Abstract: A borehole network including first and second end surface locations and at least one intermediate surface location interconnected by a subterranean path, and a method for connecting a subterranean path between a first borehole including a directional section and a second borehole including a directional section. A directional drilling component is drilled in at least one of the directional sections to obtain a required proximity between the first and second boreholes. An intersecting component is drilled, utilizing magnetic ranging techniques, from one directional section to provide a borehole intersection between the first and second boreholes, thereby connecting the subterranean path.

Abstract: In a method for producing a cased horizontal string bore extending from a well shaft, a starter drill pipe is driven into the rock mass surrounding the well shaft. A hydraulically driven drill motor is arranged in the starter drill pipe and rotates a drilling tool protruding from the leading end of the starter drill pipe. The drill motor is fixed against rotation and axial displacement by a clamping device. When the final depth of the string bore is reached, the drilling tool is retracted into the starter drill pipe by axial movement of the clamping device and a free space is formed at the drift face of the string bore. The free space is filled and sealed by injection of a quick-setting, expanding filling compound. Afterwards, the clamping device, the drill motor and the drilling tool are removed from the drill pipes.

Abstract: A microtunnelling apparatus and system that includes an external drive system having rotational and linear thrust drive means, a drill head section having drill rotor and drill rod and connecting to intermediate drill rods allowing extension of the boring hole created by the drill head section driven by the drive system. The drill head includes a modular construction having a plurality of circular disc like elements, a bearing module, a steering module, a spacer module, and a mounting module, for axial alignment and abutment and mounting within a cylindrical steering shell. Directional steering of the drill head includes a plurality of substantially radially extending channels in steering module, each with an hydraulically movable protuberance movable by control means to redirect the outer steering casing and thereby redirect the drill head section mounted on the distal end of the drill rods.

Abstract: A method of determining the arrangement of lateral boreholes to be drilled from a main borehole that traverses an underground reservoir comprising at least two layers of different fluid mobility, the method comprising: determining formation parameters in each layer of interest so as to determine the fluid mobility in each layer; and determining borehole parameters for a series of lateral boreholes in each layer, the number, arrangement and dimensions of the lateral boreholes being selected such that the drainage surface in each layer provides for substantially similar fluid drainage in each layer irrespective of the fluid mobility in that layer.

Abstract: An apparatus and method for penetrating earth strata surrounding a wellbore including a nozzle assembly, a flexible tubing connected to the nozzle assembly, and a means to position the nozzle assembly downhole in a substantially horizontal direction into earthen strata, such that the nozzle assembly is connected to one end of the flexible tubing. Embodiments can provide horizontal jetting into the earth's strata from both cased and uncased wells utilizing a rotating, swirling, pulsing or cavitating nozzles which can keep a relatively cuttings free downhole environment.

Abstract: An apparatus and method for cutting horizontally into an earthen formation including a nozzle assembly having a gauge ring mechanism and/or a centralizer mechanism that allows the nozzle assembly to remain along a consistent axis of travel during cutting. Embodiments can provide horizontal jetting into the earth's strata from both cased and uncased wells utilizing a rotating, swirling, pulsing or cavitating nozzles which can keep a relatively cuttings free downhole environment.

Abstract: A system for production of petroleum from an earth formation is provided. The system includes: at least one injection borehole for injecting a thermal source into the formation; at least one production borehole for recovering material including the petroleum from the formation; and at least one drainage borehole intersecting a portion of the at least one production borehole. Methods of recovering petroleum from an earth formation and creating a petroleum production system are also provided.

Abstract: An auger boring machine provides a continuous stroke drive assembly for driving a pilot tube to form an underground pilot hole used for guiding an auger in boring an underground pipe installation hole. The drive assembly preferably drives the pilot tube a distance at least the length of one of the pilot tube segments making up the pilot tube to substantially expedite the process. One embodiment includes a hydraulic piston-cylinder combination with a cylinder at least the length of the pilot tube segment. Alternately, a rack and a pinion drive mechanism may be used with a rack at least the length of the pilot tube segment or even more than twice that length to allow for a pair of pilot tube segments to be added simultaneously to the pilot tube. A lubricant feed system allows water to be pumped through passages formed in the pilot tube and steering head.

