of the uphole side 221A of the housing 221. The first retaining recess41OA is configured to receive the first motion-limiting protrusion 408A of the pad pusher 223therein. Similarly, the housing 221has a second retaining recess 410B extending through a cross-section of the downhole side 221B of the housing 221. In the same manner as the first retainingrecess with respect to the uphole side 221A of the housing 221, the second retaining recess 41OBis configured to receive the second motion-limiting protrusion 408B of the pad pusher 223therein. To this effect, the shapes of each of the first and second retaining recesses 410A and41 OB are designed so as to allow the first and second motion-limiting protrusions 408A, and408B to rotate freely therein from a position of full retraction (illustrated in Figure 4C), to aposition of full acceptable extension (illustrated in Figure 6C), as will be discussed in furtherdetail below. The term "full acceptable extension" or as "full extension" can refer to a full extentto which the steering pad 220 can be pivoted outwards with respect to a central axis of the tool collar 211 without the piston 224 being displaced out of the piston bore 226.

[0042] As illustrated, for example in Figures 4B and 4C, each of the first and secondretaining recesses 41OA and 41OB may have a trapezoidal shaped cross-section, with top edge422 and the bottom edge 424 thereof being parallel to each other. In some embodiments, thetrapezoidal shape may be a rectangular shape. In yet other embodiments, the trapezoidal shapemay be a square shape. The aforementioned configuration, however, is not limited thereto. Thefirst and second recesses retaining recesses 41OA and 41OB may have any shape capable ofallowing the respective first and second motion-limiting protrusions 408A and 408B to rotatefreely therein within the bounds of full retraction and full acceptable extension.

[0043] For example, in some embodiments, each of the first and second recesses retainingrecesses 41OA and 41OB may have a shape corresponding to a profile, full or partial, such as a11top or bottom, of the respective first and second motion-limiting protrusions 408A and 408B. Inother embodiments, the first and second recesses retaining recesses 41OA and 41OB may have a shape larger in cross-sectional profile than that of the corresponding first and second motion-limiting protrusions 408A and 408B. This would allow the first and second motion-limitingprotrusions 408A and 408B to rotate therein. As shall be described below in further detail,shapes or profiles of the first and second recesses retaining recesses 41OA and 41OB may bedesigned so as to restrict motion of the steering pad relative to the housing 221. Thus, motion ofthe steering pad relative to the housing 221 may be restricted by each of the first and secondmotion-limiting protrusions 408A and 408B contacting the housing 221.

[0044] Operation of the steering pad overextension prevention mechanism of someembodiments of the present disclosure will now be described below in further detail.

[0045] Figure 4C is an exploded view of a steering pad 220 of the exemplary steering head218 of Figure 4B, including motion-limiting protrusions 408A and 408B, and retaining recesses41OA and 41OB, according to some embodiments. As described above, the retaining recesses41OA and 41OB are formed with a shape or profile configured to receive the respective first andsecond motion-limiting protrusions 408A and 408B therein. As illustrated in Figure 4C, in thefully retracted position of the pad pusher 223, the third edge 420 of each of the first and secondlimiting protrusions 408A and 408B is positioned parallel to the bottom edge 424 of therespective first and second retaining recesses 41OA and 41OB. In the depicted example, the thirdedge 420 of each of the first and second limiting protrusions 408A and 408B is seated on thebottom edge 424 ofthe respective first and second retaining recesses 410A and 410B in the fully retracted position. However, the various embodiments described herein are not limited to theaforementioned configuration. In some embodiments, a gap may exist between the third edge420 of each of the first and second limiting protrusions 408A and 408B and the bottom edge 424of the respective first and second retaining recesses 41OA and 41OB in the fully retractedposition. The pad pusher 223 may be in the fully retracted position, for example, before thepiston 224 is actuated for steering the downhole tool. The pad pusher 223 may also be in thefully retracted position, for example, when the tool is moving downhole in a straight line whereminimal to no steering is necessary.

