Abstract: Systems and methods for generating pulses in a drilling fluid are described. The systems are configured to be positioned along a tubular string through which a drilling fluid flows. The systems include a housing supported along the string. A valve stator is supported by the housing and has at least one flow path that extends from an upstream end to a downstream end of the valve stator. A valve rotor is positioned adjacent the valve stator and configured to selectively obstruct the at least one flow path. An axial gap is present between the valve rotor and the valve stator. A motor is coupled to the valve rotor to rotate the valve rotor relative to the valve stator and an axial release assembly having a rotational element is configured to adjust the axial gap between the valve rotor and the valve stator based on a rotation of the rotational element.

Abstract: The disclosed jarring device generates two jarring impacts at the end points of a reciprocating hammer assembly. Initially, flow of pressurized fluid through the jarring device is obstructed by a deformable member. The resulting increase in fluid pressure upstream of the deformable member causes compression of a spring and downstream movement of the hammer assembly to generate a first jarring impact. A further increase in fluid pressure beyond a threshold, causes a release of the obstruction by either deforming the member or by slicing it by pushing it through a slicer. Releasing of the obstruction causes decompression of the spring, and upstream sliding of the hammer assembly to generate a second jarring impact.

Abstract: A downhole jarring apparatus for use in jarring an object in a bore comprises a first jarring portion including a first impact surface and a second jarring portion including a second impact surface. The apparatus includes a rotatable jarring arrangement operable to translate a rotational drive movement to cause relative axial movement of the first and second impact surfaces to establish axial impact therebetween.

Abstract: The disclosed jarring device generates two jarring impacts at the end points of a reciprocating hammer assembly. Initially, flow of pressurized fluid through the jarring device is obstructed by a deformable member. The resulting increase in fluid pressure upstream of the deformable member causes compression of a spring and downstream movement of the hammer assembly to generate a first jarring impact. A further increase in fluid pressure beyond a threshold, causes a release of the obstruction by either deforming the member or by slicing it by pushing it through a slicer. Releasing of the obstruction causes decompression of the spring, and upstream sliding of the hammer assembly to generate a second jarring impact.

Abstract: Systems, tools, and methods include using a milling assembly with a catch mechanism configured to maintain a connection between the drill string and the mill in the event a primary connection between the mill and catch mechanism fails. A primary connection may support the weight of the mill by using a connection between the drill string and the mill. The catch mechanism may operate as a back-up or redundant connection and may support the weight of the mill by coupling the catch mechanism to both the mill and the drill string.

Abstract: A non-conductive composite insert is provided between conductive portions, useful, for example, in downhole EM telemetry applications as an external “gap sub” in a drill collar, or as a sonde-based internal gap. In a preferred embodiment, the composite is made from a glass-fiber reinforced plastic, and separates non-magnetic conductive portions made from stainless steel. The composite insert provides a slanted or tapered transition into the conductive portions at either or both ends of the insert. The transitions on the composite insert may comprise one or more tapered surfaces, which may be male or female in configuration with respect to matching transitions on the conductive portions. The transitions may be bonded together by adhesive, or alternatively may be threaded.

Abstract: A valve apparatus for in a wellbore. The apparatus may include: a housing fluidly connected to a work string, with the housing having an internal portion having a guide pin; a mandrel concentrically disposed within the internal portion of the housing, the mandrel having a piston attached at a first end of the mandrel and a mandrel cap attached at a second end of the mandrel, and wherein the mandrel contains a circulation port and a jet positioned within the piston, the jet operatively configured to receive the fluid and create a pressure drop during fluid flow through the jet; a guide bushing disposed about the mandrel, the guide bushing having a predetermined guide path contained on the guide bushing and wherein the predetermined guide path is operatively associated with the guide pin; and, a spring operatively disposed within the mandrel. A method for setting a down hole tool in a wellbore is also disclosed.

Abstract: A technique facilitates control over the orientation of a bottom hole assembly. The bottom hole assembly comprises an orienting tool having a dual-spline drive which, in turn, comprises a first lead screw portion and a second lead screw portion having threads of a first pitch and a second pitch, respectively. A motor is connected to the dual-spline drive to impart rotational motion with respect to the first threads having the first pitch. A difference in pitch between the first pitch and the second pitch enables the rotational motion imparted by the motor to be converted to a slower, higher torque, output via the second lead screw portion. As a result, the orienting tool is able to provide a selective, high torque, low-speed adjustment to the drilling orientation of the bottom hole assembly.

