Mud hydraulic operated rotary steerable system

Abstract

A rotary steerable drilling system for drilling a borehole comprising a rotary drill bit and a drill string defining a fluid passageway and a drilling fluid for flowing through the fluid passageway. The drill string comprising a bottom hole assembly including a housing, a flow7 channel in the fluid passageway and a valve disposed in the fluid passageway and aligned with the flow7 channel. An actuator is connected to the valve and allowed to move the valve relative to the flow channel to generate a pressure pulse in the drilling fluid in the fluid passageway based on varying a relative position between the valve and the flow channel and creating a differential pressure across the fluid passageway. A piston in hydraulic communication with the differential pressure extends radially from the housing and engages the borehole wall upon the differential pressure.

Description

Attorney Docket No.: 65DRL-510615-WO-2 (000240)MUD HYDRAULIC OPERATED ROTARY STEERABLE SYSTEM CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U. S. Provisional Application Serial No. 63 / 728,551 filed on December 5, 2024, entitled “Mud Hydraulic Operated Rotary Steerable System”, U. S. Provisional Application Serial No. 63 / 728,557 filed on December 5, 2024, entitled “Combined Rotary Steerable and Mud Pulse Telemetry’ Tool”, and U. S, Provisional Application Serial No. 63 / 728,561 filed on December 5, 2024, entitled “Force Balanced Dual Valve Pulser System”.

[0002] This application is also related to co-pending International Patent Application filed on December 5, 2025, entitled “Combined Rotary Steerable and Mud Pulse Telemetry Tool” and naming Volker Peters as inventor and Baker Hughes Oilfield Operations LLC as Applicant (ref. 65DRL-510769-WO-2), co-pending International Patent Application filed on December 5, 2025, entitled “Force Balanced Dual Valve Pulser System” and naming Volker Peters and Bastian Sauthoff as inventors and Baker Hughes Oilfield Operations LLC as Applicant (ref.65TEL-510983-WO-2), co-pending U. S. Non-Provisional Application filed on December 5, 2025, entitled “Drill Bit Steering System” and naming Behrend Bode, Volker Peters, and Bastian Sauthoff as inventors and Baker Hughes Oilfield Operations LLC as Applicant (ref.65DDR-511659-US-1), and co-pending U. S. Non-Provisional Application No. 19 / 410,852 filed on December 5, 2025, entitled “Force Balanced Dual Valve Systems For Steering Tool And Methods Of Using The Same” and naming Bastian Sauthoff and Thomas Wettmarshausen as inventors and Baker Hughes Oilfield Operations LLC as Applicant (ref. 65DDR-511601-US-1).-1- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)BACKGROUND OF THE INVENTION1. Field of Invention

[0003] The present invention relates generally to downhole tools and more particularly to rotary steerable systems and methods of use.2. Description of Prior Art

[0004] Drilling systems having earth boring drill bits on an end of a drill string are commonly used in the oil and gas industry for creating wells drilled into hydrocarbon bearing geologic formations. The drill bit is rotationally affixed to the drill string in some drilling systems. A rotary drilling system has a drill string having a bottom hole assembly (BHA) connected to the drill bit which is rotatably driven from a drilling rig on the surface having either a top drive or rotary table to rotate the drill string and the drill bit to bore through the subterranean formation, in other varieties of drilling systems, the drill bit rotates with respect to the drill string. The drill bit can be driven downhole by a downhole drive, as for example a mud motor. A downhole mud motor is sometimes employed for rotating the drill bit while the drill string does not rotate or rotates at a different speed.

[0005] During rotary drilling operations, a drilling fluid (also referred to as “’drilling mud” or simply ‘"mud”) is pumped from the surface down the drill string through the BHA and the drill bit into an annulus between the drill string and the borehole wall and then returned to the surface along with cuttings from the formation.

[0006] Oftentimes when drilling a borehole (also referred to as wellbore) in a subsurface formation, it is desirable to drill some portion of the borehole w ith a curvature or deviation to direct the borehole to a desired target. In such instances it is necessary for the drilling operator to be able to control or "steer" the direction of the drill bit. Steering assemblies such as rotaryIM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)steerable systems placed near or adjacent the drill bit can include a pad and / or piston actuation system to push against the borehole wall to change the direction of the borehole being drilled.

[0007] Prior art systems utilize drilling fluid hydraulic systems operating with a portion of the drilling fluid flow while guiding the main portion of the flow towards the drill bit and bit nozzles. After actuation the piston retracts and discharges the drilling mud into the annulus The pad and piston actuation system therefore operates with a smaller fraction (typically below 10%) of the drilling fluid flow (“bypass flow”) that is guided through a bypass channel directly to the annulus in the borehole, A valve is operated to guide the drilling fluid into cylinder and piston devices to actuate the pads / pistons against the borehole wall / formation. After actuation the piston retracts and discharges the drilling fluid into the annulus between the drill string and the borehole wall (for example, through a relief channel and / or a sealing gap) thereby bypassing the drill bit (i.e., without flowing through the drill bit). An additional telemetry device including a second valve is used in another section of the BHA, doubling the amount of required actuated mud valves.

[0008] Operating prior art drilling fluid hydraulic activated devices pose several challenges:

[0009] The bypass flow requires filter screens to prevent larger debris and particles from entering the valve, cylinder, piston and discharge components;

[0010] Filter, valve, flow channels and discharge components may get blocked by sediments, particles or lost circulation materials (LCM). Blocked and / or plugged hydraulics may cause inability to steer;

[0011] Discharge through a relief channel and / or sealing gap can cause erosion;

[0012] Discharge through the relief channel and / or sealing gap is enforced by activation of an opposite pad / piston which causes a reduction of steer force (also referred to as steering force);-3- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)

[0013] The hydraulics depend on pre-selected fluids handling hardware, such as nozzles, valves, restrictions, etc. in the RSSMPT, and the drill bit, flow rate and density of the drilling fluid flow, and restricting operating parameters;

[0014] Steer forces cannot be adjusted for a given flow density and pre-set choice of nozzles; and

[0015] Proportional steering, which uses adjustable force vectors according to the demanded force and direction, is not possible.

[0016] It is desirable to have a drilling fluid hydraulic operated rotary steerable system that overcomes some or all of the above-described challenges and shortcomings of the prior art.SUMMARY OF THE INVENTION

[0017] A mud hydraulic operated rotary steerable system is disclosed. The mud hydraulic operated rotary steerable system uses a telemetry-like mud valve that chokes a substantial volume (or a major portion of) flow and uses tire resulting differential pressure to selectively actuate steering pistons and / or pads. The disclosed rotary steerable system does not utilize a non-rotating sleeve and hence operates pistons / pads in a cyclic manner and once per revolution for creating curvatures. The rotary steerable system takes advantage of a mud pulse actuation system that allows fast (>30 Hz) valve actuation and thus can be applicable to piston / pad actuation greater than 400 rpm (7 Hz) at relatively low power demand.

[0018] In one aspect, the mud hydraulic operated rotary steerable system operates piston / pad devices that selectively apply force against the borehole wall without a flow bypass.-4- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)

[0019] Operating the pad / piston of the mud hydraulic operated rotary steerable system without a non-rotating sleeve from the main mud flow and -without a bypass device enables dynamic steering independent from bit pressure drop, bypass sizes, current mud flow rate and density.

[0020] The mud hydraulic operated rotary steerable system of the present invention provides one or more of the following advantages:

[0021] Bit pressure drop independent;

[0022] Pad force adjustable;

[0023] Flow rate independent;

[0024] No filter screen required;

[0025] No bypass through cylinder / piston;

[0026] Relief immediate, no restriction through relief bore;

[0027] Plugging resistant (same LCM restrictions as pulser valve); and

[0028] Low power drive.BRIEF DESCRIPTION OF DRAWINGS

[0029] Other objects, features and advantages will occur to those skilled in the art from the following description of the embodiments and the accompanying drawings, in which:

[0030] FIG. 1 illustrates a partial cross-sectional view of a directional drilling system of an onshore well having a bottom hole assembly including a rotary steerable tool according to embodiments of the present invention;-5- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)

[0031] FIG. 2 is a sectional view of a mud hydraulic operated rotary steerable system according to a first embodiment of the present invention;

[0032] FIG. 3 is a sectional view of a mud hydraulic operated rotary steerable system according to a second embodiment;

[0033] FIG. 4 is a sectional view of a mud hydraulic operated rotary steerable system according to a third embodiment;

[0034] FIG. 5 is a sectional view of a mud hydraulic operated rotary steerable system according to a fourth embodiment;

[0035] FIG. 6 is a sectional view of a mud hydraulic operated rotary steerable system according to a fifth embodiment;

[0036] FIG. 7 is a sectional view of a mud hydraulic operated rotary steerable system according to a sixth embodiment;

[0037] FIG. 8 is a sectional view of a mud hydraulic operated rotary steerable system according to a seventh embodiment;

[0038] FIG. 9 is a sectional view of a mud hydraulic operated rotary steerable system according to an eighth embodiment;

[0039] FIGS. 10 and 11 are sectional views of examples of control electronics and power sources for the mud hydraulic operated rotary steerable system;

[0040] FIG. 12 is a three dimensional view of an aspect of a mud hydraulic operated rotary steerable system including pad assemblies;IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)

[0041] FIGS. 13 and 14 are graphs showing examples of cyclic steering pressure pulses at different frequencies and steering pressures;

[0042] FIG. 15 is a graph of an example illustrating a telemetry system using pulse position coding;

[0043] FIG. 16 is a graph illustrating an example of high frequency pressure pulse signals superimposed on steering pulses for sending coded information to the surface;

[0044] FIG. 17 is a graph illustrating an alternative example of sending coded information to the surface by omitting steering pulses at certain slots during the steering process;

[0045] FIG. 18 is a graph illustrating another alternative example of sending coded information to the surface by placing high frequency pressure pulses at certain slots without superimposing the high frequency pressure pulses on the steering pulses;

[0046] FIG. 19 is a graph illustrating the technique shown in FIG. 16 but where the tool is rotating at a higher speed;

[0047] FIG. 20 is a graph illustrating the technique shown in FIG. 17 but where the tool is rotating at a higher speed;

[0048] FIG. 21 is a graph illustrating the technique shown in FIG. 18 but where the tool is rotating at a higher speed;

[0049] FIGS. 21a-21c are graphical representations of pressure changes over time and corresponding bit values;

[0050] FIG, 22 is a sectional view of a mud hydraulic operated rotary’ steerable system according to another embodiment of the present invention;-7- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)

[0051] FIG. 23 is a sectional view of a mud hydraulic operated rotary steerable system according to yet another embodiment of the present invention;

[0052] FIG. 24 is a perspective view of an aspect of a mud hydraulic operated rotary steerable system including a plurality of axially-aligned adjacent ball pistons; and

[0053] FIG. 25 is a perspective view of an aspect of a mud hydraulic operated rotary steerable system including a plurality of angularly offset adjacent ball pistons.DETAILED DESCRIPTION OF INVENTION

[0054] The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure can be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term “about” includes + / - 5% of a cited magnitude. In an embodiment, the term “substantially” includes + / - 5% of a cited magnitude, comparison, or description. In an embodiment, usage of the term “generally” includes + / - 10% of a cited magnitude,

[0055] It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation.-8- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)

[0056] It can further be understood that the reference to cylinder / piston devices represents devices or any type of biasing elements in general that can technically be used to actuate or expand or extend and apply force to adjacent components, e.g. as a result of fluid pressure and fluid flow hydraulically connected to such devices. Examples include but are not limited to: cylinder / piston devices, metal bellows devices, rubber bellows devices, fiber reinforced bellows, sags or pillows devices, cylinder / ball devices, thermoplastic bellows devices and others.

