Abstract: A method of steering a drill bit to form an opening in a subsurface formation, comprises a) determining a distance from design of a well, and b) determining an angle offset from design of the well wherein angle offset from design is the difference between the inclination and azimuth of the hole and the inclination and azimuth of plan, c) wherein at least one distance from design and at least one angle offset from design are determined in real time based, at least in part, on a position of the hole at the last survey, a position at a projected current location of the bit, and a projected position of the bit.

Abstract: The present invention relates to a navigation system for navigating a drill head out of or in collision with a casing in a first borehole. The system comprises a drill head drilling a second borehole; a drill string made of several tubulars mounted into one tubular string by means of a connection means, the drill head being mounted onto one end of the drill string; and a plurality of logging units arranged with one logging unit in or in relation to each connection means. Each logging unit comprises a data transmitter and a data receiver for sending and receiving data between the logging units; and a detector, at least one logging unit comprising an emitter. Furthermore, the invention relates to a navigation method using the navigation system.

Abstract: A bottom-hole assembly (202), BHA, for drilling a borehole (204, 301) in an earth formation (208, 300), comprising a percussion drill bit (208), a percussion mechanism adapted to strike the drill bit (208), at least one sensor (226, 228, 230, 232, 234) for measuring a physical quantity and converting it into an electrical signal, and converting means (237) for converting the electrical signal into a digital signal, and a method for transmitting data from such a bottom-hole assembly (202) positioned in a borehole (204, 301), the bottom-hole assembly (202) and the method being characterized by encoding the digital signal by controlling the percussion mechanism and time periods between two impacts delivered by the percussion mechanism on the drill bit (208) during drilling, and transmitting the encoded digital signal by waves generated by the impacts delivered by the percussion mechanism on the drill bit (208). A system which comprises said bottom-hole assembly (202).

Abstract: A system and method for surface steerable drilling are provided. In one example, the method includes monitoring operating parameters for drilling rig equipment and bottom hole assembly (BHA) equipment for a BHA, where the operating parameters control the drilling rig equipment and BHA equipment. The method includes receiving current inputs corresponding to performance data of the drilling rig equipment and BHA equipment during a drilling operation and determining that an amount of change between the current inputs and corresponding previously received inputs exceeds a defined threshold. The method further includes determining whether a modification to the operating parameters has occurred that would result in the amount of change exceeding the defined threshold and identifying that a problem exists in at least one of the drilling rig equipment and BHA equipment if no modification has occurred to the operating parameters. The method includes performing a defined action if a problem exists.

Abstract: A system and method for surface steerable drilling are provided. In one example, the system receives toolface information for a bottom hole assembly (BHA) and non-survey sensor information corresponding to a location of the BHA in a borehole. The system calculates an amount of incremental progress made by the BHA based on the non-survey sensor information and calculates an estimate of the location based on the toolface information and the amount of incremental progress. The system repeats the steps of receiving toolface information and non-survey sensor information and calculating an amount of incremental progress to calculate an estimate of a plurality of locations representing a path of the BHA from a first survey point towards a second sequential survey point.

Abstract: A method and a device for controlling a drill rig (1) which includes a carrier vehicle with at least one feed-beam (3), wherein a drill machine (2) is movable to-and-fro, wherein rig parameters are set by a control unit (6) and wherein each one of a plurality of operating modes (M1-M6) includes specified operating settings for different operating parameters of the rig. Each operating mode (M1-M6) is selectable such that operation of the rig is related to a particular type of rock, in which drilling is to be performed, and each operating mode (M1-M6) includes operating settings that are adapted to the prevailing type of rock. The invention also concerns a drill rig.

Abstract: Apparatus, systems, and methods may operate to couple a tubular member to a bottom hole assembly, dispose at least one adjustable stabilizing member on the tubular member, and control at least one of a radial extension of the adjustable stabilizing member and an axial position of the adjustable stabilizing member relative to the bottom hole assembly to adjust a borehole trajectory, wherein the adjustable stabilizing member is adjustable in both radial and axial directions. Additional apparatus, systems, and methods are disclosed.

Abstract: A drilling rig for automatically executing rocking of a drill string with a moveable top drive using a control system having a processor and data storage connected to a torque pin sensor, a speed sensor; a remote control enabling a user to actuate automatic remote rocking, drilling, orienting and making up of a drill string using the top drive that provides simultaneous right hand and left hand torque applied to the drill string while simultaneously controlling speed of turning of the drill string. A drilling rig for orienting drill pipe, drilling with drill pipe and making up drill pipe into a drill string using the automated control system.

