Abstract: An assembly to recover hydrocarbon gas from a seabed comprises one or more self-propelled drilling devices that include hydrocarbon sensors and a sublimation mechanism to induce sublimation of crystallized hydrates into hydrocarbon gases. As the drilling device moves through the wellbore, hydrocarbon deposits are detected and the sublimation mechanism induces sublimation of the deposits to release hydrocarbon gases up through the formation to the seabed. A bladder is positioned atop the wellbore to capture the release hydrocarbon gas and transfer it to a surface vessel for collection.

Abstract: A drilling method includes assigning values to behaviors of drilling parameters during a drilling operation; forming multiple parameter signatures, each of the parameter signatures comprising a respective combination of the values; comparing the parameter signatures to multiple event signatures, each of the event signatures being indicative of a respective drilling event; and controlling the drilling operation in response to at least a partial match resulting from comparing the parameter signatures to the event signatures.

Abstract: Embodiments of a downhole drilling assembly generally include a rotatable lower drilling assembly, a rotatable upper drilling assembly, and a drill bit, wherein the upper drilling assembly contains a mud motor adapted for clockwise rotation of its stator and counter-clockwise rotation of its rotor, whereby the lower drilling assembly is rotatable in the opposite direction of the upper drilling assembly or maintainable in a non-rotating state. The apparatus further includes sensors adapted to continuously measure physical properties and/or drilling parameters and a mechanism for continuously transmitting information relating thereto to the surface.

Abstract: An apparatus including a stationary section having a first central fluid passage and operably connected to a drilling fluid inlet and a conduit, a rotating and reciprocating section having a second central fluid passage and operably connected to a tubular, wherein the rotating and reciprocating section reciprocates along a longitudinal axis and rotates in conjunction with the tubular and the conduit, and a third section having a third central fluid passage in fluid communication between the first and second central fluid passages, where the third section is operably disposed between the first and rotating and reciprocating sections to permit the rotating and reciprocating section to slide axially even during rotation and to permit only rotational motion at an end adjacent the stationary section.

Abstract: Logging tools and methods for obtaining a three-dimensional (3D) image of the region around a borehole. In at least some embodiments, a 3D imaging tool rotates, transmitting pulses that are approximately a nanosecond long and measuring the time it takes to receive reflections of these pulses. Multiple receivers are employed to provide accurate triangulation of the reflectors. In some cases, multiple transmitters are employed to obtain compensated measurements, i.e., measurements that compensate for variations in the receiver electronics. Because reflections occur at boundaries between materials having different dielectric constants, the 3D imaging tool can map out such boundaries in the neighborhood of the borehole. Such boundaries can include: the borehole wall itself, boundaries between different formation materials, faults or other discontinuities in a formation, and boundaries between fluids in a formation.

Abstract: Displaying data associated with drilling a borehole. At least some of the illustrative embodiments are methods including: reading data associated with drilling of a first borehole, at least one datum of the data based on a controllable parameter; calculating an operational value related to drilling the first borehole, the calculating in real-time with reading the data and the operational value based on the data; determining a target value of the operational value, the determining in real-time with reading the data and the target value at least in part based on the data; displaying a first borehole trajectory on a display device; superimposing a first coordinate system over the first borehole trajectory on the display device, the superimposing proximate to a distal end of the first borehole trajectory; and plotting, within the first coordinate system, an indication of the operational value and an indication of the target value.

Abstract: An electrical power generation system includes a flux switching machine (FSM) including an FSM rotor operatively connected to an FSM stator, the FSM rotor operatively connected to a shaft, wherein the FSM includes an electrical input/output (i/o) in electrical communication with the FSM stator, and a permanent magnet machine (PMM) including a PMM rotor operatively connected to a PMM stator, the PMM rotor operatively connected to a the shaft, wherein the PMM is electrically connected to the FSM.

Abstract: An apparatus and method for remotely adjusting the hydraulic horse power per square inch (HSI) of a drill bit. The apparatus and method may allow the nozzle geometry to be varied remotely without the need to pull the drill string outside the hole. This nozzle may include a body configured to be secured within the rotary drill bit, and a fluid passage within that body that leads to an orifice. The geometry of the fluid passage may be variable, and varying it may result in a change in the nozzle HSI; this may allow drilling different rock formations to be optimized in different drilling environments. Different placements of the nozzle, such as within the inner flow passage or between the inner flow passage and annular flow passage for controlling flow profile within a wellbore, a tubular string or a flow conduit, may be envisioned.