[0046] Figure SA illustrates a perspective sectional view of an exemplary embodiment of a steering head 218 including a rotatable pad pusher 223, according to some embodiments. Figure125B illustrates a sectional view of the exemplary steering head 218 of Figure SA, including thepad pusher 223 disposed in a partially extended position, according to some embodiments.Figure 5C is an exploded view of a steering pad of the exemplary steering head of Figure 5B, including motion-limiting protrusions 408A and 408B and retaining recesses 41OA and 410B,according to some embodiments.

[0047] In operation, the pad pusher 223 may be actuated by applying of hydraulic fluid (e.g.,mud flow described above with respect to Figure 2) to the piston 224. This causes the piston 224to move up the piston bore 226 along the curved piston liner. Motion of the piston 224 along thepiston liner causes a corresponding rotation of the integrally formed steering pad about the pivot axis. Figure 5C illustrates a configuration in which the pad pusher 223 is in a partially extendedposition. The partially extended position is a position between the fully retracted and the fullyextended positions. When the steering pad 220 rotates as a result of the piston force, which canbe exerted on the piston by pressure of mud against the piston in a direction of extension, thefirst and second motion-limiting protrusions 408A and 408B rotate within the respectiveretaining recesses 41OA and 41OB, along a same path of curvature as the steering pad 220. Thus,the orientation of first and second motion-limiting protrusions 408A and 408B within therespective retaining recesses 41OA and 41OB changes from the illustration in Figure 4C to that inFigure 5C. Because the pad pusher 223 has not yet reached the limit of full acceptableextension, the first and second motion-limiting protrusions 408A and 408B may continue torotate freely within the respective retaining recesses 41OA and 41OB.

[0048] Figure 6A illustrates a perspective sectional view of an exemplary embodiment of a steering head 218 including a rotatable pad pusher 223, according to some embodiments. Figure6B illustrates a sectional view of the exemplary steering head of Figure 6A, including a padpusher 223 disposed in a fully retracted position, according to some embodiments. Figure 6C isan exploded view of a steering pad of the exemplary steering head of Figure 6B, includingmotion-limiting protrusions and retaining recesses, according to some embodiments. Figure 6C illustrates a configuration in which the pad pusher 223 is in a fully extended position. The fully extended position is a position beyond which if the steering pad further extends, the piston islikely to become displaced from the piston liner and piston bore 226. As illustrated, in Figure 6C, in the fully extended position, the first edge 416 abuts the top edge 422 of the respectiveuphole and downhole sides 221A and 221B of the housing 221. In this way, the top edges, e.g.,13edge 422 of each of the retaining recesses 41OA and 41OB act as a stop to restrict further rotationof the pad pusher 223 about the pivot axis. Additionally, in the fully extended position, the first edge 416 extends parallel to the top edge 422 of the respective first and second retaining recesses410A and 410B.

[0049] Advantageously, various embodiments described herein can prevent the steering padfrom rotating further than intended for the desired steering capability. Further, due to thecapability of restricting rotation of the steering pad, the aforementioned configuration providesthe advantage of preventing or minimizing the risk of the piston becoming displaced from thepiston liner and piston bore. As a result, the piston may be prevented from becoming stuck afterbeing displaced from the piston liner. Since the piston may be prevented from being removedfrom the liner, the chances of debris entering the liner and impeding steering control areminimized. The some embodiments described herein thus protect the steering head fromadditional damage.