Abstract: The present disclosure relates to a tunneling apparatus including a pipe string having a distal end and a proximal end. The pipe string includes a plurality of pipe-sections connected end-to end. The pipe string also includes a cutting head coupled to a distal-most one of the pipe-sections. The pipe string defines a vacuum passage that extends through the pipe string from the proximal end to the distal end of the pipe string. A source of vacuum is in fluid communication with the vacuum passage for drawing cuttings through the vacuum passage. A blockage sensor can be used for sensing whether a precursor blockage condition exists within the vacuum passage. A source of air pressure can be used to force air distally through the pipe string to assist in moving cuttings proximally through the vacuum passage.

Abstract: The present disclosure relates to a backreamer including a distal end configured for connection to product and a proximal end configured for attachment to a distal end of a drill string. The backreamer includes a backreaming cutter having a cutting side that faces toward the proximal end of the backreamer. The backreamer also includes a proximal assembly that extends between the proximal end of the backreamer and the backreaming cutter. The proximal assembly defines a vacuum passage for removing material cut by the backreaming cutter. The backreamer further includes a drive stem for transferring torque to the backreaming cutter for rotating the backreaming cutter. The drive stem is rotatably supported within the proximal assembly such that the drive stem and the backreaming cutter are rotatable relative to the proximal assembly. The backreamer additionally includes a distal assembly that extends between the backreaming cutter and the distal end of the backreamer.

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 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: An internally rotating nozzle for facilitating drilling through a subterranean formation is rotatably mounted internally within a housing connected to a hose for receiving high pressure fluid. The rotor includes at least two tangential jets oriented off of center for ejecting fluid to generate torque and rotate the rotor and cut a substantially cylindrical tunnel in the subterranean formation.

Abstract: A method and apparatus for completing a lateral channel in a subterranean formation using a flexible hose with a waterjet that may be directed down a well casing and into a waterjet guide. The waterjet guide has a diverter assembly configured to receive and divert the flexible hose in a shortened radius. The diverter assembly includes an inlet curvature and a pivot curvature, where the pivot curvature pivots between stowed and deployed configurations in response to forces provided through a mandrel assembly communicably coupled thereto.

Abstract: An auger boring machine includes a common power source for powering a drive motor which rotates an auger and a drive assembly which drives a pilot tube to form a pilot hole in the earth which is followed by the auger. The drive assembly is movable into and out of the operational position of the auger to allow the auger to be mounted on the drive motor. Preferably the drive assembly is removably mounted on the frame of the auger boring machine. An electric generator and hydraulic pump are powered by the common power source for operating various components of the drive assembly.

Abstract: A cutting device for downhole operations comprises a first cutting structure, and a second cutting structure, wherein at least the second cutting structure is selectively presentable for operation. A method of performing a downhole cutting operation comprises running into a well bore a cutting device comprising a plurality of cutting structures, performing a first cutting operation with a first cutting structure of the cutting device, selectively presenting a second cutting structure of the cutting device, and performing a second cutting operation with at least the second cutting structure. The method may further comprise aligning the cutting device to allow the second cutting structure to be selectively presented.

Abstract: An horizontal directional drilling (HDD) system having dynamically scalable control settings is disclosed.

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 and system for controlling a horizontal directional drilling machine having a boring tool. A rate of rotation and a rate of thrust are selected by an operator. Controls allow an automatic boring operation mode to be initiated to maintain the selected rate of rotation and thrust without further input from the operator. Periodically, when the rotation and thrust are interrupted, such as to modify the drill string, the automatic boring operation mode is interrupted. The automatic boring operation mode may be resumed without requiring the operator to select the rate of rotation and rate of thrust. The rate of rotation is resumed before the rate of thrust to reduce drill string shock loads and increase drilling performance.

