Abstract: A pressure pulse generator for a downhole drilling tool is provided. The pressure pulse generator includes a stator with an orifice through which a stream of fluid passes, and a rotor intended to rotate opposite the stator to allow the flow of more or less liquid exiting the orifice of the stator. The rotor is equipped with an orifice, and the two orifices present a communicating area for the passage of the stream of fluid. The rotor is capable of passing fluid therethrough. A turbine with blades rotatable in response to fluid flow through the rotor may also be provided. The turbine is operatively connected to the rotor via a drive shaft. The fluid flow through the rotor may be used to rotate the turbine and provide power usable in the downhole tool.

Abstract: The invention is directed to a borehole logging apparatus for deep well drilling, with a signal transmitter for transmitting measured data obtained while drilling from a borehole through the drilling fluid to the earth's surface, and with an elongated housing which is adapted for insertion in the drilling fluid conduit of a drill string. Accommodated in the housing is a flow regulator with a control piston, which controls the cross-section of opening of a bypass opening in response to the pressure differential generated by a flow restrictor and in response to the force of a spring in such manner that the part of the drilling fluid current fed to the signal transmitter through the flow restrictor is maintained substantially constant, and the remaining excess drilling fluid current is routed to the drilling fluid conduit via the bypass opening.

Abstract: The present invention provides a semi-passive two-way borehole communication system and method. The system includes a surface source signal generator for generating an acoustic signal. The acoustic source signal is transmitted downhole, and a downhole controllable reflector reflects a portion of the source signal back toward the surface. The reflector is controlled such that an echo signal is created, which contains information to be carried to the surface. A surface receiver is used to detect the echo signal, and a surface controller is used to decode the echo signal.

Abstract: A method and apparatus for transmitting information to the surface from down hole in a well in which a pulser is incorporated into the bottom hole assembly of a drill string that generates pressure pulses encoded to contain information concerning the drilling operation. The pressure pulses travel to the surface where they are decoded so as to decipher the information. The pulser includes a stator forming passages through which drilling fluid flows on its way to the drill bit. The rotor has blades that obstruct the flow of drilling fluid through the passages when the rotor is rotated into a first orientation and that relieve the obstruction when rotated into a second orientation, so that oscillation of the rotor generates the encoded pressure pulses. An electric motor, under the operation of a controller, drives a drive train that oscillates the rotor between the first and second orientations.

Abstract: An anti-plugging oscillating shear valve system for generating pressure fluctuations in a flowing drilling fluid comprising a stationary stator and an oscillating rotor, both with axial flow passages. The rotor oscillates in close proximity to the stator, at least partially blocking the flow through the stator and generating oscillating pressure pulses. The rotor passes through two zero speed positions during each cycle, facilitating rapid changes in signal phase, frequency, and/or amplitude facilitating enhanced data encoding. The rotor is driven by a electric motor disposed in a lubricant filled housing. In one embodiment, the housing to shaft seal is a flexible bellows. In one embodiment, a torsional spring is attached to the motor and the resulting spring mass system is designed to be near resonance at the desired pulse frequency. The torsion spring may be a solid torsion bar or a magnetic spring.

Abstract: A telemetry system involving a shear-type mud pulser valve as the preferred embodiment is described. The control system includes a motor driver for the mud pulser which, in essence, moves one movable plate with respect to a stationary plate to create openings of various sizes. Pressure is sensed uphole of the pulser valve and is compared in real time to the desired pressure pulse amplitude. By allowing different relative rotational positions of the rotatable plate with respect to the stationary plate, different amplitudes can be achieved to further enhance the transmission of data to the surface. The control system compensates for wear in the mud pulser valve itself as well as drastic changes in mud flow and pressure. The configuration is simple and not prone to fouling from grit or other particles in the mud.