[0050] Furthermore, by integrating the overextension prevention into the geometry of thesteering pad and pad retention housings, it is possible to advantageously simplify the tool designby eliminating the need for additional stops in the steering head. This results in a moreeconomical and more easily produced design. Additionally, the operating life of the tool isextended, for example, by virtue of not needing to provide additional stops which wouldpotentially be subject to wear and breakage. Since the pad stops are provided in a same plane asthe forces being applied to the pad pusher, the positioning of the pad stops (retaining recessesand limiting protrusions) provides better mechanical advantage over the forces the pad stops arecounteracting. The stop distance can be changed prior to being run into the hole to select a desired minimum or maximum extension of the pad pusher using either different h sized limitingprotrusions 408A and 408B or different positioned edges such as 422 or other ways to adjust theallowable pivot distance of the steering pad. In such instances it may be desirable to limit theallowable extension such that the pads do not extend beyond the diameter of the pervious casingor liner inner diameter for the interval being drilled so as to avoid the risk of the steering padfrom getting caught on the bottom of the casing or liner when pulling the tool out of the hole orother potential obstructions. Hence the allowable swing or pivot range of steering pad may beselectable.14[0051) Various examples of aspects of the disclosure are described as numbered clauses (1,2, 3, etc.) for convenience. These are provided as examples and do not limit the subjecttechnology. Identification of the figures and reference numbers are provided below merely asexamples for illustrative purposes, and the clauses are not limited by those identifications.[0052) Clause 1: A steering head for steering a drill string, the steering head comprising: a pad pusher including a steering pad and a piston integrally formed, the steering pad having a pivot axis, and being rotatable about the pivot axis between retracted and extended positions, thepad pusher further including a motion restrictor to restrict rotation about the pivot axis; and ahousing having a motion restrictor disposed at a position corresponding to the pad pushermotion restrictor, wherein the pad pusher motion restrictor is engageable with the housingmotion restrictor to restrict motion of the steering pad relative to the housing.[0053) Clause 2: The steering head of Claim 1, wherein: the pad pusher motion restrictorcomprises a first motion restrictor at an uphole side thereof, and a second motion restrictor at adownhole side thereof; the housing motion restrictor comprises a first motion restrictor at anuphole side thereof, and a second motion restrictor at a downhole side thereof; and the firstmotion restrictor of the pad pusher engages the first motion restrictor of the housing, and thesecond motion restrictor of the pad pusher engages the second motion restrictor of the secondhousing to restrict the motion of the steering pad relative to the housing.[0054) Clause 3: The steering head of Claim 2, wherein: the first motion restrictor of the padpusher comprises one of a first motion-limiting protrusion or a first retaining recess, and the first motion restrictor of the housing comprises a remaining one of the first motion-limitingprotrusion or the first retaining recess; and the second motion restrictor of the pad pushercomprises one of a second motion-limiting protrusion or a second retaining recess, and thesecond motion restrictor of the housing comprises a remaining one of the second motion-limitingprotrusion or the second retaining recess;[0055) Clause 4: The steering head of Claim 1, wherein the first and second motionrestrictors of the pad pusher comprise first and second motion-limiting protrusions extendinglaterally from the respective uphole and downhole sides; and the first and second motionrestrictors of the housing comprise first and second retaining recesses respectively, configured toreceive the respective first and second motion-limiting protrusions therein.15Clause 5: The steering head of Clause 4, wherein each of the first and second

[0056] retaining recesses comprises a trapezoidal cross-section, with top and bottom edges thereof beingparallel.

[0057] Clause 6: The steering head of Clause 5, wherein the trapezoidal shaped cross-section comprises a cross-section having a rectangular shape.

[0058] Clause 7: The steering head of Clause 5, wherein the trapezoidal cross-sectioncomprises a cross-section having a square shape.

[0059] Clause 8: The steering head of Clause 4, wherein a cross-section of each of the firstand second motion-limiting protrusions tapers in size along a plane orthogonal to an uphole-downhole direction of the steering pad.

[0060] Clause 9: The steering head of Clause 8, wherein the size comprises a height of thecross-section of each of the first and second motion-limiting protrusions.

[0061] Clause 10: The steering head of Clause 4, wherein each of the first and second motion-limiting protrusions comprise a first edge, a second edge parallel to the first edge, and a thirdangularly oriented edge coupled to at least one ofthe first and second edges.

[0062] Clause 11: The steering head of Clause 10, wherein in a fully retracted position ofthe pad pusher, the third edge is positioned parallel to a bottom edge of the respective first andsecond retaining recesses.

