A drill bit comprises a bit body having a longitudinal axis and a blade extending radially outward from the longitudinal axis along a face region and axially along a gauge region. A gauge region includes a gauge feature and first and second recessed regions extending axially above and below the gauge feature, respectively. The gauge feature comprises an outermost surface extending radially beyond outer surfaces of the blade in the recessed regions. A method of drilling a borehole comprises rotating the bit about the longitudinal axis, engaging a formation with cutting elements mounted to the face region, and increasing a lateral force applied substantially perpendicular to the longitudinal axis such that radially outer surfaces in the gauge region engage the formation and such that side cutting exhibited by the bit is initially minimal and substantially constant and subsequently increases in a substantially linear manner with increasing lateral force.

A hydraulic jetting assembly is provided herein. The jetting assembly includes a jetting hose, with a jetting nozzle at its distal end. The jetting nozzle comprises a tubular stator body having a fluid discharge slot, and a tubular rotor body residing within a bore of the stator body. The jetting nozzle has one or more bearings residing between the stator body and the surrounding rotor body to accommodate relative rotational movement. The jetting nozzle includes a proximal end configured to sealingly connect to an end of a jetting hose, and to receive a high pressure jetting fluid. Preferably, the nozzle has an outer diameter that is equivalent to or slightly larger than an outer diameter of the jetting hose. Preferably, the jetting assembly has at least three actuator wires configured to induce a controlled bending moment at its distal end, thereby providing for a steerable downhole tool. Jetting collars may be placed along the jetting hose to overcome drag force.

A drill bit subsystem can include a drill bit, a processor, and a non-transitory computer-readable medium for storing instructions and for being positioned downhole with the drill bit. The instructions of the non-transitory computer-readable medium can include a machine-teachable module and a control module that are executable by the processor. The machine-teachable module can receive depth data and rate of drill bit penetration from one or more sensors in a drilling operation, and determine an estimated lithology of a formation at which the drill bit subsystem is located. The control module can use the estimated lithology to determine an updated location of the drill bit subsystem, and control a direction of the drill bit using the updated location and a drill plan.

A drilling apparatus may alter a direction of travel of a drill bit as it forms a borehole in the earth by furnishing the borehole with a cross-sectional shape that urges the drill bit in a radial direction. Such a cross-sectional shape may comprise two circular arcs, one larger than the apparatus and one smaller. The apparatus may be urged away from the smaller circular arc and into the open space provided by the larger circular arc. Such an apparatus may comprise an axial body and a cutting element extendable in a single radial direction from an exterior of the axial body. Extension of the cutting element may allow it to engage and degrade an inner wall of the borehole. An abrasion-resistant gauge pad protruding from the exterior of the body may ride against the borehole wall and urge the body radially.

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

A rotary downhole tool, for example in the form of a drill bit, is described that includes a tool body, the body defining a gauge region, and at least one gauge roller rotatably mounted to the body.

A system and method to reduce a whirl effect on a rotation of a drill string with an AC induction motor mechanically coupled to a rotary drilling system and configured to drive the rotary drilling system and the drill string attached thereto. Additionally, the system includes an electronic inverter to generate supplied power for the AC induction motor and a controller configured to drive the operation of the electronic inverter to impose a virtual drive characteristic relating a torque output of the motor with speed of the motor, determine a desired nominal operating point, and determine presence of whirl in the drill string from torque of the rotary drilling system and speed of the drill string.

A downhole drilling apparatus may comprise a rotatable body with fixed cutting elements protruding from an exterior thereof. To form a subterranean borehole, the fixed cutting elements, spaced at a constant radius from a rotational axis of the body, may degrade an earthen formation as the body rotates. The body may also have a rotatable cutting element protruding from its exterior. To remove material from an interior wall of the borehole, the rotatable cutting element may be positioned in a first rotational orientation wherein it extends radially beyond the constant radius of the fixed cutting elements. An amount of material being removed may be altered by rotating the rotatable cutting element into a second rotational orientation wherein it remains radially within the constant radius.

A drill bit comprises a bit body having a longitudinal axis and a blade extending radially outward from the longitudinal axis along a face region and axially along a gauge region. A gauge region includes a cutting element located proximate to an uphole edge of the blade in the gauge region. A remainder of the gauge region is free of cutting elements mounted thereon. A method of drilling a borehole comprises rotating the bit about the longitudinal axis, engaging a formation with cutting elements mounted to the face region, and increasing a lateral force applied substantially perpendicular to the longitudinal axis such that the cutting element engages the formation and such that side cutting exhibited by the tool is initially minimal and substantially constant and subsequently increases in a substantially linear manner with increasing lateral force.

A steerable earth boring assembly which includes an annular collar and a drive shaft with a drill bit, where the shaft pivots with respect to the collar. An upper portion of the shaft inserts into an orientation sleeve which resides in the collar. An axial bore is obliquely formed through the orientation sleeve, and in which the upper portion inserts. An angular offset between the drive shaft and collar is changed by adjusting azimuthal positions of the orientation sleeve with respect to the collar. A brake assembly is included for applying a restraining force onto the orientation sleeve.