Abstract: A drill bit having fixed Polycrystalline Diamond Compact cutters is used to drill a borehole having a core stump therein. A plurality of additional fixed Polycrystalline Diamond Compact cutters are disposed in the dome of the bit and are usable to concentrate stresses in the top end of the core stump to facilitate the cutting down of the core stump.

Abstract: A method of removing cuttings includes the steps of disposing a pipe string in a high-angle wellbore, circulating mud through the wellbore and creating a viscous coupling layer of mud spiraling about a section of the pipe string. Wherein the wellbore may be deviated from vertical thirty degrees or greater. The viscous coupling layer desirably extends outwardly beyond the outside diameter of the tooljoint upsets in the section of the pipe string. A pipe joint for creating a viscous coupling layer of drilling fluid spiraling about the pipe to remove cuttings from high angle wells includes an elongated tubular having an outer surface extending between opposing tooljoints, tooljoint upsets and projections provided on substantially the entire outer surface.

Abstract: A system and method for cutting windows for lateral wellbore drilling. A method of cutting a window through a sidewall structure for drilling a lateral wellbore through the window includes the steps of: providing an internal profile in the sidewall structure; then installing the sidewall structure in a parent wellbore; and then cutting the window through the sidewall structure, the cutting step including engaging a cutting tool with the internal profile. The cutting step may include resisting lateral displacement of the cutting tool due to engagement between the cutting tool and the internal profile.

Abstract: A biased door member is provided in an external wall of a drill rod supply magazine mounted on a horizontal directional drilling (HDD) machine. The door member swings inwardly from a first position parallel to the external wall to a second position within the distal column. At least one cut-out is formed in the external wall at the bottom of the retaining guides located at the longitudinal ends of the magazine. The cut-out creates a window through which the added drill rod is inserted. In operation, a drill rod is moved through the biased door member and window cut-outs into the distal column. The pocket of a rod transfer mechanism is positioned below the last column, and a rod lifter lowers the added drill rod into the pocket. The rod transfer mechanism then moves the added drill rod into alignment with the drill string.

Abstract: A method of completing a lateral channel in a coal seam using a flexible hose with a waterjet that may be directed down a well casing and into a guide shoe. The guide shoe defines a window configured to open into the coal seam and allow the waterjet to engage the coal seam in a substantially horizontal direction. High pressure fluid is then pumped into the waterjet to make a lateral channel therein, and the flexible hose is rigid enough to allow an operator to manually-move the flexible hose.

Abstract: The present application is directed to an apparatus for forming one or more holes in a wellbore casing, the apparatus comprising a deflector assembly and a drive assembly to drive said deflector assembly, wherein the deflector assembly may be optionally assembled at a surface of the wellbore prior to casing hole formation, and to methods employing the apparatus.

Abstract: An internally rotating nozzle for facilitating drilling through a subterranean formation is rotatably mounted internally within a housing connected to a hose for receiving high pressure fluid. The rotor includes at least two tangential jets oriented off of center for ejecting fluid to generate torque and rotate the rotor and cut a substantially cylindrical tunnel in the subterranean formation.

Abstract: A process to increase the area of microbial stimulation in a process of methane gas recovery in a multi seamed coal bed/methane dewatering and depressurizing production system by first utilizing an underbalanced multilateral drilling technique. At this point in the process one could introduce the microorganisms into the horizontal well bore to achieve a greater area of stimulation of the coal bed than would a vertical well. An even more preferred method would to first drill a series of lateral wells off of the horizontally drilled well bore, so as to increase or maximize the area of coal bed which is being covered. At that point, one would take the steps of what is known in the art of introducing a particular type of microorganism, which would then be injected via the plurality of lateral bores into the coal bed formation, to maximize the area of penetration, which would include, most, if not all, of the area of the coal bed through the series of lateral wells.

