Abstract: A autonomous borehole data transmission apparatus for transmitting measurement data from measuring instruments at the downhole end of a drill string by generating pressure pulses utilizing a transducer longitudinally responsive to magnetic field pulses caused by electrical pulses corresponding to the measured downhole parameters.

Abstract: Improved techniques are provided for drilling a deviated borehole through earth formations utilizing a rotary bit powered by a drill motor, and for obtaining information regarding the borehole or earth formations. A sensor permanently positioned in the drilling string between the drill bit and the drill motor detects a downhole parameter. An MWD tool may be provided within a non-magnetic portion of the drill string for receiving and transmitting a sensor representative signal to the surface. The sensor signal allows the drilling operation to be altered, and highly reliable and near-bit information thus improves the drilling operation.

Abstract: A transducer is described especially for use in providing acoustic transmission in a borehole. The transducer includes a multiple number of magnetic circuit gaps and electrical windings that have been found to provide the power necessary for acoustic operation in a borehole while still meeting the stringent dimensional criteria necessitated by boreholes. Various embodiments conforming to the design are described. Moreover, the invention includes transition and reflector sections, as well as a directional coupler and resonator arrangement particularly adapted for borehole acoustic communication.An acoustic communication system is described especially designed for use in providing acoustic transmission of information in a borehole. The communication system comprises a surface transceiver and at least one downhole transceiver. The surface transceiver operates in conjunction with a host computer that sends commands to the downhole transceiver.

Abstract: A method for deriving reservoir lithology and fluid content for a target location from pre-stack seismic reflection data. The method uses inversion of pre-stack seismic reflection data for both the target location and a calibration location having known subsurface lithology and fluid content to derive the subsurface lithology and fluid content at the target location. The inversion process is preferably a viscoelastic inversion to account for the effects of friction on seismic wave propagation. The results of the inversion process are a set of subsurface elastic parameters for both the target and calibration locations. Relative magnitudes of these subsurface elastic parameters are compared, together with the known subsurface lithology and fluid content at the calibration location, to derive the subsurface lithology and fluid content at the target location.

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: The present invention relates to a method and a transmitter/receiver for transferring signals through a medium in pipes or hoses, whereby at a transmitter side pressure pulses are generated of various frequencies or in various frequency ranges, and for the purpose of providing a technology which eliminates error sources, it is proposed according to the invention that the pressure pulses be generated at the transmitter side as an organised and defined bit pattern in order thereby to achieve one or two-way alphanumeric communication.

Abstract: The acoustic detector in a mud pulse telemetry system includes a one dimensional waveguide disposed between a pressure transducer and a conduit carrying drilling fluid to a drill string. The waveguide, which may include a flexible hydraulic hose, increases the amplitude of the acoustic mud pulse signal received at the transducer located at the termination end by a factor of two or more. In addition, the waveguide may be substantially filled with a fluid having a viscosity higher than the viscosity of the drilling fluid so as to provide a means to dampen high frequency noise, and thereby improve the signal-to-noise ratio at the pressure transducer.

Abstract: An acoustic detector in a mud pulse telemetry system includes a bypass loop in parallel with a section of the main mud line that supplies drilling mud to a drill string. The detector includes a pair of pressure sensing ports in the bypass line, and one or more pressure transducers for detecting the pressure at different locations in the bypass loop so that the differential pressure can be measured. The bypass loop has a small internal passageway relative to the main mud supply line and may include a constriction so as to create two regions in the passageway that differ in cross sectional areas. Forming the pressure sensing ports in the regions of differing cross sectional areas allows the pressure transducers to more precisely detect the mud pulse signals. Because of its relatively small cross sectional area, only a small fraction of the drilling mud flows through the bypass loop. The bypass loop may thus be constructed of hydraulic hose and a relatively small rigid body having a central through bore.