Abstract: A boring tool that is moved by a drill string to form an underground bore. A transmitter transmits a time varying dipole field as a homing field from the boring tool. A pitch sensor detects a pitch orientation of the boring tool. A homing receiver is positionable at a target location for detecting the homing field to produce a set of flux measurements. A processing arrangement uses the pitch orientation and flux measurements with a determined length of the drill string to determine a vertical homing command for use in controlling depth in directing the boring tool to the target location such that the vertical homing command is generated with a particular accuracy at a given range between the transmitter and the homing receiver and which would otherwise be generated with the particular accuracy for a standard range, different from the particular range. An associated system and method are described.

Abstract: Methods and apparatus for using a quill to steer a hydraulic motor when elongating a wellbore in a direction having a horizontal component, wherein the quill and the hydraulic motor are coupled to opposing ends of a drill string, by monitoring an actual toolface orientation of a tool driven by the hydraulic motor via monitoring a drilling operation parameter indicative of a difference between the actual toolface orientation and a desired toolface orientation, and then adjusting a position of the quill by an amount that is dependent upon the monitored drilling operation parameter.

Abstract: A modular power source includes an outer housing, a generator module, and a control module. The generator module and the control module are electrically interconnected and are positioned to lie within a module space formed within the outer housing. Electricity is produced by the generator module during rotation of the modular power source.

Abstract: A boring tool moves having a pitch orientation, a yaw orientation and a roll orientation and is steerable underground using the roll orientation. A maximum drill string curvature is established for steering. The boring tool is advanced over a path segment. An averaged roll characteristic is determined for movement of the boring tool along the path segment. A path segment pitch orientation is established based on at least one measured pitch orientation along the path segment. Using the maximum drill string curvature in combination with the averaged roll characteristic and the path segment pitch orientation, the yaw orientation is determined. The averaged roll characteristic is determined based on a series of incremental roll measurements that are spaced across the path segment. A set of coupled ordinary differential equations is used to characterize movement of the boring tool.

Abstract: A tunneling system is disclosed that includes a surface power-controller, umbilical tether, robotic tender, and robotic tunneling device. This system allows the robotic tunneling device to efficiently create new tunnels using the power and fluids provided from the surface through the robotic drilling tender, as well as a way to efficiently manage cuttings below surface. The system is designed to operate not only when the well is not producing, but also on a continuous basis while the well is producing.

Abstract: A drilling system for drilling a borehole in an underground formation, comprises a rotary drill bit, a drilling drive mechanism that is capable of applying both rotating the drill bit and applying an axial force to the drill bit, and a control system that is capable of controlling the drive mechanism so as to control rotation of the drill bit and the axial force applied to the drill bit in order to control the depth of cut created by the drill bit when drilling through the formation. A method of drilling a borehole in an underground formation with a rotary drill bit, comprises applying rotation and an axial force to the drill bit and controlling the rotation and axial force so as to control the depth of cut created by the drill bit when drilling through the formation.

Abstract: A method for directing bore-hole drilling in a target earth formation includes the following steps: providing drilling equipment having a bottom hole assembly that includes a controllable directional drilling subsystem, and a logging-while-drilling directional measurement tool with a look-around and look-ahead capability; determining the presence of a predetermined type of formation characteristic in the target formation; and navigating a drill path in the target formation with the drilling equipment, including receiving measurement signals from the directional measurement tool, obtaining, from the received measurement signals, indications of formation parameters with respect to the formation characteristic in the target formation, and controlling the directional drilling subsystem to drill in a direction determined as a function of the obtained indication of formation parameters.

Abstract: A wireless communication and drill string telemetry system. The communication system is used for communicating information along a drill string between a boring tool and a boring machine. An insulator assembly provides an electrically insulated gap between the drill string communication path and a soil engaging electrode for the electrical return path. A transmitter assembly includes a data transmitter for encoding and transmitting a data signal. A signal coupler couples the data signal to the drill string and provides a controlled electrical connection between the drill string communication path and the soil engaging electrode. The signal coupler comprises a transformer and a current regulating circuit to adjust a voltage across the transformer's primary winding. A receiver assembly is disposed proximate the drilling machine and includes a toroidal pickup coil and a signal processing assembly.