Abstract: A portable drilling device for use in horizontal boring through a substrate beneath an impediment includes a motor mounted on an inclined stabilizer bar. The inclined stabilizer bar includes a handle for use by the operator of the drilling unit which allows the operator to guide the unit during operation. A shaft is operatively mounted on the motor and is rotatably carried by the stabilizer bar. The shaft is in turn attached to an auger which is rotatably carried within a bearing housing assembly that is attached to the inclined stabilizer bar at a predetermined angle. A skid shoe is mounted underneath the shaft-auger attachment point and is attached to both the housing and the inclined stabilizer bar, whereby, when the motor is engaged the shaft and the auger are rotated in order to bore a horizontal opening through the substrate beneath an impediment such as a sidewalk or driveway.

Abstract: The drilling of a casing bit and any other equipment in the casing with another casing bit where at least two casing bits of different diameter and having associated casing sections may be assembled to form a drilling assembly for drilling subterranean formations, the at least two casing bits and casing sections are arranged in a telescoping relationship.

Abstract: The present application is directed an apparatus for installing boreholes in the formation surrounding a main wellbore, the apparatus comprising an indexing tool comprising an indexing deflector and a deflector shoe; the deflector shoe comprising an opening therethrough configured to receive a borehole forming member; wherein the indexing deflector is configured to direct the deflector shoe from a first setting to at least a second setting for the installation of boreholes at each setting through said opening; to methods employing the apparatus, and methods for using the indexing tool to locate and access boreholes.

Abstract: Provided are drill stem assemblies with ultra-low friction coatings for subterraneous drilling operations. In one form, the coated drill stem assemblies for subterraneous rotary drilling operations include a body assembly with an exposed outer surface including a drill string coupled to a bottom hole assembly or a coiled tubing coupled to a bottom hole assembly and an ultra-low friction coating on at least a portion of the exposed outer surface of the body assembly, wherein the coefficient of friction of the ultra-low friction coating is less than or equal to 0.15. The coated drill stem assemblies disclosed herein provide for reduced friction, vibration (stick-slip and torsional), abrasion and wear during straight hole or directional drilling to allow for improved rates of penetration and enable ultra-extended reach drilling with existing top drives.

Abstract: System and methods for creating shaped, non-circular boreholes in rocks especially for use with geothermal heat pump applications and for increasing wellbore support in applications such as horizontal oil and gas drilling are described. The systems and methods when applied to geothermal heat pumps create an elliptical shaped hole that is optimized for placing heat transfer tubes with a minimum of grout used. The significantly reduced cross-sectional area of the elliptical borehole also increases the overall drilling rate in rock and especially in hard rocks. In horizontal hard-rock drilling, creation of a horizontal non-circular borehole or modification of a circular borehole to a non-circular geometry is used to stabilize the borehole prior to casing insertion, and may also allow the use of lower mud pressures improving drilling rates. The system uses a non-contacting drilling system which in one embodiment uses a supersonic flame jet drilling system with a movable nozzle that swings between pivot points.

Abstract: A horizontal directional drilling system is used to drive operation of a guidable reamer assembly connected to a drill string. The guidable reamer assembly preferably has a cutting member with a central longitudinal axis and a support member also having a central longitudinal axis. The longitudinal axes of the cutting member and the support member are collinear when the reamer assembly is in the non-steering position and laterally displaced when in the steering position. The assembly and method of this invention provide for increased control of reaming operations and product pipe placement.

Abstract: Method for drilling horizontal or deviated fresh water wells through such volcanics as occur in Hawaii, including hard lavas and fragmented interbeds that are prone to caving. The method provides effective means to drill into basal aquifers directly underlain by salt water, or into compartmented or confined aquifers or perched aquifers. The method uses deviated drilling and may use formation grouting, casing or drill-stem drilling, percussion or rotary drilling and all combinations thereof.

Abstract: A drilling system including a drill head configured to couple to a drill string. The drill head including an offset adapter, a one-way clutch, and a drill bit. The drill head being configured to provide straight drilling along a first axis, and deviated drilling along a second axis. The drilling system further including a gearbox configured to provide selective rotational operation corresponding to the straight drilling and the deviated drilling. The drilling system also including control systems to control the selected rotational operation of the gearbox.