Abstract: A drilling apparatus comprised of a multiplicity of subassemblies for drilling an open-hole extension from within an existing cased borehole located in a geological formation for the production of oil and gas. In one embodiment, one subassembly includes a motor located within a cased section of the borehole that rotates a drill pipe segment attached to a rotary drill bit in the open-hole to drill the open-hole extension of the well. In another embodiment, a shroud encloses the motor located within the cased portion of the well that is used to control the mud flow to and from the bit in the open-hole during the drilling process.

Abstract: A downhole device comprising a mandrel suitable for connection to a drilling assembly, a housing surrounding the mandrel with the housing being suitable for connection to the alternate end of a drilling assembly and a compensating mechanism configured to adjust an axial force applied to said mandrel by changing the relative position of the mandrel with respect to the housing.

Abstract: A system for use with a subterranean well can include a fluid oscillator which discharges pulsating fluid from a tubular string in a direction at least partially toward an end of the tubular string proximate a surface of the earth. A method can include discharging a fluid from the tubular string, thereby applying a reaction force to the tubular string, which reaction force biases the tubular string at least partially into the well. Another method can include discharging a pulsating fluid from a fluid oscillator in a direction at least partially toward an end of the tubular string, and drilling into an earth formation with a drill bit connected at an opposite end of the tubular string in the well.

Abstract: A system and method for sampling formation fluids is described. The system include a fluid sampling tool (200) with an elongated tool body (201). A cache of fluid containers may be disposed within the tool body. Each of the fluid containers within the cache of fluid containers may be individually deployable from the fluid sampling tool while the fluid sampling tool is positioned within a borehole. The fluid sampling tool may also include a pump in fluid communication with the cache of fluid containers.

Abstract: The use in a drillstring of a positive displacement motor (PDM) with both an output upwardly and an output downwardly to devices spaced at least by the PDM.

Abstract: Method and drill string valve assembly for closing a conduit through which a high pressure fluid flows. The drill string valve assembly includes first, second and third portions forming an elongated housing having an inside cavity; and a drill string valve provided inside the cavity, to extend from the first portion to the third portion. The second portion has an extension that fits inside a groove of the third portion and prevents the second portion to linearly move relative to the third portion and also allows the second portion to rotate relative to the third portion, and the second portion has a distal region provided with a thread configured to engage a corresponding thread of the first portion such that a rotation of the second portion relative to the third portion determines a tight connection between the first portion and the second portion.

Abstract: A method of drilling a wellbore includes drilling the wellbore by injecting drilling fluid through a drill string extending into the wellbore from surface and rotating a drill bit of the drill string. The drill string further includes a circulation sub having a port closed during drilling. The drilling fluid exits the drill bit and carries cuttings from the drill bit. The drilling fluid and cuttings (returns) flow to the surface via an annulus formed between an outer surface of the tubular string and an inner surface of the wellbore. The method further includes after drilling at least a portion of the wellbore: halting drilling; sending a wireless instruction signal from the surface to a downhole portion of the drill string by articulating the drill string, acoustic signal, or mud pulse, thereby opening the port; and injecting drilling fluid through the drill string and into the annulus via the open port.

Abstract: Equipment for the construction of piles includes a drilling rod and a tool (10) mounted at a lower end thereof. The tool includes a hollow central shaft (11) with a door (18) for the concrete; a screw (12) integral with the shaft (11); a compactor (13) positioned along the screw (12); a base (14) of semicircular shape provided at the lower end of the screw (12); a plate (15) superimposed under the base (14) and rotating around the shaft (11) for alternatively assuming an open position, in condition of excavation wherein it superimposes on the base, and a reclosed position, in condition of compaction wherein it forms a surface circular with the base (14). Excavation teeth (16) are fixed to the lower end of the tool and an additional tooth (19) is constrained to the plate (15) that during the casting is outside of the tool in the condition of compaction.

Abstract: A mud saver valve is constructed so that the valve seats self align preventing the loss of fluid when the valve is in the closed position. One or both seats can skew their longitudinal axes to get the alignment.