Abstract: A nonlinear equalizer aids in transmitting data with more speed and accuracy by reducing nonlinear signal distortion such as found in a mud transmission channel in an MWD telemetry system. The nonlinear equalizer receives an input signal that is modified by at least one nonlinear function element. The nonlinear equalizer also includes multiple linear equalizers: one such linear equalizer receives the unmodified input signal, and the other linear equalizers receive output signals from the nonlinear function elements. Output signals of the linear equalizers are summed to provide the nonlinear equalizer's output signal.

Abstract: A well communication pulser is solenoid controlled but energized by an actuator responsive to the pressure drop across the signal valve. The signal valve is spring biased toward a closed state but the actuator urges it toward an open state with a force proportional to the pressure drop. When in the off-pulse state the spring is sized to yield an operating pressure for the pulser. A servo valve controls pressure admitted to the actuator to cause it to move to the on-pulse state to develop signal pressure. The servo valve is spring biased open to cause a pressure signal to be generated but it has a second actuator responsive to the pressure drop which will overcome the servo opening spring and move the servo to the off-pulse, or closed, state. The pulser would oscillate continually between the two states but a solenoid controlled latch automatically secures the servo when it arrives at either state.

Abstract: A telemetry system employs a periodic pseudorandom training sequence to effectively initialize an adaptive digital FIR filter-equalizer for optimal communications between a surface modem and downhole measuring equipment, without requiring any changes to the normal logging configuration or any special operator intervention. In a "training mode", an electronic source in a downhole sonde transmits a predetermined training sequence to a surface modem via a cable. The source preferably transmits the training sequence continuously until the surface modem has acclimated itself to the characteristics of the multiconductor cable by adaptively configuring the filter-equalizer, thereby enabling the surface modem to accurately interpret data received from the sonde despite attenuation, noise, or other distortion on the cable. The filter-equalizer adjusts itself in response to an error signal generated by comparing the filter-equalizer's output with a similar training sequence provided by a training generator.

Abstract: The acoustic detector in a mud pulse telemetry system includes a one dimensional waveguide disposed between a pressure transducer and a conduit carrying drilling fluid to a drill string. The waveguide, which may include a flexible hydraulic hose, increases the amplitude of the acoustic mud pulse signal received at the transducer located at the termination end by a factor of two or more. In addition, the waveguide may be substantially filled with a fluid having a viscosity higher than the viscosity of the drilling fluid so as to provide a means to dampen high frequency noise, and thereby improve the signal-to-noise ratio at the pressure transducer.

Abstract: A vortex chamber fluid pulser selectively produces pressure pulses in fluid flowing therethrough by the alternating insertion and retraction of a flow-disrupting tab into and out of an annular vortex chamber having an inlet and a pair of opposed axial outlets. Insertion of the tab disrupts the normally radial flow of fluid through the chamber and outlets causing the flow to become vortical; retraction of the tab causes a second pressure pulse as the flow returns to radial, sending a sequence of pressure pulses capable of carrying encoded signals to a transducer remotely located in the fluid.

Abstract: In accordance with illustrative embodiments of the present invention, a measuring-while-drilling system includes a sensor sub positioned at the lower end of a downhole motor assembly so that the sub is located near the drill bit. The sub houses instrumentalities that measure various downhole parameters such as inclination of the borehole, the natural gamma ray emission of the formations, the electrical resistivity of the formations, and a number of mechanical drilling performance parameters. Sonic or electromagnetic telemetry signals representing these measurements are transmitted uphole to a receiver associated with a conventional MWD tool located above the motor, and telemetered by this tool to the surface substantially in real time. The system has particular application to accurate control over the drilling of extended reach and horizontally drilled wells.

Abstract: A method and apparatus for sonic logging using a measuring while drilling telemetry system as the sonic source is provided. Transducers are provided for receiving acoustic energy from the formation surrounding the borehole. The transducers produce a signal which is processed and telemetered to the surface using the measuring while drilling system.