[0063] Clause 12: The steering head of Clause 10, wherein in a fully extended position ofthe pad pusher, the first edge abuts a top edge of the respective first and second retainingrecesses to restrict further rotation of the pad pusher about the pivot axis in a first direction.

[0064] Clause 13: The steering head of Clause 12, wherein in the fully extended position ofthe pad pusher, the first edge extends parallel to the top edge of the respective first and secondretaining recesses to restrict further rotation of the pad pusher about the pivot axis in a firstdirection.

[0065] Clause 14: The steering head of Clause 4, wherein the steering pad has a semi-circular cross-sectional profile and the pad pusher is attached to the tool via a pivot coupling.

[0066] Clause 15: A method of assembling a steering head of a rotary steerable tool forsteering a drill string, wherein the steering head includes a steering pad and a piston formed as apad pusher having first and second motion restrictors, and a housing having first and secondmotion restrictors, the method comprising: positioning the pad pusher with respect to the housing16to align each of the first and second motion restrictors of the pad pusher with the respective firstand second motion restrictors of the housing; engaging (1) the first motion restrictor of the pad pusher with the first motion restrictor of the housing, and (2) the second motion restrictor of thepad pusher with the second motion restrictor of the housing to restrict a rotational motion thesteering pad relative to the housing; and pivotally coupling the pad pusher to the housing about apivot axis of the steering pad, wherein the pad pusher is rotatable about the pivot axis betweenretracted and extended positions.

[0067] Clause 16: The method of Clause 15, further comprising coupling the pad pusher to acollar of the tool via the housing.

[0068] Clause 17: The method of Clause 16, wherein the pad pusher motion restrictorcomprises a first motion restrictor at an uphole side thereof, and a second motion restrictor at adownhole side thereof, and the housing motion restrictor comprises a first motion restrictor at anuphole side thereof, and a second motion restrictor at a downhole side thereof, the methodfurther comprising: restricting the motion of the steering pad relative to the housing by engaging(1) the first motion restrictor of the pad pusher with the first motion restrictor of the housing, and(2) the second motion restrictor of the pad pusher with the second motion restrictor of thehousing.

[0069] Clause 18: The method of Clause 17, wherein: the first motion restrict or of the padpusher comprises one of a first motion-limiting protrusion or a first retaining recess, and the firstmotion restrictor of the housing comprises a remaining one of the first motion-limitingprotrusion or the first retaining recess; and the second motion restrictor of the pad pushercomprises one of a second motion-limiting protrusion or a second retaining recess, and thesecond motion restrictor of the housing comprises a remaining one of the second motion-limitingprotrusion or the second retaining recess;

[0070] The steering head of Clause 18, wherein: the first and second motion restrictors of thepad pusher comprise first and second motion-limiting protrusions extending laterally from therespective uphole and downhole sides; and the first and second motion restrictors of the housingcomprise first and second retaining recesses respectively, configured to receive the respectivefirst and second motion-limiting protrusions therein.17

[0071] Clause 19: The method of Clause 18, wherein a cross-section of each of the first andsecond motion-limiting protrusions tapers in size in a direction from the downhole side to theuphole side of the steering pad.

[0072] Clause 20: The method of Clause 19, wherein the size comprises a height of the cross-section of each of the first and second motion-limiting protrusions.

[0073] Clause 21: The method of Clause 18, wherein each of the first and second motion-limiting protrusions each comprise a first edge, a second edge parallel to and disposed below thefirst edge, and a third edge angularly positioned with respect to the first and second edges.

[0074] Clause 22: The method of Clause 21, wherein in a fully retracted position of the padpusher, the third edge is positioned parallel to a bottom edge of the respective first and secondretaining recesses.

[0075] Clause 23: The method of Clause 21, wherein in a fully extended position of the padpusher, the first edge abuts a top edge of the respective first and second retaining recesses torestrict further rotation of the pad pusher about the pivot axis in a first direction.