[0057] FIG. 1 shows an elevation, partial cross-sectional view of a typical onshore rotary well drilling system for forming a borehole H in a geological formation G in which the present invention can be utilized. The system includes a drilling rig R at the earth’s surface 3 (also referred to as “surface” within the context of this disclosure) connected to a drill string 2. A bottom hole assembly (BHA) 20 at the lower end of the drill string 2 is connected to a drill bit B. Typically, the drilling rig R supports, lowers and rotates the drill string 2 and the drill bit B. A drilling fluid system M delivers drilling fluid or mud F at the surface 3 from a drilling fluid tank 4 into a fluid passageway or bore 24 of the drill string 2. The drilling fluid F is pumped down the fluid passageway 24 and through the BHA 20 and the drill bit B. The drilling fluid F exits the drill bit B and enters an annulus 6 between the drill string 2 or BHA 20 and the borehole wall W of the borehole H and returns to the surface 3 with cuttings from the borehole H (arrows depicting flow of drilling fluid F down through the drill string 2 and up through the annulus 6). A surface data acquisition and control system C having a processor / controller is communicatively coupled to the BHA 20, including various downhole data acquisition tools and sensing devices. The surface data acquisition and control system C can communicate with the downhole devices in various manners, The communication means can be, for example, hardwired, or wireless. Hardwired communication can be implemented by wires or optical fibers. The BHA 20 can include various components and equipment, such -9- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)as drill collars, stabilizers, reamers, shocks, hole-openers, logging-while-drilling (LWD) equipment, measurement-while-drilling (MWD) equipment, sensors, steering assemblies and other downhole instruments. The sensors commonly include rotational velocity (RPM), toolface, inclination and azimuth sensors, for example accelerometers, inclinometers, magnetometers and rate gyros. Certain of the equipment, systems and techniques are used for gathering downhole data while drilling without needing to remove the drill pipe from the well. The BHA design can vary greatly depending on the complexity of the well.

[0058] FIG. 2 shows a cross-section of one embodiment of a mud hydraulic operated rotary steerable system or tool, generally referred to as 10. The steerable tool 10 is part of the BHA 20 and includes a housing 22 having the fluid passageway 24 therethrough. The upper end of the housing 22 is connected (for example, mechanically connected) to the drill string 2 and the lower end of the housing 22 is connected (for example, mechanically connected) to the drill bit B having one or more bit nozzles Bn. Drilling fluid F is flowing from drill string 2 through the fluid passageway 24 of rotary steerable tool 10 to the drill bit B. Within the housing 22 is an actuator assembly 26 for controlling the drilling fluid F flow into at least first and second channels 28 and 30, respectively, of the fluid passageway 24 by means of first and second valves 32 and 34, respectively. The fluid passageway 24 is divided in first and second channels 28, 30 which are in fluid communication with and form part of the drill string 2 and fluid passageway 24 and can be formed in a bias unit 40. In one or more embodiments, the first channel 28 is parallel to and adjacent to the second channel 30. The first and second channels 28, 30 have first and second inlet ends 28i, 30i, respectively, and first and second outlet ends 28o, 30o, respectively. The first and second outlet ends 28o, 30o of the respective first and second channels 28, 30 includes first and second restriction members 36 and 38, respectively. Each of the first and second valves 32, 34 has a “closed” position in which drilling fluid F flow' from the drill string 2 through the respective first and second channels 28, 30 to the drill bit B -10- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)is restricted or more restricted and an “open” position in which the drilling fluid F flow from the drill string 2 through the respective first and second channels 28, 30 to the drill bit B is unrestricted or less restricted. In the context of this disclosure, the more restricting / less restricting positions of a valve can be referred to as “closed position” and “open position”, respectively. However, it is to be understood that in the “open” position the drilling fluid F flow from the drill string 2 to the drill bit B can still be restricted while in the “closed” position the drilling fluid F flow from the drill string 2 to the drill bit B can still be more than zero. In that sense, the “open” position is to be understood to refer to a less restricting position and the “closed” position is to be understood to refer to a more restricting position. FIG. 2 shows the second valve 34 in the “closed” position and the first valve 32 in the “open” position allowing the majority of drilling fluid F to flow into and through the first channel 28 and a small amount of drilling fluid F to flow into and through the second channel 30. Notably, the complete flow of drilling fluid F through fluid passageway 24 goes through either the first valve 32 and first channel 28 or the second valve 34 and second channel 30. The first and second valves 32 and 34, respectively, can either partially or fully block the flow of the drilling fluid F in the first and second channels 28 and 30, respectively, when in the restricted position.

[0059] In one or more embodiments, the full flow of drilling fluid F is forced through the double channel 28, 30 assembly continuously and the volume of flow is constant. It is to be understood that as one of the valves 32, 34 approaches the restricted position, the fluid pressure in the drilling fluid F flow through fluid passageway 24 from the drill string 2 to the drill bit B temporarily increases and forces tire drilling fluid F flow from the drill string 2 to the drill bit B through the unrestricted or less restricted channel.

[0060] Proportional steering is enabled by adjusting the distance of the valves 32, 34 relative to the first and second inlet ends 28i, 30i (i.e. adjusting gaps 28g, 30g) of the first and second-11- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)channels 28, 30 to control the amount of flow restriction through the first and second channels 28, 30. Proportional steering generally refers to steering with a controlled steering force, for example a controlled first piston force PF1 by the first piston 46 and / or a controlled second piston force PF2 by the second piston 48. As an example, as the drilling fluid F flow from the drill string 2 to the drill bit B is increasingly restricted in the second channel 30, the fluid pressure P2 in the drilling fluid F flowing from the drill string 2 to the drill bit B within the second channel 30 decreases whereas the fluid pressure Pl in the drilling fluid F flowing from the drill string 2 to the drill bit B within the first channel 28 temporarily increases and adjusts a first piston force PF1 accordingly, which in turn enables proportional steering (i.e., adjusting the steering vector in size and direction according to current steering demands).

[0061] In some embodiments, the bias unit 40 shown in FIG. 2 comprises first and second biasing elements, herein also referred to as pistons 46 and 48 movably received in first and second cylinders 42 and 44, respectively. Those skilled in the art will understand that the term “cylinder” in the context of this disclosure does include any opening that is configured to accept a movable piston, including openings of various cross-section, such as but not limited to openings with circular, elliptical, triangular, quadrangular (e.g., rectangular), pentagonal crosssections, etc. In some embodiments, the pistons 46, 48 and cylinders 42, 44, are oriented radially relative to a longitudinal axis of the housing 22 and in fluid communication with the first and second channels 28 and 30, respectively. The pistons 46, 48 are hydraulically displaceable outwardly for engagement with the borehole wall W. The radially outward surface of the pistons 46, 48 can comprise a steering pad 70 (FIG. 12) for engagement with tire borehole wall W. The steering pad 70 and piston 46, 48 can be formed as separate components that are coupled together or can be formed integrally. As used herein, tire term “biasing element” or “piston” is to be understood to also optionally include a steering pad unless stated otherwise. FIG. 12 illustrates a pair of steering pads 70 connected, for example via hinges 85,-12- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)to a pair of steering pad holders 72 mounted to the housing 22. Although not shown, in some embodiments a steering pad retract spring 87 (e.g., a torsion spring) is provided to retract the steering pad 70 to the retracted position when the piston(s) 46 are not pushing the steering pad 70 outwardly. It is to be understood that one or more pistons 46 can be used with each steering pad 70. In FIG. 12, two pistons 46 are shown engaging each steering pad 70 (similar to the arrangement shown in FIG, 6), The steering pad 70 in the upper portion of FIG. 12 is shown in its retracted position with the steering pad 70 in the lower portion shown deployed by the pistons 46.

[0062] Referring to FIG. 2, a piston seal 47 forms a seal between tire piston 46, 48 and respective cylinder 42, 44. As shown in FIG. 2, the first and second pistons 46, 48 are coupled together with a connecting rod 50 and a retract spring 52. The first piston 46 can include an inner cavity 46c having an opening 46o through which the connecting rod 50 extends. One end of the connecting rod 50 can be attached to the second piston 48 and the other end of the connecting rod 50 can include an enlarged head 50h. The retract spring 52 can extend around the connecting rod 50 and be captured in the inner cavity 46c between the opening 46o of the cavity 46c and the head 50h of the rod 50. In embodiments, a seal 54 such as a seal ring provides a seal between the connecting rod 50 and a channel divider wall 40w of the bias unit 40 to prevent high pressure fluid in one channel 28, 30 from passing to the other channel 28, 30.

