Abstract: Various embodiments are directed to a method and apparatus for horizontal directional drilling with a tool library. Various methods include storing a plurality of operational tool profiles in memory, the operational tool profiles of the plurality respectively associated with a plurality of boring tools attachable to a drill string for HHD and each of the operational tool profiles of the plurality including operating parameters for the boring tool of the plurality with which the operational profile is associated, and selectively displaying the operational tool profiles on a display screen based on user input.

Abstract: A remote controlled tilting power swivel capable of being tilted to any angle up to an adjustable maximum tilt angle. The tilting power swivel angle of tilt can be adjusted to line up with pipe staged at various angles as required by different rigs. Adjusting the maximum extension of the tilt cylinder allows the power swivel to repeat a desired angle for the duration of a job. The system requires the addition of only one hydraulic fluid supply hose, thereby allowing a simple live hose reel with four hoses. The tilting power swivel promotes safety, efficiency, and saves time by eliminating the need for a stabbing man hanging in the derrick.

Abstract: A method for using a power swivel with tilt capable of being tilted to any angle up to an adjustable maximum tilt angle. The method allows adjusting the tilting power swivel's angle of tilt to line up with pipe staged at various angles as required by different rigs. The method allows for adjusting the maximum extension of the tilt cylinder, and further allows the power swivel to be repeatedly positioned at a desired angle for the duration of a job. The method requires the addition of only one hydraulic fluid supply hose, thereby allowing a simple live hose reel with four hoses. The method for using a power swivel with tilt promotes safety, efficiency, and saves time by eliminating the need for a stabbing man hanging in the derrick.

Abstract: A system for damping vibration in a drill string can include a valve assembly having a supply of a fluid, a first member, and a second member capable of moving in relation to first member in response to vibration of the drill bit. The first and second members define a first and a second chamber for holding the fluid. Fluid can flow between the first and second chambers in response to the movement of the second member in relation to the first member. The valve assembly can also include a coil or a valve for varying a resistance of the fluid to flow between the first and second chambers.

Abstract: A wellbore machining device is proposed for machining a tubular component of a wellbore. The device includes a control unit at the surface level of the wellbore and a down-hole tool unit connected to the control unit through a wire line. The tool unit includes an elongated guide member, a tool member movably supported on the guide member with respect to at least three axes of motion and a plurality of actuators controlled by the control unit and adapted to move the tool member with respect to the axes of motion. The tool unit further includes two anchor members each mounted to an axial end of the guide member and adapted to releasably clamp the tool unit to the tubular component. The control unit and the tool unit form a computer numerical control device (CNC device) wherein the actuators are electric servo motors controlling an actual position of the tool member with respect to a path and/or a sequence of desired position defined by the control unit.

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: An automated rod manipulator system for moving a drill rod section from a storage magazine to a drill rig and connecting the drill rod to a drill string of the drill rig without manual manipulation of any parts. The automated rod manipulator system may comprise a magazine to store and dispense a plurality of drill rod sections, a carriage to convey one of the plurality of drill rod sections from the magazine to a transfer position; and a gripping arm coupled to a drill rig mast of a drilling rig, the gripping arm operable to convey one of the plurality of drill rod sections from a transfer position to a position aligned with a spindle center line of the drilling rig. The automated rod manipulator may also include a control system and an alignment assembly for aligning the drill rod section on a spindle centerline of the drill rig.

Abstract: Methods and apparatuses for producing a planar cavern are provided. The planar cavern is formed by first creating a continuous bore that extends through a subsurface resource deposit. The drill head used to create the bore can be steered in response to information about the concentration of the resource in the strata through which the drill head is passing, in order to keep the bore within resource deposit. The continuous bore can be formed by connecting first and second bores at a point within the subsurface resource deposit. After the continuous bore has been formed, a sawing assembly is placed within the continuous bore. The sawing assembly is then moved, in a continuous or in a reciprocating fashion, within the continuous bore. As the sawing assembly is moved, it is maintained under tension, to create a planar cavern. By thus exposing a large area of the resource deposit, a relatively large amount of the resource deposit can be dissolved in a solvent introduced to the planar cavern per unit time.