Abstract: A method and apparatus for communicating coded messages in a wellbore between a transmission node and a reception node is provided. The coded messages are messages are impressed upon a fluid column which extends between the transmission node and the reception node. A transmission apparatus is provided at the transmission node which is in communication with the fluid column, for altering pressure of the fluid column to generate at least a portion of the coded message. A reception apparatus is provided at the reception node. The reception apparatus includes a rigid structural component with an exterior surface which is in direct contact with fluid column and an interior surface which is not in contact with the fluid column, and a sensor assembly which detects elastic deformation of the rigid structural component. The transmission apparatus is utilized to alter pressure of the fluid column in a predetermined pattern to generate at least one coded message.

Abstract: A system is disclosed for generating and transmitting data signals to the surface of the earth while drilling a borehole, the system operating by generating pressure pulses in the drilling fluid filling the drill string. The system is designed to maximize signal strength while minimizing the probability of jamming by drilling fluid particulates. The system uses a rotary valve modulator consisting of a stator with flow orifices through which drilling fluid flows, and a rotor which rotates with respect to the stator thereby opening and restricting flow through the orifices and thereby generating pressure pulses. The flow orifices with the stator in a “closed” position are configured to reduce jamming, and to simultaneously minimize flow area in order to maximize signal strength. This is accomplished by imparting a shear to the fluid flow through the modulator, and minimizing the aspect ratio and maximizing the minimum principal dimension of the closed flow area.

Abstract: A reverse VSP system is provided and uses a frequency-controllable modulator of an MWD tool as a downhole seismic source. The modulator has a rotor and stator arranged to provide substantially sinusoidal outputs, and is controlled to provide a "Vibroseis"-type frequency sweep (preferably from 1 Hz to 50 Hz). With the bit of the MWD tool in contact with the bottom of the borehole, the force generated by the frequency-controllable modulator will generate measurable axial compressional (P-) waves. These waves which move through the formation are detected by an array of geophones on the formation surface, and a reference signal is obtained by a kelly-mounted accelerometer or strain gauge. The reference signal and signals obtained by the geophones are processed using known signal processing techniques.

Abstract: A pressure pulse generator, or "pulser," and methods for operation are described. The pulser is constructed of a stator and rotor mounted within a housing, each being configured with a central hub and one or more radially extending lobes. An equal number of ports are spaced between the lobes. The lobes of the rotor are cross-sectionally tapered in the streamwise direction. The rotor and stator are maintained within the housing in a coaxial spaced relation from each other. The axial distance between the rotor and stator may be selectively varied by a linear actuator. In a preferred embodiment, the linear actuator comprises a conventional solenoid assembly which is operably associated with the rotor to move it axially within the housing with respect to the stator between a first position, wherein the distance between the rotor and stator is reduced, and a second position, wherein the distance between the rotor and stator is increased. The linear actuator is energized in response to signals from an encoder.

Abstract: A self-propelled turbo siren modulator assembly is disclosed for use in an MWD system. The turbo siren includes a fixed turbine deflector located upstream from a rotor, which in turn is located upstream from a fixed stator. Drilling mud flowing through the turbine deflector causes the rotor to rotate independent of any external drive device. The rotor and stator preferably have a similar configuration, which includes at least one lobe and at least one port so that the rotor alternatively blocks or permits mud flow through the port(s) of the stator to create a cyclical acoustic wave signal, with a frequency that depends upon the number of lobes on the rotor and the velocity of the drilling mud. Encoded measurement data is modulated on the carrier frequency wave through the use of amplitude modulation, frequency modulation or phase shift modulation, or a combination thereof to maximize data rates.

Abstract: A fluid-powered siren of the type used for communicating information between points of a wellbore. In one aspect, responsiveness of the siren's rotor to low flow rates is improved through application of greater torque to the siren rotor. Also, improved capturing and channeling action by the turbine rotor fins causes fluid flow to drive the turbine rotor and siren rotor combination more efficiently than it can drive a siren rotor directly as may be the case in other fluid-powered sirens. In another aspect, the system provides for control of the rotational speed of the siren rotor in instances wherein the fluid flow rate is too high. Control is affected by use of an epicyclical gear reducer which is positioned between the turbine rotor and the siren rotor to operably interconnect the two components.