[0063] FIG. 2 shows the first valve 32 in the retracted position allowing the upstream drilling fluid F to flow into the first channel 28 while the second valve 34 restricts the flow of drilling fluid F into the second channel 30. Descriptions of subject matter disposed within the wellbore H using the term “uphole” or “upstream” refer to a relative direction within wellbore H towards the earth’s surface 3, and usage of the term “downhole” or “downstream” refer to a-13- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)relative direction deeper within wellbore H away from the earth's surface 3. The first restriction member 36 at the outlet end 28o of the first channel 28 contributes to an increase in the fluid pressure Pl within the first channel 28 which acts on the first piston 46. As a result of the positions of the first and second valves 32, 34, a pressure differential exists between the first and second channels 28, 30 with the fluid pressure Pl in the first channel 28 being higher than the fluid pressure P2 in the second channel 30. The higher fluid pressure P 1 in the first channel 28 acts on the first piston 46 and forces the first piston 46 radially outward. Concurrently as the first piston 46 moves radially outward, the connecting rod 50 and the retract spring 52 can radially retract the second piston 48 inwardly. As the pressure differential between fluid pressures Pl and P2 reduces, as for example by repositioning the first and second valves 32, 34 approximately equidistant from the first and second inlet ends 28i, 30i, the temporary increase in in the first channel pressure P2 in the second channel 30 with the decrease in fluid pressure Pl can cause the second piston 48 to temporarily move slightly radially outward, with the connecting rod 50 and the retract spring 52 forcing the first piston 46 radially inward. A similar process and result occurs when the valves 32, 34 are repositioned such that the second valve 34 is in the retracted position and the first valve 32 restricts drilling fluid F flow from the drill string 2 to the drill bit B into the first channel 28. In this position, the high pressure is in the second channel 30 and the second piston 48 is forced radially outwardly. The spring coupling reduces the side force of the piston 46, 48 against tire borehole wall W and thus reduces friction, wear, abrasion, and rock damage.

[0064] As stated above, the drilling fluid F at fluid pressure P2 passes through the nozzles Bn of the drill bit B and mto the annulus 6 at or near the rotary steerable system or tool 10 where the fluid pressure decreases to fluid pressure P3.-14- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)

[0065] The first piston force PF1 equals the pressure difference between fluid pressures Pl and P3 (P3 being the fluid pressure in the annulus 6 at or near tire rotary steerable system or tool 10) multiplied by the areaofthe first piston 46 (Aist piston), which can be stated as PF1=(P1-P3)*A1st piston. The second piston force PF2 equals the pressure difference between fluid pressure P2 and fluid pressure P3 multiplied by the area of the second piston 48 (Aznd piston), which can be stated as PF2=(P2-P3)*A2nd piston. For the embodiments having the connecting rod 50 coupling the first and second pistons 46, 48, as shown in FIG. 2, the second piston force PF2 acts against the first piston force PF1. Thus, the steering force would calculate to the first piston force PF 1 less the second piston force PF2, which can be represented as PF1-PF2. With the areas of the first and second pistons 46, 48 equal (i.e., A1st piston = A2nd piston = Apiston), the steering force calculates to Apiston*(P1-P2), irrespective of the differential pressure across the drill bit B (P2-P3). In other words, the rotary steerable tool 10 is independent of drill bit pressure drop, Uris is similarly true for the following embodiments discussed below and shown in FIGS. 3, 4, 6, 8, 9 and 10.

[0066] The actuator assembly 26 is depicted in FIG. 2 as a reciprocating actuator having a crankshaft 56, drive 58 and linkage 60 connected to first and second valve rods 32r, 34r of the first and second valves 32, 34, respectively. The reciprocating actuator assembly 26 of FIG. 2 can utilize rod springs 62 to balance (hydraulic and / or dynamic) valve forces. In this embodiment, the valves 32, 34 are locomotively connected. In other words, as one valve moves axially the other valve concurrently moves axially the same distance but in the opposite direction. Any of various configurations and mechanisms can be used to affect force balancing. In addition to or in place of the balancing mechanics described above, the mechanical connection of the force balancing mechanics can include rack and pinion gearboxes, crank or cam devices, wobble plates, hydraulic coupling (cylinder piston devices with hydraulic communication) rocker lever mechanisms and others. It can also be appreciated that the drive -15- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)58 can be connected to the force balancing mechanism by means of a bevel gear, a hypoid gear, a worm gear, a swash plate, or any other means to translate from a rotating or oscillating (motor) motion from the drive 58 to a rocking motion at the balancing mechanics. The actuator assembly 26 can be sealed and filled with an appropriate lubrication fluid, such as mineral or synthetic oil. The oil-filled actuator assembly 26 can further include a pressure compensator 80 (FIG. 2) such as a piston, bellows, or similar device to compensate the internal lubricant pressure to the drilling fluid F pressure Pl. The pressure compensator 80 shown in FIG. 2 features a cylinder 82, a piston 84, and a seal 86. The valves 32, 34 can be force balanced reciprocating valve as disclosed in assignee’s U. S. Patent 11,892,093. Although a mud pulse valve according to U. S. Patent 11,892,093 is displayed here as a suitable device to generate pressure pulses, alternatively, the valve can be a shear valve (such as an oscillating shear valve), a poppet valve, or any other valve capable to be operated at the required frequency and capable of generating sufficient differential pressure to operate the RSSMPT tool. Alternative examples for such valves include, but are not limited to, those disclosed in U. S. Patent 7,808,859, U. S. Patent 5,586,084, U. S. Patent 7,417,920, U. S. Patent 8,917,575, and U. S. Patent 11,499,420.

[0067] Referring to FIG. 2, the actuator assembly 26 opens the first channel 28 when needed to be open by moving the first valve 32 to the open or retracted position. At the same time, the second channel 30 is restricted by the second valve 34 being in the restricted position. As a result, the first channel 28 receives a higher flow rate of drilling fluid F and thus a higher fluid pressure Pl is established in the first channel 28. The second channel 30 has a restricted flow rate and in turn operates with a reduced fluid pressure P2. The magnitude of the difference between fluid pressure Pl and fluid pressure P2 is controlled by the positions of the first and second valves 32, 34 and the size of the first and second restriction members 36, 38. Additionally, the magnitude of the pressure difference will be affected by current flow -16- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)parameters, such as the flow rate and density of the drilling fluid F. The differential pressure between fluid pressure Pl and fluid pressure P2 controls the piston (steer) force of the rotary steerable system 10. The arrows on the pistons 46, 48 represent first and second piston forces PF1 and PF2, respectively. The actuator assembly 26 axially positions the valves 32, 34 with respect to restriction channels 28, 30 and according to current steering force demand, considering actual flow rate and fluid density, thus in turn controlling the pressure in channels 28 and 30 accordingly and dynamically during operation of tire steering unit. In order to adjust differential pressure between fluid pressure Pl and fluid pressure P2 in reasonable range (e.g. between 5 and 50 bar), in some embodiments, fixed first and second restriction members 36 and 38 can be selected prior to deploying the tool and according to the expected range of flow and density for the particular deployment. However, in some embodiments, one or more of restriction members 36, 38 are adjustable restriction members 36, 38. For example, the aperture of restriction members 36, 38 can be adjusted using an aperture sizing feature 28s, 30s that can be located in a portion of the RSSMPT tool 10 that surrounds the restriction members 36, 38 (e.g., aperture sizing features 28s, 30s can be located in bias unit 40). The aperture sizing feature 28s, 30s enter the restriction members 36, 28 from respective sides of the restriction members 36, 38. Different penetration depths of the aperture sizing features 28s, 30s from the side of the restriction members 36, 38 create different aperture sizes of restriction members 36, 38 and thus alter the pressure drop across restriction members 36, 38. In various embodiments, the aperture sizing features 38s, 30s can be one or more pins or screws. Hie use of the aperture sizing features 38s, 30s makes it unnecessary to access and / or exchange the restriction members 36, 38, for example through the bit box, as would be the case for non-adjustable restriction members.

[0068] One aspect of the embodiment shown in Fig. 2 as well as in other embodiments further discussed below is that since the first and second pistons 46, 48 are in direct hydraulic -17- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)communication with the first and second channels 28, 30, no bypass is required. In other words, the difference of the average flow rate of the drilling fluid F flowing through the first and second channel 28, 30 of the RSSMPT tool 10 (for example through the first and second valve 32, 34) and the average flow rate of the drilling fluid flowing through the drill bit B is small or even zero. In embodiments, the average flow rate of the drilling fluid F flowing through the drill bit B can be 80% or more (such as 90% or more or even 95% or more) of the average flow rate flowing through the first and second channel 28, 30 of the RSSMPT tool 10. The average flow rate refers to a flow rate that is averaged over several revolutions of the RSSMPT tool 10, such as averaged over 3 revolutions, 10 revolutions or even over 50 revolutions of the RSSMPT tool 10, In other words, the valves 32, 34 and the respective inlet ends 28i and 30i selectively restrict the main flow through the fluid passageway 24 of the RSSMPT 10. Charge and discharge of piston fluid (i.e., the fluid that is in contact with one or more of pistons 46, 48 and actuates one or more of pistons 46, 48 to extract from RSSMPT 10 and to temporarily extend into annulus 6 of borehole H) is coupled to the main drilling fluid flow, thus there is no need for filters, no small discharge elements, and no risk for plugging or blockage of steering pistons. This is different to a concept where a valve is used to open and close a piston fluid passageway to selectively actuate a steering piston while the flow through the fluid passageway flows almost independently of whether such valve is in its open or closed position. For example, in concepts where a valve is used to open and close a piston fluid passageway to selectively actuate a steering piston while the flow through the fluid passageway flows almost independently of whether such valve is in its open or close position, the flow through the fluid passageway and the flow through the piston fluid passageway is typically much different while an implication of the embodiments disclosed herein is that the average flow rate through the first channel 28 and the average flow rate through the second channel 30 is at least of the same order of magnitude. For example, if one of the average flow rates through the first and second-18- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)channels 28, 30 is smaller than the other of the average flow rates through the first and second channels 28, 30, the ratio of the smaller flow rate over the larger flow rate can be larger than 0.1, such as 0.25 (for example, 0.67 or even 0.75). One implication of a design as disclosed herein where the main flow through fluid passageway 24 is selectively restricted by valves 32, 34 operating within and against the main drilling fluid F flow through fluid passageway 24 is that pressure pulses will be generated by the selective restriction of the main flow through fluid passageway 24 by valves 32, 34, such that these pressure pulses are large enough to be measurable at the earth’s surface 3. In embodiments, unlike prior art systems, none of the flowing drilling fluid F is diverted from the pistons 46, 48 into the annulus 6. Hence, pistons 46, 48 are actuated without any portion of drilling fluid F bypassing drill bit B.

