Patent Description:
When drilling a wellbore, the drill bit may be turned by a rotation of the drill string or by a downhole motor. The downhole motor may be used to rotate the drill bit while the drill string is stationary. In such a drill string, the bottom hole assembly (BHA), located at the end of the drill string, may include the downhole motor, the drill bit, and a bearing section. The bearing section couples between the motor sub and the drill bit and houses the drive shaft which couples between the drill bit and the downhole motor. The bearing section couples to the drive shaft through one or more bearings to allow rotation of the drive shaft as the bearing section remains generally stationary within the wellbore.

During a directional drilling operation, a bent sub having an adjustable or fixed bend is typically included in the BHA between the downhole motor and the bearing section. The bent sub introduces an angle in the progression of the wellbore by angling the bearing section and therefore the drill bit relative to the downhole motor. However, the introduced external angle may, for example and without limitation, limit the ability to operate the drill string in rotary mode because of the increased bit orbit diameter, increased friction, and increased vibration or shock on the drill string.

<CIT> discloses a method for forming a bearing assembly having the features of the pre-characterizing portion of claim <NUM> and generally refers to an adjustable bent housing consisting of three tubular members arranged end to end in relation, wherein each tubular member has an internal bore. A central tubular member is disposed between first and second tubular members. An internal tubular member extends into and engages the interior bores of the three tubular members.

The present invention is set out in the claims. Any embodiment not falling within the scope of the claims is included for illustrative purposes only.

The present disclosure provides for a method for forming a bearing assembly. The method may include providing an upper housing blank. The upper housing blank may have a generally cylindrical outer surface. The longitudinal axis of the upper housing blank may define a bore longitudinal axis. The method may include forming a bore through the upper housing blank. The bore may define an upper bearing housing bore. The upper bearing housing bore may be formed concentrically with the bore longitudinal axis. The method may include machining the outer surface of the upper housing blank to form an upper bearing housing outer surface. The upper bearing housing outer surface may be generally cylindrical. The longitudinal axis of the upper bearing housing outer surface may define a bearing housing longitudinal axis. The bearing housing longitudinal axis may intersect the bore longitudinal axis at an angle. The method may include positioning a driveshaft within the upper bearing housing bore.

An aspect not according to the present invention also provides for a bearing assembly for a downhole tool. The bearing assembly may include an upper bearing housing. The upper bearing housing may include an upper bearing housing outer surface. The upper bearing housing outer surface may be generally cylindrical along a bearing housing longitudinal axis. The upper bearing housing may include an upper bearing housing bore formed therein defining an upper bearing housing inner surface. The upper bearing housing bore may be generally cylindrical and may be formed along a bore longitudinal axis. The bore longitudinal axis may be formed at an angle to the bearing housing longitudinal axis. The bearing assembly may include a lower bearing housing. The lower bearing housing may be mechanically coupled to the upper bearing housing. The lower bearing housing may include a lower bearing housing bore formed along the bore longitudinal axis defining a lower bearing housing inner surface. The bearing assembly may include a driveshaft positioned within and concentric with the upper bearing housing bore and the lower bearing housing bore such that it extends along the bore longitudinal axis.

An aspect not according to the present invention also provides for a bottomhole assembly. The bottomhole assembly may include a bearing assembly. The bearing assembly may include an upper bearing housing. The upper bearing housing may include an upper bearing housing outer surface. The upper bearing housing outer surface may be generally cylindrical along a bearing housing longitudinal axis. The upper bearing housing may include an upper bearing housing bore formed therein defining an upper bearing housing inner surface. The upper bearing housing bore may be generally cylindrical and may be formed along a bore longitudinal axis. The bore longitudinal axis may be formed at an angle to the bearing housing longitudinal axis. The bearing assembly may include a lower bearing housing. The lower bearing housing may be mechanically coupled to the upper bearing housing. The lower bearing housing may include a lower bearing housing bore formed along the bore longitudinal axis defining a lower bearing housing inner surface. The bearing assembly may include a driveshaft positioned within and concentric with the upper bearing housing bore and the lower bearing housing bore such that it extends along the bore longitudinal axis. The bottomhole assembly may include a transmission housing mechanically coupled to the upper bearing housing. The bottomhole assembly may include a transmission shaft positioned within the transmission housing, the transmission shaft mechanically coupled to the driveshaft.