Abstract: The downhole flow control means or downhole blowout preventor (downhole BOP) of the present invention is adapted for use during reverse circulation drilling with both concentric drill pipe and concentric coiled tubing. The downhole BOP comprises an inner tube member having an inner passage therethrough and an outer casing forming an annular passage between the inner tube member and the outer casing. The inner passage and the annular passage of the downhole BOP is in fluid communication with the inner passage and annular passage, respectively, of the concentric drill pipe or concentric coiled tubing. The downhole BOP further comprises two valve means, preferably a check valve and a ball valve, for closing off the annular passage and the inner passage of the downhole BOP, respectively. In a preferred embodiment, the downhole BOP further comprises an electric actuator for opening and closing the ball valve.

Abstract: A downhole tool comprises a body defining a fluid inlet and two or more fluid outlets. A valve arrangement cycles the proportion of fluid directed from the inlet to each of the outlets. One of the outlets may be associated with a fluid pressure responsive device, such as a cleaning blade.

Abstract: A downhole flow pulsing device comprises a housing connected in series with a drill string and a valve with a rotating portion in the housing arranged to vary an area of a flow passage through the housing. A fluid actuated positive displacement motor drives rotation of the valve. A drive link permits the rotating portion of the valve to be optionally coupled directly to the motor of the drill string. The valve includes radially oriented rotating ports intermittently communicating with surrounding fixed ports and a bypass channel. Axial displacement of the rotating ports relative to the fixed ports and bypass channel permits amplitude of the downstream fluid pulses to be adjusted. The valve includes a number of circumferentially spaced ports which differs from a prescribed number of pressure fluctuations in the fluid for each full rotation of the rotor of the drill motor.

Abstract: An embodiment of the apparatus includes a housing having a first flow bore and a second flow bore, the first flow bore having a drilling fluid flowing therein, a device disposed in the second flow bore to receive a fluid flow, and a diverter disposed between the first and second flow bores, the diverter having a first position preventing the drilling fluid from flowing into the second flow bore and a second position allowing a portion of the drilling fluid to flow into the second flow bore and through the device. Another embodiment includes a variable second position directing the drilling fluid into the second flow bore at a variable flow rate. A further embodiment includes a drill collar as the housing and a power generation assembly as the device to receive the fluid flow. Embodiments of a method of diverting a fluid flow in a downhole tool include diverting a portion of a first fluid flow to a second flow bore, and further varying a flow rate of the fluid to the second flow bore.

Abstract: A drill bit is disclosed that in one configuration may include at least one cutter on a face section of the bit and at least one opening proximate the at least one cutter configured to discharge fluid under pressure onto the formation to create a fluid cushion between the drill bit and the formation during a drilling operation. An actuation device associated with the drill bit may be utilized to provide fluid under pressure to the at least one opening.

Abstract: The present invention relates to a diverter tool used in a pipe string used to lower a liner and a cutting apparatus on the end thereof into a partially cased wellbore. The diverter tool has a diverter body that defines a longitudinal flow passage and has the diverter ports defined therethrough to communicate a drilling fluid displaced through the pipe string into the liner into an annular space around the diverter tool. The diverter tool has a closure member so that when the wellbore is drilled to its desired depth, the diverter ports through which drilling fluid is diverted may be closed and the liner may be cemented in the wellbore.

Abstract: One or more components of a wellbore drilling assembly utilize a modular construction to facilitate assembly, disassembly, repair and/or maintenance of a wellbore drilling assembly and/or to extend the overall operating capabilities of the drilling assembly. In one embodiment, a modular construction is used for an APD Device, a motor driving the modular APD Device, a comminution device, and an annular seal. Individual modules can be configure have different operating set points, operating parameters and characteristics (e.g., rotational speeds, flow rates, pressure differentials, etc.) and/or different responses to given environmental factors or conditions (e.g., pressure, temperature, wellbore fluid chemistry, etc.). In one embodiment, the high-pressure seals used in conjunction with the APD Device and/or motor is a hydrodynamic seal that provides a selected leak or flow rates. Optionally, the seal is modular to provide different degrees of leak rates and/or different functional characteristics.

Abstract: One or more components of a wellbore drilling assembly utilize a modular construction to facilitate assembly, disassembly, repair and/or maintenance of a wellbore drilling assembly and/or to extend the overall operating capabilities of the drilling assembly. In one embodiment, a modular construction is used for an APD Device, a motor driving the modular APD Device, a comminution device, and an annular seal. Individual modules can be configure have different operating set points, operating parameters and characteristics (e.g., rotational speeds, flow rates, pressure differentials, etc.) and/or different responses to given environmental factors or conditions (e.g., pressure, temperature, wellbore fluid chemistry, etc.). In one embodiment, the high-pressure seals used in conjunction with the APD Device and/or motor is a hydrodynamic seal that provides a selected leak or flow rates. Optionally, the seal is modular to provide different degrees of leak rates and/or different functional characteristics.

