Abstract: A method and apparatus for reaming or enlarging a borehole with the ability to drill cement, cement float equipment, and debris out of a casing without substantial damage to the casing interior or the reaming apparatus.

Abstract: The present invention is a bi-center drill bit designed to drill out the cement and other material in the casing and then proceed to drill out the full gauge drilling diameter borehole with a diameter greater than the inside of the casing. The bi-center drill bit is configured with non-drilling bearing elements that contact with the casing when the bit is drilling the cement without allowing the gauge cutting elements of the bi-center drill bit to contact the casing. The bi-center drill bit also has a cutting element configuration which prevents reverse scraping of the cutting elements when drilling both the cement and the formation.

Abstract: A reamer for drilling a hole having a diameter larger than a pass through diameter in one aspect includes a body having reaming blades affixed at azimuthally spaced apart locations. These blades have cutters attached at selected positions. An outermost surface of each blade conforms to a radially least extensive one, from a longitudinal axis of the reamer, of a pass through and a drill circle, The drill circle is substantially coaxial with the axis. The pass-through circle is axially offset from the drill circle and defines a section wherein the pass-through circle extends from the axis past the drill circle, so that cutters disposed on the reaming blades in the section drill at full drill diameter, while avoiding wall contact at the pass-through diameter. In another aspect, the reamer includes a pilot hole conditioning section including azimuthally spaced apart blades affixed to the body longitudinally ahead of the reaming blades.

Abstract: A bi-center bit adapted to be consecutively used in casing and in formation without the need of removing the bit from the borehole, the bit comprising a bit body defining a proximal end adapted for connection to a drill string, a distal end and a pass-through gauge, where the distal end defines a pilot bit and an intermediate reamer section, where each the pilot and reamer section define a cutting face. A plurality of cutting or wear elements are situated on cutting blades disposed about the cutting face of the pilot and reamer sections. Cutting or wear elements are disposed on one or more of the blades which extend to or are proximate to the pass-through gauge define an angle between the line of contact on the cutting or wear element and the material to be drilled of between 5-45 degrees.

Abstract: A bi-center downhole drilling bit is disclosed, which bit includes a body defining proximal and distal ends, where said distal end defines a pilot and a reamer where the reamer defines a first cutting face having a selected diameter “d” and the pilot defines a second cutting face having a selected diameter less than “d”, where each the first and second cutting faces includes upsets defining proximal and distal surfaces where the distal surfaces are provided with cutting elements and the proximal surfaces are provided with one or more gauge pads.

Abstract: An improved bi-center drill bit and drill bit assembly includes a cylindrical body having a first diameter section and a smaller second diameter section, each section provided with a threaded end. The cylindrical body includes a longitudinal internal channel with a side channel terminating in a sidewall nozzle. Attached to the external surface of the first diameter section is a rotary cone drill bit with the rotary cone positioned in a trailing position from a stream of drilling fluid from the sidewall nozzle. Two stabilizers are mounted to the cylindrical body substantially opposite from the drill bit to stabilize operation of the bit assembly.

Abstract: A bi-center drill bit includes pilot and reaming blades affixed to a body at azimuthally spaced locations. The blades have PDC cutters attached at selected positions. In one aspect, the pilot blades form a section having length along the bit axis less than about 80 percent of a diameter of the section. In another aspect, selected pilot blades and corresponding reaming blades are formed into single spiral structures. In another aspect, shapes and positions of the blades and inserts are selected so that lateral forces exerted by the reaming and the pilot sections are balanced as a single structure. Lateral forces are preferably balanced to within 10 percent of the total axial force on the bit. In another aspect, the center of mass of the bit is located less than about 2.5 percent of the diameter of the bit from the axis of rotation. In another aspect, jets are disposed in the reaming section oriented so that their axes are within about 30 degrees of normal to the axis of the bit.

