An example apparatus for controlling the direction of drilling a borehole includes an outer housing having non-uniform stiffness and an inner housing at least partially within and rotationally independent from the outer housing and having non-uniform stiffness, A drive shaft may be at least partially within the inner housing. At least one of the outer housing and the inner housing may include a tubular structure with at least one of multiple materials with different stiffness, and a portion with less structural material than another portion.

A rotary tool for operation within an underground borehole or within tubing in a borehole has a tool body and at least one sensor-containing unit attached to the tool body and positioned to contact the conduit wall. The sensor-containing unit includes an exterior portion to contact the borehole or tubing wall and one or more sensors is located in a cavity between the exterior portion and the tool body. The sensor-containing unit may be formed from the exterior portion, an attachment portion for attachment to the tool body, and one or more connecting portions extending between the attachment and exterior portions, with the sensor-containing cavity between the attachment and exterior portions. Possible rotary tools include drill bits, reamers, mills, stabilizers, and rotary steerable systems.

Certain aspects and features relate to a drilling system usable to drill a borehole. The drilling system may include a first housing defining a main fluid flow path and a second housing defining a bypass flow path toward an annulus of a wellbore. A flow control choke may be positioned between the first housing and the second housing. The flow control choke may include a rotatable section and a stationary section that is stationary relative to the rotatable section. The stationary section may have a curved interface with the rotatable section for restricting a flow of a drilling fluid through the bypass flow path.

The disclosure includes a power section for a bottom hole assembly for use in a wellbore. The power section may include a stator, the stator including a housing, a stator insert, and a payload housing. The payload housing may be positioned on an outer surface of the housing, and the payload housing may include a payload pocket. The power section may include a rotor, the rotor rotatable eccentrically within the stator.

A lateral wellbore is formed from a high side of a horizontal portion of a primary wellbore with a drill bit assembly that has a selectively extendable pilot bit. The drill bit assembly is mounted on a lower end of a drill string. A bit guide is disposed adjacent the drill bit assembly for urging the drill bit assembly in a lateral direction against the high side of the primary wellbore. Rotating the drill bit assembly while urging the drill bit assembly upward creates a groove in a subterranean formation adjacent the primary wellbore. This forms a ledge at a far end of the groove. The drill string is then drawn back from the groove, and the pilot bit is deployed. Urging the drill bit assembly forward engages the pilot bit with the ledge, providing leverage for retaining the drill bit assembly in an orientation for excavating the lateral wellbore.

Rotary steerable drilling apparatus and methods utilizing apparatus comprising a shaft, a multi-angle strike ring axially repositionable along the shaft, an articulated member coupled to the shaft, and a steering member carried by the articulated member. An actuator is operable to maintain an angular offset of the articulated member relative to the shaft by maintaining azimuthally-dependent contact between the multi-angle strike ring and the steering member.

A downhole motor for directional drilling includes a driveshaft assembly including a driveshaft housing and a driveshaft rotatably disposed within the driveshaft housing, a bearing assembly including a bearing housing and a bearing mandrel rotatably disposed within the bearing housing, wherein the bearing mandrel is configured to couple with a drill bit, a bend adjustment assembly including a first position that provides a first deflection angle between a longitudinal axis of the driveshaft housing and a longitudinal axis of the bearing mandrel, and a second position that provides a second deflection angle between the longitudinal axis of the driveshaft housing and the longitudinal axis of the bearing mandrel that is different from the first deflection angle, and one or more hydraulic pumps configured to actuate the bend adjustment assembly between the first position and the second position.

An apparatus for drilling curved and straight sections of a wellbore is disclosed that in one non-limiting embodiment includes a drilling assembly configured to include a drill bit at an end thereof that can be rotated by a drive in the drilling assembly and by the rotation of the drilling assembly, and wherein the drilling assembly includes: a deflection device that (i) tilts a section of the drilling assembly within a selected plane when the drilling assembly is substantially rotationally stationary to allow drilling of a curved section of the wellbore by rotating the drill bit by the drive; and (ii) straightens the section of the drilling assembly when the drilling assembly is rotated to allow drilling of a straight section of the wellbore.

A method for causing a desired drilling direction of a steerable subterranean drill in consideration of a contemporaneously detected formation tendency force acting on a drill bit of the steerable subterranean drill. The method includes detecting, utilizing a steering direction setting device, a direction and magnitude of a formation tendency force acting on the drill bit of the steerable subterranean drill. Further the steering direction setting device is configured to contemporaneously cause the drill bit of the steerable subterranean drill to drill in the desired direction, counteracting the formation tendency force based on the detected direction and magnitude of the formation tendency force acting on the drill bit.

A technique facilitates drilling applications by providing a unique flex joint. In one embodiment, the flex joint has an adjustable bending stiffness while being much more compact than conventional flex joints. The flex joint also may be designed to de-couple bending moments from the tool joints and, in some applications, can operate as an active vibration and shock control sub by incorporating suitable sensors and a hydraulic actuator system. The design also enables incorporation of other features, such as electrical insulation features disposed above and/or below the flex joint. In some applications, the flex joint also may have an electrical feed through.