Abstract: A reamer for underground boring is provided. The reamer includes at least: (a) a center mandrel, wherein the center mandrel defines a mandrel axis; (b) a plurality of radial members extending radially from the center mandrel; (c) a plurality of cutting heads, wherein each of the cutting heads: (i) is supported by at least one of the radial members; (ii) is arcuately spaced-apart around the center mandrel from the other cutting heads; (iii) has a rounded surface; and (d) a plurality of cutting teeth on the rounded surface of each of the cutting heads. A method of horizontal drilling with the reamer is also provided.

Abstract: An oil tool forms holes or perforations which extend horizontally away from the borehole and into the formation for recovering additional oil and gas from the formation. The tool provides a downhole tool capable of drilling horizontally into a formation and further capable of operating in a relatively small well bore, such as those having a diameter of less than six inches. In addition, the tool does not tend to spiral or otherwise deviate from horizontal during drilling operations. The tool of the present invention includes a drill capable of drilling or tunneling through the formation, a magazine or carrier which contains a plurality of hollow joints or segments, a hydraulic pump and a mechanism for assembling and disassembling the segments. Once in place, the assembly mechanism removably attaches a segment from the magazine to the drill.

Abstract: A casing exit joint with an easily milled and low density barrier. A casing exit joint for use in drilling a lateral wellbore outwardly from a parent wellbore includes a generally tubular window structure having a window formed through a sidewall of the structure. An outer sleeve is disposed external to the window structure, so that the sleeve overlies the window. A hardenable substance supports the sleeve against deflection toward the window. A method of drilling a lateral wellbore extending outwardly from a parent wellbore includes the steps of: providing a casing exit joint including a hardenable substance positioned in a sidewall of the casing exit joint; then installing the casing exit joint in the parent wellbore; and then cutting through the hardenable substance in order to provide access for drilling the lateral wellbore.

Abstract: A bottom hole assembly 10 for drilling a deviated borehole includes a positive displacement motor (PDM) 12 or a rotary steerable device (RSD) 110 having a substantially uniform diameter motor housing outer surface without stabilizers extending radially therefrom. In a PDM application, the motor housing 14 may have a fixed bend therein between an upper power section 16 and a lower bearing section 18. The long gauge bit 20 powered by the motor 10 may have a bit face 22 with cutters 28 thereon and a gauge section 24 having a uniform diameter cylindrical surface 26. The gauge section 24 preferably has an axial length at least 75% of the bit diameter. The axial spacing between the bit face and the bend of the motor housing preferably is less than twelve times the bit diameter. According to the method of the present invention, the bit may be rotated at a speed of less than 350 rpm by the PDM and/or rotation of the RSD from the surface.

Abstract: A pilot tube drive assembly used with an auger boring machine includes a height adjustment mechanism for aligning the pilot tube path of travel with an axis about which an auger of the machine rotates during trenchless installation of underground pipe. A drive mechanism mounted on a drive assembly frame drives the pilot tube to form a pilot hole in the ground for guiding the auger. The height adjustment mechanism may include shorter and taller mounting assemblies which are typically removably mounted on the drive assembly frame. The shorter and taller mounting assemblies may be alternately mounted on the frame at the same location. Typically, the mounting assemblies are removably mounted on spaced rails of an auger boring machine frame via mounting legs which are removably inserted into openings in the spaced rails by an actuating mechanism between the rails.

Abstract: A pilot tube for an auger boring machine has a lubrication through passage formed therein through which water or another lubricant may be pumped during the driving of the pilot tube to facilitate formation of a pilot hole in the earth which is subsequently followed by an auger in forming a trenchless hole for laying underground pipe. Preferably, the lubrication passage extends to exit openings adjacent or on a steering head. A lubrication feed swivel is connected the trailing end of the pilot tube for feeding the water into the pilot tube while allowing rotation of the pilot tube for the steering thereof during the process of driving the pilot tube.