Abstract: An autodriller provides an automatic self calibration system to predict both axial and rotational friction coefficients from the surface measurements such as hookload and surface torque while a drill bit is off bottom. The friction coefficients are used to calculate the friction forces between drillstring and the wellbore while the bit is on bottom during drilling operation to estimate downhole weight on the bit and bit torque, and use the estimates to alter the drilling process.

Abstract: The invention is a system and methods for conducting automated, unmanned and unattended drilling operations. The system comprises an unmanned and unattended landing and launch vehicle capable of navigating to a location and reversibly coupled to an automated drilling platform. The automated drilling platform can autonomously conduct drilling operations, such as, collecting core samples. Automated drilling operations may comprise deploying a core drilling rigid mast that autonomously feeds pipe sections onto the rigid mast proportional to depths drilled, then extracting the pipe sections containing core samples sequentially from the mast head, securing the core samples in the launch and landing vehicle, retracting the mast head from the bore line and securing it in the launch and landing vehicle. Once drilling is complete, the automated drilling platform may be de-coupled from the landing and launch vehicle before re-launching the vehicle and returning the samples to an accessible terrain or location.

Abstract: An apparatus for estimating at least one of a dynamic motion of a portion of interest of a drill string and a static parameter associated with the portion of interest, the apparatus having: a plurality of sensors operatively associated with the drill string at at least one location other than the portion of interest; and a processing system coupled to the plurality of sensors, the processing system configured to estimate at least one of the dynamic motion and the static parameter using a measurement from the plurality of sensors as input.

Abstract: The present specification describes a drill bit for drilling a cavity. The drill bit may include a chassis, a plurality of gauge pad sets, and at least one gauge pad structure. The chassis may be configured to rotate about an axis. The plurality of gauge pad sets may each include at least one gauge pad. The at least one gauge pad structure may moveably couple at least one of the gauge pads of at least one of the plurality of gauge pad sets with the chassis.

Abstract: This disclosure relates in general to a method and system for controlling a drilling system for drilling a borehole in an earth formation. More specifically, but not by way of limitation, embodiments of the present invention provide systems and methods for controlling dynamic interactions between the drilling system for drilling the borehole and an inner surface of the borehole being drilled to steer the drilling system to directionally drill the borehole. In another embodiment of the present invention, data regarding the functioning of the drilling system as it drills the borehole may be sensed and interactions between the drilling system for drilling the borehole and an inner surface of the borehole may be controlled in response to the sensed data to control the drilling system as the borehole is being drilled.

Abstract: Disclosed are systems and methods for monitoring drilling fluid components in real time. One system includes solids control equipment fluidly coupled to a borehole and configured to receive drilling fluid from the borehole, the solids control equipment having a first optical computing device arranged adjacent the inlet and configured to optically interact with the drilling fluid as it enters the solids control equipment and thereby generate a first output signal corresponding to a characteristic of the drilling fluid, a second optical computing device arranged adjacent the outlet and configured to optically interact with the drilling fluid as it exits the solids control equipment and thereby generate a second output signal corresponding to the characteristic of the drilling fluid, and a signal processor communicably coupled to the first and second optical computing devices and configured to receive the first and second output signals and provide a resulting output signal.

Abstract: A method for directional drilling of a wellbore includes automatically rotating a drill string having a steerable drilling motor at an end thereof in a first direction so that a measured torque related parameter thereon reaches a first value. The drill string is automatically rotated in a second direction so that the measured torque related parameter reaches a second value lower than the first value. A rate of release of the drill string is automatically controlled so that at least one of selected drilling fluid pressure and a range thereof is maintained.

Abstract: An implement pose control system and method is provided for a machine. The system and method include determining an actual implement pose having a first actual angle component relative to the first implement rotational axis and a second actual angle component relative to the second implement rotational axis. A desired implement pose may be determined that has first and second desired angle components relative to the first and second implement rotational axes. First and second axis errors may be determined, and the first and second actuators may be automatically operated in response to the error signals.