An aspect not according to the present invention also provides for a method. The method may include providing a bearing assembly. The bearing assembly may include an upper bearing housing having an upper bearing housing outer surface. The upper bearing assembly may include a control piston positioned within a control piston cylinder. The control piston cylinder may be formed in the outer surface of the upper bearing housing. The upper bearing assembly may include a control port formed in the upper bearing housing. The control port may be in fluid communication with the control piston cylinder. The upper bearing assembly may include a control valve assembly positioned at the upper end of the upper bearing housing. The control valve assembly may include a fluid supply port formed in the upper bearing housing in fluid communication with the interior of the upper bearing housing. The control valve assembly may include a valve actuator pivotably coupled to the upper end of the upper bearing housing by a pivot pin. The pivot pin may be tubular. The valve actuator may include a valve port formed therein in fluid communication with the fluid supply port through the pivot pin. The control valve assembly may include an output port formed in the upper bearing housing in fluid communication with the control port. The output port may be in fluid communication with the valve port when the valve actuator is in an open position and out of fluid communication with the valve port when the valve actuator is in a closed position. The method may include positioning the valve actuator in the open position such that the valve port and output port are in fluid communication. The method may include providing fluid pressure from the interior of the upper bearing housing to the control piston cylinder through the fluid supply port, valve port, output port, and control port. The method may include extending the control piston. The method may include rotating the bearing assembly. The method may include pivoting the valve actuator from the open position to the closed position by rotational forces acting on the valve actuator. The method may include preventing fluid communication between the valve port and output port by the valve actuator. The method may include retracting the control piston.

The present disclosure is best understood from the following detailed description when read with the accompanying figures.

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting.

<FIG>, <FIG> depict bearing assembly <NUM>. Bearing assembly <NUM> may be used to couple driveshaft <NUM> to a power section of a drilling string for use in a wellbore. Driveshaft <NUM> may include bit box <NUM> positioned at a lower end of driveshaft <NUM>. As used herein, the terms "upper" and "lower" refer to relative directions while bearing assembly <NUM> is positioned within a wellbore towards the surface and away from the surface respectively. Bit box <NUM> may, for example and without limitation, be used to couple a drilling bit to driveshaft <NUM>. Driveshaft <NUM> may include coupler <NUM> for coupling driveshaft <NUM> to a shaft such as a transmission shaft of a power section such as an electric motor, turbine, or positive displacement mud motor.

Bearing assembly <NUM> may include upper bearing housing <NUM>. Upper bearing housing <NUM> may include upper bearing housing outer surface <NUM>. Upper bearing housing outer surface <NUM> may be generally cylindrical. The cylindrical surface of upper bearing housing outer surface <NUM> may define bearing housing longitudinal axis AH. Upper bearing housing <NUM> may include upper bearing housing bore <NUM> formed therethrough defining upper bearing housing inner surface <NUM> Upper bearing housing inner surface <NUM> may be generally cylindrical. The cylindrical surface of upper bearing housing inner surface <NUM> may define bore longitudinal axis AB. Bearing housing longitudinal axis AH and bore longitudinal axis AB may intersect at a point denoted bend point ⊕. Upper bearing housing bore <NUM> may be formed such that bore longitudinal axis AB is at an angle to bearing housing longitudinal axis AH, denoted angle α in <FIG>.

Bearing assembly <NUM> may include lower bearing housing <NUM>. Lower bearing housing <NUM> may be mechanically coupled to upper bearing housing <NUM>. Lower bearing housing <NUM> may be mechanically coupled to upper bearing housing <NUM> by a repeatable connection such as a threaded coupling depicted in <FIG> as threaded interface <NUM>, which may form a fluid seal as discussed herein below. Lower bearing housing <NUM> may include lower bearing housing bore <NUM> formed therethrough defining lower bearing housing inner surface <NUM>. Lower bearing housing bore <NUM> and upper bearing housing bore <NUM> may be connected and substantially concentric along bore longitudinal axis AB.