Abstract: A method of operating a drill string includes receiving signals indicative of rotation of a bottom hole assembly (BHA) of the drill string; receiving signals indicative of the torque experience by the BHA; determining from the received signals an average slipping torque and a maximum sticking torque; determining a friction ratio based on the maximum sticking torque and the average slipping torque; and generating an indication that the friction ratio exceeds a limit.

Abstract: A well drilling method can include detecting a drilling event by comparing a parameter signature generated during drilling to an event signature indicative of the drilling event, and automatically controlling a drilling operation in response to at least a partial match resulting from comparing the parameter signature to the event signature. A well drilling system can include a control system which compares a parameter signature for a drilling operation to an event signature indicative of a drilling event, and a controller which controls the drilling operation automatically in response to the drilling event being indicated by at least a partial match between the parameter signature and the event signature.

Abstract: A system and method for surface steerable drilling are provided. In one example, the system receives feedback information from a drilling rig and calculates an estimated position of a drill bit in a formation based on the feedback information. The system compares the estimated position to a desired position along a planned path of a borehole. The system calculates multiple solutions if the comparison indicates that the estimated position is outside a defined margin of error relative to the desired position. Each solution defines a path from the estimated position to the planned path. The system calculates a cost of each solution and selects one of the solutions based at least partly on the cost. The system produces control information representing the selected solution and outputs the control information for the drilling rig.

Abstract: A method for automated drilling of a borehole in a subsurface formation includes drilling the borehole using a set of drilling control variables assigned a set of values. An automated drilling index of the drilling is monitored. The automated drilling index of the drilling is a combination of a first index that depends on a rate of penetration of the drilling and a second index that depends on a mechanical specific energy of the drilling. The values assigned to the set of drilling control variables are selectively adjusted at least once during the drilling based on the monitoring of the automated drilling index.

Abstract: A boring tool moves having a pitch orientation, a yaw orientation and a roll orientation and is steerable underground using the roll orientation. A maximum drill string curvature is established for steering. The boring tool is advanced over a path segment. An averaged roll characteristic is determined for movement of the boring tool along the path segment. A path segment pitch orientation is established based on at least one measured pitch orientation along the path segment. Using the maximum drill string curvature in combination with the averaged roll characteristic and the path segment pitch orientation, the yaw orientation is determined. The averaged roll characteristic is determined based on a series of incremental roll measurements that are spaced across the path segment. A set of coupled ordinary differential equations is used to characterize movement of the boring tool.

Abstract: A method for forming a subsurface wellbore is disclosed. The method includes operating a drilling string in a first direction of rotation. A first motor located near the end of the drilling string is operated in a direction of rotation opposite that of the drilling string. A drill bit is rotated using a second motor that is coupled to the first motor.

Abstract: The present invention relates to systems and methods for controlling downhole motors. One aspect of the invention provides a valve-controlled downhole motor including: a downhole motor and a spool valve. The downhole motor includes a sealed chamber having a first port and a second port, a stator received within the sealed chamber, and a rotor received within the stator. The spool valve includes a barrel and a spool received within the barrel. The barrel includes an inlet port, an exhaust port, a first feed port, a second feed port, a first return port, and a second return port. The inlet port is located in proximity to the first feed port and second port. The exhaust port is located in proximity to the first return port and the second return port. The spool includes a first gland and a second gland.

Abstract: A wellbore drilling system includes a weight on bit controller configured to generate a normalized weight on bit output, a drilling torque controller configured to generate a normalized toque on bit output, and a differential pressure controller configured to generate a normalized differential pressure output. The system further includes a rate of penetration controller that is configured to multiply a rate of penetration setpoint with the normalized weight on bit output, the normalized torque on bit output, and the normalized differential pressure output to generate a rate of penetration output.

Abstract: Some embodiments of the invention concern HDD in an automatic drilling mode. Such embodiments can include maintaining a constant output parameter while performing a drilling operation using an HDD rig (20) having a thrust pump, generating hydraulic fluid pressure measurements from one or more pumps of the HDD rig, comparing the hydraulic fluid pressure measurements to a variable pressure limit, calculating a derivative value using the measured hydraulic fluid pressure measurements, comparing the derivative value to a derivative threshold, decreasing the variable pressure limit when the derivative value exceeds the derivative threshold, wherein the amount that the variable pressure limit is decreased is based on one or more of the hydraulic fluid pressure measurements, and reducing output of the thrust pump when the comparison of the hydraulic fluid pressure measurements to the variable pressure limit indicates that one or more of the hydraulic fluid pressure measurements exceed the variable pressure limit.