Abstract: The presence of organosulfur compounds in a substance may make analyses of the substance difficult, particularly in the presence of interfering compounds. Methods for analyzing a substance may comprise: providing a substance comprising an organosulfur compound; optically interacting electromagnetic radiation with the substance and an integrated computational element; and analyzing for the organosulfur compound in the substance using the integrated computational element.

Abstract: A directional drilling tool is provided, which comprises a first end (2) attachable to a drill string, and a second end (4) attachable to a drill bit. A swivel section (6) is provided intermediate the first and second ends (2,4) and has a first swivel member (18) non-rotatably attached to the first end (2) and a second swivel member (20) rotatably coupled to the first swivel member (18) and rotatable relative thereto about a first axis of rotation which is co-axial with a longitudinal axis (LI) of the tool. A first actuator is adapted to selectively rotate the second swivel member (20) about the first axis of rotation.

Abstract: A drilling machine includes a compressor coupled to a prime mover through a hydraulic clutch, wherein the hydraulic clutch is repeatably moveable between engaged and disengaged conditions. The compressor is allowed to provide air and is restricted from providing air in response to the hydraulic clutch being in the engaged and disengaged conditions, respectively. The hydraulic clutch is moveable between the engaged and disengaged conditions during operation of the prime mover.

Abstract: A method for sequencing drill holes for a mobile drill rig is disclosed. The method may include receiving a hole pattern having a plurality of planned holes and generating at least a first group of parallel pathways and a second group of parallel pathways between the plurality of holes of the hole pattern. The first group of pathways may be angled relative to the second group of pathways. The method may also include selecting between the first group of pathways and the second group of pathways based on which group of pathways includes fewer total pathways.

Abstract: This disclosure relates in general to a method and system for controlling a drilling system for drilling a borehole in an earth formation. More specifically, but not by way of limitation, embodiments of the present invention provide systems and methods for controlling dynamic interactions between the drilling system for drilling the borehole and an inner surface of the borehole being drilled to steer the drilling system to directionally drill the borehole. In another embodiment of the present invention, data regarding the functioning of the drilling system as it drills the borehole may be sensed and interactions between the drilling system for drilling the borehole and an inner surface of the borehole may be controlled in response to the sensed data to control the drilling system as the borehole is being drilled.

Abstract: A distributed drilling simulation system includes a choke manifold, a high pressure manifold, a blowout preventer console, a choke console, a remote console, a driller console, a teacher console and a graphic projecting unit, wherein the driller console, the remote console, the blowout preventer console, the choke console, the choke manifold, and the high pressure manifold are interconnected through a PPI (processor/peripheral interface) protocol. The teacher console is connected with the PPI protocol through a PPI interface. A communication program and a main control program run on a main control computer and a graphic processing program runs on a graphic computer. The invention has the advantages of realizing high-degree top driving drilling simulation, enhancing the field sense for teaching and training, shortening the training period and reducing the training cost.

Abstract: A system includes a valve subassembly configured to be disposed along an internal flowline exit of a first internal flowline within a downhole drilling module. The valve subassembly includes an active valve configured to regulate flow of a fluid through the internal flowline exit and a passive valve configured to be passively controlled based on a differential pressure between a first volume of the downhole drilling module and a second volume surrounding the downhole drilling module.

Abstract: A drill bit direction system and method is disclosed that modifies or biases the stochastic movement of the drill bit to change a drilling direction of a drilling system. The direction of the drill bit is monitored to determine if the direction happens to align in some way with a preferred direction. If the direction isn't close enough to a preferred or desired direction, stochastic motion of the drill bit in the borehole may be controlled and/or motion of the drill bit under a side force acting on the drill bit to direct the drilling may be focused or biased to modify the direction of drilling closer to the preferred direction. Any of a number of stochastic motion control mechanisms or biasing mechanisms can be used. Some embodiments can resort to conventional steering mechanisms to supplement the stochastic motion control or side force biasing mechanisms.