Abstract: Improved techniques are provided for drilling a deviated borehole through earth formations utilizing a rotary bit powered by a drill motor, and for obtaining information regarding the borehole or earth formations. A sensor permanently positioned in the drilling string between the drill bit and the drill motor detects a downhole parameter. An MWD tool may be provided within a non-magnetic portion of the drill string for receiving and transmitting a sensor representative signal to the surface. The sensor signal allows the drilling operation to be altered, and highly reliable and near-bit information thus improves the drilling operation.

Abstract: A measuring while drilling assembly utilizes two transmission channels connected in cascade in order to transmit a signal of a sensed downhole condition from a location near a downhole drill bit to a surface receiver. A first transmission channel has its downhole end connected to a first signal generator and its uphole end connected to a second signal generator. The second signal generator includes a pulser. A second transmission channel has its downhole end connected to the pulser and its uphole end connected to a pressure transducer at the surface of the earth.

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: This disclosure is directed to a displacement amplifier for forming acoustic pulses and more particularly to one which incorporates a flexible movable lightweight diaphragm of rectangular configuration. It has upper and lower ends which are connected to opposing piston rods driven by duplicate pistons and double acting cylinders. The cylinders are located at opposite ends of the diaphragm or membrane. They are supported in an elongate tool which positions the flexible membrane in a generally rectangular window. This enables the membrane to flex as the pistons are driven, thereby enabling the flexure of the membrane to form dipole source for radially directed compression waves transmitted from the membrane in the window.

Abstract: A method for transmitting data from the bottom of a well to the surface is disclosed. The method includes measuring data indicative of at least one drilling condition at the bottom of a well, transmitting into a stream of drilling mud injected into a well pipe string a series of encoded pressure pulses representative of the data measurement, and detecting the encoded pulses at the surface using a pressure sensor which is in communication with the stream of drilling mud as it is being injected into an inlet of the pipe string. The method also includes, as a way of improving data detection, using a surface sensor to measure vibrations in the pipe string which are generated as a result of the propogation of the encoded pulses through the drilling mud.

Abstract: A transducer is described especially designed for use in providing acoustic transmission in a borehole. The transducer includes a multiple number of magnetic circuit gaps and electrical windings that have been found to provide the power necessary for acoustic operation in a borehole while still meeting the stringent dimensional criteria necessitated by boreholes. Various embodiments conforming to the design are described. Moreover, the invention includes transition and reflector sections, as well as a directional coupler and resonator arrangement particularly adapted for borehole acoustic communication.

Abstract: Gas influx into a wellbore, which is commonly referred to as a "kick", is detected during active drilling of the borehole. In a preferred embodiment of the invention a determination of mud pump noise round trip transit time T by evaluating a function T=(n-.PHI./2.pi.)f where .PHI. is the phase between standpipe and annulus signals and f is the frequency of a drill fluid oscillation caused by a mud pump and n is an integer which is incremented or decremented until the rate of change of T with respect to frequency is zero. An alarm signal is generated when the rate of change of T with respect to time exceeds a predetermined threshold. In another embodiment of the invention a determination of the Doppler frequency shift of a mud pump signal expressed as a ratio signal, .DELTA.f/f.sub.0 where .DELTA.f is the change in frequency measured at the annulus from the frequency f.sub.0 of the mud pump signal measured at the standpipe.

Abstract: A method is presented for obtaining borehole measurements using measurement-while-drilling apparatus wherein mud pulse telemetry signals are decoded from the annulus pressure signals (as opposed to the standpipe pressure signals). The data bearing signals are enhanced by combining the annulus pressure signals and standpipe pressure signals using addition, multiplication or correlation techniques.

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 mud pulser for measurement-while-drilling applications is disclosed which employs piezoelectric transducers to provide for variations in the mud flow through a mud pulser sleeve. The piezoelectric transducers used in the mud pulser are comprised of two piezoelectric elements bonded together in a bender bar transducer configuration, thin metallic sheets to improve the rigidity of the transducer and to protect the ceramic material and electrodes from the effects of abrasive drilling fluid, and simplified mounting means.