Abstract: Method and apparatus for substantially cleaning fill from a borehole, variously including in preferred embodiments disturbing, particulate solids of fill while RIH, entraining particulates while POOH, jetting downhole while RIH and jetting uphole while POOH, and controlling at least one of a pump rate regime or a POOH rate regime.

Abstract: Canister, sealing method and composition for sealing a borehole. The canister includes a container with slurry inside the container, one or more slurry exits at one end of the container, a pump at the other end of the container, and a piston inside that pushes the slurry though the slurry exit(s), out of the container, and into a borehole. An inflatable packer outside the container provides stabilization in the borehole. A borehole sealing material is made by combining an oxide or hydroxide and a phosphate with water to form a slurry which then sets to form a high strength, minimally porous material which binds well to itself, underground formations, steel and ceramics.

Abstract: A preferred novel circulating sub includes an electric motor, hydraulic intensifier, connecting rod, valve sleeve, valve plug, and angled nozzles. Upon activation of the circulating sub the electric motor drives the valve sleeve over the valve plug, causing a flow of drilling fluid to exit the angled nozzles. Upon deactivation of the circulating sub, the electric motor removes the valve sleeve from the valve plug, allowing the flow of drilling fluid to once again flow to the drill bit. Because the electric motor is reversible, the circulating sub can be repeatedly activated and deactivated.

Abstract: A preferred novel circulating sub includes an electric motor, hydraulic intensifier, connecting rod, valve sleeve, valve plug, and angled nozzles. Upon activation of the circulating sub the electric motor drives the valve sleeve over the valve plug, causing a flow of drilling fluid to exit the angled nozzles. Upon deactivation of the circulating sub, the electric motor removes the valve sleeve from the valve plug, allowing the flow of drilling fluid to once again flow to the drill bit. Because the electric motor is reversible, the circulating sub can be repeatedly activated and deactivated.

Abstract: Downhole flow pulsing apparatus comprises a housing (14) for location in a drillstring, the housing (14) defining a throughbore to permit passage of fluid through the housing. A valve (27, 30) is located in the bore and defines a flow passage (29, 31). The valve includes a valve member (27) which is movable to vary the area of the passage (29, 31) to provide a varying fluid flow therethrough. A fluid actuated positive displacement motor (15, 16) is associated with the valve member (27). In a preferred embodiment, the apparatus is provided in combination with a drill bit (5) and a pressure responsive device, such as a shock-sub (3), which expands or retracts in response to the varying drilling fluid pressure created by the varying flow passage area. The expansion or retraction of the shock-sub (3) provides a percussive effect at the drill bit.

Abstract: A rock-crushing rotary drill bit includes a body having a rock-crushing roller rotatably mounted thereon by bearings. The body includes a first flushing channel for conducting flushing fluid to flush the bearings, and a second flushing channel for discharging flushing medium outside of the bit body to flush away cuttings. The second flushing channel terminates in a discharge recess which defines a linear center axis. A nozzle is disposed at a downstream end of the discharge recess, and a valve element is disposed at an upstream end of the discharge recess. The valve element is spring-biased for closing the discharge recess, the valve element being openable against the spring bias in response to a sufficient pressure build-up of flushing medium within the second flushing channel. The valve element includes a guide structure for guiding the valve element for linear movement along the center axis of the discharge recess.

Abstract: Flow control devices and associated control methods are described for use with hydraulic tools, such as those in a drill string. The described flow control device is typically incorporated into a drill string and is selectively operable in either a flow-through mode or a valve control mode. In the valve control mode, fluid pressure is increased or decreased within the drill string to selectively actuate a valve which is associated with the flow control device. In the flow-through mode, fluid pressure may be increased or decreased without operating the valve. Techniques are described for selectively moving the flow control device between the flow-through mode and the valve control mode. Wellbore fluid pressure readings provide signals to a rig operator for selectively moving the device in this manner.