Abstract: A method of drilling a borehole in an earth formation using a drill string including a control system for controlling the borehole trajectory. The control system is operable to receive a selected signal, to determine the borehole depth from at least one length increment and the number of times the selected signal is received, and to use the borehole depth as input parameter for controlling the borehole trajectory in correspondence with a desired borehole trajectory. While drilling, for each length increment that the drill string is lowered into the borehole, transmitting the selected signal to the control system; inducing the control system to determine the borehole depth from said length increment and the number of times the selected signal is received; and operating the control system to use the borehole depth as input parameter for controlling the borehole trajectory in correspondence with the desired borehole trajectory.

Abstract: A downhole tool string, comprising a tool string bore and a drill bit located at the bottom of the tool string. The drill bit comprises a body intermediate a shank and a working surface. The working surface may comprise a substantially coaxial rotationally isolated jack element with a portion of the jack element extending out of an opening formed in the working surface to engage a subterranean formation. The tool string may comprise a driving mechanism adapted to rotate the jack. The clutch assembly disposed within the tool string bore may comprise a first end in communication with the jack element and second end in communication with the driving mechanism.

Abstract: Disclosed is a novel autonomous excavating apparatus capable of solving conventional problems. The autonomous excavating apparatus comprises an apparatus body including a lower body 101 formed in a cylindrical shape and combined with a conical-shaped lower end, and a spiral blade 102 provided on an outer peripheral surface of the lower body 101 in the form of a right-handed screw. The lower body 101 has an internal space provided with a wheel 103 which has a rotary shaft 104 rotatably supported relative to the lower body 101 through bearings 105, 106. A motor 108 is fixed to the lower body 101 at a position above the wheel 103, and an output shaft of the motor is coaxially connected to the rotary shaft 104. Thus, the motor 108 can drivingly rotate the wheel 103 relative to the lower body 101.

Abstract: An apparatus for controlling a vibration of a drill string, the apparatus including: a plurality of sensors in operable communication with the drill string; and a controller in operable communication with the plurality of sensors, the controller connectable to a drill string motivator and capable of outputting a signal to the drill string motivator to control the vibration of the drill string.

Abstract: A boring tool moves having a pitch orientation, a yaw orientation and a roll orientation and is steerable underground using the roll orientation. A maximum drill string curvature is established for steering. The boring tool is advanced over a path segment. An averaged roll characteristic is determined for movement of the boring tool along the path segment. A path segment pitch orientation is established based on at least one measured pitch orientation along the path segment. Using the maximum drill string curvature in combination with the averaged roll characteristic and the path segment pitch orientation, the yaw orientation is determined. The averaged roll characteristic is determined based on a series of incremental roll measurements that are spaced across the path segment. A set of coupled ordinary differential equations is used to characterize movement of the boring tool.

Abstract: A changepoint detector for modeling data received from at least one sensor in a proces in the hydrocarbon industry. The data is segmented into a plurality of segments and fo each segment a model is assigned and the data corresponding to the segment fit to tha model. A plurality of segmentations are thus provided and these segmentations ar evaluated and assigned weights indicative of the fit of the models of the segmentation t the underlying data. The segmentation models are further used to calculate a result tha may be input to a process control program.

Abstract: A boring tool that is moved by a drill string to form an underground bore. A transmitter transmits a time varying dipole field as a homing field from the boring tool. A pitch sensor detects a pitch orientation of the boring tool. A homing receiver is positionable at a target location for detecting the homing field to produce a set of flux measurements. A processing arrangement uses the pitch orientation and flux measurements with a determined length of the drill string to determine a vertical homing command for use in controlling depth in directing the boring tool to the target location such that the vertical homing command is generated with a particular accuracy at a given range between the transmitter and the homing receiver and which would otherwise be generated with the particular accuracy for a standard range, different from the particular range. An associated system and method are described.

Abstract: Embodiments include a method for the autonomous drilling of ground holes by a drill rig including a drilling arrangement. The method includes the step of utilising an autonomous drilling procedure to control the drilling arrangement to drill a hole after locating the drill rig in a position where the hole is to be drilled.

Abstract: A drilling system makes measurements of at least one drilling parameter such as downhole weight on bit, bit torque, bit revolutions, rate of penetration and bit axial acceleration, and at least one measurement responsive to formation properties. One or more processors use the measurements of drilling parameters and formation properties to adjust drilling parameters.