[0076] Clause 24: The method of Clause 23, wherein in the fully extended position of thepad pusher, the first edge extends parallel to the top edge of the respective first and secondretaining recesses to restrict further rotation of the pad pusher about the pivot axis in a firstdirection.18WHAT IS CLAIMED IS:1. A steering head for steering a drill string, the steering head comprising:a pad pusher including a steering pad and a piston, the steering pad having a pivot axisand being rotatable about the pivot axis between retracted and extended positions, the padpusher further including a motion restrictor to restrict rotation about the pivot axis; anda housing having a motion restrictor disposed at a position corresponding to the padpusher motion restrictor, wherein the pad pusher motion restrictor is engageable with thehousing motion restrictor to restrict motion of the steering pad relative to the housing.2. The steering head of Claim 1, wherein:the pad pusher motion restrictor comprises a first motion restrictor at an uphole sidethereof, and a second motion restrictor at a downhole side thereof;the housing motion restrictor comprises a first motion restrictor at an uphole sidethereof, and a second motion restrictor at a downhole side thereof; andthe first motion restrictor of the pad pusher engages the first motion restrictor of thehousing, and the second motion restrictor of the pad pusher engages the second motionrestrictor of the second housing to restrict the motion of the steering pad relative to thehousing.3. The steering head of any of Claims 1-2, wherein:the first motion restrictor of the pad pusher comprises one of a first motion limitingprotrusion or a first retaining recess, and the first motion restrictor of the housing comprises aremaining one of the first motion-limiting protrusion or the first retaining recess; andthe second motion restrictor of the pad pusher comprises one of a second motionlimiting protrusion or a second retaining recess, and the second motion restrictor of thehousing comprises a remaining one of the second motion-limiting protrusion or the secondretaining recess.4. The steering head of any of Claims 1-3, wherein:the first and second motion restrictors of the pad pusher comprise first and second19motion-limiting protrusions extending laterally from the respective uphole and downhole sides;and the first and second motion restrictors of the housing comprise first and second retainingrecesses respectively, configured to receive the respective first and second motion-limitingprotrusions therein.5. The steering head of any of Claims 1-4, wherein each of the first and second retainingrecesses comprises a trapezoidal cross-section, with top and bottom edges thereof beingparallel.6. The steering head of any of Claims 1-5, wherein a cross-section of each of the firstand second motion-limiting protrusions tapers in size along a plane orthogonal to an upholedownhole direction of the steering pad and wherein the size comprises a height of the cross-section of each of the first and second motion-limiting protrusions.7. The steering head of any of Claims 1-6, wherein each of the first and secondmotion- limiting protrusions comprise a first edge, a second edge parallel to the first edge,and a third angularly oriented edge coupled to at least one of the first and second edges and wherein in a fully retracted position of the pad pusher, the third edge is positioned parallelto a bottom edge of the respective first and second retaining recesses.8. The steering head of any of Claims 1-7, wherein in a fully extended position of thepad pusher, the first edge abuts a top edge of the respective first and second retainingrecesses to restrict further rotation of the pad pusher about the pivot axis in a first direction and wherein in the fully extended position of the pad pusher, the first edge extends parallel to thetop edge of the respective first and second retaining recesses to restrict further rotation of thepad pusher about the pivot axis in a first direction.9. A method of assembling a steering head of a rotary steerable tool for steering a drillstring, wherein the steering head includes a steering pad and a piston formed as a pad pusherhaving first and second motion restrictors, and a housing having first and second motionrestrictors, the method comprising:20positioning the pad pusher with respect to the housing to align each of the first andsecond motion restrictors of the pad pusher with the respective first and second motionrestrictors of the housing;engaging (1) the first motion restrictor of t he pad pusher with the first motionrestrictor of the housing, and (2) the second motion restrictor of the pad pusher with thesecond motion restrictor of the housing to restrict a rotational motion the steering pad relative tothe housing; andpivotally coupling the pad pusher to the housing about a pivot axis of the steering pad,wherein the pad pusher is rotatable about the pivot axis between retracted and extendedpositions.10. The method of Claim 9 , further comprising coupling the pad pusher to a collar ofthe tool via the housing.11. The method of any of Claims 9 -10, wherein the pad pusher motion restrictorcomprises a first motion restrictor at an uphole side thereof, and a second motion restrictor at adownhole side thereof, and the housing motion restrictor comprises a first motion restrictor atan uphole side thereof, and a second motion restrictor at a downhole side thereof, the methodfurthercomprising:restricting the motion of the steering pad relative to the housing by engaging ( 1) thefirst motion restrictor of the pad pusher with the first motion restrictor of the housing, and (2)the second motion restrictor of the pad pusher with the second motion restrictor of thehousing.12. The method of any of Claims 9 -11, wherein:the first motion restrictor of the pad pusher comprises one of a first motion limitingprotrusion or a first retaining recess, and the first motion restrictor of the housing comprises aremaining one of the first motion-limiting protrusion or the first retaining recess; andthe second motion restrictor of the pad pusher comprises one of a second motionlimiting protrusion or a second retaining recess, and the second motion restrictor of thehousing comprises a remaining one of the second motion-limiting protrusion or the secondretaining recess;2113. The steering head of any of Claims 9 -12, wherein:the first and second motion restrictors of the pad pusher comprise first and secondmotion-limiting protrusions extending laterally from the respective uphole and downholesides; andthe first and second motion restrictors of the housing comprise first and secondretaining recesses respectively, configured to receive the respective first and second motion-limiting protrusions therein.14. The method of any of Claims 9 -13, wherein a cross-section of each of the first andsecond motion-limiting protrusions tapers in size in a direction from the downhole side to theuphole side of the steering pad and wherein each of the first and second motion-limitingprotrusions each comprise a first edge, a second edge parallel to the first edge, and a thirdangularly oriented edge coupled to at least one of the first and second edges.15. The method of any of Claims 9 -14, wherein in a fully retracted position of the padpusher, the third edge is positioned parallel to a bottom edge of the respective first andsecond retaining recesses and wherein in a fully extended position of the pad pusher, thefirst edge abuts a top edge of the respective first and second retaining recesses to restrictfurther rotation of the pad pusher about the pivot axis in a first direction.22