[0069] FIG. 3 shows a second embodiment of the mud hydraulic operated rotary steerable system or tool, generally referred to as 11, in which the first and second valves 32, 34 of the first embodiment have been modified and the first and second restriction members 36, 38 have been removed. As shown in FIG. 3, the first valve 232 has a first inlet valve 232i and a first outlet valve 232o connected by a first valve rod 232r. Similarly, the second valve 234 has a second inlet valve 234i and a second outlet valve 234o connected by a second valve rod 234r. When the first inlet valve 232i of the first valve 232 is retracted from the first inlet end 28 i, the first outlet valve 232o of the first valve 232 is proximal to the first channel outlet end 28o. Concurrently, the second inlet valve 234i of the second valve 234 is close or adjacent to the second inlet end 30i, and the second outlet valve 234o of the second valve 234 is distal from the second channel outlet 30o. The first and second inlet valves 2321, 234i can close completely at the extreme forward position (i.e,, restricted), however, a gap 28h, 30h can exist between the first and second channel outlet ends 28o, 30o and the first and second outlet valves 232o, 234o, respectively, when the first and second valves 232, 234, respectively, are in the retracted position. For example and with reference to FIG. 3, if the second inlet valve 234i is closed -19- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)completely a gap can exist between the first outlet valve 232o of the first valve 232 and the outlet end 28o of the first channel 28.

[0070] Referring to FIG. 3, at the same time that the second inlet valve 234i blocks or partially blocks the fluid entrance into the second channel 30, because of the mechanical (locomotive) coupling of the first and second valves 232, 234, the first outlet valve 232o closes or partially closes the outlet end 28o of the first channel 28. In this position, a differential pressure (Pl higher than P2) is created by the partial blocking of the first and second channels 28 and 30. This pressure drop is variable and in response to positioning of the valve components.

[0071] Referring to FIG. 3, with such arrangement the differential pressure between the fluid pressure Pl in the first channel 28 and the fluid pressure P2 in the second channel 30 and thus the steering force can be controlled independently on large variations of current flow rate and density. If a higher steering force is required, the first inlet valve 232i opens further and the first valve outlet 232o closes further, creating an increase of first fluid pressure P l in the first channel 28 and therefore an increase in force at the first piston 46. At the same time, the second valve inlet 234i restricts drilling fluid F entry into the second channel 30 while the second valve outlet 234o further opens the connection to fluid pressure P2, thus relieving force and drilling fluid F from the second piston 48. Additionally, the reciprocating actuator assembly 26 according to FIG. 3 can further utilize first and second valve forces to cancel each other by means of the crankshaft / rocker lever and the rod springs 62 can be omitted.

[0072] FIG. 4 shows a third embodiment of the mud hydraulic operated rotary steerable system or tool, generally referred to as 12, The rotary steerable tool 12 of the third embodiment is very similar to the rotary steerable tool 11 of FIG. 3 with a slight modification to the piston arrangement. Referring to FIG. 4, the first and second pistons 346 and 348, respectively, can -20- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)be identical to one another and coupled together via a connecting rod 350. In FIG. 4, the first and second pistons 346 and 348 are rigidly coupled to one another via the connecting rod 350. As a result of the rigid coupling, the first and second pistons 346 and 348 are always a fixed distance apart and when one piston moves a distance outwardly, the other piston moves inwardly the same distance. As discussed above with respect to the second embodiment, the first and second inlet valves 232i, 234i can close completely at the extreme forward position, however, a gap 28h, 30h will exist at the first and second outlet valves 232o, 234o when the first and second valves 232, 234, respectively, are in their retracted position.

[0073] FIG. 5 shows a fourth embodiment of the mud hydraulic operated rotary steerable system or tool, generally referred to as 13. The rotary steerable tool 13 of the fourth embodiment is very similar to the rotary steerable tool 12 of FIG. 4. One difference is that the connecting rod 350 (FIG. 4) is not present in the fourth embodiment of the rotary’ steerable tool 13. As a result, the first and second pistons 446 and 448 in the fourth embodiment are not coupled to each other, mechanically (i.e., by a rigid connection and / or an elastic connection), and are only coupled hydraulically by drilling fluid F so that they can move in at least one direction independently of one another. In this embodiment, retraction of the piston 446, 448 does not automatically occur upon a decrease in fluid pressure. For example and with reference to FIG. 5, when the actuator assembly 26 repositions the second inlet valve 234i from the retracted position to the closed position (while concurrently repositioning the first inlet valve 232i from the closed position to the retracted position), the pressure in the second channel 30 decreases while the pressure in the first channel 28 increases causing the first piston 446 to temporarily extend radially. With the decrease of pressure in the second channel 30, the second piston 448 is allowed to move radially inward, for example, if it comes into contact with the borehole wall W. As discussed above with respect to the second and third embodiments, the-21- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)first and second inlet valves 232i, 234i can close completely at the extreme forward position, however, a gap 28h, 30h will exist at the first and second outlet valves 232o, 234o.

[0074] Without the pistons 446, 448 being coupled to one another, the steering force is calculated by the force difference of the two opposing pistons 446, 448 acting against the borehole wall W in opposite directions. As discussed above, the first piston force PF1 equals the pressure difference between fluid pressure Pl and fluid pressure P3 multiplied by the area of the first piston 446, which can be stated as PF1=(P1-P3)*A1st piston and the second piston force PF2 equals the pressure difference between fluid pressure P2 and fluid pressure P3 multiplied by tire area of the second piston 448, which can be stated as PF2=(P2-P3)*A2nd piston. Without the piston coupling, both pistons 446, 448 slide against the borehole wall W and sliding drag will thus be higher as compared to the embodiments with the piston coupling. Without piston coupling, both pistons 446, 448 will be pushed out by the respective pressure drop across the drill bit B as referred to above. In the case without the piston coupling, the pressure drop across the drill bit B is added to the force of both pistons, thus not affecting the steering force or direction but the drag against the borehole wall W during rotation.

[0075] FIG. 6 shows a fifth embodiment of the mud hydraulic operated rotary steerable system ortool, generally referred to as 14, The rotary steerable tool 14 ofthe fifth embodiment is very' similar to the rotary steerable tool 12 of FIG. 4. The rotary steerable tool 14 includes a plurality of first pistons 346a, 346b in hydraulic communication w ith the fluid pressure in the first channel 28 and a plurality of second pistons 348a, 348b in hydraulic communication w'ith the fluid pressure in the second channel 30. FIG. 6 shows the upstream pair of pistons 346a, 348a coupled to one another with a connecting rod 350a and tire downstream pair of pistons 346b, 348b coupled to one another with a connecting rod 350b. It is to be understood that the upstream and downstream pairs of pistons can be rigidly coupled, spring coupled or uncoupled.-22- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)The plurality of pistons as shown in FIG. 6 can be used to decrease the required differential pressure for steering. As discussed above with respect to the second, third and fourth embodiments, the first and second inlet valves 232i, 234i can close completely at the extreme forward position, however, a gap will exist at the first and second outlet valves 232o, 234o.

[0076] FIG, 7 shows a sixth embodiment of the mud hydraulic operated rotary steerable system or tool, generally referred to as 15. The rotary steerable system 15 is a simplified arrangement of the actuator and valve mechanics, using a singular reciprocating valve 634 to actuate a piston 646. This arrangement could be beneficial for restricted design space of a small tool size and for minimized complexity and cost.

[0077] With reference to FIG. 7, the bias unit 640 includes a first channel 628 and a second channel 630. The first and second channels 628, 630 are in fluid communication with and form part of the drill string 2 and fluid passageway 24. The first and second channels 628, 630 have an inlet end 628i, 630i, respectively, and an outlet end 628o, 630o, respectively. The outlet end 628o of the first channel 628 can include a first restriction member 636. The reciprocating valve 634 is preferably axially aligned with the second channel 630, which can be centrally located.

[0078] The piston 646 is movably received within a cylinder 642 in the bias unit 640. The piston 646 can include an outer shoulder 646s having a diameter larger than the diame ter of the remainder of the piston 646 and the bias unit 640 includes a recess 640r for receiving an optional piston retract spring 652 surrounding the piston 646 which is contained in the recess 640r by the outer shoulder 646s of the piston 646. The piston 646 is hydraulically displaceable by the fluid pressure in the first channel 628. The steering piston 646 can be retracted by the retract spring 652 when no flow or a low rate of flow is pumped through the first channel 628. it can be appreciated that retract springs 652 can be included in each of the devices as presented -23- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)in FIGS. 2 to 11). It can also be appreciated that retract springs 652 can also be coupled to the steering pads 70. Other examples for retract spring can include torsion springs coupled to the axis of a steering pad 70 (FIG. 12).

[0079] As discussed above with respect to the valves of the previous embodiments, the reciprocating valve 634 has a restricted position as shown in FIG. 7 and an open or less restricted position. The actuator assembly 626 controls the position of the valve 634 with respect to the inlet end 630i of the second channel 630. Additionally, the actuator assembly 626 positions the valve 634 from and between the restricted position and the open (i.e., retracted) position. Drilling fluid F flow to the inlet end 628i of the first channel 628 is unimpeded irrespective of the position of the valve 634. When the valve 634 is in the retracted position, drilling fluid F freely flows into and through the second channel 630 and also flows into and through the first channel 628. In the retracted position of the valve 634, the fluid pressure in the first channel 628 is decreased and the retract spring 652 forces the piston 646 radially inward. When the valve 634 is moved to the restricted position the drilling fluid F flow from the drill string 2 to the drill bit B and pressure decreases in the second channel 630 and increases in the first channel 628 forcing the piston 646 to move radially outward and compress the retract spring 652. The valve 634 can either partially or fully block the drilling fluid F flow from the drill string 2 to the drill bit B to the second channel 630.

[0080] FIG. 8 shows a seventh embodiment of the mud hydraulic operated rotary steerable system or tool, generally referred to as 16. The rotary steerable system 16 is also a simplified arrangement of the actuator and valve mechanics, using a singular, reciprocating valve 634 to actuate first and second pistons 746 and 748, respectively. This arrangement could be beneficial for restricted design space of a small tool size and for minimized complexity and cost. In the seventh embodiment of the rotary’ steerable tool 16, the second piston 748 is used-24- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)to bias the drill bit B pressure drop outward force of the steering piston 746. Tire fluid pressure P2 acts on the second piston 748. The second piston 748. by means of the connecting rod 750. pulls the first piston 746 inwardly, reducing the effective force. The second piston 748 is not used for steering purposes and will not engage with tire borehole wall W.