Abstract: A control apparatus for controlling a multi-phase rock drilling event carried out with a rock drilling rig. In a display of the rock drilling rig or a control unit thereof, a first section is settable for substantially invariable information sources and a second section for information sources to be changed according to the rock drilling situation. Further, a situation-specific rock drilling definition is set in the control apparatus about at least one information source, information relating to which is to be displayed during the rock drilling situation. The working phase of the rock drilling event is checked, and an information source suitable for the phase is selected on the basis of the definition. Information relating to the at least one selected information source is displayed in the display part during execution of the rock drilling phase.

Abstract: A system having a number of land units [100, 4000, 5000] is disclosed which operates to efficiently find and create boreholes [5] to one or more underground targets [1]. Each of the land units [100, 4000, 5000] may be remotely controlled from a central command unit [6000]. The land unit also may be self-controlled, or partially controlled by the central command unit [6000]. The system [10] is reconfigurable to reallocate tasks to functional land units [100, 4000, 5000] which were originally allocated to land units which have been destroyed and are now non-functional.

Abstract: A system and method of interfacing a drilling machine with one of a number of different walk-over guidance systems involves receiving an ID signal from a particular walk-over guidance system selected for use with the drilling machine. A protocol library associated with the particular walk-over guidance system is accessed in response to the ID signal. The protocol library is used to effect communication between the particular walk-over guidance system and a control system of the drilling machine during cooperative use of the particular walk-over guidance system and drilling machine. Using the protocol library involves converting, as prescribed by the protocol library, locator signals received from the particular walk-over guidance system from a locator protocol to a common protocol used by the control system of the drilling machine. Locator and drilling machine data of various types can be presented to a drilling machine operator via an on-board display.

Abstract: Methods and apparatus for using a quill to steer a hydraulic motor when elongating a wellbore in a direction having a horizontal component, wherein the quill and the hydraulic motor are coupled to opposing ends of a drill string, by monitoring an actual toolface orientation of a tool driven by the hydraulic motor via monitoring a drilling operation parameter indicative of a difference between the actual toolface orientation and a desired toolface orientation, and then adjusting a position of the quill by an amount that is dependent upon the monitored drilling operation parameter.

Abstract: A downhole tool string, comprising a tool string bore and a drill bit located at the bottom of the tool string. The drill bit comprises a body intermediate a shank and a working surface. The working surface may comprise a substantially coaxial rotationally isolated jack element with a portion of the jack element extending out of an opening formed in the working surface to engage a subterranean formation. The tool string may comprise a driving mechanism adapted to rotate the jack. The clutch assembly disposed within the tool string bore may comprise a first end in communication with the jack element and second end in communication with the driving mechanism.

Abstract: A variable frequency down hole drill, includes a drill bit, a reciprocating piston operable to deliver an impact load to the drill bit, and means for changing the frequency with which the piston delivers impact loading to the drill bit, also resulting in a change in overall power of the drill. The means for changing frequency and overall power may operate during continuous operation of the drill. The means for changing the frequency and overall power may include a valve for selectively changing the effective volume of a drive or return chamber, an actuator for changing the timing of placing the drive or return chamber in communication with exhaust, or a system for changing the frequency in response to sensing an predetermined operating parameter of the drill, such as pressure or piston position.

Abstract: A method of controlling operation of a rock drilling rig, and a rock drilling rig. A rate of flow of a flushing medium of the rock drilling rig is determined, and the operation of the rock drilling rig is controlled on the basis of the determined rate of flow by influencing pressure of the flushing medium.

Abstract: Methods and apparatus for using a quill to steer a hydraulic motor when elongating a wellbore in a direction having a horizontal component, wherein the quill and the hydraulic motor are coupled to opposing ends of a drill string, by monitoring an actual toolface orientation of a tool driven by the hydraulic motor via monitoring a drilling operation parameter indicative of a difference between the actual toolface orientation and a desired toolface orientation, and then adjusting a position of the quill by an amount that is dependent upon the monitored drilling operation parameter.

Abstract: A steering tool is movable by a drill string to form an underground bore along an intended path. A sensing arrangement of the steering tool detects its pitch and yaw orientations at a series of spaced apart positions along the bore, each position is characterized by a measured extension of the drill string. The steering tool further includes a receiver. At least one marker is positioned proximate to the intended path, for transmitting a rotating dipole field to expose a portion of the intended path to the field for reception by the receiver. The detected pitch orientation, the detected yaw orientation and the measured extension of the drill string are used in conjunction with magnetic information from the receiver to locate the steering tool. The steering tool may automatically use the magnetic information when it is available. A customized overall position determination accuracy can be provided along the intended path.