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: In conducting measurement operations in drill holes useful downhole information is obtained by selectively filtering data signals carrying the information from mixed signals. The mixed signals result from a mixture of the data signals and interfering signals. The data signals are arranged in a coded sequence of individual signals having a characteristic shape. Control signals representing the characteristic shape are produced. The mixed signals, which are received on the surface from a downhole location, and the control signals are converted to resultant signals that represent the data signals, wherein the effect of interfering signals is diminished.

Abstract: Improved techniques are provided for drilling a deviated borehole through earth formations utilizing a rotary bit powered by a drill motor, and for obtaining information regarding the borehole or earth formations while drilling. An inclinometer is positioned below the drill motor and within a sealed cavity of a housing fixed to a drill motor sub, and a transmitter within the sealed cavity forwards acoustic or radial wave signals to a receiver provided in a measurement-while-drilling tool. The MWD tool may be provided within a non-magnetic portion of the drill string, and further houses an accelerometer for sensing borehole direction. Both borehole inclination and directional signals are transmitted to the surface by the MWD tool, and the drilling trajectory is altered in response to the signals.

Abstract: In accordance with the present invention, several methods are presented for the detection of gas into an offshore marine riser (e.g., riser gas). In a first embodiment of this invention, an acoustic transmitter is positioned on or nearby the subsea blowout preventor stack and imparts continuous low frequency waves into the annular fluid in the marine riser. These imparted waves define pressure perturbations which are received by a pressure transducer positioned on the riser at a location above the acoustic transmitter. Gas detection in the riser is then indicated by determining the rate of change of certain characteristics of the output. The output characteristics are preferably the moduli and phase angles of the acoustic fundamentals and their harmonics.

Abstract: The short hop communication link includes a sensor module positioned downhole from a motor in a well. The module includes sensors that monitor operational, directional and environmental parameters downhole and provide an electrical data signal indicative thereof. Sensors may also be positioned in the drill bit for obtaining parameters related to the bit, and communicating data signals reflecting the sensed parameters to the sensor module. The sensor module includes a transceiver, with an annular anrenna, for transmitting electromagnetic sensor data signals to a point above the motor. A control module, which also includes a transceiver with an annular antenna, is located above the motor, and receives the electromagnetic signals from the sensor module reflecting the sensed parameters. In addition, the control module is capable of transmitting command signals to the sensor module requesting data regarding desired parameters.

Abstract: Gas influx into a wellbore, called A "kick", is detected by two different, yet complementary methods during active drilling of the borehole. The first method is based upon the existence of standing wave patterns generated by pressure oscillations of the drilling rig mud pumps. Such standing wave patterns form time sequences of maximum and minima as a gas slug moves upwardly in the annulus. The time between such peaks of such oscillations is measured and forms the basis for generation of one first kick signal. A continuous increase in the phase between annulus and drill string standing waves forms the basis for another standing wave kick signal. The second method uses acoustic signals from a downhole source near the bottom of the borehole which are transmitted at different speeds in the annulus mud and in the interior drill string mud, where the annulus mud may be gas cut. A difference in arrival time between the signals is determined, and if large enough, causes a second kick signal to be generated.

Abstract: This invention deals with a telemetering system in logging while drilling which utilizes pressure pulses in the drilling fluid circulation system. More specifically this invention deals with generation of pressure pulses in the "regime of hydraulic shock waves" as distinct from the "regime of slow variation of pressure." Both regimes have been defined in the disclosure. A means has been provided for generating hydraulic shock waves by rapidly changing the rate of flow of the circulation fluid by means of a downhole valve. The downhole information controls the actuation of the valve which generates a succession of wavelets each of which comprises two distinguishable pulses of opposite polarity. The signal received at the surface is processed by a digital filter system in order to improve the signal to noise ratio.