[0081] With reference to FIG, 8, the bias unit 740 includes a first channel 728 and a second channel 730. The first and second channels 728, 730 are in fluid communication with and form part of the drill string 2 and fluid passageway 24. The first and second channels 728, 730 have an inlet end 728i, 730i, respectively, and an outlet end 728o, 730o, respectively. The outlet end 728o of the first channel 728 includes a first restriction member 736. The reciprocating valve 634 can be axially aligned with the second channel 730, which can be centrally located. The valve 634 can either partially or fully block the drilling fluid F flow from the drill string 2 to the drill bit B to the second channel 730,

[0082] The bias unit 740 shown in FIG. 8 comprises the steerable first piston 746 and the second piston 748. The pistons 746, 748 can be oriented radially relative to the longitudinal axis of the housing 22 and in fluid communication with the first and second channels 728 and 730, respectively. The pistons 746, 748 are hydraulically radially displaceable and the first piston 746 is displaceable for engagement with the borehole wall W. Tire radially outward surface of the piston 746 can comprise a steering pad (such as steering pad 70). In some embodiments, apiston seal 747 forms a seal between the piston 746, 748 and bias unit 740. As showm in FIG. 8, the first and second pistons 746, 748 are coupled together with a connecting rod 750 and a retract spring 752. The first piston 746 includes an inner cavity 746c having an opening 746o through which the connecting rod 750 extends. One end of the connecting rod 750 is attached to the second piston 748 and the other end of the connecting rod 750 can include an enlarged head 750h, The retract spring 752 can extend around the connecting rod 750 and-25- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)be captured in the inner cavity 746c between the cavity opening 746o and the rod head 750h. In some embodiments, a seal ring 754 provides a seal between the connecting rod 750 and a channel divider wall 740w of the bias unit 740 to prevent high pressure fluid in one channel 628, 630 from passing to the other channel 628, 630.

[0083] FIG, 8 shows the valve 634 in the restricted position restricting the flow of drilling fluid F into the second channel 730 and allowing the drilling fluid F to flow into and through the first channel 728. The restriction member 736 at the outlet end 728o of the first channel 728 contributes to an increase in the fluid pressure within the first channel 728 which acts on the first piston 746, forcing the first piston 746 radially outward. As a result of the restricted position of the valve 634, a pressure differential exists between the first and second channels 728, 730 with the fluid pressure Pl in the first channel 728 being higher than the fluid pressure P2 in the second channel 730. The high fluid pressure Pl in the first channel 728 acts on the first piston 746 and forces the first piston 746 radially outw ard. Concurrently as the first piston 746 moves radially outward, the retract spring 752 can compress and the second piston 748 retracts. As the pressure differential between fluid pressures Pl and P2 reduces, as for example by repositioning the valve 634 to an open position, the retract spring 752 extends forcing the first piston 746 inwardly.

[0084] FIG. 9 shows an eighth embodiment of the mud hydraulic operated rotary steerable system or tool, generally referred to as 17. The rotary steerable system 17 is a simplified arrangement of the actuator and valve mechanics, using a singular, reciprocating valve 832 to actuate a piston 846. The rotary steerable system 17 includes a bias unit 840 having a first channel 828 in fluid communication with and forming part of the drill string 2 and fluid passageway 24. The first channel 828 has an inlet end 828i and an outlet end 828o. Tire-26- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)reciprocating valve 832 can be axially aligned with the first channel 828, which can be centrally located within the bias unit 840.

[0085] As shown in FIG. 9, the reciprocating valve 832 has an inlet valve 832i and an outlet valve 832o connected by a valve rod 832r. When the inlet valve 832i of the reciprocating valve 832 is retracted from the first channel inlet 8281, the first outlet valve 832o is proximal to the first channel outlet 828o.

[0086] The piston 846 is movably received within a cylinder 842 in the bias unit 840. The piston 846 can include an outer shoulder 846s having a diameter larger than the diameter of the remainder of the piston 846 and the bias unit 840 includes a recess 840r for receiving an optional piston retract spring 852 surrounding the piston 846 which is contained in the recess 840r by tire outer shoulder 846s of the piston 846. lire piston 846 is hydraulically displaceable by the fluid pressure in the first channel 828. Tire steering piston 846 can be retracted by the retract spring 852 when the inlet valve 832i is positioned closer to the channel inlet 828i than the outlet valve 832o is to the channel outlet 828o, It can also be appreciated that retract springs 852 can also be coupled to the steering pads (such as to steering pad 70). Other examples for retract springs can include torsion springs coupled to the axis of a steering pad 70 as show u in FIG. 12.

[0087] Another embodiment of the mud hydraulic operated rotary steerable system or tool, generally referred to as 21, is shown in FIG, 22. Tire rotary steerable tool 21 is similar to the rotary steerable tool 10 of FIG. 2. lire similarities generally include the drive 58, first and second valves 32 and 34, respectively, first and second channels 28 and 30 respectively, first and second restriction members 36 and 38, respectively, and first and second cylinders 42 and 44, respectively. The primary difference is that the first and second biasing elements or pistons are ball pistons 46B and 48B, respectively, and the ball pistons 46B, 48B are not connected to -27- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)one another. The first and second ball pistons 46B and 48B in this embodiment are not coupled to each other, mechanically or rigidly, and are allowed to move independently of one another. The ball pistons 46B, 48B can be spherical, elliptical, or can have otherwise curved surfaces (all of which commonly referred to as “ball pistons” within the context of this disclosure and can have the advantage of being configured to roll against the formation and thus reduce friction and wear. Since the ball pistons 46B, 48B are energized by the drilling fluid F, the rolling friction against the cylinders 42, 44 is low. Retraction of tire ball piston 46B, 48B does not automatically occur upon a decrease in fluid pressure. It is to be understood that the ball pistons 46B, 48B can be prevented from outward removal from the cylinders 42, 44, as for example by a lip or some other technique which reduces the inner diameter of the cylinders at or near the radial outer portion of the cylinders.

[0088] Optionally, nozzle adjusters 90 can be incorporated for the purpose of adju sting the pressure drop across the first and second restriction members 36 and 38, respectively. In some embodiments, the nozzle adjusters 90 are located near or adjacent to the restriction members 36, 38. In one embodiment as shown in FIG, 22, the nozzle adjuster 90 can be a pin adapted to be inserted into the housing 22 or bias unit 40 from the outer surface to be easily removable or exchangeable. There can be different length pins for different flow rates and / or drilling fluid densities. Alternatively, the pins can be adjusted in depth instead of exchanging pins of different lengths.

[0089] FIG. 22 shows the first valve 32 in the retracted position allowing the upstream drilling fluid F to flow into the first channel 28 while the second valve 34 restricts the flow of drilling fluid F into the second channel 30. The first restriction member 36 at the outlet end 28o of the first channel 28 contributes to an increase in the fluid pressure Pl within the first channel 28 which acts on the first ball piston 46B. As a result of the positions of the first and-28- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)second valves 32, 34, a pressure differential exists between the first and second channels 28, 30 with the fluid pressure Pl in the first channel 28 being higher than the fluid pressure P2 in the second channel 30, The higher fluid pressure P l in the first channel 28 acts on the first ball piston 46B and forces the first ball piston 46B radially outward. As the pressure differential between fluid pressures Pl and P2 reduces, as for example by repositioning the first and second valves 32, 34 approximately equidistant from the first and second inlet ends 28i, 30i, the increase in fluid pressure P2 with the decrease in fluid pressure Pl can cause the second ball piston 48B to move slightly radially outward while the first ball piston 46B can move slightly radially inward. A similar process and result occurs when the valves 32, 34 are repositioned such that the second valve 34 is in the retracted position and the first valve 32 restricts drilling fluid F flow from the drill string 2 to the drill bit B into the first channel 28. in this position, the high pressure is in the second channel 30 and the second ball piston 48B is forced radially outwardly.|0090] Another embodiment of the mud hydraulic operated rotary steerable system or tool, generally referred to as 23, is shown in FIG, 23. The rotary steerable tool 23 is similar to the rotary steerable tool 13 of FIG. 5. The similarities generally include the actuator assembly 26, first and second valves 232 and 234, respectively, having first and second inlet 232i, 234i and first and second outlet valves 232o, 234o, respectively, first and second channels 28 and 30 respectively, and first and second cylinders. The primary’ difference is that the first and second pistons are ball pistons 46B and 48B, respectively. As discussed with respect to the embodiment of FIG. 22, the ball pistons 46B, 48B can be spherical, elliptical, or can have otherwise curved surfaces (all of which commonly referred to as “ball pistons” within the context of this disclosure and can have the advantage of being configured to roll against the formation and thus reduce friction and wear. Since the ball pistons 46B, 48B are energized by the drilling fluid F, the rolling friction against the cylinders 42, 44 is low. Retraction of the -29- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)ball piston 46B, 48B does not automatically occur upon a decrease in fluid pressure. For example and with reference to FIG. 23, when the actuator assembly 26 repositions the second inlet valve 234i from the retracted position to the closed position (while concurrently repositioning the first inlet valve 232i from the closed position to the retracted position), the pressure in the second channel 30 decreases while the pressure in the first channel 28 increases causing the first ball piston 46B to extend radially. With the decrease of pressure in the second channel 30 the second ball piston 48B is allowed to move radially inward, for example, if it comes into contact with the borehole wall W. As discussed above with respect to the second and third embodiments, the first and second inlet valves 2321, 234i can close completely at the extreme forward position, however, a gap will exist at the first and second outlet valves 232o, 234o.

[0091] It is to be understood that the ball pistons 46B, 48B can be prevented from outward removal from the cylinders 42, 44, as described above.

[0092] With respect to the ball piston embodiments shown in FIGS. 22 and 23, it is to be understood that there can be more than one ball on a given side to increase side force and / or to reduce stress at the wall contact. FIGS. 24 and 25 show a couple of exemplary arrangements having a plurality of balls on each side. Referring to FIG. 24, a plurality of ball pistons 46B are shown aligned axially in the longitudinal direction of the tool. It is to be understood that the plurality of ball pistons 46B would be in fluid communication with the first channel 28 (FIG. 22). Although not shown in FIG. 24, a similar number of ball pistons 48B can be similarly arranged on the opposite side and in fluid communication with the second channel 30 (FIG. 22). As shown in FIG. 24, one or more securement plates 92 can be secured to the bias unit 40 and / or housing 22 (FIG. 22) with fasteners 94, with the securement plate 92 including an opening 96, that can be circular, for receiving a portion of the ball piston 46B. In some-30- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)embodiments, the plate opening 96 is smaller in diameter than the diameter of the ball piston 46B to prevent removal of the ball piston 46B from the cylinder 42 (FIG. 22).