Abstract: Soil-displacing screw auger which contains an auger tube (1); a double displacement body (2) equipped with a hollow shaft (8) fixed to the auger tube (1) and containing an upper part (6) which constitutes a closed screw the radius of which increases towards its lower extremity and a lower part (7) which constitutes a closed screw the radius of which decreases towards its lower extremity, preferably with the same pitch as the upper part (6); a lower tube the diameter of which is smaller than twice the largest radius (R2) of the displacement body and which is situated between the lower part (7) of the displacement body (2) and the lower extremity of the auger; a screw blade (4) welded onto the outer casing of the lower tube, which rotates in the same sense as the lower part (7) of the displacement body (2) and an auger tip (5) connected to the lower extremity of the lower tube, with the special characteristic that the lower tube of the auger is an intermediate tube (3) with an outer diameter (D3) which is small

Abstract: A bi-center drill bit includes pilot and reaming blades affixed to a body at azimuthally spaced locations. The blades have PDC cutters attached at selected positions. In one aspect, the pilot blades form a section having length along the bit axis less than about 80 percent of a diameter of the section. In another aspect, selected pilot blades and corresponding reaming blades are formed into single spiral structures. In another aspect, shapes and positions of the blades and inserts are selected so that lateral forces exerted by the reaming and the pilot sections are balanced as a single structure. Lateral forces are preferably balanced to within 10 percent of the total axial force on the bit. In another aspect, the center of mass of the bit is located less than about 2.5 percent of the diameter of the bit from the axis of rotation. In another aspect, jets are disposed in the reaming section oriented so that their axes are within about 30 degrees of normal to the axis of the bit.

Abstract: A rock drilling tool includes a drill body on which a radially extendible reamer is mounted. The reamer, when extended, enlarges the hole diameter to enable a hole casing to be pulled down by the tool. The body includes a front pilot bit, a rear shank adapted to be connected to a drill string, and a guiding member disposed between the pilot bit and the rear shank for pulling the hole casing along with the tool. The pilot bit, the rear shank and the guiding member are non-removable from one another. The reamer, which is mounted between the guiding member and the pilot bit, is formed of two U-shaped pieces that are hinged together to enable the reamer to be installed and removed.

Abstract: A rotary drill bit for use in drilling holes in subsurface formations comprises a bit body having a leading face and a gauge region, a number of blades formed on the leading face of the bit and extending outwardly away from the axis of the bit so as to define between the blades a number of fluid channels leading towards the gauge region, a number of cutting elements mounted side-by-side along each blade, and a number of nozzles in the bit body for supplying drilling fluid to the fluid channels for cleaning and cooling the cutting elements. In each of the fluid channels, adjacent the gauge region, is an opening into an enclosed passage which passes internally through the bit body to an outlet which, in use, communicates with the annulus between the drill string and the wall of the borehole being drilled. The gauge region of the drill bit comprises a substantially continuous bearing surface which extends around the whole of the gauge region.

Abstract: An improved bi-center bit with improved directional stability and wear resistance is disclosed, which bit optimally utilizing a plurality of shaped PDC cutting elements selectively situated about the cutting surfaces of the pilot and the reamer to produce a minimal force imbalance, where further the pilot bit and the reamer are force balanced to further reduce imbalance in the operation of the tool.

Abstract: A cutter head for retrieving earth samples, in particular for taking underwater samples, has, because of frustum-shaped cutting wheels, an approximately round bore cross section. In an associated boring jig, a tube with a cross section corresponding approximately to the bore cross section is placed above the cutter head. With a regrasping system, the tube can be moved vertically relative to a work table lying on the bore surface. The boring jig may be lowered from a ship to the sea bottom to conduct the boring process.

Abstract: Drill for making a pole in the ground, whereby this drill (9) is provided with a passage (15) and whereby this drill has at the bottom a screw-shaped displacement part (11) of which the outside increases in radius upwardly, up to a diameter larger than that of the drill tube (8), characterized in that the displacement part (11) passes with its upper extremity into a cylindrical part (12) which is provided on its mantle with at least a screw blade (13) which runs in the shape of a screw in the same direction as the displacement part (11), but of which the pitch (S2) is larger than the pitch (S1) of the displacement part (11).

