According to aspects of the present disclosure, systems and methods for a closed-loop speed/position control mechanism. An example system may include a housing and a planetary gearbox disposed within the housing, wherein a ring gear of the planetary gearbox is coupled to the housing, a sun gear of the planetary gearbox is coupled to a drive shaft, and a planetary carrier of the planetary gearbox is coupled to an output shaft. A controller may receive measurements from sensors proximate to the output shaft and use those measurements to transmit control signals to change the rotation of the drive shaft. In this way, the output shaft may be rotated independently of the housing by controlling the rotation of the drive shaft. In example systems, the output shaft may be a sonde or an offset mandrel coupled to a drill bit. The rive shaft may be coupled to a fluid-controlled controlled drive mechanism and rotation may be controlled by adjusting flow control valve. The closed-loop system may be used to set a target rotation speed of said output shaft or may be used to maintain the output shaft in a constant position or orientation despite housing rotation.

A rotary transfer mechanism is disclosed for a motor, pump, or other downhole tool that accommodates the eccentric motion of a rotor without the need for a flex shaft, articulating joint or CV joint. In one configuration, the rotor is coupled to the drive shaft at a radial offset from the drive shaft axis. The orbiting motion of the rotor, rather than rotation of the rotor about its own axis, generates a torque on the drive shaft, by applying a tangential force to the drive shaft at the location of the radial offset. The radial offset may be set equal to the orbital radius so that no radial movement or flex is required at the drive shaft to accommodate the eccentric rotor movement.

The present disclosure provides a portable seafloor drill rig for a submersible for multi-point core drilling, including a power head, a reduction gear box, an emergency jettison device, a drilling tool, and a temperature and pressure-retaining device. a water supply connector and the power head are arrange on a top plate of the reduction gear box. An output shaft of the power head is connected to an input shaft of the reduction gear box, and an output shaft of the reduction gear box is provided with a central hole, which is in communication with a water inlet hole of the water supply connector. An output shaft of the reduction gear box is connected to the emergency jettison device, and the temperature and pressure-retaining device can perform temperature and pressure-retaining storage of the core drilled by the drilling tool.

A method comprises rotating a drill bit of a drilling system at at least 1000 rpm. The drill system can comprise a drill feed, a drill head comprising a motor and coupled to the drill feed, a drill string, comprising at least one drill rod, operatively coupled to the drill head so that the drill head is configured to axially and rotationally drive the drill string, and the drill bit coupled to the bottom end of the drill string.

Clutch assemblies and related systems are provided. In some embodiments, the system comprises the clutch assembly, a circulation assembly, and an actuation mechanism operatively connected to the clutch assembly and the circulation assembly. In some embodiments, the clutch assembly allows for selective rotation of a bottom hole assembly of a drill string and the circulation assembly allows for selective exhausting of drilling fluid from the drill string. Related drill strings and methods for drilling a borehole are also provided.

A method for constructing a wellbore includes drilling a wellbore along a trajectory using a bit; reaming the diameter of a portion of the drilled wellbore to enlarge a portion of the wellbore; and altering the trajectory of the bit by applying a lateral force to the enlarged diameter wellbore. Reaming the diameter of the portion of the drilled wellbore increases the dogleg of the wellbore.

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 harmonic gear drive includes an input shaft and an output shaft. The input shaft is mechanically coupled to a wave generator which has a varying diameter. The wave generator is positioned within a flex spline which includes external teeth. The external teeth of the flex spline engage with internal teeth of a fixed spline and an output spline when the major diameter of the wave generator is aligned therewith. The output spline has a different number of teeth from the input spline such that, as the wave generator is rotated and the flex spline rotates, the output spline is rotated relative to the fixed spline.

A drill string system includes a drill bit disposed at a distal end of a drill string. A clutch is coupled with the drill bit. A mud motor is coupled to the clutch, and the mud motor is operable to receive a drilling fluid therein and transfer torque to the drill bit through the clutch. The clutch disengages upon application of a torque exceeding a predetermined threshold.

A tool for building a wellbore includes a tool body with a flow passage extending axially therethrough, a piston chamber formed radially through the tool body that intersects the flow passage of the tool body, a piston disposed in the piston chamber, at least one actuation element that exerts a force between the piston and the piston chamber, and a sleeve disposed within the flow passage of the tool body that includes at least one cutout. When the sleeve is in a first position within the tool body, the cutout is axially offset from the piston, and when the sleeve is in a second position, the cutout is axially aligned with the piston.