Abstract: Methods for recovering a LWD or MWD data signal in the presence of mud pump noise are provided and generally comprise calibrating the drilling mud pressure as a function of the mud pump piston position, and then tracking the piston position during transmission of the LWD or MWD data signal and using the calibration information to subtract out the mud pump noise. Calibration is accomplished in the absence of the LWD or MWD data signal to provide a correlation between mud pump piston position and the drilling mud pressure. Then, when the LWD or MWD data signal is being generated, the mud pump piston position is tracked such that the pressure due to the pump can be subtracted and the LWD or MWD signal recovered.

Abstract: Variable control of the stroke and timing of the poppet in a pressure pulse generator system provides desired control for varying down hole conditions. A stepper motor interconnected to the poppet provides variable acceleration and variable position for the poppet under the control of a motor controller and motor driver which establish the number of steps and timing of steps for the motor. Various valve position profiles are provided in a memory for specific stroke and acceleration operation of the valve under varying down hole conditions and signaling requirements.

Abstract: Methods and apparatus for telemetering information between spaced locations in a well drilling system including a borehole filled with drilling fluid, including transmitting at a first location, which may be at the earth's surface, a sequence of pressure pulses, and detecting at a second location, which may be at downhole equipment located in the drill string adjacent the drill bit, the pressure pulses.

Abstract: A downhole signal generating mud pulser has a poppet and orifice signal valve to variably resist the drilling fluid stream. The poppet is upstream of the orifice and is moved by a piston in fluid communication with opposite flow related sides of the signal valve such that more pressure drop across the valve applies more piston force to open the valve. The poppet is spring biased toward the orifice and the piston force and spring balance when a preselected operating pressure exists. A servo valve controls flow in a by-pass loop to apply additional pressure to the piston to create a signal pulse when open. The servo valve is urged closed by flow in the servo loop and the closing is retarded by a dashpot to determine signal duration. The servo valve is spring biased to open and is automatically latched closed by a latch that responds to a solenoid actuated to release the servo valve.

Abstract: An apparatus for transmitting data to the surface of the earth in a borehole having a tubular drill string for circulating drilling fluid between the surface of the earth and downhole including a signal generator for providing electrical signals indicating a measured downhole condition, a valve within the apparatus moveable between a closed and an open condition for controlling, at least in part, the flow of drilling fluid, the valve being moved from closed toward open condition by the application of a first force, such as of a solenoid, and sequentially by a second force, such as a hydraulic fluid pressure differential across a piston to rapidly move the valve to the open condition, thereby creating a negative pressure pulse in the drilling fluid which pressure pulse is receivable at the earth's surface.

Abstract: A method of and a device for remotely-controlling at least one piece of drill string equipment from an instruction issued from the surface. The method includes issuing from the surface a first information sequence to cause a first predetermined action according to a predetermined sequence, detection of a condition indicative of a second sequence resulting from the first sequence, comparison of this second sequence with another predetermined sequence, and operating the equipment only if there is similarity between the latter two sequences. The method can be applied to actuation of a variable-angle bent element.

Abstract: The present invention comprises a method and apparatus for estimating and identifying the channel filter characteristics of the drilling fluid communictions channel (e.g. standpipe) based on surface decoding of the MWD data signal. The channel filter characteristics can be mathematically defined by the transfer function of the channel. The transfer function is a mathematical model defining the input-output relationship of a physical system. The present invention may also characterize the channel filter defined by the drilling mud in the annulus between the borehole and the drillstring.

Abstract: A method and apparatus for establishing a remote communications link from the rig floor to the downhole MWD system is presented. In accordance with the present invention, the state of a physical condition downhole is changed in a predetermined timed sequence. This state change is controlled on the surface at the drilling platform and detected downhole by the MWD system. The desired operating mode of the MWD system is then determined based on the detected time sequence of the state changes. Preferred embodiments of the present invention utilize two different state changes which are detectable downhole and which can be controlled at the surface. In a first embodiment, the state changes comprise a preselected timed sequence of powering the MWD system up or down. This power cycling is accomplished by operating the mud pump in an ON/OFF sequence which will cause the MWD turbine to similarly be powered up or down.