Abstract: A wellbore drilling system is disclosed herein, in which the system includes a weight on bit controller configured to generate a normalized weight on bit output, a drilling torque controller configured to generate a normalized toque on bit output, and a differential pressure controller configured to generate a normalized differential pressure output. The system further includes a rate of penetration controller that is configured to multiply a rate of penetration setpoint with the normalized weight on bit output, the normalized torque on pit output, and the normalized differential pressure output to generate a rate of penetration output.

Abstract: A system for steering the direction of a borehole advanced by cutting action of a rotary drill bit by periodically varying the rotation speed of the drill bit. The steering system comprises a motor disposed in a bent housing subsection and operationally connected to a drill string and to the drill bit. The rotation speed of the drill bit is periodically varied by periodic varying the rotation speed of the motor or by periodic varying the rotation speed of the drill string. Periodic bit speed rotation results in preferential cutting of material from a predetermined arc of the borehole wall which, in turn, resulting in borehole deviation. Both the drill string and the drill motor are rotated simultaneously during straight and deviated borehole drilling.

Abstract: A downhole motor assembly for driving a drill bit. The assembly includes a hydraulic drive section with a stator and a rotor located inside the stator to form a flow path between the stator and the rotor. Fluid flowing through the flow path in response to a pressure differential across the hydraulic drive section creates an operative force to rotate the drill bit. The assembly also includes a regulation mechanism that includes a valve and a fluid flow diversion bore for diverting at least some fluid from the flow path when the pressure differential across the hydraulic drive section is greater than or equal to a transition pressure differential.

Abstract: A boring tool moves having a pitch orientation, a yaw orientation and a roll orientation and is steerable underground using the roll orientation. A maximum drill string curvature is established for steering. The boring tool is advanced over a path segment. An averaged roll characteristic is determined for movement of the boring tool along the path segment. A path segment pitch orientation is established based on at least one measured pitch orientation along the path segment. Using the maximum drill string curvature in combination with the averaged roll characteristic and the path segment pitch orientation, the yaw orientation is determined. The averaged roll characteristic is determined based on a series of incremental roll measurements that are spaced across the path segment. A set of coupled ordinary differential equations is used to characterize movement of the boring tool.

Abstract: A system and method of interfacing a drilling machine with one of a number of different walk-over guidance systems involves receiving an ID signal from a particular walk-over guidance system selected for use with the drilling machine. A protocol library associated with the particular walk-over guidance system is accessed in response to the ID signal. The protocol library is used to effect communication between the particular walk-over guidance system and a control system of the drilling machine during cooperative use of the particular walk-over guidance system and drilling machine. Using the protocol library involves converting, as prescribed by the protocol library, locator signals received from the particular walk-over guidance system from a locator protocol to a common protocol used by the control system of the drilling machine. Locator and drilling machine data of various types can be presented to a drilling machine operator via an on-board display.

Abstract: Aspects of this invention include methods for surveying a subterranean borehole. In one exemplary aspect, a change in borehole azimuth between first and second longitudinally spaced gravity measurement sensors may be determined directly from gravity measurements made by the sensors and a measured angular position between the sensors. The gravity measurement sensors are typically disposed to rotate freely with respect to one another about a longitudinal axis of the borehole. Gravity MWD measurements in accordance with the present invention may be advantageously made without imposing any relative rotational constraints on first and second gravity sensor sets. The present invention also advantageously provides for downhole processing of the change in azimuth between the first and second gravity sensor sets. As such, Gravity MWD measurements in accordance with this invention may be advantageously utilized in closed-loop steering control methods.

Abstract: A drilling apparatus includes an upper drill string, a lower drill string including a rotary drilling motor, an orientable rotatable connection between the drill strings, a reactive torque control device associated with the orientable rotatable connection, an orientation sensing device for providing a sensed actual orientation of the lower drill string, and a feedback control system configured to actuate the control device in response to the sensed actual orientation to achieve a target orientation of the lower drill string. A drilling method includes actuating the control device to prevent relative rotation of the drill strings, providing a sensed actual orientation of the lower drill string, comparing the sensed actual orientation with a target orientation of the lower drill string, actuating the control device to allow the lower drill string to rotate to provide the target orientation, and actuating the control device to prevent relative rotation of the drill strings.