Driveshaft <NUM> may be positioned within upper bearing housing bore <NUM> and lower bearing housing bore <NUM>. Driveshaft <NUM> may be tubular and may extend substantially along bore longitudinal axis AB. Driveshaft <NUM> may be rotatable within upper bearing housing <NUM> and lower bearing housing <NUM>. Driveshaft <NUM> may be rotated relative to bearing assembly <NUM> while the drill string is stationary, defining a sliding mode of operation.

One or more bearings may be positioned between driveshaft <NUM> and one or both of upper bearing housing <NUM> and lower bearing housing <NUM>. For example, one or more radial bearings such as upper radial bearing <NUM> may be positioned between driveshaft <NUM> and upper bearing housing inner surface <NUM> and lower radial bearing <NUM> may be positioned between driveshaft <NUM> and lower bearing housing inner surface <NUM>. Upper radial bearing <NUM> and lower radial bearing <NUM> may, for example and without limitation, reduce friction between driveshaft <NUM> and upper and lower bearing housings <NUM>, <NUM> while driveshaft <NUM> is rotated. Upper radial bearings <NUM> and lower radial bearings <NUM> may resist lateral force between driveshaft <NUM> and upper and lower bearing housings <NUM>, <NUM> during a drilling operation. Because driveshaft <NUM> is at angle α to the direction weight is applied to the drill bit, radial and lateral forces may be applied against upper radial bearings <NUM> and lower radial bearings <NUM>. By forming upper radial bearings <NUM> and lower radial bearings <NUM> as oil bearings as discussed further herein below, greater forces may be exerted on upper radial bearings <NUM> and lower radial bearings <NUM> than in an embodiment utilizing drilling fluid cooled bearings. One or more thrust bearings <NUM> may be positioned between driveshaft <NUM> and one or both of upper and lower bearing housings <NUM>, <NUM>. Thrust bearings <NUM> may, for example and without limitation, resist longitudinal force on driveshaft <NUM> such as weight on bit during a drilling operation. Upper radial bearings <NUM>, lower radial bearings <NUM>, and thrust bearings <NUM> may each include one or more of, for example and without limitation, diamond bearings, ball bearings, and roller bearings.

One or more of upper radial bearing <NUM>, lower radial bearing <NUM>, and thrust bearings <NUM> may be oil-lubricated bearings. The annular portion of upper bearing housing bore <NUM> and lower bearing housing bore <NUM> about driveshaft <NUM> may be filled with oil. Upper bearing housing bore <NUM> may include piston <NUM>. Piston <NUM> may be an annular body adapted to seal between driveshaft <NUM> and upper bearing housing inner surface <NUM> and slidingly traverse longitudinally. Piston <NUM> may separate upper bearing housing bore <NUM> into an oil filled portion, denoted <NUM> and a drilling fluid filled portion denoted <NUM>. Drilling fluid filled portion <NUM> may be fluidly coupled to upper bearing housing bore <NUM> such that pressure from drilling fluid positioned therein causes a corresponding increase in pressure within oil filled portion <NUM>, thereby pressure balancing the oil lubricating one or more of upper radial bearing <NUM>, lower radial bearing <NUM>, and thrust bearings <NUM> with the surrounding wellbore. One or more seals <NUM> may be positioned between one or more of driveshaft <NUM> and lower bearing housing <NUM>, driveshaft <NUM> and upper bearing housing <NUM>, driveshaft <NUM> and piston <NUM>, and piston <NUM> and upper bearing housing <NUM>. One or more fluid paths <NUM> may be positioned to fluidly couple between upper bearing housing bore <NUM> and drilling fluid filled portion <NUM>. Fluid paths <NUM> may provide resistance to fluid flowing into drilling fluid filled portion <NUM> to, for example and without limitation, reduce fluid loss. One or more high pressure seals may be positioned between piston <NUM> and upper bearing housing bore <NUM>, and fluid paths <NUM> may not need to produce the resistance as described. Because oil-filled portion <NUM> is sealed from drilling fluid filled portion <NUM>, bearing assembly <NUM> may be utilized with an air drilling operation or with highly abrasive or corrosive drilling fluid without compromising upper radial bearing <NUM>, lower radial bearing <NUM>, and thrust bearings <NUM>.