Abstract: A self-propelled turbo siren modulator assembly is disclosed for use in an MWD system. The turbo siren includes a fixed turbine deflector located upstream from a rotor, which in turn is located upstream from a fixed stator. Drilling mud flowing through the turbine deflector causes the rotor to rotate independent of any external drive device. The rotor and stator preferably have a similar configuration, which includes at least one lobe and at least one port so that the rotor alternatively blocks or permits mud flow through the port(s) of the stator to create a cyclical acoustic wave signal, with a frequency that depends upon the number of lobes on the rotor and the velocity of the drilling mud. Encoded measurement data is modulated on the carrier frequency wave through the use of amplitude modulation, frequency modulation or phase shift modulation, or a combination thereof to maximize data rates.

Abstract: In a Measurement-While-Drilling system, selecting the fixed frequency in a pulse signal generator utilizes constructive interference to enhance the signal level in an amplitude modulated signal. The pulse generation system preferably includes a plurality of mud sirens in tandem to further enhance signal level and to provide multiple amplitude levels to increase data transmission rate.

Abstract: An integrated modulator and turbine-generator includes a turbine impeller which is directly coupled by a drive shaft to a modulator rotor downstream from the impeller. The modulator rotor is further coupled by a drive shaft and a gear train to a three phase alternator downstream of the modulator rotor. The modulator stator blades are arranged downstream of and adjacent to the modulator rotor and the alternator is provided with a Hall effect tachometer. The turbine impeller directly drives the modulator rotor and the alternator generates power. The speed of rotation of the modulator rotor is adjusted by reference to the speed of rotation of the alternator as indicated by the tachometer and to a reference frequency.

Abstract: A LWD tool is disclosed comprising, a stator, a rotor which rotates relative to the stator thereby effecting a signal in the borehole fluid flowing therethrough, a brushless DC motor coupled to the rotor for driving the rotor, a position sensor coupled to the motor for sensing the rotational position of the motor, motor drive electronics coupled to motor for driving the motor, and a microprocessor coupled to the position sensor and to the drive electronics for controlling the drive signals to the motor based on the actual and desired positions of the motor. By controlling the drive signal to the motor, the speed of the motor is controlled, thus effecting changes in frequency and/or phase of the signal in the borehole fluid or mud. With the ability to change the frequency and/or phase, different encoding techniques such as PSK-type and FSK-type can be used.

Abstract: A downhole tool (100) for generating pressure pulses in a drilling fluid comprising an elongate body (107, 127) and a plurality of blades (116) spaced around the body. The blades are each divided into an independent front section (116a) and rear section (116b), forming a set of front sections and a set of rear sections, at least one of the set of front sections and the set of rear sections being mounted for rotation and being angularly displaceable relative to each other between a first position in which the sections are aligned and a second position in which the rear sections obstruct fluid flow between the front sections to generate a pressure pulse. The tool includes a first set of driving blades in front of the blades (116) for generating a torque on the blade sections, the driving blades being curved in a first direction, and an escapement means (129) which is radially movable to permit stepwise rotation of the blade sections, and thus to move the blade sections between the first and second positions.

Abstract: Methods and apparatus for determining whether an encoder of a borehole tool is jammed are disclosed. The borehole tool has a motor with a drive shaft which is coupled to and drives an encoder, a position sensor coupled to the motor for sensing the position of the motor, and a microprocessor coupled to the position sensor and to the motor in a feedback loop, with the microprocessor controlling the movement of the motor based on the sensed position of the motor and the desired position of the motor. The method for determining jamming includes: determining, at a first plurality of times, positions of the motor from the position sensor; determining position errors of the motor from the positions of the motor and desired positions of the motor as determined by the microprocessor; and determining whether the encoder is jammed based on whether the position error exceeds a threshold value.

Abstract: A LWD tool is disclosed comprising, an encoder for generating a signal in the borehole fluid flowing therethrough, a brushless DC motor coupled to the encoder, a position sensor coupled to the motor for sensing the rotational position thereof, motor drive electronics coupled to motor for driving the motor, a microprocessor coupled to the position sensor and to the drive electronics for controlling the drive signals to the motor based on the actual and desired positions of the motor, and a magnetic positioner which is coupled to one of the drive shafts of the system. By controlling the drive signal to the motor, the speed of the motor is controlled, thus effecting changes in frequency and/or phase of the signal. The magnetic positioner, includes inner S magnets extending in a first arc, inner N magnets extending in a second arc, outer S magnets extending in a third arc, and outer N magnets extending in a fourth arc, where the inner magnets rotate with the drive shaft.