Abstract: Apparatus and associated methods are provided which facilitate underbalanced drilling and completion of wells. In a described embodiment of a well control valve, the valve is opened and closed when a drill string is displaced therethrough. A shifting device is carried on a drill bit and deposited in the valve when the drill string enters and opens the valve. The valve is closed and the shifting device is retrieved from the valve when the drill string is tripped out of the well. A packer hydraulic setting tool usable in conjunction with the well control valve in underbalanced completions is also provided.

Abstract: A subterranean sampling system of the direct push type that employes an elongated push tube in combination with hydraulic means to force the push tube down through subterranean strata includes an improved sampler unit which basically includes a sample retaining cylinder surrounding an elongated slotted tube with a pierce member at the distal end and, at the proximal end, a tube guide member plus an adapter unit by which the sampler unit is connected to the lower end of the push tube. The system enables a new fluid sampling method in which the sampler unit is manipulated by the push tube into three modes. In the first mode, the slotted tube is within the cylinder so none of its slots extend proximally of the cylinder and no ambient fluid can enter. In the second mode, the slotted tube is moved out of the cylinder so only some of its slots extend proximally of the cylinder whereby ambient fluid may enter the cylinder.

Abstract: A process and apparatus for high pressure drilling are disclosed. The apparatus comprises an essentially solid drill head with horizontally extendable nozzle arms hingedly connected by shear pins thereto. Flow of high pressure fluid both extends the nozzle arms and flows through the nozzle arms, thereby fracturing and shearing material surrounding the drill head. Cessation of fluid flow returns the arms to the vertical position.

Abstract: A closure mechanism for preventing fluid access to an inner tube of a core barrel assembly is disclosed in which the closure mechanism is configured to move from an open, or unoccluded, condition to an occluded condition in response to increased fluid flow rates and pressure differentials occurring at the closure mechanism. The closure mechanism is also configured to maintain occlusion of the inner tube under substantially all types of drilling conditions, and particularly those where conventional closure mechanisms may fail, such as in horizontal drilling. The closure mechanism generally includes a conduit structure associated with the inner tube, and having a seat, an occlusion structure, such as a ball, and releasing structure which maintains the occlusion structure in spaced relationship to the seat until increasing pressure differentials result in release of the occlusion structure to register with the seat.

Abstract: This invention relates to flow pulsing methods and apparatus for various applications including downhole drilling equipment and in particular to an improved flow pulsing method and apparatus of this type to be connected in a drill string above a drill bit with a view to securing improvements in the drilling process.

Abstract: An actuator for an appliance associated with a ducted body, through the duct of which flows an incompressible fluid, includes a differential piston axially moveable within the duct and operatively connected to the appliance. The piston has a tubular shape and a central bore which includes a first profiled throttling portion the minimum internal diameter of which is smaller than the internal diameter of the duct. A protruding profiled element secured in the duct body is disposed coaxially with the piston and cooperates therewith for selectively increasing the loss of head of the incompressible fluid as it flows in the direction of circulation. A spring is arranged between the piston and part of the drill-string for biasing the piston in a direction of movement opposite the direction of circulation of the incompressible fluid. A measurement device is provided for measuring the pressure of the incompressible fluid at the first end of the drill-string.

Abstract: This invention relates to flow pulsing methods and apparatus for various applications including downhole drilling equipment and in particular to an improved flow pulsing method and apparatus of this type to be connected in a drill string above a drill bit with a view to securing improvements in the drilling process.

Abstract: A manually operated downhole for an underground earth boring apparatus having a pneumatically operated earth boring tool. A drill pipe is connected to the tool and to a source of pneumatic fluid. A valve is positioned in the drill pipe substantially adjacent to the tool between the tool and the source of pneumatic fluid. This downhole valve controls the flow of pneumatic fluid to the tool. The valve is operable in response to pushing or pulling on the drill pipe.

Abstract: An apparatus for producing pressure pulses in an oil well fluid medium is established which includes a main valve member moveable relative to a supporting member by a pressure gradient between two flow channels. The main valve body is longitudinally moveable relative to the supporting body, and a gap is provided between the two bodies. The gap is opened for fluid flow which prevents the development of dead water zones and the buildup of sedimentary deposits to prevent restriction of movement between the two bodies. The gap includes one or more throttle zones to assist in maintaining the necessary gradient between the two flow channels.