Because driveshaft <NUM> is longitudinally aligned with and rotates along bore longitudinal axis AB, driveshaft <NUM> and any bit coupled to bit box <NUM> thereof may rotate at angle α relative to bearing housing longitudinal axis AH, and may therefore allow for a wellbore drilled thereby to be steered in a direction corresponding with the direction of angle α, defining a toolface of bearing assembly <NUM>. Bend point ⊕ may be positioned at a location nearer to bit box <NUM> than coupler <NUM> of driveshaft <NUM>. Positioning bend point ⊕ nearer to bit box <NUM> may, for example and without limitation, allow a drill bit coupled to bit box <NUM> to be positioned closer to bearing housing longitudinal axis AH while remaining oriented at angle α to bearing housing longitudinal axis AH than an embodiment in which bend point ⊕ is positioned closer to coupler <NUM>. By positioning the drill bit closer to bearing housing longitudinal axis AH, rotary drilling operations in which the entire drill string is rotated, the drill bit may cut more efficiently, as depicted in <FIG>, the bit orbit diameter Di is the same as the diameter of the drill bit.

Upper bearing housing <NUM> may include sensor pocket <NUM> formed therein. Sensor pocket <NUM> may be formed in upper bearing housing <NUM> at a radial orientation generally corresponding with the thickest portion of upper bearing housing <NUM>. Sensor pocket <NUM> may be used to hold one or more sensors or other equipment including, for example and without limitation, one or more drilling mechanics sensors, drilling dynamics sensors, or logging while drilling sensors.

According to the present invention, and with respect to <FIG>, in order to form bearing assembly <NUM>, upper housing blank <NUM> is provided as depicted in <FIG>. Upper housing blank <NUM> may be used as stock material for the formation of upper bearing housing <NUM> and is generally cylindrical. Upper bearing housing bore <NUM> is formed through upper housing blank <NUM> as depicted in <FIG>. Upper bearing housing bore <NUM> is formed along an axis concentric with the longitudinal axis of upper housing blank <NUM>, defining bore longitudinal axis AB. Female interface 117a of threaded interface <NUM> is formed in upper housing blank <NUM> also along bore longitudinal axis AB.

Lower housing blank <NUM> is mechanically coupled to upper housing blank <NUM> at threaded interface <NUM> as depicted in <FIG>. Lower housing blank <NUM> may already be formed having male interface 117b of threaded interface <NUM> or any corresponding portion of a coupler as discussed herein above. Lower housing blank <NUM> may be tubular already having lower bearing housing bore <NUM> formed therein such that lower bearing housing bore <NUM> is concentric with bore longitudinal axis AB when lower housing blank <NUM> is coupled to upper housing blank <NUM>.

Outer surface <NUM> of upper housing blank <NUM> and lower housing blank <NUM> may be machined as depicted in <FIG>. Outer surface <NUM> may be turned, for example, on a lathe to form one or both of upper bearing housing outer surface <NUM> and lower bearing housing outer surface <NUM>. One or both of upper bearing housing outer surface <NUM> and lower bearing housing outer surface <NUM> may be formed such that they are generally cylindrical and oriented longitudinally on bearing housing longitudinal axis AH at angle α to bore longitudinal axis AB. One or both ends of <NUM>, <NUM> of upper housing blank <NUM> and lower housing blank <NUM> respectively may be machined such that they are formed in a plane normal to bearing housing longitudinal axis AH. End <NUM> of lower bearing housing <NUM> may be left unmachined such that it is parallel to the drill bit coupled to bit box <NUM>. The result of the machining operations may therefore result in bearing assembly <NUM> as depicted in <FIG>.

Lower housing blank <NUM> may be formed into the desired configuration of lower bearing housing <NUM> before installation to upper housing blank <NUM> prior to installation to upper housing blank <NUM>. Lower bearing housing <NUM> may not be machined as described previously. As depicted in <FIG>, lower bearing housing <NUM> may be a standard lower bearing housing such that lower bearing housing bore <NUM> is concentric with lower bearing housing outer surface <NUM>.