Abstract: Systems and methods are provided for expert systems for well completion using Bayesian decision networks to determine well completion recommendations. The well completion expert system includes a well completion Bayesian decision network (BDN) model that receives inputs and outputs recommendations based on Bayesian probability determinations. The well completion BDN model includes a treatment fluids section, a packer section, a junction classification section, a perforation section, a lateral completion section, and an open hole gravel packing section.

Abstract: The present invention provides a mechanism to remotely initiate actuation of a device positioned in a borehole. The disclosure includes a magnetically initiated actuation mechanism.

Abstract: Systems and methods are provided for an underbalanced drilling (UBD) expert system that provides underbalanced drilling recommendations, such as best practices. The UBD expert system may include one or more Bayesian decision network (BDN) model that receive inputs and output recommendations based on Bayesian probability determinations. The BDN models may include: a general UBD BDN model, a flow UBD BDN model, a gaseated (i.e., aerated) UBD BDN model, a foam UBD BDN model, a gas (e.g., air or other gases) UBD BDN model, a mud cap UBD BDN model, an underbalanced liner drilling (UBLD) BDN model, an underbalanced coil tube (UBCT) BDN model, and a snubbing and stripping BDN model.

Abstract: Provided is apparatus for use in resonance enhanced rotary drilling, which apparatus comprises: (i) an upper load-cell for measuring static and dynamic axial loading; (ii) a vibration isolation unit; (iii) optionally an oscillator back mass; (iv) an oscillator for applying axial oscillatory loading to the rotary drill-bit; (v) a vibration transmission unit; (vi) a lower load-cell for measuring static and dynamic axial loading; (vii) a drill-bit connector; and (viii) a drill-bit, wherein the upper load-cell is positioned above the vibration isolation unit and the lower load-cell is positioned between the vibration transmission unit and the drill-bit, and wherein the upper and lower load-cells are connected to a controller in order to provide down-hole closed loop real time control of the oscillator.

Abstract: Methods and systems are described for improved drilling operations through the use of real-time drilling data to predict bit wear, lithology, pore pressure, a rotating friction coefficient, permeability, and cost in real-time and to adjust drilling parameters in real-time based on the predictions. The real-time lithology prediction is made by processing the real-time drilling data through a multilayer neural network. The real-time bit wear prediction is made by using the real-time drilling data to predict a bit efficiency factor and to detect changes in the bit efficiency factor over time. These predictions may be used to adjust drilling parameters in the drilling operation in real-time, subject to override by the operator. The methods and systems may also include determining various downhole hydraulics parameters and a rotary friction factor. Historical data may be used in combination with real-time data to provide expert system assistance and to identify safety concerns.

Abstract: The disclosure relates to a mining vehicle and a method of moving a boom of a mining vehicle. The boom is provided with several boom joints and there is a mining work device at a distal end of the boom. One or more boom joint positions are determined and stored in a memory medium. A control unit of the mining vehicle may automatically move the boom to a predetermined transport position.

Abstract: Predicting a drill string stuck pipe event. At least some of the illustrative embodiments are methods including: receiving a plurality of drilling parameters from a drilling operation; applying the plurality of drilling parameters to an ensemble prediction model comprising at least three machine-learning algorithms operated in parallel, each machine-learning algorithm predicting a probability of occurrence of a future stuck pipe event based on at least one of the plurality of drilling parameters, the ensemble prediction model creates a combined probability based on the probability of occurrence of the future stuck pipe event of each machine-learning algorithm; and providing an indication of a likelihood of a future stuck pipe event to a drilling operator, the indication based on the combined probability.

Abstract: A method for aggregating data for a drilling operation. The method includes acquiring the data from a number of data sources associated with the drilling operation, synchronizing a timing of the data for aggregating the data to generate synchronized aggregated data, determining a drilling context based on the synchronized aggregated data, and assigning the determined drilling context to the synchronized aggregated data. The method further includes analyzing the synchronized aggregated data in the drilling context to generate an analysis and presenting the analysis to at least one user.