[0093] FIG. 25 illustrates an alternative embodiment to the longitudinally-aligned plurality of ball pistons shown in FIG. 24. In FIG. 25, the plurality of ball pistons 46B on a given side are angularly offset to increase borehole centering efficiency as opposed to placing the ball pistons 46B in line on opposing sides to the tool. The ball pistons 46B positioned on a given side point to one side of the tool, but with an angular offset. As one example, the angular offset can be 10° between each cylinder. Reasonable ranges would be from 0° (longitudinally aligned) to rotated by 90°. In FIG. 25, a 90° rotation would be created by an angular offset of 45° between each cylinder.

[0094] FIGS. 10 and 11 show examples of control electronics and power sources. Although the actuator, valving and piston arrangements shown in FIGS. 10 and 11 correspond with the arrangements shown in FIG. 4, it is to be understood that any of the other actuator, valving and piston arrangements, including other combinations of such, are equally applicable and within the scope of the present invention.

[0095] FIG, 10 shows a turbine 102 coupled to an alternator 104, and a controller / electronics module 106. The controller / electronics module 106 is electrically connected to the alternator 104, for example by an electrical conductor or wire 108, and the actuator assembly 26 is connected, for example by electrical conductor or wire 110, to the controller / electronics module 106. As the drilling fluid F flows through the fluid passageway or bore 24 of the drill string 2, the drilling fluid F flows through the turbine 102 before passing the actuator assembly 26 and valve(s) and then through the flow channels. The turbine 102 and alternator 104 convert the mechanical energy into electricity to power the-31- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)controller / electronics module 106. In FIG. 11, the turbine 102 and alternator 104 (FIG. 10) have been replaced by a battery 112.

[0096] An exemplary operation of drilling a deviated borehole H using the rotary steerable tool of the present invention will now be described with reference to FIGS. 1, 4 and 11; however, it is to be understood that the operation also applies to the other disclosed embodiments. Because the BHA 20 including the rotary steerable tool 12 are rotating during drilling of the borehole H, it is challenging to keep the drill bit B directed to a target location that is not aligned with the longitudinal axis of the BHA 20. Tire point to which the drill bit B is to drill in the borehole H is stationary although the rotary steerable tool 12 and BHA 20 are rotating about the axis of the BHA 20. As a result, the first and second pistons 346, 348 which provide the steering force by pushing against the borehole wall W must continuously be controlled to push against a particular location of the borehole wall W to control the direction of the drill bit B. In order to push the drill bit B in the target direction the first and second pistons 346, 348 must be extended yvhen they are located at a certain point or certain circumferential portion or length along the repeating 360° path of the pistons 346, 348 relative to the borehole wall W Thus, for each revolution of tire BHA 20 and rotary steerable tool 12 during a drilling deviation, each of the first and second pistons 346, 348 can be extended and retracted one time during each revolution of tire rotary steerable tool 12. With reference to FIG, 4, the actuator assembly 26 controls the first and second valves 232, 234 which direct the flow of drilling fluid F to selectively urge the desired pistons yvith a desired force at a given time and for a given duration.

[0097] With reference to FIG. 11, the actuator assembly 26 is controlled by the controller / electronics module 106. The controller / electronics module 106 can be configured to receive information from sensors such as RPM, toolface, inclination and azimuth sensors.-32- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)The sensors can be used to determine the RPM, toolface, inclination and direction of the rotary steerable tool 12. Such sensors can be located within the electronics module 106 or in other locations in the drill string 2 or BHA 20. The sensors are well known in the industry. The controller / electronics module 106 receives and transmits information from and to the surface. The controller 106 processes information and controls the actuator assembly 26 such that the desired differential fluid pressure is applied to the desired piston forcing the piston against the borehole wall W in a timed manner and engaging the piston with the borehole wall W at a controlled direction while the drill string 2 and BHA 20 are rotating.

[0098] In the disclosed embodiments, the actuator assembly 26, 626 controls one or two valves which direct the flow of drilling fluid F to selectively urge the desired pistons with a desired force at a given time for a given duration. The rotary steerable tool uses the actuator assembly to generate a pressure pulse in the drilling fluid F in the fluid passageway 24 by varying the relative position between the valve member(s) and the flow channel(s) of the fluid passageway creating a differential pressure across the fluid passageway. Referring to FIG. 3 as an example, as a result of the mechanical coupling the second inlet valve 234i blocks the second inlet end 30i into the second channel 30 when the first outlet valve 232o closes the outlet end 28o of the first channel 28. In this position, a differential pressure (fluid pressure Pl higher than fluid pressure P2) is created by the partial blocking of first and second channels 28 and 30, respectively. This pressure drop is variable and in response to positioning of the valve components.

[0099] As discussed above with respect to the second embodiment of the rotary steerable system 11, the first and second inlet valves 232i, 234i can close completely at the extreme forward position, however, a gap should exist at the first and second outlet valves 232o, 234o.-33- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)The same is true for the rotary steerable systems 12, 13, 14, 17, 18 and 19 of FIGS. 4, 5, 6, 9, 10 and 11, respectively.

[0100] The actuator assembly controls the position of the valves for example based upon the current flow rate, current fluid density, and demanded differential pressure. The present invention allows for the magnitude of the pressure difference between the fluid pressures Pl and P2, also referred to as the signal pressure to be adjustable with respect to the existing flow rate and density of the drilling fluid F. Such adjustment is desired to omit complex preparation before deploying the tool. Without such adjustment and with fixed open and close valve positions, the signal pressure (fluid pressure Pl minus fluid pressure P2) would be greatly affected by the current flow and density situation for a particular deployment, which would require the tool to be disassembled and mechanically adjusted prior to each deployment. As an example, the flow rate between two different deployments can vary by 100% (first deployment flow x, second deployment flow 2x), the density between two consecutive deployments (first deployment density x, second deployment density 2x). Since there exists a quadratic relation between flow and pressure drop and a linear relation between density and pressure drop, the signal pressure for the second deployment of the above example would be 8 times (22■ 2) the signal pressure from the first deployment and considering fixed valve positioning, regardless of current flow and density. Such deviation in pressure drop would not be acceptable and thus demands either manual adaption (adjustment) or positioning with respect to current flow and density. There are several methods known in the art to detect current flow and density at a downhole location and inside a downhole tool. Both values can be obtained from a turbine 102 / alternator 104 device (FIG. 10), for example by systems and methods disclosed in US20250020033. Alternatively, such valves as disclosed here, can also be used to measure current flow and density situations, applying certain routines and algorithms. For example, the pressure drop across one or more valves can be measured and -34- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)mud flow rate and / or density can be calculated from that measured pressure drop across the one or more valves or the pressure drop across the one or more valves can be even controlled by controlling the gap (e.g., gaps 28g, 28h, 30g, 30b) in response to the measurement of the pressure drop across the one or more valves. Yet another method to react on changing flow and density situations and thus position the valves accordingly can include sending respective values from the surface to the downhole tool (downlink),

[0101] The controller / electronics module 106 calculates a certain demand for a steering vector. While the direction is controlled by the timing of valve actuation with respect to actual RPM, toolface and / or azimuth, the piston force is controlled by tire pressure drop as explained above. The pressure drop in turn depends on the current flow rate pumped through the fluid passageway (and the valve assembly), of the density of the drilling fluid F (and potentially also viscosity to a minor extent) and on the amount of restriction (valve position). For example, the movement of a valve (such as valves 32, 34, 232, 232i, 232o, 234, 234i, 234o) can be controlled, e.g., by controller circuitry within controller / electronics module 106. For example, the controller / electronics module 106 can control up to which level the valve closes its respective inlet or outlet end (such as inlet ends 28i, 30i or outlet ends 28o, 30o), thereby controlling the height of the pressure pulses that are created by closing the valve. That is, controller / electronics module 106 can control remaining gap (such as gap 28g, 28h, 30g, 30h) between the valve and the respective inlet or outlet end thereby controlling the amount of piston force (such as piston force PF1 or PF2) that acts on a piston (such as piston 46, 48) to steer the rotary steerable system or tool. For example, gap (such as gap 28g, 28h, 30g, 30h) can be controlled to be smaller in situations where higher piston force is required and can be controlled to be wider when lower piston force is needed. Thus, controlling the movement of the valve, and thereby the piston force allows to apply control of the piston force, commonly-35- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)referred to as proportional steering in embodiments. Taking all these factors into consideration, a precise steering vector can be calculated and adjusted.

[0102] For example, if the tool is currently drilling a horizontal section (90° inclination) and it is desired to steer downwards (less than 90° inclination) with 50% force, the valve is activated (creating pressure in the respective steering piston chamber) at a time when the steering piston is approaching a position facing upwards (with respect to gravity), thus creating a force direction downwards (i.e., lower than horizontal, less than 90° inclination). This would define the steering direction. Hie steering force would be adjusted by the respective pressure drop during this period.

[0103] As shown in the various embodiments, the steerable pistons can be rigidly coupled (FIGS. 4 and 6), not coupled (FIG. 5), or coupled through retract springs (FIGS. 2 and 3). Spring or rigid coupling reduces the side force of the piston against the borehole wall W and thus reduces friction, wear, abrasion, and rock damage. Pistons that are not coupled (FIG. 5) and don’t have individual retract springs 652 extend when a flow is established. Piston forces are biased by the pressure drop across the drill bit B (fluid pressure P2 - fluid pressure P3). As explained above, the rotary steerable tools of FIGS. 2, 3, 4, 6, 8, 9, 10 and 11 are independent of drill bit B pressure drop. The steering force is not affected by piston coupling.

[0104] As explained above, the rotary steerable tools of FIGS. 2, 3, 4, 6, 8, 9, 10 and 11 can feature individual piston retract springs 652 or steering pad retract springs (either linear springs or torsion springs, such as steering pad retract springs 87). Forthose rotary steerable tools that do not have coupled pistons (e.g., pistons coupled by rigid couplings, such as pistons 343, 348, 346a, 346b, 348a, 348b coupled by connecting rods 350, 350a, 350b or pistons coupled by couplings including springs, such as pistons 746, 748 coupled by connecting rod 750 via retract spring 752), the pressure drop across the drill bit B (fluid pressure P2 - fluid pressure P3) and -36- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)resulting side force of the piston (such as pistons 746, 748) against the borehole wall W and thus friction can at least be partially biased by sizing retract springs (such as retract spring 752) according to the expected pressure drop across the drill bit B. In an exemplary’ embodiment, the pressure drop across the drill bit B is expected to be 10 bar at operating drilling fluid F flow from the drill string 2 through the drill bit B and such 10 bar pressure can exert the steering piston by 5000 N force. Sizing the retract springs (such as retract spring 752) to retract the piston (such as pistons 746, 748) or steering pad 70 by such force would offset the extra force created by the pressure drop across the drill bit B and thus reduce the extra friction, wear, abrasion, and rock damage. It can be appreciated that such retract springs are difficult to be fitted into the available design space and therefore partial offset of the extra side force caused by the pressure drop across the drill bit B can be achieved. A good option for a long and compressed spring can be an elongated torsion rod in line with the axis for the optional steering pad 70 and attached to the tool housing 22 and steering pad 70 respectively,

[0105] The steerable pistons are actuated by the drilling fluid F provided to and through the flow channels. In the first through fifth embodiments shown in FIGS. 2-6, the rotary steerable tool includes two or more steerable pistons and / or steering pads, each capable of extending radially from the housing 22 to push against the borehole wall W at controlled select times. The first through fourth embodiments (FIGS. 2-5) of the rotary steerable tool include two steerable pistons radially aligned and the fifth embodiment (FIG. 6) comprises four steerable pistons attached to two steering pads. Devices are not limited to such number of pistons.