As depicted in <FIG>, bearing assembly <NUM> may be formed such that bend point ⊕ is at a desired location along driveshaft <NUM>, discussed herein as between bit box <NUM> and coupler <NUM> of driveshaft <NUM>. Bend point ⊕ may be positioned at a location (labeled location B) that is substantially aligned with the connection between lower bearing housing <NUM> and upper bearing housing <NUM> as depicted in <FIG>. Lower bearing housing <NUM> and upper bearing housing <NUM> may be formed separately as discussed herein above with respect to <FIG> as the need to time lower bearing housing <NUM> and upper bearing housing <NUM> in order to properly form a seal therebetween while allowing rotation of driveshaft <NUM> is minimized. Lower bearing housing <NUM> and upper bearing housing <NUM> may be interchangeable with other such components. Lower bearing housing <NUM> may be substantially concentric with bore longitudinal axis AB.

Bend point ⊕ may be positioned at a location (labeled location A) that is closer to bit box <NUM> than location B as depicted in <FIG>. The bit orbit diameter as further discussed herein below may be reduced from a bend point ⊕ located further from bit box <NUM>. Lower bearing housing <NUM> and upper bearing housing <NUM> may be machined together as discussed herein above.

Bend point ⊕ may be positioned at a location (labeled location C) that is closer to coupler <NUM> than location B as depicted in <FIG>. Feasible maximum angles α may be increased over a bend point ⊕ positioned closer to bit box <NUM>.

As depicted in <FIG>, <FIG>, bearing assembly <NUM> may be coupled to transmission housing <NUM> by upper coupler <NUM> forming BHA. Transmission housing <NUM> may couple between upper bearing housing <NUM> and a power section which may include a downhole motor such as a mud motor, turbine, gear-reduced turbine, or electric motor. Transmission shaft <NUM> may be positioned within transmission housing <NUM> and may couple to coupler <NUM> of driveshaft <NUM> to, for example and without limitation, transfer rotational power to driveshaft <NUM>. Transmission housing <NUM> may be formed such that it includes a bend and therefore forms bent sub <NUM>. The direction of bend of bent sub <NUM> may be positioned such that it is aligned with the toolface of bearing assembly <NUM>, thereby increasing the effective bend of bearing assembly <NUM>. A scribe line may be formed on an outer surface of one or both of bearing assembly <NUM> and transmission housing <NUM> in alignment with the direction of bend such that bearing assembly <NUM> and transmission housing <NUM> may be properly aligned. Timing ring <NUM> may be positioned between transmission housing <NUM> and bearing assembly <NUM> to ensure the alignment. As depicted in <FIG>, bearing assembly <NUM> or transmission housing <NUM> may include contact pad <NUM> on an outer surface thereof. Contact pad <NUM> may be positioned on a side of bearing assembly <NUM> or transmission housing <NUM> opposite the toolface thereof. Contact pad <NUM> may contact the surrounding wellbore and may, for example and without limitation, assist with directional drilling.

As depicted in <FIG>, by using both an internal bend of bearing assembly <NUM> and the external bend of bent sub <NUM>, the drill bit may be positioned at a desired bit angle γ relative to drill string longitudinal axis AD made up of angle β between drill string longitudinal axis AD and bearing housing longitudinal axis AH and angle α between bore longitudinal axis AB and bearing housing longitudinal axis AH. Bit orbit diameter D<NUM> for a given bit angle γ may be less than the bit orbit diameter D' of a drilling bit of a BHA having only a bent sub <NUM> having the same bit angle y' as depicted in <FIG>. By reducing bit orbit diameter D<NUM>, the drill string may be rotatable at a higher RPM, thereby increasing rate of penetration while forming the wellbore in rotary mode. For example, in some cases, a bit angle y' of a BHA having only a bent sub <NUM> may be limited in its ability to rotate or limited in maximum rotation speed within the wellbore depending on the bit angle y' due to the increase in bit orbit diameter D'. As depicted in <FIG>, a desired bit angle γ may be made up of angle α and angle β, thereby allowing the angle β of bent sub <NUM> to be reduced, thereby increasing the ability to rotate and the maximum speed of rotation due, for example and without limitation, to reduced side loading and cyclical fatigue. Additionally, wellbore cleaning, weight transfer, friction, and rate of penetration may likewise be increased. In some embodiments not according to the present invention, for example and without limitation, angle α may range between <NUM>° and <NUM>°. For example and without limitation, angle β may range between <NUM>° (a straight sub) and <NUM>°.