Abstract: Methods and systems are provided that enable the removal or reduction of moisture and any other volatile substances within downhole tools. A purging gas can be allowed to flow into the downhole tool, where it begins to interact with and dry the moisture present as well as dilute the gaseous environment therein. Then purging gas then can exit the tool, thereby removing the moisture and any other potentially polluting or corrosive gases in the tool. A vacuum pump and desiccant jar assembly also can be used to further remove moisture from the tool.

Abstract: According to one embodiment, the disclosure relates to a roller cone drill bit including a bit body having at least one support arm extending therefrom, a cone assembly containing bearings or retaining balls and rotatably mounted on a journal extending from each support arm, a lubricant reservoir disposed in each support arm, a lubricant chamber disposed in each support arm and fluidly coupled to the bearings or retaining balls, a bore disposed in each support arm to communicate lubricant between the lubricant reservoir and the lubricant chamber, and a pressure release mechanism disposed within the bore. The pressure release mechanism may be operable to relieve lubricant from the lubricant reservoir into the lubricant chamber when lubricant pressure within the lubricant reservoir exceeds pressure of the lubricant in the lubricant chamber. According to another embodiment, the disclosure relates to methods of relieving lubricant in such a bit.

Abstract: Apparatus and methods for controlling and communicating with one or more tools in a downhole tool string including a tractor, an auxiliary tractor tool, a logging tool, a safety sub, a release mechanism, a unit containing sensors for monitoring downhole conditions, a setting tool, and a perforating gun. Control and communication are accomplished by sending signals from the surface to control switches in the control units on the tool, with redundant switches for safety, to state machines in the respective control units, each state machine returning a signal verifying switch status to the surface. The state machine need not return a signal including a unique identifier.

Abstract: A method and equipment for displaying holes to be drilled when drilling holes into rock with a rock-drilling rig having control equipment and a display belonging thereto and measuring means for defining the direction and position of a drill rod, by using a pre-designed drilling plan defined in a three-dimensional coordinate system, in which a starting point (19a to 21a) and end point (19b to 21b) is defined for each hole to be drilled. A base plane running through the end point (19b to 21b) of the hole and parallel to the projection plane is defined for each hole (19 to 21), and a projection of the intersection of a hole or its extension created when drilling in accordance with the current location of the drill rod and the defined base plane is displayed with a graphical location symbol on the projection plane.

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: Systems and methods for drilling a plurality of densely packed wells to efficiently utilize available drilling space. In accordance with one embodiment, a method of drilling densely packed wells may include drilling a second well using magnetic ranging while drilling to control a distance between the second well and a first well (the first well being either existing or drilled immediately prior to starting to drill the second well), and drilling a third well using magnetic ranging while drilling to control a distance between the third well and the first and second wells.

Abstract: A system and method for monitoring underground drilling in which vibration is monitored by creating a model of the drill string using finite element techniques or finite difference techniques and (i) predicting vibration by inputting real time values of operating parameters into the model, and then adjusting the model to agree with measured vibration data, (ii) predicting the weight on bit and drill string and mud motor speeds at which resonance will occur, as well as when stick-slip will occur, so that the operator can avoid operating regimes that will result in high vibration, (iii) determining vibration and torque levels along the length of the drill string based on the measured vibration and torque at one or more locations, (iv) determining the remaining life of critical components of the drill string based on the history of the vibration to which the components have been subjected, and (v) determining the optimum drilling parameters that will avoid excessive vibration of the drill string.

Abstract: A system and method for the drilling of ground holes by a track steer drill rig including a drilling arrangement that permits the speed of drilling holes to be balanced against the stability of the hole thus formed.

Abstract: A control system for an automatic drilling tool changer apparatus for use with a drilling rig includes a drilling control device programmed with a control scheme for controlling the automatic drilling tool changer apparatus, and a user interface coupled to the drilling control device for initiating actions of the automatic drilling tool changer apparatus and for interactively monitoring a status of the automatic drilling tool changer apparatus. The control scheme includes steps for an automatic drilling tool change-out operation, and the drilling control device and the user interface are configured to communicate with the automatic drilling tool changer apparatus over a network.