[0106] The pistons and cylinders of the embodiments can be made from tungsten carbide and the valves are can be made from tungsten carbide or comparable wear resistant material such as ceramics, hardened steel, or other base material with wear resistant coating applied-37- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)(e.g. physical vapor deposition (PVD) / chemical vapor deposition (OVD) coating, high velocity oxygen fuel (HVOF) coating or equivalent).

[0107] The mud hydraulic operated rotary steerable system uses a telemetry-like drilling fluid valve that chokes the entire volume (or a major portion of) flow and uses the resulting differential pressure to selectively actuate steering pistons and / or steering pads, Tire disclosed rotary steerable system does not utilize a non-rotating sleeve as used in some prior art rotary steerable systems, and hence operates pistons / steering pads in a cyclic maimer and once per revolution for creating curvatures. The rotary steerable system takes advantage of a mud pulse actuation system that allows fast valve actuation and is applicable to piston / steering pad actuation of 400 rpm (7 Hz) at relatively low power demand.

[0108] Hie present invention takes advantage of operating piston pressures and relief from the main flow as opposed to bypass flow operated systems of prior art devices and is therefore not restricted in piston size and quantity, respectively flow towards piston(s) to charge and discharge with steering pressure,

[0109] It is to be understood that the pistons of the disclosed embodiments can be charged and discharged rapidly and as opposed to prior art systems literally without lag, even at high rpm and large piston sizes.

[0110] The above-described embodiments of the rotary steerable system can also be used to provide mud pulse telemetry data to the earth’s surface 3. The rotary steerable system can operate the steering function and the telemetry function at the same time. As discussed below', the steering function requires a rather low frequency to actuate the steering device twice per revolution (except FIG. 7 which is once per revolution) and the telemetry signal, operating at a higher frequency, can be superimposed on the steering pressure pulse or in other manners as described below.-38- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)

[0111] Details and methods for the mud pulse telemetry communication of data between downhole and the surface for use with the tool 100 will now be described.

[0112] The two piston / steering pad design shown in FIGS. 3-5, 8, 10 and 11 including the four piston / steering pad design shown in FIG. 6 creates cyclic pressure pulses for steering with two times the rotary frequency. As discussed above, the steering pressure can be altered from low to high values and is dependent on the position of the valve restricting flow. The needed steering pressure can be lower, for example, when the turn or change in direction is more gradual. FIG. 13 shows an example of a tool rotation of 60 rpm, a steering pressure of approximately 20 bar produced at 2 Hz. A steering assembly is selectively actuated during the RSSMPT tool 10 rotation to push the drill bit B into the desired direction. This actuation can be assumed to require a periodic (e.g., sinusoidal or according to an absolute value of a sinusoid) pressure actuation with a certain amplitude 620 (FIG, 13) and a period 610 over one RSSMPT tool 10 rotation. The toolface angle of the steering piston at the time of the pressure amplitude of the periodic pressure actuation determines the current steering direction (up, down, left, right, for example corresponding to a toolface angle of 0°, 180°, 270°, and 90°, respectively) with respect to the earth formation G For example, if the toolface angle where the piston 62 is periodically actuated is at 45°, the RSSMPT tool 10 steers into a toolface direction of 225° (i.e., generally to the opposite side). The steering actuation is considered to create a low frequency periodic pressure signal. FIG, 14 shows an example of a tool rotation of 120 rpm, approximately 13 bar steering pressure amplitude produced at 4 Hz corresponding to a period of 0.25 seconds. These examples of pressure and rpm are merely for illustrative purposes.

[0113] One method of telemetry system currently in use is pulse position coding. Pulse position coding for mud pulse telemetry systems and methods are disclosed for example by-39- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)US4908804A and US4787093A. Pulse position coding uses timeslots and positions pulses inside such slots. Information is coded with the position of one or more pulses in fixed numbers of slots. FIG. 15 is an example showing a pulse position coding scheme, exemplary pulse position coding schemes are found in U. S. 4,908,804 and U. S. 4,787,093. This coding scheme is known to be quite robust and efficient, and is known to operate with a minimum number of actuations with maximum bit rate information which reduces wear and power consumption.

[0114] The surface system recognizes the steering pressure frequency and adapts slot length to the steering pulses, and such (variable) frequency can be used to define the slot length. Information can be coded as a sequence of pulses with respect to the slots. Typically, the information is coded in binary as a sequence of zeroes ("‘0”) and ones (“1”).

[0115] FIG. 16 shows an example for a superimposed high frequency mud pulse telemetry signal 92 to a steering pulse 93 having a steering pressure of approximately 20 bar amplitude produced at 4 Hz (corresponding to a period 610 of 0.25 seconds) at a RSSMPT tool rotational velocity of 120 rpm. Those skilled in the art will appreciate that the RSSMPT tool rotational velocity can also be expressed in Hertz (for example, an RSSMPT tool rotational velocity of 120 rpm is equivalent to 2 Hz) and that in some embodiments, the steering pressure signal frequency is said RSSMPT tool rotational velocity in Hertz multiplied by the number of steering pistons (such as pistons 46, 48, for example). As shown, in this embodiment, the high frequency telemetry signal 92 is of short duration 95 compared to the duration 98 of the steering pulse 93 (corresponding to the period 610 of the steering pulse 93 of 0.25 seconds) when the steering valve is near to or at the closed position, thus reducing the valve stroke for the superimposed high frequency pressure pulse. For example, in one embodiment the duration 95 of the high frequency telemetry signal 92 is 70% or less (such as 50% or less or even 35% or less) of the duration 98 or period 610 of the steering pulse 93. In the example shown in FIG.-40- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)16, the information is coded within eight slots over a two second interval with each slot length 0.25 second corresponding to the period 610 of the steering pulse 93 signal. The 4 Hz steering pulse of approximately 20 bar in each slot is representative of the binary bit “0”. In FIG. 16, pressure pulses of approximately 10 bar and 30 Hz are shown superimposed on the steering pulse in the 2nd, 5th, and 7thslots (representative of the binary bit ‘T”). This correlates to a bit sequence of 01001010. The bit sequence is detected at the surface 3. In some embodiments, the high frequency pressure pulse is superimposed on the 20 bar steering pulse as shown in FIG. 16.

[0116] It is to be understood that the same information can be coded in other manners. FIG.17 show's the same information (bit sequence of 01001010) coded without using the high frequency pressure pulse 92, 92a and by omitting the steering pulse 93a within the 2nd, 5th, and 7thslots. In this example, the absence of the 20 bar steering pulse within the slot represents the binary bit “1”, whereas the presence of the steering pulse within the slot represents the binary bit “0”. This particular example loses some of the steering capacity as a result of the omitted steering pulses.

[0117] Yet another way of coding the same information can be accomplished by placing high frequency pulses at certain slots, but without superimposing them to the steering pulses as illustrated in FIG. 18. FIG. 18 shows a bit sequence of 01001010 coded by placing high frequency pressure pulses 92a at certain slots 97a but replacing rather than superimposing them to the steering pulses 93a. In the example illustrated in FIG. 18, the high frequency pressure pulse 92a is approximately 15 bar and 30 Hz. In this example, the presence of the high frequency pressure pulse 92a and absence of the 20 bar steering pulse 93a within the slot 97a represents the binary bit “1”, whereas the presence of the steering pulse 93a within the slot 97a represents the binary bit “0”. It is to be understood that the pressures and frequencies shown-41- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)in the examples are only for illustrative purposes and are not limiting to the present invention as other pressures and frequencies can be used.

[0118] Using the methods according to FIGS. 17 and 18 will have little, if any, effect on the steering direction due to the stochastic nature of coded information. However, the methods according to FIGS, 17 and 18 will affect the steering dogleg capabilities because not every possible piston / steering pad actuation is fully used for steering. The method of FIG. 18 is better in this respect as compared to the method of FIG. 17 where no force is created during a full slot length. Since pulse position coding is using fewest possible pulses (historically to conserve energy and pulser wear), negative effects can be tolerable.

[0119] The method illustrated in FIG. 16 will not negatively affect the steering vector, however, it might not be applicable at higher rpm (6 revolutions per second) as illustrated in FIG. 19. The decoder at the surface 3 may not be able to sufficiently distinguish the timing (pulse position) of the short duration burst (30 Hz, 10 bar) over the 12 Hz steering signal. However, transferring the methods of FIGS. 17 and 18 to high rpm seem applicable.

[0120] FIG. 20 shows a 360 rpm scenario with respective slot length of 0.083 second or 12 Hz. The tool rotates 12 revolutions during the 2 second duration and sends three consecutive bit sequences in the 2nd, 5th, and 7th slots of an eight-slot length duration (8*0.083 = 0.66 s). Tire coding technique is similar to that shown in FIG. 17. The bit sequence of FIG. 20 is 010010100100101001001010.

[0121] In the example in FIG 21, the RSSMPT tool rotates with 360 rpm, and, thus, a 12 Hz steering pressure signal 93c (rotary actuation) is displayed for an arrangement with 2 steering pistons (such as pistons 46, 48). Hie length of slot 97c in this case is 1 second / 12 = 0.0833 second corresponding to half the duration required for one RSSMPT tool rotation. In the example, the telemetry signal 92c is selected to have a 15 bar telemetry signal -42- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)(corresponding to the pressure amplitude 620) at a telemetry signal frequency of 30 Hz for pulse position coding. FIG. 21 shows a scenario for pulse position coding. Slots 2, 5, 7, and 10 are filled with telemetry signal 92c at a much higher frequency, which is in this example 30 Hz at 15 bar telemetry signal pressure amplitude, The coding technique is similar to that shown in FIG. 18. The bit sequence of FIG. 21 is 01001010 0100101001001010.

