Abstract: A roll stabilised unit comprises a tool housing (30) rotatably mounted within a tool collar (28), the tool housing (30) having rotatably mounted thereon a first impeller (36), a variable torque transmission arrangement (38) being provided to allow the torque transmitted from the first impeller (36) to the housing (30) to be controlled, and a second impeller (40) fixed relative to the housing (30) so as to be rotatable with the housing (30).

Abstract: A control method for use with a steerable drilling system comprises the steps of inputting parametric model data representative of drilling conditions and using the data to determine achievable drilling directions.

Abstract: A downhole motor arrangement for a directional drilling comprises a first motor component (22), a second motor component (24) encircling at least part of the first motor component (22), and a third motor component (26) encircling at least part of the second motor component (24), the first and second motor components (22, 24) having surfaces associated therewith adapted to define isolated cavities, the application of fluid under pressure thereto causing relative rotation between the first and second motor components (22, 24), the second and third motor components (24, 26) having surfaces associated therewith adapted to define isolated cavities, the application of fluid under pressure thereto causing relative rotation between the second and third motor components (24, 26).

Abstract: The rotor of a downhole motor includes a mandrel having at least one radial lobe, and an elastomeric tubular sleeve compressed about the mandrel so as to establish frictional engagement therebetween. The sleeve is compressed about the mandrel through one of various processes, including heat shrinking, vacuum shrinking, and stretching.

Abstract: Methods and apparatuses to direct a drill bit of a directional drilling assembly are disclosed. The methods and apparatuses employ the use of bi-directional actuators that are capable of displacing a hybrid steering sleeve in positive and negative directions. The bi-directional actuators are capable of greater control and precision in their actuations than traditional “engaged-disengaged” unidirectional actuators, thereby allowing for more precise directional drilling operations. The bi-directional actuators are preferably driven by drilling fluids and may optionally be shielded to lessen the erosive effects thereof.

Abstract: Methods and apparatuses to determine the rate of penetration of a subterranean drilling assembly into a formation are disclosed. The methods and apparatuses generate rate of penetration by integration axial acceleration data with respect to time and applying a correction factor. The correction factor, meant to account for the effect of gravity on the acceleration data, is determined when rotational velocity of the drilling assembly relative to the formation is zero.

Abstract: The present invention provides an apparatus for the communication of power or data signals across the rotating gap of two tubular members, such as the stator and rotor of a mud motor, and between said rotating members of a drill string through inductive couplers located axially along the drill string.

Abstract: Methods and apparatuses to determine the rate of penetration of a subterranean drilling assembly into a formation are disclosed. The methods and apparatuses generate rate of penetration by integration axial acceleration data with respect to time and applying a correction factor. The correction factor, meant to account for the effect of gravity on the acceleration data, is determined when rotational velocity of the drilling assembly relative to the formation is zero.

Abstract: A steerable system comprises a fluid powered motor 10 having a rotor 16 and a stator 18, and a bias arrangement having a plurality of bias pads 34 connected to the stator 18 so as to be rotatable therewith, the bias pads 34 being moveable to allow the application of a side load to the steerable system.

Abstract: The present invention provides methods of measuring downhole the curvature of a borehole and, in a particular application of the invention, using the curvature information as an input component of a bias signal for controlling operation of a downhole bias unit in a directional drilling assembly.

Abstract: A control method for use with a steerable drilling system comprises the steps of inputting parametric model data representative of drilling conditions and using the data to determine achievable drilling directions.

Abstract: A two stage filter for drilling fluid using downhole tools filters solid materials from the drilling fluid and has a first, outer filter section and a second, inner filter section. A portion of the drilling fluid flowing through the first section is received by the second section, and passed on to the fluid using device of the tool. A flow area of the first filter section is greater than a flow area of the second filter section.

Abstract: A two stage filter for drilling fluid using downhole tools filters solid materials from the drilling fluid and has a first, outer filter section and a second, inner filter section. A portion of the drilling fluid flowing through the first section is received by the second section, and passed on to the fluid using device of the tool. A flow area of the first filter section is greater than a flow area of the second filter section.

Abstract: A method for drilling a borehole, comprising transmitting a directional signal to a downhole processor, and maintaining the desired drill bit azimuthal direction by using the downhole processor to evaluate an actual drill bit azimuthal direction relative to the desired drill bit azimuthal direction, and using the downhole processor to adjust the actual drill bit azimuthal direction by controlling the directional drilling device.

Abstract: In downhole drilling tools, a first set of inexpensive and/or relatively small sensors that typically have lower accuracy and higher drift than conventional downhole sensors are located in the drill string adjacent to the bit. A second set of highly accurate sensors is located in a more protected location higher in the drill string away from the drill bit. As drilling progresses these sensors pass through the same portion of the formation measured by the first set of sensors. Key properties are measured by the second set of sensors which allow a calibration offset to be applied the data measured by the first set of sensors.

Abstract: A control method for use with a steerable drilling system comprises the steps of inputting parametric model data representative of drilling conditions and using the data to determine achievable drilling directions.

Abstract: A bottom hole assembly is rotatably adapted for drilling directional boreholes into an earthen formation. It has an upper stabilizer mounted to a collar, and a rotary steerable system. The rotary steerable system has integral drilling motor, an upper section connected to the collar, a steering section, and a drill bit arranged for drilling the borehole attached to the steering section. The steering section is joined at a swivel with the upper section. The steering section is actively tilted about the swivel. A lower stabilizer is mounted upon one of the upper section or the steering section such that the swivel is intermediate the drill bit and the lower stabilizer.

Abstract: A bottom hole assembly is rotatably adapted for drilling directional boreholes into an earthen formation. It has an upper stabilizer mounted to a collar, and a rotary steerable system. The rotary steerable system has an upper section connected to the collar, a steering section, and a drill bit arranged for drilling the borehole attached to the steering section. The steering section is joined at a swivel with the upper section. The steering section is actively tilted about the swivel. A lower stabilizer is mounted upon the steering section such that the swivel is intermediate the drill bit and the lower stabilizer.

Abstract: The present invention provides methods of measuring downhole the curvature of a borehole and, in a particular application of the invention, using the curvature information as an input component of a bias signal for controlling operation of a downhole bias unit in a directional drilling assembly.