Abstract: System and method for deploying multiple antennas in an array configuration with unobstructed electromagnetic access to a formation outside of a casing, sequencing the transmitted signal to control the direction of transmission into the formation, receiving the reflected signals, and locating the position of the reflection based on the scanned transmission signal orientation and the direction of the received signal. Such a deployment of an antenna array with unobstructed electromagnetic access to the formation outside of the casing, sequencing of the interrogation signal, and analysis of the received signal relative to the transmitted signal direction form the basis for reflection image rendering as the transmitted signal is scanned by a sequenced stimulus signal.

Abstract: A top drive control system with a remote control having a processor and data storage connected to a torque pin sensor, a speed sensor, a remote control, which enables a user to actuate automatic remote rocking, drilling, orienting and making-up of a drill string using the top drive and provides simultaneous right hand and left hand torque applied to the drill string while simultaneously controlling speed of turning of the drill string. The top drive control system includes computer instructions for automated orienting of drill pipe, automated drilling with drill pipe and automated making-up of drill pipe into a drill string.

Abstract: A drill collar assembly allows a sensor to be mounted with the same standoff from a borehole wall independent of the size of stabilizer and borehole involved. A sensor component disposes in a receptacle in the drill collar, but does not affix in the receptacle. Instead, a stabilizer fits on the drill collar and covers the receptacle, and the sensor component mounts directly to the underside of the stabilizer so the component “floats” or “suspends” in the receptacle. The sensor component can mount at a stabilizer blade so the sensor can be positioned in closer proximity to the borehole wall to measure parameters of interest. Because the drill collar and sensor component can be used in different sized boreholes, different sized stabilizers may be positioned on the drill collar to account for the different sized boreholes while the sensor still has the same standoff.

Abstract: An expandable tubular assembly includes an expander for expanding a tubular. The expander may be hydraulically actuated. A bore obstruction object may be received in a receptacle sleeve that is a modular component of the expandable tubular assembly. In this respect, the expandable tubular assembly may be quickly fitted with a receptacle sleeve designed to receive selected type of bore obstruction object.

Abstract: The present invention relates to a marine riser isolation tool in particular to an autonomous marine riser isolation tool having a robotic plug installation device that is adapted for positioning a pipeline isolation plug in a vertical pipe such as a marine riser, resulting in sealing of the marine riser.

Abstract: Disclosed are systems and methods for preventing backdriving of a mud motor through its output. One disclosed mud motor may include a housing having a longitudinal axis, a rotor disposed within the housing and configured to rotate generally about the longitudinal axis in a first direction with respect to the housing when a flow of fluid is provided to the power generator, an output shaft at least partially disposed within the housing and coupled to the rotor, and an anti-reverse bearing arranged radially between the output shaft and the housing and configured to support the output shaft within the housing and allow rotation of the output shaft in the first direction but resist rotation of the output shaft in a second direction about the longitudinal axis with respect to the housing, the second direction being opposite the first direction.

Abstract: A downhole rotational rate control apparatus, adapted for coupling to the lower end of a drill string, includes a progressive cavity (PC) motor, a driveshaft, a mud flow control valve, and an electronics section. Drilling mud flowing downward through the drill string is partially diverted to flow upward through the PC motor and out into the wellbore annulus, with the mud flow rate and, in turn, the PC motor speed being controlled by the mud flow control valve. The control valve is actuated by a control motor in response to inputs from a sensor assembly in the electronics section. The PC motor drives the driveshaft and a controlled downhole device at a specific zero or non-zero rotational rate. By varying the rotational rate of the PC motor relative to the rotational rate of the drill string, the tool face orientation or non-zero rotational speed of the controlled device in either direction can be varied in a controlled manner.

Abstract: Compositions, structures and methods that relate to films having switchable reflectivity and anti-reflectivity depending on ambient conditions, such as temperature. A film with switchable reflectivity and anti-reflectivity includes a nanostructured first layer having nanopillars associated with nanowells. A hydrogel occupies at least a portion of the nanowells. As the hydrogel moves from a dehydrated state to a hydrated state, the surface of the film switches from being reflective to being anti-reflective in a repeatable and reversible process.

Abstract: In a method for drilling a borehole real time geosteering data, including natural gamma ray data is obtained for a plurality of borehole positions for drilling a borehole along a projected trajectory. A formation layer having a thickness equal to or greater than the natural gamma ray sphere of influence and having a first lithology is identified. Data is processed for subsequent borehole positions. Upon location of the boundary of a formation layer of different lithology within the natural gamma ray sphere of influence, at least two points of the different formation layer boundary are determined by using the inverse problem methods, and an extrapolation ahead of the drill bit of at least two points is made utilizing the boundary to determine whether to change the borehole trajectory.