[0122] FIGS. 21a-21c are graphical representations of pressure changes over time and corresponding bit values. FIG. 21a represents an embodiment with variable RPM and telemetry’ signal 92c still in sync with variable steering pressure signal 93c. This is still suitable for pulse positioning where pulse slots are not defined by time but by pressure variations of the steering signal.

[0123] FIG. 21 b is an embodiment with uniform RPM and telemetry signal 92c not in sync with uniform steering pressure signal 93c. The surface decoder separates high and low frequencies of the signal to obtain a series of ‘T’s and “0”s. In this embodiment, time is measured uphole and downhole to identify ‘T’s and “0”s.

[0124] FIG. 21c is an embodiment with variable RPM and telemetry signal 92c NOT in sync with variable steering pressure signal 93c, The surface decoder separates high and low frequencies of the signal to yield to a series of “T’s and “0”s. Time is measured uphole and downhole to identify “T’s and “0”s.

[0125] in addition to the above, there can be other ways to telemeter information using this system.

[0126] Thus, as described above and shown in the drawings, the mud hydraulic operated rotary steerable system can be used to steer the direction of the drill bit and also to convey telemetry’ signals to the surface using a variety' of techniques.-43- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)

[0127] Nomenclature:1. drill bit B2. Bit nozzles Bn3. surface data acquisition and control system C4. drilling fluid / mud F5. borehole H6. geological formation G7. drilling fluid system M8. fluid pressure Pl in the first channel9. fluid pressure P2 in the second channel10. fluid pressure in annulus P3 at or near the rotary steerable system or tool11. first piston force PF112. second piston force PF213. drilling rig R14. borehole wall W15. drill string 216. earth’s surface 317. drilling fluid tank 418. annulus 619. mud hydraulic operated rotary’ steerable system 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 2320. bottom hole assembly (BHA) 2021. housing 2222. fluid passageway or bore 2423. actuator assembly 2624. first channel 2825. first inlet end 28i26. outlet end 28o27. second channel 3028. inlet end 30i29. outlet end 30o30. gap 28g, 28h, 30g, 30h31. first valve 3232. first valve rod 32r33. second valve 3434. second valve rod 34r35. first restriction member 3636. second restriction member 3837. bias unit 4038. channel divider wall 40w39. first cylinder 4240. second cylinder 4441. first biasing element or piston 4642. first biasing element or ball piston 46B43. inner cavity 46c44. opening 46o45. piston seal 4746. second biasing element or piston 4847. second biasing element or ball piston 48B-44- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)48. connecting rod 5049. head 50h50. retract spring 5251. seal 5452. crankshaft 5653. drive 5854. linkage 6055. rod springs 6256. steering pad 7057. steering pad holder 7258. pressure compensator 8059. cylinder 8260. piston 8461. seal 8662. nozzle adjuster 9063. securement plate 9264. fasteners 9465. opening 9666. turbine 10267. alternator 10468. controller / eiectronics module 10669. electrical conductor 10870. electrical conductor 11071. first valve 23272. first inlet valve 232i73. first outlet valve 232o74. first valve rod 232r75. second valve 23476. second inlet valve 234i77. second outlet valve 234o78. second valve rod 234r79. first biasing element or piston 346, 346a, 346b80. second biasing element or piston 348, 348a, 348b81. connecting rod 350, 350a, 350b82. first biasing element or piston 44683. second biasing element or piston 44884. actuator assembly 62685. first channel 62886. inlet end 628i87. outlet end 628o88. second channel 63089. inlet end 630i90. outlet end 630o91. valve 63492. first restriction member 63693. bias unit 64094. recess 640r95. cylinder 64296. biasing element or piston 64697. shoulder 646s-45- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)98. piston retract spring 65299. first channel 728100. inlet end 728i101. outlet end 728o102. second channel 730103. inlet end 730i104. outlet end 730o105. first restriction member 736106. bias unit 740107. channel divider wall 740w108. first biasing element or piston 746109. inner cavity 746c110. opening 746o111. piston seal 747112. second biasing element or piston 748113. connecting rod 750114. head 750h115. retract spring 752116. seal ring 754117. first channel 828118. inlet end 828i119. outlet end 828o120. reciprocating valve 832121. inlet valve 832i122. outlet valve 832o123. valve rod 832r124. bias unit 840125. recess 840r126. cylinder 842127. biasing element or piston 846128. outer shoulder 846s129. retract spring 852

[0128] The present invention described herein is well adapted to carry’ out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While one or more embodiments of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. Although the invention has been described with reference to exemplary embodiments, it should be appreciated by those of skill in the art that various modifications are well within the scope and spirit of this disclosure. Further, those of skill in the art will appreciate that the invention is-46- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)not limited to any specific embodiment and / or application and that the various embodiments described herein are illustrative and not restrictive.-47- IM-#10733717.5

Claims

Attorney Docket No.: 65DRL-510615-WO-2 (000240)CLAIMSWhat is claimed is:

1. A rotary steerable drilling system for drilling a borehole through the earth’s subsurface, the rotary steerable drilling system comprising:a housing configured to be mechanically connected to a drill bit and a drill string;a fluid passageway in the housing configured to guide a flow of a drilling fluid from the drill string to the drill bit;a valve disposed in the fluid passageway, the valve configured to temporarily increase the pressure in at least a portion of the drilling fluid flowing from the drill string to the drill bit; anda biasing element in hydraulic communication with the increased pressure, the biasing element extending into an annulus between a borehole wall of the borehole and the housing in response to the increased pressure.

2. The rotary steerable drilling system of claim 1, wherein the piston has a curved surface and / or wherein the piston includes a steering pad.

3. The rotary steerable drilling system of claims 1 and 2, wherein the fluid passageway is divided in a first channel configured to guide a first portion of the flow of the drilling fluid from the drill string to the drill bit and a second channel configured to guide a second portion of the flow of the drilling fluid from the drill string to the drill bit, wherein the first channel is in fluid communication with the piston, and wherein the valve is configured to selectively-48- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)restrict the flow of the drilling fluid from the drill string to the drill bit through at least one of the first channel and the second channel.

4. The rotary steerable drilling system of claims 1 - 3, wherein the drilling fluid flows through tire valve at a first averaged flow rate and through the drill bit at a second averaged flow rate, and wherein the second averaged flow rate is 80% of the first averaged flow rate or more.

5. The rotary steerable drilling system of claims 1 - 4. wherein the rotary steerable drilling system is communicatively coupled to a toolface sensor or an RPM sensor and the valve is periodically actuated in response to measurements of the toolface sensor or the RPM sensor.

6. The rotary steerable drilling system of claims 1 - 5, wherein the valve is periodically actuated to steer the drill bit through the earth’s subsurface and to communicate via a mud pulse telemetry system through the drill string.

7. The rotary steerable drilling system of claim 6, wherein the first and the second biasing element are mechanically coupled by at least one of a spring and a rod.

8. The rotary steerable drilling system of claim 3, wherein the first portion of the flow flows with a first averaged flow rate through the first channel and the second portion of the flow flows with a second flow' rate through the second channel, and wherein one of the first averaged flow rate and the second averaged flow rate is smaller than the other of the first averaged flow rate and the second averaged flow rate, and wherein the ratio of the smaller averaged flow' rate to the other averaged flow rate is larger than 0.1.

9. The rotary steerable drilling system of claims 3 and 8, wherein the biasing element is a first biasing element in hydraulic communication with the first channel and wherein the rotary¬ steerable drilling system is further comprising a second biasing element in hydraulic-49- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)communication with the second channel, the second biasing element temporarily extending into the annulus between the borehole wall of the borehole and the housing.

10. The rotary steerable drilling system of claim 9, wherein the valve is a first valve and the temporarily increased pressure is first temporarily increased pressure in the first channel the rotary steerable drilling system further comprising a second valve disposed in the fluid passageway, tire second valve configured to generate a second temporarily increased pressure in the second channel, wherein the second biasing element temporarily extends into the annulus in response to the second temporarily increased pressure.

11. A rotary steerable drilling system for drilling a borehole, comprising:a drill bit;a drill string being rotatable from the earth’s surface or from a downhole drive, the drill string including a bottom hole assembly;a drilling fluid for flowing through the fluid passageway;the bottom hole assembly including:a housing mechanically connected to tire drill bit and the drill string;a fluid passageway in the housing configured to guide a flow of a drilling fluid from the drill string to the drill bit;a valve disposed in the fluid passageway, the valve configured to temporarily increase the pressure in at least a portion of the drilling fluid flowing from the drill string to the drill bit;-50- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)a biasing element in hydraulic communication with the increased pressure, the biasing element extending into an annulus between a borehole wall of the borehole and the housing in response to the increased pressure.

12. A method of drilling a borehole through the earth’s subsurface comprising:obtaining a rotary steerable drilling system comprising:a housing configured to be mechanically connected to a drill bit and a drill string,a fluid passageway in the housing configured to guide a flow of a drilling fluid from the drill string to the drill bit,a valve disposed in the fluid passageway, anda biasing element in hydraulic communication with the drilling fluid; using the valve to temporarily increase the pressure in at least a portion of the drilling fluid flowing from the drill string to the drill bit;extending the biasing element into an annulus between a borehole wall of the borehole and the housing in response to the increased pressure.

13. The method of claim 12, wherein the fluid passageway is divided in a first channel and a second channel, and wherein the first channel is in fluid communication with the piston, the method further comprising,guiding a first portion of the flow of the drilling fluid from the drill string to the drill bit into the first channel and a second portion of the flow of the drilling fluid from the drill string to the drill bit into the second channel;-51- IM-#10733717.5Attorney Docket No.: 65DRL-510615-WO-2 (000240)selectively restricting, with the valve, the flow of the drilling fluid from the drill string to the drill bit through at least one of the first channel and the second channel.

14. The method of claims 12 - 13, further comprising periodically actuating the valve to steer the drill bit through the earth’s subsurface and to communicate via a mud pulse telemetry system through the drill string.

15. The method of claim 13, wherein the biasing element is a first biasing element in hydraulic communication with the first channel and wherein the rotary steerable drilling system is further comprising a second biasing element in hydraulic communication with the second channel, the method further comprising temporarily extending the second biasing element into the annulus between the borehole wall of the borehole and the housing.-52- IM-#10733717.5

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