Abstract: Disclosed are systems and methods of producing from multiple production zones with a single trip multi-zone completion system. One single trip multi-zone completion system includes an outer completion string having at least one sand screen arranged thereabout and a flow control device movably disposed within the at least one sand screen between an open position and a closed position, and an insert string arranged within the outer completion string and having at least one control and data acquisition module disposed thereon, the at least one control and data acquisition module having one or more mechanical coupling mechanisms extending therefrom and configured to locate and move the flow control device between the open and closed positions.

Abstract: A method and system to aid and/or train well control personnel by measuring the actual hydraulic delay and pressure attenuation of operator choke changes during well control operations or simulations. This provides the choke operator with an anticipated drillpipe pressure as soon as the choke is adjusted, accounting for hydraulic delay, pressure attenuation and prior choke adjustments that are currently travelling through the wellbore as well as reflections of the transient pressure waves against the pumps and choke. The technique that is described utilizes only three inputs, and works without knowledge of or inputting data such as well depth, pipe and hole geometry, mud properties, temperature, water depth, land, offshore platform or floating (subsea BOP's) drilling rigs.

Abstract: The invention provides a system for automatic control of the drilling an oil well. The system includes an autodrilling interface enabling parameter input data to be input and enabling the display of system output data, a controller, a hydraulic control system and at least one sensor configured to the hydraulic control system. The controller receives parameter input data from the autodrilling interface and at least one sensor and provides output instructions to the hydraulic control system such that the hydraulic control system operates to control drilling based on controller instructions and sensor data.

Abstract: A method of assessing hole cleaning effectiveness of drilling comprises a) determining a mass of cuttings removed from a well wherein determining the mass of cuttings removed from a well comprises: i) measuring a total mass of fluid entering a well; ii) measuring a total mass of fluid exiting the well; and iii) determining a difference between the total mass of fluid exiting the well and total mass of fluid entering the well; b) determining a mass of rock excavated in the well; and c) determining a mass of cuttings remaining in the well wherein determining the mass of cuttings remaining in the well comprises: determining a difference between the determined mass of rock excavated in the well and the determined mass of cuttings removed from the well.

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 system and method for monitoring underground drilling in which vibration is monitored by creating a model of the drill string using finite element techniques or finite difference techniques and (i) predicting vibration by inputting real time values of operating parameters into the model, and then adjusting the model to agree with measured vibration data, (ii) predicting the weight on bit and drill string and mud motor speeds at which resonance will occur, as well as when stick-slip will occur, so that the operator can avoid operating regimes that will result in high vibration, (iii) determining vibration and torque levels along the length of the drill string based on the measured vibration and torque at one or more locations, (iv) determining the remaining life of critical components of the drill string based on the history of the vibration to which the components have been subjected, and (v) determining the optimum drilling parameters that will avoid excessive vibration of the drill string.

Abstract: A system for drilling a borehole according to the present invention includes a control system and a drill rig, including a water injection system and an air injection system. The control system receives information from the drill rig that relates to at least one drill parameter. The control system processes information relating to the drill parameter, determines whether to implement a hole defect mitigation routine, including a drilling phase defect mitigation routine or a retraction phase defect mitigation routine following completion of the drilling phase. The control system determines whether the drill parameter is within a predetermined specification for the monitored drill parameter, chooses a hole defect mitigation routine based on the monitored drill parameter when the monitored drill parameter is outside the predetermined specification, and controls the drill rig to implement the chosen hole defect mitigation routine.

Abstract: A drilling system and method are provided. The drilling system comprising a tool body, a drill bit, a mechanism for applying weight to the drill bit (“WOB”), and a control system for controlling the rate of rotation of the drill bit (“RPM”) and the weight applied to the bit during drilling. The control system is configurable to a first mode in which RPM and WOB are controlled to maintain power on the drill bit at a predetermined maximum, and a second mode in which RPM and WOB are controlled to maintain a predetermined depth of cut (“DOC”). In use, the control system is adapted to switch between the first and second modes depending on drilling conditions.

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.