Claims

WHAT IS CLAIMED IS:

1. A steering head for steering a drill string, the steering head comprising:a pad pusher including a steering pad and a piston, the steering pad having a pivot axis and being rotatable about the pivot axis between retracted and extended positions, the pad pusher further including a motion restrictor to restrict rotation about the pivot axis; anda housing having a motion restrictor disposed at a position corresponding to the pad pusher motion restrictor, wherein the pad pusher motion restrictor is engageable with the housing motion restrictor to restrict motion of the steering pad relative to the housing.2.The steering head of Claim 1, wherein:the pad pusher motion restrictor comprises a first motion restrictor at an uphole side thereof, and a second motion restrictor at a downhole side thereof;the housing motion restrictor comprises a first motion restrictor at an uphole side thereof, and a second motion restrictor at a downhole side thereof; andthe first motion restrictor of the pad pusher engages the first motion restrictor of the housing, and the second motion restrictor of the pad pusher engages the second motion restrictor of the second housing to restrict the motion of the steering pad relative to the housing.3.The steering head of any of Claims 1-2, wherein:the first motion restrictor of the pad pusher comprises one of a first motion limiting protrusion or a first retaining recess, and the first motion restrictor of the housing comprises a remaining one of the first motion-limiting protrusion or the first retaining recess; andthe second motion restrictor of the pad pusher comprises one of a second motion limiting protrusion or a second retaining recess, and the second motion restrictor of the housing comprises a remaining one of the second motion-limiting protrusion or the second retaining recess.4.The steering head of any of Claims 1-3, wherein:the first and second motion restrictors of the pad pusher comprise first and second motion-limiting protrusions extending laterally from the respective uphole and downhole sides; and the first and second motion restrictors of the housing comprise first and second retaining recesses respectively, configured to receive the respective first and second motion-limiting protrusions therein.

5. The steering head of any of Claims 1-4, wherein each of the first and second retaining recesses comprises a trapezoidal cross-section, with top and bottom edges thereof being parallel.