Abstract: In a method for use in dry, rotary, crushing full-area drilling, use is made of suction air alone for removing cuttings produced during drillings. To carry out the method, two suction nozzles (13) are arranged on the underside of a cutterhead (1). These nozzles together have a substantially diametrical extent and the length of a radius on the cutterhead and are provided with suction intakes (14A) in the vicinity of the periphery of the cutterhead. The suction intakes (14A) are connectible a common suction channel (11) in the drill string (6) of the cutterhead. The suction channel (11) has substantially constant diameter.

Abstract: A rotary mining bit is particularly suitable for use in the drilling of blasting holes in the mining industry, but may also be used for drilling wells and the like in both soft materials and hard, rocky materials. The bit comprises a central hollow body with a plurality of wings extending outwardly therefrom, with each wing having a leading edge with a plurality of cutting tooth sockets disposed therealong and each of the sockets having a cutting tooth affixed therein. The outermost cutting teeth on each wing describe a gauge row diameter, which defines the diameter of a hole formed using the present bit. The outermost cutting teeth are each angled outwardly, away from the axis of the bit and lateral edge of the wing. An inner or apex row of teeth describes a smaller cutting circle diameter, with intermediate teeth on each row preferably being irregularly spaced between the outermost and innermost teeth on each respective wing, so each intermediate tooth describes a different diameter circle from the others.

Abstract: An improved bi-center with improved directional stability and wear resistance is disclosed, said bit optimally utilizing a plurality of shaped PDC cutting elements selectively situated about the cutting surfaces of the pilot and the reamer to produce a minimal force imbalance, where further said pilot bit and the reamer are force balanced to further reduce imbalance in the operation of the tool.

Abstract: A reaming apparatus for enlarging a borehole, including a tubular body having one or more longitudinally and generally radially extending blades circumferentially spaced thereabout. Each of the blades carries highly exposed cutting elements, on the order of fifty percent exposure, on its profile substantially all the way to the gage. At least one of the blades is a primary blade for cutting the full or drill diameter of the borehole, while one or more others of the blades may be secondary blades which extend a lesser radial distance from the body than the primary blade. A secondary blade initially shares a large portion of the cutting load with the primary blade while the borehole size is in transition between a smaller, pass through diameter and drill diameter. It functions to enhance the rapidity of the transition while balancing side reaction forces, and reduces vibration and borehole eccentricity.

Abstract: A pilot bit is provided with an elongated body member and three blades that extend radially from and spirally along the body member. As compared to conventional two bladed pilot bits, the outer edge and leading tip of the third blade removes additional spoil which increases penetration rates. The pilot bit also includes an adapter which is inserted in an auger shaft and releasably secured thereto with a fastener, such as a bolt. The adapter includes a surface that cooperates with a key that is secured to the auger shaft to take the torque load off the bolt. In this manner, deformation of the auger shaft bolt holes and bolt fatigue is minimized.

Abstract: Apparatus is provided for installing a pipeline in borehole comprising a pulling pipe drawn by a drill string and an articulating joint coupling the pulling pipe to the pipeline. The articulating joint allows an angle to be formed between the pulling pipe and the pipeline. A reamer is used to clear the borehole as the pipeline is installed. The reamer includes a plurality of radially-oriented nozzles for directing fluid away from the stem of the reamer in order to clean the teeth of the reamer without directing the cuttings and other debris toward areas in which accumulation is likely to occur. Deflecting nozzles prevent the outermost radially-oriented nozzles from overcutting the borehole.