Abstract: A rotating pulse valve for use in a mud pulse telemetry system is presented. In accordance with the invention, a valve is diametrically mounted in a channel of a segment of a drill string wherein drilling fluids flows. The valve comprises blades which are configured so as to be impelled (i.e., rotated) by the flow of the drilling fluid. An escapement mechanism is employed to restrain the valve in selected positions thereby at least partially obstructing the flow of the drilling fluid which results in generating positive pressure pulses or waves in the drilling fluid in response to downhole conditions.

Abstract: A borehole data transmission apparatus whereby a centrifugal pump impeller(s) is used to provide a turbine stage having substantial pressure characteristics in response to changing rotational speed of a shaft for the pressure pulsing of data from the borehole through the drilling mud to the surface of the earth.

Abstract: A downhole tool for generating pressure pulses in a drilling fluid comprising an elongated body and a plurality of blades spaced around the body. The blades are each divided into an independent front section and rear section, forming a set of front sections and a set of rear sections, at least one of the set of front sections and the set of rear sections being mounted for rotation such that the front and rear sections are angularly displaceable relative to each other between a first position in which the sections are aligned and a second position in which the rear sections obstruct fluid flow between the front sections to generate a pressure pulse. The tool includes a means for generating a torque on the blade sections, and an escapement means which is radially movable to permit stepwise rotation of the blade sections, and thus to move the blade sections between the first and second positions.

Abstract: A hydromechanical signal transmitter for generating pressure pulses in a drilling fluid to transmit telemetry information of a well-logging operation includes a stator fixed in a cylindrical housing having at least a pair of axially aligned fluid passages, and a disc shaped rotor disposed between the passages, rotatable between a first limit position wherein an opening in the rotor passes drilling fluid flowing through the pair of passages and a second limit position wherein a disc portion of the rotor throttles the flow of the fluid. A revisable d.c. motor drives the rotor from one limit position to the other in response to information signals provided to the motor. Means is provided to stop the rotor at each limit position, including radial stop faces on a drive shaft connecting the motor to the rotor and a stop pin in the housing. A plurality of circumferentially spaced passages and rotor openings may be provided.

Abstract: A downhole MWD tool for generating pressure pulses in a drilling fluid comprises an elongate body for positioning in a drill collar and a plurality of blades spaced around the body. Each blade is divided into an independent front section and rear section one of the front and rear sections being mounted on a rotatable shaft such that the front and rear sections are angularly displaceable relative to one another between a first position in which the sections are aligned and a second position in which the rear blades obstruct fluid flow between the front sections to generate a pressure pulse. A hydraulic actuator is operable to rotate the shaft, and is powered by the pressure difference in the drilling fluid between an upstream end of the tool and a position downstream of the tool.

Abstract: A mechanical oscillator driven by drilling fluid flow pumped down a drill string bore is combined with sensors and controls to produce a downhole drilling fluid pressure pulse generator for use in drill strings for Measurement While Drilling (MWD) pipe bore telemetry.A fluid flow responsive valve designed to be put in continual motion by fluid flow is associated with a motion stop lock so that, on release, a discrete digital fluid pressure change is generated. A downhole instrument package controls the lock release in a timed sequence, so that a series of pressure changes represent information to be decoded at the earth surface to determine downhole parameters sensed by the instrument package.The active elements of the downhole system may be installed in the drill string or lowered as a shuttle package down the drill bore.The fluid pressure pulse generating apparatus can be classified as a fluid flow excited oscillator or an auto-cycling pulse generator.