6. The steering head of any of Claims 1-5, wherein a cross-section of each of the first and second motion-limiting protrusions tapers in size along a plane orthogonal to an uphole downhole direction of the steering pad and wherein the size comprises a height of the crosssection of each of the first and second motion-limiting protrusions.7.The steering head of any of Claims 1-6, wherein each of the first and second motion- limiting protrusions comprise a first edge, a second edge parallel to the first edge, and a third angularly oriented edge coupled to at least one of the first and second edges and wherein in a fully retracted position of the pad pusher, the third edge is positioned parallel to a bottom edge of the respective first and second retaining recesses.

8. The steering head of any of Claims 1-7, wherein in a fully extended position of the pad pusher, the first edge abuts a top edge of the respective first and second retaining recesses to restrict further rotation of the pad pusher about the pivot axis in a first direction and wherein in the fully extended position of the pad pusher, the first edge extends parallel to the top edge of the respective first and second retaining recesses to restrict further rotation of the pad pusher about the pivot axis in a first direction.9.A method of assembling a steering head of a rotary steerable tool for steering a drill string, wherein the steering head includes a steering pad and a piston formed as a pad pusher having first and second motion restrictors, and a housing having first and second motion restrictors, the method comprising: positioning the pad pusher with respect to the housing to align each of the first and second motion restrictors of the pad pusher with the respective first and second motion restrictors of the housing;engaging (1) the first motion restrictor of the pad pusher with the first motion restrictor of the housing, and (2) the second motion restrictor of the pad pusher with the second motion restrictor of the housing to restrict a rotational motion the steering pad relative to the housing; andpivotally coupling the pad pusher to the housing about a pivot axis of the steering pad, wherein the pad pusher is rotatable about the pivot axis between retracted and extended positions.10.The method of Claim 9 , further comprising coupling the pad pusher to a collar of the tool via the housing.

11. The method of any of Claims 9 - 10 , wherein the pad pusher motion restrictor comprises a first motion restrictor at an uphole side thereof, and a second motion restrictor at a downhole side thereof, and the housing motion restrictor comprises a first motion restrictor at an uphole side thereof, and a second motion restrictor at a downhole side thereof, the method furthercomprising:restricting the motion of the steering pad relative to the housing by engaging ( 1) the first motion restrictor of the pad pusher with the first motion restrictor of the housing, and (2) the second motion restrictor of the pad pusher with the second motion restrictor of the housing.12.The method of any of Claims 9 - 11 , wherein:the first motion restrictor of the pad pusher comprises one of a first motion limiting protrusion or a first retaining recess, and the first motion restrictor of the housing comprises a remaining one of the first motion-limiting protrusion or the first retaining recess; andthe second motion restrictor of the pad pusher comprises one of a second motion limiting protrusion or a second retaining recess, and the second motion restrictor of the housing comprises a remaining one of the second motion-limiting protrusion or the second retaining recess; 13.The steering head of any of Claims 9 - 12 , wherein:the first and second motion restrictors of the pad pusher comprise first and second motion-limiting protrusions extending laterally from the respective uphole and downhole sides; andthe first and second motion restrictors of the housing comprise first and second retaining recesses respectively, configured to receive the respective first and second motionlimiting protrusions therein.

14. The method of any of Claims 9 - 13 , wherein a cross-section of each of the first and second motion-limiting protrusions tapers in size in a direction from the downhole side to the uphole side of the steering pad and wherein each of the first and second motion-limiting protrusions each comprise a first edge, a second edge parallel to the first edge, and a third angularly oriented edge coupled to at least one of the first and second edges.15.The method of any of Claims 9 - 14 , wherein in a fully retracted position of the pad pusher, the third edge is positioned parallel to a bottom edge of the respective first and second retaining recesses and wherein in a fully extended position of the pad pusher, the first edge abuts a top edge of the respective first and second retaining recesses to restrict further rotation of the pad pusher about the pivot axis in a first direction.