Abstract: A method for drilling a wellbore includes operating at least one motor coupled within a drill string to turn a drill bit at an end thereof. An automatic drill string rotation controller causes rotation of the drill string in a first direction until a measured parameter related to torque on the drill string reaches a first selected value. The automatic drill string rotation controller causes rotation of the drill string in a second direction until the measured parameter related to torque is reduced to a second selected value. The drill string is axially advanced to cause the drill bit to extend the wellbore.

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 device is capable of autonomously burrowing into the earth and, when at depth, discharging a fluid into a geologic formation. The device includes a component body holding a computer controller; a battery; a motor; and a coiled hose. A drill head external to the component body is equipped with a spiral blade that burrows down pulling the component body with it. A cylindrical shell surrounding the component body creates an annulus where debris from the drill head flows upward. The coiled hose is released from the component body as the device descends. An electrical cable may be co-wound with the coiled hose or may be embedded in the wall of the coiled hose. Fluid may be conveyed through the coiled hose to a discharge valve in the component body. The discharge valve is connected to a telescoping discharge nozzle.

Abstract: A technique facilitates drilling of wellbores with a steerable system having a plurality of pads which may be selectively actuated in a lateral direction to apply a side force. Application of the side force is used to steer a drill bit. A valve system is positioned to control delivery of actuating fluid under pressure to individual pads in a manner that enables steering of the drill bit. The valve system allows drilling along a desired curve by controlling the flow of actuating fluid under pressure to specific steering pads at specific angular positions. The valve system also allows drilling along a desired trajectory by preventing exposure of the pads to the pressurized actuating fluid.

Abstract: Apparatus and method for automated drilling of a borehole in a subsurface formation. In one embodiment, a method includes selecting at least one control variable. A drilling performance objective having a value that is influenced by drilling of the borehole using the at least one control variable is defined. A first interval of the borehole is drilled maintaining the at least one control variable at a first value. A second interval of the borehole is drilled maintaining the at least one control variable at a second value. A third interval of the borehole is drilled maintaining the at least one control variable at a third value. The third value is selected based on a comparison of the values of the drilling performance objective while drilling the first interval and second interval to a predetermined optimal value of the drilling performance objective.

Abstract: A drilling control and information system comprising: a rig site network (102) including a drilling equipment controller (112) and a drilling parameter sensor (116); a downhole sensor (118) communicatively coupled to the rig site network; a data center (104) communicatively coupled to the rig site network; a remote access site (106) communicatively coupled to the data center; and a pressure management application (300) communicatively coupled to the rig site network, wherein the pressure management application receives pressure data from the drilling parameter sensor and the downhole sensor and issues an operating instruction to the drilling equipment controller.

Abstract: A bottomhole assembly (BHA) coupled to a drill string includes one or more controllers, and a hole enlargement device that selectively enlarges the diameter of the wellbore formed by the drill bit. The hole enlargement device includes an actuation unit that may move extendable cutting elements of the hole enlargement device between a radially extended position and a radially retracted position. The actuation unit may be responsive to a signal that is transmitted from a downhole and/or a surface location. The hole enlargement device may also include one or more position sensors that transmit a position signal indicative of a radial position of the cutting elements. In an illustrative operating mode, one or more operating parameters of the hole enlargement device may be adjusted based on one or more measured parameters. This adjustment may be done in a closed-loop or automated fashion and/or by human personnel.

Abstract: An automatic drilling apparatus having a tool body, a motive device connected to the tool body, and a drill bit connected to the tool body. The apparatus also includes a setting tool connected to the body, at least one sensor disposed on the tool body, and a computer disposed in the tool body, wherein the computer is configured to actuate the motive device, the drill bit, the setting tool, and the at least one sensor.

Abstract: A method and apparatus for estimating the instantaneous rotational speed of a bottom hole assembly at the lower end of a drill string. In one embodiment, a method includes driving the drill string by a drilling mechanism at the upper end of the drill string. A fundamental frequency of stick-slip oscillations suffered by the drill string is estimated. Variations in a drive torque of the drilling mechanism are determined. Known torsional compliance of the drill string is combined with the variations in the drive torque. An output signal representing the instantaneous rotational speed is provided.

Abstract: A method of controlling a direction of a toolface of a bottom hole assembly for slide drilling, comprises a) synchronizing the toolface wherein synchronizing the toolface comprises determining a relationship between the rotational position of the down hole toolface with a rotational position at the surface of the formation for at least one point in time, b) stopping rotation of the drill string coupled to the bottom hole assembly, c) controlling torque at the surface of the drill string to control a rotational position of the toolface, and d) commencing a slide of the drill string.