Abstract: A transmitter comprises an impeller assembly rotatable by a liquid flow, and an electrical generator having a stator and a rotor arranged to be driven by the impeller assembly. The impeller assembly comprises a main impeller portion and a secondary impeller portion angularly displaceable relative to one another about the axis of rotation of the impeller assembly in response to a change in load of the generator so as to vary the pressure drop across the rotating impeller assembly. Thus appropriate variation of the load of the generator may be used to control the impeller assembly in such a manner as to transmit pressure signals within the liquid flow. Such a transmitter is particularly suitable for transmitting measurement data to the surface from a measuring instrument at the end of a drill string within a borehole. Furthermore such a transmitter can be constructed so as to be readily retrievable without requiring withdrawal of the drill string from the borehole.

Abstract: In a fluid communication device such as a measure-while-drilling well-logging tool of the type in which the information concerning the downstream parameters that are measured is transmitted upstream, e.g. to the surface of the earth, in the form of positive pressure pulses in the drilling fluid, a pressure modulator for generating the pulses is driven by the drilling fluid passing through the tool. The pressure modulator is controlled by a solenoid actuated latching means which has low power requirements as compared to known measure-while-drilling logging tools.

Abstract: A pressure pulse generator which generates relatively sinusoidal pressure pulses in a fluid flowing in a borehole is disclosed. The pressure pulse generator for a MWD tool broadly comprises: a housing adapted to be connected in a tubing string so that fluid flowing in the string will at least partially flow through the housing; a stator mounted within the housing and having a plurality of lobes with intervening gaps; a rotor coaxial to the stator which rotates relative to the stator and which is mounted within the housing and has a plurality of lobes with intervening gaps between adjacent lobes, wherein the lobes of the rotor and stator are arranged such that as the rotor rotates relative to the stator, the area of the adjacent gaps between the lobes of the stator and rotor through which the fluid may flow in a direction parallel to the borehole varies approximately with the inverse of the square root of a linear function of a sine wave.

Abstract: An improved acoustic signal generator has rotor and stator elements, each having a plurality of radially-extending lobes and intervening ports relatively positioned and configured to establish fluid dynamic forces that bias the generator into an open position, thereby imparting a "stable open" characteristic to the generator. The rotor is located downstream of the stator, and rotor lobes are outwardly tapered in the downstream direction and have underlap relative to the upstream stator lobes. The invention is especially suited for use in oil industry MWD operations to communicate downhole measurement data to a well surface during drilling. In one embodiment, undercuts on the rotor lobes impart a flutter action which clears debris.

Abstract: Multistate mud pulsing is achieved by generating both positive and negative pulses within a drill string by means of a plurality of selectively operable bypass passages around a restriction to primary mud flow within a drill string or by venting to outside of the drill string. A fraction of the hydraulic mud is drawn from a location upstream from the restriction into a valve manifold. The removed fraction of hydraulic mud is selectively communicated from the valve manifold either to a point inside a drill string downstream from the restriction or to a point exterior to the drill string in annulus between the outside of the drill string in the borehole. Mud reinjected downstream from the restriction creates a positive pressure pulse within the drill string. Mud which is diverted to the annulus outside of the drill string creates a negative mud pulse within the drill string.

Abstract: A logging-while-drilling tool includes a housing positioned in a drill string, a shaft journaled in the housing, a turbine stage or stages, a rotor or rotors, the latter mounted on the shaft outside of the housing and driven by the drilling fluid and a braking device for variably controlling the rotational speed of the rotor in order to produce pressure pulses which are transmitted to the surface through the drilling fluid. A generator or other energy storing device is provided to power an electronic package which interprets downhole conditions for transmission of the same as pressure pulses.

Abstract: Information is conveyed from a downhole location within a wellbore being drilled by producing pressure and velocity of flow variations from the steady state drilling fluid pressure and velocity of flow so as to set up transient acoustic waves that propagate to the surface through the drilling fluid within the drill string. The acoustic waves are detected at the surface to obtain the propagated information. According to this invention, a simple and reliable method of recovering the propagated information is to monitor the pressure of the gas filled side of the accumulator or desurger device that is coupled to the drilling fluid line adjacent the pump.

