Abstract: This invention relates to a torque control device for a downhole drilling assembly, the torque control device being adapted for connection to a drill bit. The torque control device includes an outer sleeve and an inner shaft, the outer sleeve being movable longitudinally relative to the inner shaft. The torque control device has a cylinder, a piston located within the cylinder, and a rotary valve to control the volume of the cylinder. The volume of the cylinder can be changed by way of the rotary valve whereby to adjust the weight on bit and thereby control the torque upon the drill bit.

Abstract: This invention relates to an articulating component (16) of a downhole assembly, and to a downhole steering assembly. There is provided an articulating component (16) having a first end (40) and a second end (42), the articulating component being adapted to transmit torque between the first end and the second end. The articulating component has a pivotable coupling (46) between its first and second ends and at least one control element for the pivotable coupling, the control element(s) having an active condition in which the pivotable coupling is substantially locked against pivoting movement, and an inactive condition in which the pivotable coupling is unlocked. In a downhole steering assembly the articulating component is located downhole of the steering component whereby to protect the steering component from unwanted vibrations generated downhole, or uphole of the steering component whereby to protect the steering component from unwanted vibrations generated uphole, or both.

Abstract: This invention relates to a controllable deflection tool. The controllable deflection tool is likely to have its greatest utility as part of a downhole assembly to steer a drill bit during drilling for oil and gas. There is provided a controllable deflection tool having a first end and a second end, the tool having: a conduit for a working fluid; a rotary element adapted for rotation within the tool; a deflection member; a vane motor configured to rotate the deflection member relative to the rotary element; and a valve for controlling the flow of working fluid to the vane motor. There is also provided a downhole steering assembly and a method of steering a downhole drilling assembly incorporating the controllable deflection tool.

Abstract: This invention relates to braking mechanism for a downhole tool such as a steering tool. The braking mechanism comprises: a body adapted for mounting upon the tool; at least one braking member which is movably mounted upon the body; a resilient biasing means biasing the braking member away from the body; and a damping mechanism connected to the braking member, the damping mechanism providing a damping force opposing movements of the braking member relative to the body, the damping force being dependent upon the rate of movement of the braking member.

Abstract: This invention relates to a steering component, to a steering assembly, and to a method of steering a drill bit in a borehole. The steering component is adapted for connection to a drill string, the drill string carrying a drill bit and a motor for rotating the drill bit. The steering component comprises: a rotatable driveshaft adapted for connection between the drill bit and the motor; a drive mechanism; and an offsetting component; the drive mechanism providing a rotatable connection between the drill string and the offsetting component whereby the drill string can rotate relative to the offsetting component. The drive mechanism is adapted to drive the offsetting component to rotate in an opposed direction to the driveshaft, so as to counter the rotation of the offsetting component which is induced by friction within the componentry as the driveshaft rotates. The steering component and method are likely to have their greatest utility in steering a drill bit during drilling for oil and gas.

Abstract: This invention relates to a controllable deflection tool. The controllable deflection tool is likely to have its greatest utility as part of a downhole assembly to steer a drill bit during drilling for oil and gas. There is provided a controllable deflection tool having a first end and a second end, the tool having: a conduit for a working fluid; a rotary element adapted for rotation within the tool; a deflection member; a vane motor configured to rotate the deflection member relative to the rotary element; and a valve for controlling the flow of working fluid to the vane motor. There is also provided a downhole steering assembly and a method of steering a downhole drilling assembly incorporating the controllable deflection tool.

Abstract: This invention relates to a steerable drill bit arrangement, in particular for the use in drilling boreholes for oil and gas extraction. According to the invention there is provided a steerable drill bit arrangement comprising a drill bit, a steering component and a stabilizer, the steering component being adapted to provide a steering force which in use can drive the drill bit along a non-linear path, the stabilizer being located between the drill bit and the steering component and in use providing a fulcrum for the steering force provided by the steering component, the position of the fulcrum provided by the stabilizer being adjustable relative to the drill bit and the steering component. In use, the position of the fulcrum can be adjusted to vary the maximum curvature of the borehole and to suit the rock type(s) being drilled.

Abstract: This invention relates to a downhole assembly and to a cutter assembly, and in particular to a downhole assembly including an apparatus for breaking up large-scale material which is present behind a drill bit, and to a cutter assembly for use in such a downhole assembly. The downhole assembly is suitably for use in a drillstring, the downhole assembly comprising a drill bit, a sensitive component, and at least one rotatable set of cutter blades located between the drill bit and the sensitive component.

Abstract: This invention relates to a downhole assembly and to a cutter assembly, and in particular to a downhole assembly including an apparatus for breaking up large-scale material which is present behind a drill bit, and to a cutter assembly for use in such a downhole assembly. The downhole assembly is suitably for use in a drillstring, the downhole assembly comprising a drill bit, a sensitive component, and at least one rotatable set of cutter blades located between the drill bit and the sensitive component.

Abstract: This invention relates to a steering assembly and to a steering component, suitable for use in drilling operations for oil and gas. The steering assembly comprises a downhole motor which can rotate the drill bit, and a steering component. The steering component has a shaft and a set of elements for engaging the borehole in use. The shaft has a longitudinal axis. The set of elements has a centerline and is movable relative to the shaft between a first position in which the centerline is offset from the longitudinal axis of the shaft by a first distance, and a second position in which the centerline is offset from the longitudinal axis of the shaft by a second distance. In use in drilling operations, movement of the set of elements from the first position to the second position alters the degree of curvature of the drilled hole.