Abstract: An apparatus and method of performing a wellbore operation. The apparatus includes a drill bit that has a cavity at an end thereof and a communication device placed in the cavity. The communication device includes a first section and a second section. An outer dimension of the second section is greater than an outer dimension of the first section. The second section includes a conduit configured to allow passage of a conductor from the drill bit to a location outside the drill bit so as to provide a direct connection of the conductor from the drill bit to an element outside the drill bit.

Abstract: Exemplary methods, systems and components disclosed herein provide propagation of light signals from an external source to a borehole mining mole which includes an optical/electric transducer configured to provide propulsive power for the borehole mining mole and its associated mineral prospecting tools. Some embodiments include one or more umbilicals connected from a remote source location to an onboard reel incorporated with the borehole mining mole. The umbilicals are spooled outwardly or inwardly from the onboard reel during traverse of the borehole mining mole along a path in an earthen environment.

Abstract: A position and velocity measuring tool for use on a top drive of a drilling rig having a variable frequency drive connected to an electric motor and power supply. The position and velocity measuring tool further has a processor connected to the variable frequency drive and a data storage and computer instructions for presenting an operator directional drilling steering system dashboard with numerous visual components which creates and uses a virtual encoder eliminating a failure point of a mechanical encoder.

Abstract: Wellbore drilling apparatus and methods are provided. The apparatus includes a reaming subassembly including one or more reamers configured to ream a wellbore. The reaming subassembly defines a cutting aggressiveness that is variable while the reaming subassembly is disposed in a wellbore. The apparatus also includes an actuator coupled with the reaming subassembly and configured to vary the cutting aggressiveness of the reaming subassembly in response to an actuation signal.

Abstract: A dynamic data compression system for forming and transmitting data from a downhole location within a borehole penetrating the earth to a surface location includes a data source that forms raw data sets of a formation contacting the borehole, the raw data sets being formed at a fixed rate and a data rate sampler that determines a transmission rate of a transmission channel. The system also includes a compression engine configured to compress the raw data sets according to compression parameters to form compressed data sets. The compression parameters are dynamically changed based on the transmission rate.

Abstract: A locking clutch to selectively transmit torque from a stator of a downhole tool to a rotor of the downhole tool includes at least one locking pawl radially between the rotor and the stator and configured to engage at least one recess formed in an outer periphery of the rotor, and a biasing mechanism configured to bias the at least one locking pawl into an engaged position. The at least one locking pawl includes a load path, two pivot axes, and a mass center. The at least one locking pawl transmits force from the stator to the rotor along the load path when in the engaged position, and centrifugal force urges the at least one locking pawl into a disengaged position when the rotor is rotated about one of the two pivot axes above a disengagement speed.

Abstract: This application is directed to a pressure balanced mud motor. The mud motor includes a power section to rotate a passageway housing and propel fluid through a passageway disposed in the passageway housing. The mud motor also includes a hydraulic apparatus for balancing a pressure drop experienced across a bearing assembly due to frictional flow of fluid through the passageway.

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 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: Described herein is a reamer tool (100) having a body (105) with bays (115) in which cutter arms (110) are mounted for deployment between a stowed position and a deployed position. A deployment mechanism is provided for deploying the cutter arms from their stowed position to their deployed position that maintains each cutter arm in a position that is substantially parallel to a longitudinal axis of the body (105) whilst in its stowed position and in its deployed position as well as during its deployment from its stowed position to its deployed position. A control module (300) is also described for controlling the deployment of the cutter arms (110). The control module (300) comprises a motor (310), a gearing mechanism (315) and a moveable element (320) that closes a port (385) in a first position and opens the port (385) in a second position.

Abstract: A method and apparatus for estimating the instantaneous rotational speed of a bottom hole assembly at the lower end of a drill string. In one embodiment, a method includes driving the drill string by a drilling mechanism at the upper end of the drill string. A fundamental frequency of stick-slip oscillations suffered by the drill string is estimated. Variations in a drive torque of the drilling mechanism are determined. Known torsional compliance of the drill string is combined with the variations in the drive torque. An output signal representing the instantaneous rotational speed is provided.

Abstract: Methods and systems for drilling to a target location include a control system that receives an input comprising a planned drilling path to a target location and determines a projected location of a bottom hole assembly of a drilling system. The projected location of the bottom hole assembly is compared to the planned drilling path to determine a deviation amount. A modified drilling path is created to the target location as selected based on the amount of deviation from the planned drilling path, and drilling rig control signals that steer the bottom hole assembly of the drilling system to the target location along the modified drilling path are generated.