Abstract: A sidetrack mill is provided for drilling through a cased borehole to provide a sidetracked wellbore having a final diameter, the mill comprising: a pilot mill having a tapered cutting surface being, at its largest diameter, between about 50% and about 75% of the final diameter; a second stage cutting surface being, at its smallest diameter about the diameter of the maximum diameter of the pilot mill, and being at its largest diameter, at least five percent greater in diameter than the largest diameter of the pilot mill; and a final stage cutting surface being, at its largest diameter, about the final diameter, and at the smallest cutting surface diameter, being a diameter of at least about 5% smaller than the final diameter. This mill is can rapidly penetrated casings without requiring excessive torque. The milling can be accomplished with a single trip.

Abstract: An excavating tooth includes an aperture for bolting the tooth to a shank plate and a lug configured to provide a friction fit in a recess formed in the shank plate. The bolt and lug combination prevent relative movement between the tooth and shank plate. In addition, tooth load is absorbed in the shank plate through the connection between the lug and shank plate, thereby reducing the stress transferred through the bolt.

Abstract: An auger is provided with a boring head having an arrangement for cutting relatively hard earth formations such as rock. First and second groups of drill bits are mounted to the boring head such that when the head is rotated, each bit in those groups cuts a different path at a different height to provide more than 100% coverage of the work surface being cut, while stabilizing the auger by distributing the down force of the auger over the entire work surface. The drill bits also are orientated to ensure bit rotation at relatively large attack angles (the angle the bit forms with the work surface therebeneath) of about 50.degree.-60.degree. to enhance auger penetration rates without detracting from the bit sharpening effect that results from proper bit rotation.

Abstract: A large diameter rock drill includes a tubular body and a central shaft longitudinally axially disposed with respect to the body. The shaft extends longitudinally axially above the top edge of the body and is attached to a drive means. A plurality of angularly spaced apart vertical plates are attached to the inside wall of the body and the shaft. Each of the plates has a lower edge which tapers downwardly and inwardly from the inside wall of the body toward the longitudinal axis of the drill near its lower end. The plates' lower edges taper downwardly and inwardly and have an array of closely packed pockets mounted thereon, each pocket receiving a drill tooth. The radially outermost pockets are affixed to vertically extending, outwardly projecting ribs on the body. The teeth face downwardly and outwardly, and are angled in a clockwise or counterclockwise direction.

Abstract: An auger is provided with a boring head having an arrangement for cutting relatively hard earth formations such as rock. First and second groups of drill bits are mounted to the boring head such that when the head is rotated, each bit in those groups cuts a different path at a different height to provide more than 100% coverage of the work surface being cut, while stabilizing the auger by distributing the down force of the auger over the entire work surface. The drill bits also are orientated to ensure bit rotation at relatively large attack angles (the angle the bit forms with the work surface therebeneath) of about 50.degree.-60.degree. to enhance auger penetration rates without detracting from the bit sharpening effect that results from proper bit rotation.

Abstract: The present invention pertains to a device and method for drilling a secondary or deflection hole from a cased drill hole in underground rock or geologic formations. The device disclosed herein includes a deflection wedge unit mountable via a packer in the drill hole and a pilot cutting tool, all mountable to a drill string. A deflection guide actuated by deflection ramp on the deflection wedge unit initiates the deflection drilling process.

Abstract: A post hole digger and a method of implanting a post in the ground. A boring implement having a piercing free end and also having an attachment flange is secured to an end portion of a post to be implanted in the ground. The implement has a tapered body section with a projecting serrated edge on opposed sides thereof. The serrated edges extend angularly from a common longitudinal plane and in opposed angular directions. A pipe section is secured to the implement and a garden hose is connected thereto whereby to direct a stream of water in the direction of said piercing free end whereby axial rotation and counter-rotation of said post causes the implement to bore into the ground to cause said post to descend in a bore hole. After the post is implanted the garden hose is disconnected from the pipe section by applying a pulling force on the hose.