Abstract: This invention relates to a steerable drill bit arrangement, in particular for the use in drilling boreholes for oil and gas extraction. There is provided a steerable drill bit arrangement in which the drill bit (20) is connected to a drill string (16) including a steering component (12) and a stabiliser (14), the stabiliser (14) being located between the steering component (12) and the drill bit (20), the steering component (12) being adapted to move the drill string (16) transversely relative to a borehole in which it is located, the stabiliser (14) having an inner part (32) adapted to rotate with the drill string (16) and an outer part (34) adapted to engage the borehole wall, the outer part (34) being rotatable relative to the inner part so that the outer part (34) can remain substantially stationary as the remainder of the stabiliser (14) rotates with the drill string (16).

Abstract: The rotational position of a shaft (10) with respect to a sleeve (12) is determined by using a sensor (14) rotating with the shaft (10) to detect an earth vector such as magnetic or gravitational field, using a coil (18) on the shaft in conjunction with a plurality of ferromagnetic elements (16) on the sleeve to monitor relative rotation, and calculating the rotational position from these parameters. Applicable to downhole use, particularly gamma ray measurements.

Abstract: The invention relates to a method and an apparatus for use in surveying boreholes. The method of the invention comprises the following steps: providing an instrument package in a leading end of a drillstring, the instrument package comprising first and second single-axis sensors mounted for rotation with the drillstring about the rotational axis of the drillstring, the first sensor being an accelerometer and the second sensor being a magnetic fluxgate or a rate gyro; rotating the drillstring; deriving from the first sensor the inclination angle of the drillstring at the instrument package; and deriving from the second sensor the azimuth angle of the drillstring at the instrument package.

Abstract: A borehole drilling and survey assembly includes a drill string of magnetic material, a non-magnetic drill collar, and a non-magnetic rotary drilling system including a drill bit. A near-bit survey instrument is located in the rotary drilling system at a fixed distance from the junction of the drill string and the drill collar. A second survey instrument is located in the drill collar at a fixed distance from said junction. The survey instruments measure the local values of the component of the earth's magnetic along the borehole axis, and these values are processed to remove the magnetic effects of the drillstring. The survey instruments optionally also measure gravity vector components to enable borehole heading to be derived.

Abstract: A borehole drilling and survey assembly includes a drill string of magnetic material, a non-magnetic drill collar, and a non-magnetic rotary drilling system including a drill bit. A near-bit survey instrument is located in the rotary drilling system at a fixed distance from the junction of the drill string and the drill collar. A second survey instrument is located in the drill collar at a fixed distance from said junction. The survey instruments measure the local values of the component of the earth's magnetic along the borehole axis, and these values are processed to remove the magnetic effects of the drillstring. The survey instruments optionally also measure gravity vector components to enable borehole heading to be derived.

Abstract: The invention relates to a method and an apparatus for use in surveying boreholes. The method of the invention comprises the following steps: providing an instrument package in a leading end of a drillstring, the instrument package comprising first and second single-axis sensors mounted for rotation with the drillstring about the rotational axis of the drillstring, the first sensor being an accelerometer and the second sensor being a magnetic fluxgate or a rate gyro; rotating the drillstring; deriving from the first sensor the inclination angle of the drillstring at the instrument package; and deriving from the second sensor the azimuth angle of the drillstring at the instrument package.

Abstract: Borehole orientation information, typically azimuth and inclination, is derived from measurements of gravitational and magnetic components along a borehole axis (O) and transverse thereto. The transverse components are measured by a fluxgate (12) and accelerometer (14) arranged to rotate around the borehole axis (O) at a constant angular velocity (w). The calculations necessary to derive the desired parameters are detailed.

Abstract: A borehole drilling and survey assembly includes a drill string of magnetic material, a non-magnetic drill collar, and a non-magnetic rotary drilling system including a drill bit. A near-bit survey instrument is located in the rotary drilling system at a fixed distance from the junction of the drill string and the drill collar. A second survey instrument is located in the drill collar at a fixed distance from said junction. The survey instruments measure the local values of the component of the earth's magnetic along the borehole axis, and these values are processed to remove the magnetic effects of the drillstring. The survey instruments optionally also measure gravity vector components to enable borehole heading to be derived.

Abstract: A controllable stabilizer (16; 116) in which an outer sub-assembly (22) is rotatably mounted around an inner sub-assembly (20). An annulus (58; 158) is movably mounted around the outer sub-assembly (22) to be radially displaced in a predetermined direction by selective hydraulic energisation of individual pistons (52; 152) in a piston/cylinder array (48; 148). The piston(s) selected to be energised are determined by a directionally-sensitive control system (18). The outer sub-assembly (22) carries a hydraulic pump (38; 138) operated by a driving mechanism (28; 128) carried on the inner sub-assembly (20); this pump (38; 138) provides hydraulic power for the pistons (52; 152). An alternator (34+56; 134+156) is similarly mounted and driven to provide on-board electrical power for the control system (18).