As depicted in <FIG>, <FIG>, bearing assembly <NUM> may include one or more stabilizers <NUM>.

Bearing assembly <NUM> may be used to drill a vertical or otherwise straight wellbore. Bearing assembly <NUM> may be operated in rotary mode in which the drill string to which bearing assembly <NUM> is coupled is rotated and driveshaft <NUM> is not rotated relative to the rest of bearing assembly <NUM>. Bearing assembly <NUM> may be used with straight sub <NUM>' as depicted in <FIG>, <FIG> or an adjustable sub set to a substantially <NUM>° bend as opposed to bent sub <NUM> as discussed herein above, although one having ordinary skill in the art with the benefit of this disclosure will understand that bearing assembly <NUM> may be used with bent sub <NUM> in the rotary mode. Driveshaft <NUM> may be rotated simultaneously with the drill string to which bearing assembly <NUM> is coupled.

As depicted in <FIG>, drill bit <NUM> may be rotated relative to wellbore <NUM> both by rotation of drive shaft <NUM> along bore longitudinal axis AB and by rotation of bearing assembly <NUM> along bearing housing longitudinal axis AH. Only a portion of the cutting surface of drill bit <NUM>, depicted as engaged cutting surface 15a, may be in contact with the formation of wellbore <NUM>. The rest of the cutting surface of drill bit <NUM>, depicted as disengaged cutting surface 15b, is not in contact with the formation. Disengaged cutting surface 15b may be in contact with drilling fluid and may, for example and without limitation, be able to be cooled while not in contact with the formation. Engaged cutting surface 15a may be moved between entering the formation and achieving full depth of cut in <NUM>° of rotation. Where a cutting element positioned on drill bit <NUM> may create a point loading pressure on the formation upon entering the formation utilizing a standard bit. The duration of point loading on the formation may be adjusted by varying the rotation of driveshaft <NUM> and bearing assembly <NUM>. By forming wellbore <NUM> in this way, a conical profile <NUM>' may be formed in the formation which may, for example and without limitation, reduce torque requirements and vibration during a drilling operation. Conical profile <NUM>' may, for example and without limitation, assist with maintaining verticality or straightness of wellbore <NUM>.

As depicted in <FIG>, bearing assembly <NUM>' may further include control valve assembly <NUM>. Control valve assembly <NUM> may be used to operate control pistons <NUM>. Control pistons <NUM> may be positioned within control piston cylinders <NUM> formed in an outer surface of control valve assembly <NUM>. Control pistons <NUM> may be adapted to extend by fluid pressure supplied to control piston cylinders <NUM> through control port <NUM> by control valve assembly <NUM>. Control pistons <NUM> may be adapted to extend from a side of bearing assembly <NUM>'and contact the surrounding wellbore substantially opposite to the toolface of bearing assembly <NUM>'. Control valve assembly <NUM> may supply fluid pressure to control piston cylinders <NUM> from the interior of upper bearing housing <NUM>' while bearing assembly <NUM>' is used in the sliding mode, and may reduce or prevent fluid pressure from reaching control piston cylinders <NUM> while bearing assembly <NUM>' is used in the rotary mode as described further herein below. One or more of control pistons <NUM> may include exhaust ports <NUM> as depicted in <FIG>. Exhaust ports <NUM> may be positioned to vent fluid pressure from within control piston cylinders <NUM> to the surrounding wellbore. Exhaust ports <NUM> may allow control pistons <NUM> to retract once fluid pressure is no longer supplied to control piston cylinders <NUM>. Exhaust ports <NUM> may be configured such that the flow through exhaust ports <NUM> is approximately one third of the flow through output port <NUM> of control valve assembly <NUM> as discussed below. Control pistons <NUM> may be retracted by contact with the surrounding wellbore. One or more piston retraction mechanisms <NUM> may be positioned to bias control pistons <NUM> into the retracted position. Piston retraction mechanisms <NUM> may include, for example and without limitation, one or more springs.