Abstract: A dynamic steering tool for use with a horizontal directional drilling machine. The tool comprises and inner member, an outer member, a steering member, a drill stem, and a drill bit. The drill stem extends from within a borehole to the surface while the outer member only extends the length of the inner member within the borehole. The outer member is powered via the use of a progressive cavity motor. In operation, the drill stem, inner member, and drill bit rotate in a clockwise position while the outer member rotates in a counterclockwise direction. Rotating the outer member opposite the inner member allows the outer member to remain stationary and cause the tool to steer while the inner member continues to rotate.

Abstract: Optimising the operation of a hydraulically powered rotor and stator driven drill as it drills a wellbore into the earth is described. Drilling optimization is provided measuring a first set of rotor and stator operating parameters including the speed of rotation of the rotor and rotor torque for a first period of time, generating a first set of relationships from the first set of operating parameters to enable the rotor speed and rotor torque to be predicted over a range of operating parameter values, determining from the relationships a first more optimal mode of operation, and changing at least one operating parameter to move the operation of the rotor and stator towards the more optimal mode of operation.

Abstract: The invention provides a method of optimising the rate of penetration of a hydraulically or pneumatically powered rotor and stator driven drill as it drills a wellbore into the earth, the method comprising: (a) measuring a first set of rotor and stator operating parameters including the weight applied to the drill bit, the speed of rotation of the rotor and rotor torque for a first period of time, (b) generating a first set of relationships from the first set of operating parameters to enable the rotor speed and rotor torque to be predicted over a range of operating parameter values, (c) determining the rate of penetration for the first period of time from measurements of weight applied to the bit and rotation speed of the bit, (d) determining whether any other combination of weight applied to bit and rotation speed of bit, provided by the relationships determined in step (b) are capable of providing a greater rate of penetration, and (e) adjusting at least one operating parameter to move the weight applied t

Abstract: A method for drilling a wellbore includes operating at least one motor coupled within a drill string to turn a drill bit at an end thereof. An automatic drill string rotation controller causes rotation of the drill string in a first direction until a measured parameter related to torque on the drill string reaches a first selected value. The automatic drill string rotation controller causes rotation of the drill string in a second direction until the measured parameter related to torque is reduced to a second selected value. The drill string is axially advanced to cause the drill bit to extend the wellbore.

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: Apparatus and methods to steer a hydraulic motor when elongating a wellbore having a non-vertical component that includes a quill adapted to transfer torque, rotation, or position between a drive assembly and a drillstring, a bottom hole assembly (BHA) including a toolface orientation detector and at least one measurement while drilling (MWD) instrument or wireline-conveyed instrument, and a controller configured to transmit operational control signals to minimize friction between a drillstring and a wellbore, wherein the instrument is configured to detect pressure between an external surface of the BHA and an inner diameter of the wellbore.

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 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: In certain embodiments, a steerable drilling tool is provided including a rotatable shaft extending through a housing where the shaft and the housing are separated by at least one bearing or two sets of bearings, the shaft having a first portion terminating at a first end of the shaft and a second portion terminating at a second end of the shaft. The steerable drilling tool may further include a drill bit structure operatively coupled to the first portion and a steering subsystem comprising a pair of bearings operatively coupled to the first portion. The steering subsystem may be configured to angulate the shaft by exerting force substantially through the pair of bearings. In certain embodiments, the first portion is between the first end and about one-third of the length of the shaft from the first end towards the second end.

Abstract: A method and apparatus for precisely controlling the rotation of a drill string. A sensor monitors the rotation of the drill string and transmits the rotational information to a computer. The computer controls the rotation of the motor driving the drill string and rotates the drill string through an angle input by the operator. The computer may also utilize the sensor's rotational information to oscillate the drill string between two predetermined angles. The computer may also receive orientation information from a downhole tool sensor. The downhole tool information may be combined with the rotational information to enable the computer to accurately reorient the downhole tool.

Abstract: A method and apparatus for precisely controlling the rotation of a drill string. A sensor monitors the rotation of the drill string and transmits the rotational information to a computer. The computer controls the rotation of the motor driving the drill string and rotates the drill string through an angle input by the operator. The computer may also utilize the sensor's rotational information to oscillate the drill string between two predetermined angles. The computer may also receive orientation information from a downhole tool sensor. The downhole tool information may be combined with the rotational information to enable the computer to accurately reorient the downhole tool. REEXAMINATION RESULTS The questions raised in reexamination proceeding No. 90/011,617, filed Apr. 1, 2011, have been considered, and the results thereof are reflected in this reissue patent which constitutes the reexamination certificate required by 35 U.S.C. 307 as provided in 37 CFR 1.