Abstract: The flow rate of the drilling mud within a drill string is measured by measuring the doppler frequency shift in an acoustic signal propagated from a first acoustic transducer to a second acoustic transducer laterally separated from the first acoustic transducer. Each of the transducers are disposed within the principal flow of the drilling mud. The degree of doppler shift is a measure of the flow rate of the drilling mud between the two transducers. Variations in the flow rate of the drilling mud as measured by the transducers downhole are used to transmit information or commands from the well surface to a downhole microprocessor coupled to the output of the transducers.

Abstract: A means to transmit recorded data through a fluid medium is disclosed. The preferred embodiment incorporates a positive displacement fluid pump having constant pressure pumping means connected to pump fluid through a drill string for drilling oil wells. A variable orifice means is located down hole in the drill string which changes orifice diameter responsive to sensed data. The pumped fluid is displaced by a pumping piston driven by a second piston powered by constant pressure hydraulic fluid. The pumped fluid is held at a constant pressure so that a change in orifice diameter will change the volume of the flow through the orifice and likewise change the volume of flow of the hydraulic drive fluid. The flow rate of the hydraulic drive fluid is thus gauged to thereby record the orifice diameter change and in turn receive signals transmitted by the change in orifice diameter.

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 unipolar, RZ, constant width pulse telemetry is achieved in the combinatorial set, or any desired subset of pulse sequences thereof. Each input datum W is in one-to-one correspondence with a particular pulse sequence and the correspondence of datum with pulse sequence and vice versa is implemented by any selected ordering of the pulse sequences of the combinatorial set together with a successive comparison of the magnitude of the datum with the cumulative combinatorial capacity of the set.

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: The filtering technique of the present invention cancels or minimizes noise in data signals found to be caused by dynamic variations in the drilling process. It has been discovered that the measurement of surface vibrations in the drill string and their effects on certain drilling equipment such as rotary table torque contains information that can be used to remove some or all of the pressure disturbance caused by these dynamic variations (vibrations). The result of removing some or all of the dynamic variation induced noise from the measurment-while-drilling (MWD) data signal yields a better signal to noise ratio (SNR) and therefore improves decoding of the MWD signal. In accordance with another important feature of the present invention, it has been found that improved SNR results from taking the first derivative with respect to time of the torque measurement. This first derivative measurement more closely resembles the actual disturbance in the standpipe pressure (SPP).

Abstract: Disclosed are improvements pertaining to measurement while drilling apparatus, methods, and systems, including: generation of mud pulse pressure variations in a regime of hydraulic shock waves; transmission of information carrying signals via mud pressure variations which include various interfering signals generally termed "noise" and employing special techniques involving digital filters for accomplishing reception of said information carrying signals; providing hydraulic means to automatically effect periodic closing of the valve means that produces the information carrying signals; providing electrical means to inhibit valve means operation in case of electrical failure in downhole apparatus; providing means which serve to greatly increase the number of satisfactory actuations of said valve means attainable without downhole battery recharge or replacement; providing unique pulse time codes which permit substantial increase in rate of information transmission and the accuracy and precision of such transmis

Abstract: A measurement while drilling apparatus for transmitting information carrying signals by fluid pressure changes in a borehole fluid circulation system having a flow restriction causing a high pressure zone and a low pressure zone, the apparatus having a passageway interconnecting the zones and a solenoid actuated valve interposed in the passageway, a sensor for sensing the magnitude of downhole measurements and for generating a succession of electric voltage changes indicative of the magnitude, a capacitor and a source of electric current for charging the capacitor, a circuit responsive to the sensor electric voltage changes for initiating successive discharges of the capacitor, which discharges are applied to the valve solenoid to produce successive openings and closings of the passageway thereby generating pressure changes in the borehole fluid circulation system.

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.