Abstract: Flow pulsing apparatus is adapted to be connected in a drill string above a drill bit. The apparatus includes a housing providing a passage for a flow of drilling fluid toward the bit. A turbine in the housing is rotated about an axis by the flow of drilling fluid. A valve is operated by the turbine to periodically restrict the flow through the passage to create pulsations in the flow and a cyclical water hammer effect to vibrate the housing and the drill bit during use. A cam is provided for effecting reciprocation of the valve along the axis of rotation of the turbine to effect the periodic restriction of flow.

Abstract: A simple and economical device is placed in a drill string to provide a pulsating flow of the pressurized drilling fluid to the jets of the drill bit to enhance chip removal and provide a vibrating action in the drill bit itself thereby to provide a more efficient and effective drilling operation.

Abstract: A drilling fluid pulse generator for use above a drill bit to produce pulsations in drilling fluid flow. An autocycling valve briefly interrupts the flow of fluid to bit jets to reduce the effective hydrostatic pressure at the drilling face and to hydraulic energy in the drill string to thoroughly scour the hole face when the briefly closed valve reopens. An alternate configuration provides a bypass route for fluid diverted from the bit, and the bypass includes jet nozzles to add energy to the return fluid stream to further reduce the effective hydrostatic pressure at the drilling face.

Abstract: A transformable circulation tool for reversing the path of drilling fluid at the drill bit without removing the drill string from the borehole annulus is provided by a substantially hollow body having a chamber with external ports disposed between a section of the body having a through passage and a by-pass passage in combination with a diverter mounted on a telescoping member having means for engaging the body during drilling and disengaging the body for rotation of the diverter with respect to each of the passages. A seal is rotatably mounted to the substantially hollow body between the ports to divide the well borehole into an upper conventional flow portion and a lower portion where the flow of the drilling fluid can be reversed upon command from the surface.

Abstract: Apparatus for subterranean slurry drilling and mining of granular ore, such as phosphates, with a combined drilling and mining apparatus. The apparatus includes a tool string having a drilling head and mining head that are selectively interchangeable on its upper end for drilling into one or more ore strata to be mined and thereafter to remove ore from the strata as a slurry. The drill string includes a plurality of inner and outer pipe sections connected to a mining nozzle section, to an eductor pump section, and to a drill bit at its lower end. A drilling/mining liquid is directed through the tool string during both the drilling and mining modes of operation. During drilling, liquid is directed through a foot valve into the rotating bit to wash cuttings to the surface externally of the tool. During mining, the tool string is rotated, the foot valve is closed, and a mining nozzle is opened thereby causing liquid jetting from the mining nozzle to reduce the ore to a slurry.

Abstract: A sampling drill comprising a plurality of drill rods coupled together to form a drill stem suspended from a drill head, each of the drill rods comprising a pair of substantially concentric tubular members defining an inner central passage and an annular passage, the lower end of the drill stem being fitted with a drill bit having an inner chamber adapted to be connected to the inner central passage of the drill stem, and one or more passages adapted to be connected at one end to the annular passage in the drill stem and at the other end to discharge into the inner chamber, the inner chamber being provided with openings located adjacent the cutting edges of the drill bit so that material cut by the drill bit can pass into the chamber, and means for shutting off the inner central passage to prevent material entering the inner chamber of the drill bit and entering the inner central passage.

Abstract: Subterranean slurry mining with one or more mining nozzles which, during mining, directs a high pressure jet of liquid into a granular ore matrix to reduce the ore to a slurry which is thereafter pumped to the surface by an eductor pump including a high pressure eductor nozzle. The drilling and mining apparatus includes several different types of hydraulic control systems which operates at or below system pressure and allows the apparatus to be changed between the mining and a drilling mode. During drilling, the liquid is directed through an open foot valve and drill bit into the well cavity being drilled to wash the cuttings to the surface at which time the mining and eductor nozzles are closed. During mining the control systems close the foot valve and control the opening of the mining nozzle (or nozzles) and eductor nozzle.

Abstract: In the representative embodiment of the apparatus of the present invention disclosed herein, a first ported or grooved cylindrical member is coaxially disposed within a drill string for directing drilling fluids flowing through the apparatus along one or more selected flow paths .[.through.]. .Iadd.and .Iaddend.a second ported or grooved cylindrical member .[.which.]. is coaxially arranged in the drill string adjacent to the first member for rotation in a transverse plane cutting the flow paths to cyclically obstruct these flow paths. An electric motor is cooperatively coupled by a shaft to the rotatable member for driving this member at a selected speed for developing an acoustic signal of a desired frequency as the flow paths are momentarily obstructed at periodic intervals.