Control valve assembly <NUM> may be positioned at upper coupler <NUM>' of bearing assembly <NUM>'. Control valve assembly <NUM> may include valve actuator <NUM>. Valve actuator <NUM> may be coupled to the upper end <NUM>' of upper bearing housing <NUM>' above upper coupler <NUM>'. Valve actuator <NUM> may be pivotably coupled to upper bearing housing <NUM>' by pivot pin <NUM>. Valve actuator <NUM> may be formed as an annular segment corresponding with upper end <NUM>' of upper bearing housing <NUM>' such that valve actuator <NUM> may pivot between an open position (as depicted in <FIG>) and a closed position (as depicted in <FIG>). Valve actuator <NUM> may be adapted to remain in the open position while bearing assembly <NUM>' is used in the sliding mode. Valve actuator <NUM> may be moved from the open position to the closed position (through the intermediary position depicted in <FIG>) by rotational forces, including, for example and without limitation, centrifugal force, as bearing assembly <NUM>' is used in the rotary mode as the rotation rate of bearing assembly <NUM>' increases above a desired rotation rate. One or more actuator return mechanisms <NUM> (as shown in <FIG>) may be included to bias valve actuator <NUM> to the open position as rotation of bearing assembly <NUM>' slows or stops. Actuator return mechanisms <NUM> may include, for example and without limitation, one or more springs, weights, inclined planes, or may be returned hydraulically using, for example and without limitation, pressure from the drilling fluid.

Valve actuator <NUM> may include valve port <NUM> as depicted in <FIG> and <FIG>. In some embodiments not according to the present invention, valve port <NUM> may be a hole formed through valve actuator <NUM>. Valve port <NUM> may be formed as a slot or groove in valve actuator <NUM> positioned to seal against the end of upper bearing housing <NUM>'. Valve actuator <NUM> and the upper end <NUM>' of upper bearing housing <NUM>' may include one or more seals or may be formed from or include one or more bodies to define a seal such as a diamond-to-diamond seal. One or more bearings or bushings such as diamond inserts may be positioned between valve actuator <NUM> and the upper end <NUM>' of upper bearing housing <NUM>'. Such a bearing or bushing may, for example and without limitation, act as a thrust bearing to reduce friction between valve actuator <NUM> and upper bearing housing <NUM>' as valve actuator <NUM> pivots. Valve valve actuator <NUM> may be formed from multiple subcomponents. One or more subcomponents of valve actuator <NUM> may include a slot or groove, and the subcomponents may be coupled. A seal such as an O-ring seal may be positioned between the subcomponents in order to form valve port <NUM>.

Control valve assembly <NUM> may include output port <NUM> formed in upper bearing housing <NUM>'. Output port <NUM> may open to the upper end <NUM>' of upper bearing housing <NUM>' such that valve port <NUM> is aligned with and in fluid communication with output port <NUM> when valve actuator <NUM> is in the open position and such that valve port <NUM> is not in fluid communication with output port <NUM> when valve actuator <NUM> is in the closed position. One or both of valve actuator <NUM> and upper bearing housing <NUM>' may include one or more valve inserts <NUM>, <NUM> aligned with valve port <NUM> and output port <NUM>. Valve inserts <NUM>, <NUM> may include insert ports <NUM> to allow fluid communication between valve port <NUM> and output port <NUM> when insert ports <NUM> are aligned. Valve inserts <NUM>, <NUM> may form a seal to prevent fluid communication between valve port <NUM> and output port <NUM> when valve actuator <NUM> is in the closed position and insert ports <NUM> are out of alignment. Valve inserts <NUM>, <NUM> may be formed from, for example and without limitation, PDC such that a diamond-to-diamond seal is formed. As depicted in <FIG>, valve inserts <NUM>, <NUM> may be configured such that insert ports <NUM> are round openings therethrough to fluidly couple valve port <NUM> and output port <NUM>. As depicted in <FIG>, valve inserts <NUM>, <NUM> may be configured such that insert ports <NUM>' are oblong or ovoid.

Control valve assembly may include fluid supply port <NUM> formed in upper bearing housing <NUM>'. Fluid supply port <NUM> may fluidly couple between an interior of bearing assembly <NUM>' and valve port <NUM> as depicted in <FIG>. Fluid supply port <NUM> may fluidly couple to fluid paths <NUM>' as described above. Pivot pin <NUM> may be tubular and in fluid communication with both fluid supply port <NUM> and valve port <NUM> such that fluid communication between fluid supply port <NUM> and valve port <NUM> is supplied through pivot pin <NUM>.