Abstract: A bucket auger for excavating holes for planting trees is disclosed which includes a trapezoidal cutting frame having teeth secured to the side and bottom. A central vertical shaft adapted to connect to a rotational drive mechanism is secured through upper and lower members of the frame. Two half frusto conical bucket members are pivotally suspended from the upper cross member of the cutting frame by arms such that the weight of the bucket members plus the weight of earth contained within force the bucket to remain closed during lifting of the bucket auger out of the excavation. Lifting flanges are provided for attaching lifting/opening cables to force the two bucket members open to release the earth contained therein.

Abstract: A nozzle assembly for enlarging an inground passageway produced by, for example, a boring device is disclosed herein. The nozzle assembly is comprised of a longitudinally extending nozzle body defining an interior cavity adapted to receive fluid under pressure from an external source and at least one arrangement of outwardly facing adjacent stepped surfaces which provide longitudinally spaced cutting jets directed normal to the movement of the boring device and nozzle assembly as the latter moves through a previously provided passageway in order to progressively enlarge the passageway.

Abstract: A drill bit assembly comprised of a pilot bit and a plurality of add-on reamer sections which are sized to progressively increase the diameter of the hole in measured increments. Both the pilot bit and the reamer sections have two cutter elements which take advantage of the bi-center concept and both use knife edged cutters instead of teeth to drill the hole.

Abstract: The invention relates to a device for the production of circular boreholes in soil, of the type incorporating a pair of bits driven in rotation in opposite directions, the said bits being equipped with teeth or similar members for breaking up the soil.It comprises a first pair of bits (6) which are equipped with teeth, rotating in opposite directions around two parallel axes, each of these bits having the external shape of a volume of revolution the generatrix of which consists of a circular arc corresponding to the circular cross-section of the borehole which it is intended to dig, and a second pair of bits (7) situated above the first, and the bits (14a,14b) of which have the same structural characteristics as the bits of the first pair but whose axes of rotation are offset relative to the latter.

Abstract: A hole opener for placement in a drill string having a body generally comprising a collar, a triangular mid-section, a triangular shaped pilot and a bull nose. The collar provides means for attaching the tool body to the drill string. The triangular mid-section has three longitudinal, radially spaced apart blade members that are parallel to the central axis of the tool body so that the blades can cut into the walls of the bore hole to enlarge the size of the bore hole. Three annular flow zones span the distance between the blade members so that fluids and cuttings can circulate through the bore hole. The pilot section also has three longitudinal, radially spaced apart blade members that are parallel to the central axis of the tool body bore and three annular flow zones which span the distance between the blade members of the pilot. The pilot section is downhole from the mid-section.

Abstract: Harmonic resonation of cutting elements against the earth formation is impeded in a rotary drag-type drill bit by providing connection means which yieldably and resiliently support the cutting elements from the drill bit but which deflects or vibrates with different natural resonant harmonic frequencies. The different natural harmonic frequencies tend to cancel or nullify resonance of any one of the connection means. The connection means can also be externally damped against vibrational movement.

Abstract: A rotatable cutter head for a pit boring machine used in reverse circulation drilling. The cutter head has cutter arrays including rotary cutters and drag cutters and disposed radially and circumferentially spaced positions on the cutter head, the drag cutters having the cutting ends lying generally in a conical plane having the axis coaxial with the axis of rotation of the cutter head. The rotary cutters each have cutting teeth around the circumference thereof and each tooth has an inclined side face lying in a further conical plane the central axis of which is coaxial with the axis of rotation of the rotary cutter, the inclined side face of each tooth facing generally along the inclination of the conical plane in which the cutting ends of the drag cutters lie, and the tip of each cutting tooth of each rotary cutter projecting beyond the plane in which the cutting ends of the drag cutters lie.