Abstract: Multistate mud pulsing is achieved by generating both positive and negative pulses within a drill string by means of a plurality of selectively operable bypass passages around a restriction to primary mud flow within a drill string or by venting to outside of the drill string. A fraction of the hydraulic mud is drawn from a location upstream from the restriction into a valve manifold. The removed fraction of hydraulic mud is selectively communicated from the valve manifold either to a point inside a drill string downstream from the restriction or to a point exterior to the drill string in annulus between the outside of the drill string in the borehole. Mud reinjected downstream from the restriction creates a positive pressure pulse within the drill string. Mud which is diverted to the annulus outside of the drill string creates a negative mud pulse within the drill string.

Abstract: A down-hole signal generator for a mud-pulse telemetry system comprises an annular impeller surrounding a casing and arranged to be driven by the mud passing along the drill string. The impeller serves to drive a torque control arrangement, and preferably also an electrical generator, within the casing. The torque control arrangement is switchable between two states by a signalling actuator in response to an electrical input signal. In a first state the impeller may be driven relatively easily so that it is rotated at a relatively fast speed by the mud flow, whereas, in a second state, a greater torque is required to drive the impeller so that it is rotated at a relatively slow speed. Thus suitable variation of the input signal may be used to vary the impeller speed to transmit a modulated pressure signal in the mud flow which may be sensed at the surface.

Abstract: A mud pulse telemetry system for imparting data pulses to drilling fluids circulating in a drill string including an improved valve arrangment for modulating the pressure of the circulating drilling fluid is disclosed. A rotary acting shear-type valve is arranged in a through conduit configuration so that the seat face of the valve is covered when the valve is in an open position, thus preventing impingement of abrasive fluid particles on the valve seat face during the open flow position of the valve. The rotatable gate is positively driven through an arc in opposite directions by rotary solenoids so that a gate aperture is moved into and out of axial alignment with the opening in the valve seat to generate the pressure pulse. The rotary solenoid valve also permits a tailoring of the force curve of the solenoid for maximum power in actuation of larger flow orifices. The larger flow orifice permits generation of pressure pulses of increased amplitude.

Abstract: An apparatus for the remote transmission of information from a borehole (1) to the surface of the earth is disposed in a drilling pipe string (4) of a drilling device. The drilling device further comprises a rotary drill bit (3) and a pump (5) which pumps the flushing liquid (6) downwards in the flow passage (11) of the drilling pipe string, through the rotary drill bit (3) and upwards in an annular space (7) surrounding the pipe string. The apparatus has devices for ascertaining information data (8), for converting the information data into electrical control signals (9) and for producing pressure pulses (10) in the downwardly directed flow of the flushing liquid (6). The devices are disposed in a chamber (13) which is bounded internally by the flow passage (11) and externally by an outer tube (12).

Abstract: A measurement system detects a downhole drilling variable in relation to the rotational orientation of a drill string during drilling. The system includes a downhole reference signal generator and a downhole variable signal generator. The reference signal generator is coupled downhole to the drill string for generating a downhole reference (DR) signal indicative of the angular relationship between the drill string and a directional reference, such as gravity or the earth's magnetic field. The downhole variable signal generator detects downhole parameters and generates a downhole variable (DV) signal representative of a downhole parameter of interest during drilling. The DV signal and the DR signals are thereupon processed, either downhole or uphole depending in part on the telemetry system employed. The system is especially adapted for indicating the resultant lateral force applied to the drill string at the drill bit during drilling which is useful in projecting the probable drilling direction.

Abstract: A measuring-while-drilling system having a downhole, motor-driven acoustic signal generator includes a motor speed control circuit featuring feedback compensation which accounts for varying loading conditions on the motor. The acoustic signal generator is motor driven at speeds for imparting to well fluid an acoustic signal having phase states representative of data derived from measured downhole conditions. The motor control circuit includes circuitry which forms a phase locked loop for driving the motor at a reference phase and at a substantially constant carrier frequency producing speed in the absence of data of one logic state and also includes circuitry for temporarily changing the speed of the motor, according to a pre-programmed function, to effect a predetermined amount of phase change in the carrier signal upon data of the predetermined logic state.