Output port <NUM> may be in fluid communication with control port <NUM> such that fluid pressure supplied by control valve assembly <NUM> reaches control piston cylinders <NUM> to extend control pistons <NUM>. Output port <NUM> may be formed substantially opposite to the direction of offset between upper bearing housing bore <NUM>' and upper bearing housing <NUM>', i.e. at a radial position in upper bearing housing <NUM>' where the wall thickness of upper bearing housing <NUM>' is largest. Control port <NUM> may be formed at a different radial position than output port <NUM>. Control valve assembly <NUM> may include annular flowpath <NUM> defined between upper bearing housing <NUM>' and pressure ring <NUM>. Annular flowpath <NUM> may be in fluid communication with output port <NUM> and control port <NUM>, therefore allowing fluid communication therebetween. One or more seals <NUM> may be positioned between pressure ring <NUM> and upper bearing housing <NUM>'.

Bearing assembly <NUM>' may include a single control piston <NUM>. Bearing assembly <NUM>' may include multiple control pistons <NUM>. Control pistons <NUM> may be arranged axially along bearing assembly <NUM>' aligned substantially opposite the toolface (tf) of bearing assembly <NUM>' as depicted in <FIG>. Control pistons <NUM>' and control piston cylinders <NUM>' may be arranged radially about bearing assembly <NUM>' such that when extended, the net force of control pistons <NUM>' is exerted on the surrounding wellbore in a direction substantially opposite the toolface (tf) of bearing assembly <NUM>' as depicted in <FIG>. Multiple control ports <NUM>' may be utilized.

In operation, while bearing assembly <NUM>' is operating in the rotary mode, valve actuator <NUM> may be biased by rotational forces into the closed position depicted in <FIG>. In such a position, as discussed above, control valve assembly <NUM> prevents fluid communication between fluid supply port <NUM> and control port <NUM>. Control pistons <NUM> are in the retracted position.

As bearing assembly <NUM>' slows to, for example, operate in the sliding mode, the rotational forces on valve actuator <NUM> reduce, allowing valve actuator <NUM> to pivot inward through the intermediate position of <FIG> to the open position of <FIG>. In such a position, control valve assembly <NUM> allows fluid communication between fluid supply port <NUM> and control port <NUM>. Fluid is therefore able to flow to control piston cylinders <NUM> and exert fluid pressure on control pistons <NUM>. Control pistons <NUM> extend by the fluid pressure into contact with the surrounding wellbore. In such a position, control pistons <NUM> may, for example and without limitation, exert a stabilizing force between bearing assembly <NUM>' and the wellbore. The stabilizing force may, for example and without limitation, reduce rotation of bearing assembly <NUM>' while in the sliding mode, maintain toolface angle relative to the wellbore, or increase lateral pressure between the drill bit and the wellbore to increase build angle in directional drilling operations.

Claim 1:
A method for forming a bearing assembly (<NUM>) comprising:
providing an upper housing blank (<NUM>), the upper housing blank (<NUM>) having a generally cylindrical outer surface, the longitudinal axis of the upper housing blank (<NUM>) defining a bore longitudinal axis (AB);
forming a bore through the upper housing blank (<NUM>), the bore defining an upper bearing housing bore (<NUM>), the upper bearing housing bore (<NUM>) formed concentrically with the bore longitudinal axis (AB);
machining the outer surface (<NUM>) of the upper housing blank (<NUM>) to form an upper bearing housing outer surface (<NUM>), the upper bearing housing outer surface (<NUM>) being generally cylindrical, the longitudinal axis of the upper bearing housing outer surface (<NUM>) defining a bearing housing longitudinal axis (AH), the bearing housing longitudinal axis (AH) intersecting the bore longitudinal axis (AB) at an angle;
positioning a driveshaft (<NUM>) within the upper bearing housing bore (<NUM>);
forming a female interface (117a) of a threaded interface (<NUM>) in the upper housing blank (<NUM>);
characterized in that the method further comprises mechanically coupling a lower housing blank (<NUM>) to the female interface (117a) of the upper housing blank (<NUM>) of the threaded interface (<NUM>).