Abstract: A method and a cutter for producing a large cavity filled with a uniform bed of rubblized oil shale or other material, for in situ processing. A raise drill head (72) has a hollow body (76) with a generally circular base and sloping upper surface. A hollow shaft (74) extends from the hollow body (76). Cutter teeth (78) are mounted on the upper surface of the body (76) and relatively small holes (77) are formed in the body (76) between the cutter teeth (78). Relatively large peripheral flutes (80) around the body (76) allow material to drop below the drill head (72). A pilot hole is drilled into the oil shale deposit. The pilot hole is reamed into a large diameter hole by means of a large diameter raise drill head or cutter to produce a cavity filled with rubble.

Abstract: An auger system is described having an upstanding axial stem with a pilot bit attached to the bottom of the stem. A downwardly spiraling flight structure affixed to the axial stem has a leading edge terminating in the vicinity of the pilot bit. Enhanced cutting operations are provided by way of a cutting tooth holder structure removably secured to the leading edge of the flight structure and extending from a position adjacent the stem above the pilot bit to a position proximate to the perimeter of the flight structure. The holder structure is provided with a plurality of spaced apart pockets for receiving shank portions of cutting teeth. Stresses applied to the cutting teeth during operations are distributed through the holder structure back to the flight structure by way of reinforcing webs which extend from a position proximate to each of the cutting tooth receiving pockets to a position for contact with the leading edge of the flight structure.

Abstract: Described is a rotary drill bit comprising a hollow body having a closed lower end and means on the upper end for securing the body to the lower end of a drill string. The body is provided with a plurality of flow passages and a deflecting means is provided to deflect upwardly and away from the flow passages cuttings and the like to avoid plugging the passages during drilling while permitting unimpeded flow from the passages of all the fluid passing through the hollow body.

Abstract: A drill bit including a support member and a plurality of concentrically positioned, hollow, cylindrical cutting members connected to the support member is disclosed. Each of the cutting members includes a beveled edge obliquely extending between the inner and outer surfaces thereof. The beveled edges are aligned so that a tapered cutting surface is defined.

Abstract: A directional drill attached to a drill string having periodic concentric collars is advanced in an inverted arcuate path to form a pilot hole underneath an obstacle followed by a larger concentric washover pipe. When the washover pipe reaches the surface on the other side of the obstacle a first reamer is attached to the end of the washover pipe exiting the drilling path, a second reamer of smaller diameter than the first reamer is attached to the other end of the first reamer by means providing for some separation between the two reamers, and a production casing of smaller diameter than the second reamer is attached to the other end of the second reamer with a swivel. The remaining length of the first portion of casing is supported some distance above the ground on rollers located above and beyond the exit point of the pilot hole. The reamers are operated by rotating the washover pipe and simultaneously drawing the washover pipe through the pilot hole.

Abstract: A drilling tool comprising a body having a leading face with a central recess providing the body with an annular leading cutting edge such that during drilling a central core is formed, and a central cone positioned axially in the recess for breaking up the core.

Abstract: To allow the bit to drill in formations that behave plastically, while also protecting the bit against overloading when entering a relatively soft formation, ridge-shaped elements are provided having the ridges within the rotation alloy symmetric surface defined by the scraping edges of the scraping means (natural or artificial diamonds). The flanks of the elements are positioned at an acute angle to the said surface.

Abstract: The invention relates to bore hole drills employing spaced shaped cutters in arrays separated by fluid channels in which there are positioned arrays of nozzles suitable for bit cleaning and detritus removal action.

Abstract: The invention relates to the design of earth boring bits employing shaped preform cutters containing hard abrasive materials such as diamonds.

Abstract: The apparatus comprises means for coupling to a standard raise boring head for extending the radius of the head. The apparatus comprises a support which is bolted or welded to a terminal end of the raise boring stem and to the underlying surface of the principal cutter bracket mounting platform of the head, and the support has means for selectively coupling thereto cutter mounting extension elements each of which comprise ancillary cutter bracket mounting platforms.