Abstract: Apparatus for clearing particles from a lateral drilling operation in strata beside a well. The drilling apparatus is part of a down hole unit and is configured for extending from a lateral opening of the unit into a lateral passage in the adjacent strata, and the operation of the drilling apparatus discharges particles from the lateral passage toward the lateral opening. The invention deflects or redirects the particles discharged from the lateral passage, away from the lateral opening, to prevent clogging or blocking of an internal passage or elbow through the down hole unit, using a pressurized fluid such as a gas or an emulsion. The pressurized fluid can also be configured for carrying the particles upwardly through the well to the surface, and for reducing or removing a hydrostatic head in the well.

Abstract: A method and system for mitigating risk of well collision in a field includes receiving an anti-collision standard exemption request containing a description of risk of collision between a subject well and one or more offset wells, generating an assessment of the anti-collision standard exemption request using a stored multidimensional decision matrix, reviewing the assessment, and selectively updating the decision matrix based on the review.

Abstract: An improved machine and method of horizontal drilling is disclosed wherein the machine includes a device for producing a continuous length of conduit that surrounds the drill string for simultaneous boring and positioning of the conduit.

Abstract: Disclosed is a movable boring assembly and a boring tool positioner for drilling a plurality of holes in a well casing and jetting a well production zone through the plurality of holes. All of the holes can be drilled in the casing at different angular positions, as well as different levels within the casing. The drilling tool can then be removed and a perforation jet can be reliably and accurately reoriented into the drilled holes to perforate a production zone in multiple directions and at multiple levels.

Abstract: An improved method of forming a trenchless flow line is provided. The method includes support of the boring tool at each sight relief hole using a hook extending downwardly into the hole so as to overcome the force of gravity on the tool during the pilot hole drilling step. Then, a back reaming tool is connected to the end of the boring tool, and the pipe is connected to the reaming tool, such that the reaming tool reams the pilot hole to a larger diameter ahead of the pipe, which is pulled through the hole with the reaming tool. Drilling fluid is supplied during the reaming process to form a slurry which is pushed ahead of the pipe and upwardly into the sight relief holes, as the pipe is pulled through the reamed hole.

Abstract: The invention relates to a mixing system for the preparation of a drilling fluid for horizontal drilling methods, having a high-pressure pump and a feed line for the additive medium arranged upstream of the high-pressure pump in the direction of flow.

Abstract: An apparatus and method are described for tracking the position, orientation and/or guiding a sonde as it moves through the ground in a region. The sonde transmits an electromagnetic field received by one detector. The detector includes at least one antenna for measuring at least one component of the intensity of the electromagnetic field and the detector is positioned at a fixed position with the antenna at a particular orientation within the region. Certain initial conditions are determined including the particular orientation and position of the antenna associated with the detector and an initial position and orientation of the sonde. The intensity of the electromagnetic field is obtained at a second position using the detector after the sonde moves a distance to the second position. The coordinate position of the sonde is determined using the initial conditions along with the intensity measured at the second position.

Abstract: A method and apparatus for penetrating a side of a well casing and/or drilling into earth strata surrounding the well casing, utilizing a rotating fluid discharge nozzle, and an abrasive introduced into the fluid downstream of apparatus for rotating the nozzle. Apparatus for rotating the nozzle can include a motor operable by pressurized fluid, or another suitable rotating power source The introduction of the abrasives will not adversely affect or harm the apparatus for rotating the nozzle, yet will provide the enhanced drilling capability. The abrasive stream can be used for drilling or cutting through a metal well casing, as well as cement and the adjacent strata.

Abstract: A system for monitoring deflection of a downhole tool assembly. The system comprises a beam source directing a beam at a receptor positioned proximate the downhole tool assembly. The receptor detects the position of incidence of the beam at the receptor. A processor receives signals from the receptor and determines angular deflection of the downhole tool assembly based on incidence of the beam at the receptor. Information from other orientation sensors is also used to determine magnitude and direction of deflection. Deflection information is used by an operator or a control system to maintain or correct the course of the downhole tool assembly.