Abstract: An auger for boring holes through the surface of the earth. The auger is provided with a double flight which concurrently spirals about the hub of the auger, with the leading edges of the flights being arranged in opposition to one another.Digging teeth are mounted in spaced relationship within the leading edge of each flight, with the innermost tooth of each opposed flight being located 180.degree. apart, at different radii, and at different elevations respective to one another.Other teeth are spaced 180.degree. apart and located in each leading edge. The teeth are angularly displaced from the innermost teeth and arranged at different vertical elevations and different radii respective to one another.Additional teeth may be positioned on the leading edge of either flight. Adjacent teeth located in the leading edge of either flight are progressively spaced radially and vertically respective to one another.

Abstract: A rock boring assembly for producing a straight hole for use in a drill string above a pilot boring bit of predetermined diameter smaller than the desired final hole size. The boring assembly comprises a small conical boring bit and a larger conical boring bit, the conical boring bits mounted on lower and upper ends of an elongated spacer, respectively, and the major effective cutting diameters of each of the conical boring bits being at least 10% greater than the minor effective cutting diameter of the respective bit. The spacer has a cross-section resistant to bending and spaces the conical boring bits apart a distance at least 5 times the major cutting diameter of the small conical boring bit, thereby spacing the pivot points provided by the two conical boring bits to limit bodily angular deflection of the assembly and providing a substantial moment arm to resist lateral forces applied to the assembly by the pilot bit and drill string.

Abstract: A bit is provided that includes a bit body defining a bit axis of rotation. Primary cutter means are positioned on the bit body for disintegrating the formations out to a first radial distance from said bit axis of rotation. Secondary cutter means are adapted to be connected to the bit body and selectively located in a first position for cutting between said first radial distance and a larger second radial distance and selectively located in a subsequent position between said first radial distance and an even larger subsequent radial distance. Expansion means are provided to be located between said secondary cutter means and said bit body for locating said secondary cutter means in said subsequent position.

Abstract: A frusto-conical multi-stage reamer constructed from a sequence of reamer stages is disclosed. Each reamer stage includes a central stem having a coupling at the leading end and a coupling at the trailing end. A plurality of circumferential arms extend from the central stem of each reamer stage and are inclined in a common direction with respect to the axis of the stems. The free ends of the arms are directed outwardly and forwardly with respect to the stem, and individual reamer teeth are attached to the free end of each arm. The radial extent of the arms of each stage of the sequence is a preselected increment greater than the radial extent of the arms of each preceding stage. In operation, the reamer stages are connected in sequence by the aforesaid couplings and simultaneously rotated and pulled through a pilot hole to produce an enlarged aperture.

Abstract: A directional drill attached to a drill string having periodic concentric collars is advanced in an inverted arcuate path to form a pilot hole underneath an obstacle followed by a larger concentric washover pipe. When the washover pipe reaches the surface on the other side of the obstacle a first reamer is attached to the end of the washover pipe exiting the drilling path, a second reamer of smaller diameter than the first reamer is attached to the other end of the first reamer by means providing for some separation between the two reamers, and a production casing of smaller diameter than the second reamer is attached to the other end of the second reamer with a swivel. The remaining length of the first portion of casing is supported some distance above the ground on rollers located above and beyond the exit point of the pilot hole. The reamers are operated by rotating the washover pipe and simultaneously drawing the washover pipe through the pilot hole.

Abstract: A reaming apparatus for enlarging a borehole, including a tubular body having one or more longitudinally and generally radially extending blades circumferentially spaced thereabout. Each of the blades carries highly exposed cutting elements, on the order of fifty percent exposure, on its profile substantially all the way to the gage. At least one of the blades is a primary blade for cutting the full or drill diameter of the borehole, while one or more others of the blades may be secondary blades which extend a lesser radial distance from the body than the primary blade. A secondary blade initially shares a large portion of the cutting load with the primary blade while the borehole size is in transition between a smaller, pass through diameter and drill diameter. It functions to enhance the rapidity of the transition while balancing side reaction forces, and reduces vibration and borehole eccentricity.