Abstract: An improved servo-driven pulser is disclosed, for use in measurement while drilling applications. In the pulser, a battery powered on-board DC electric motor is used to operate a servo-valve, which in turn adjusts internal tool fluid pressures to cause operation of a main valve to substantially reduce mud flow to a drill bit, thereby creating a positive pressure pulse detectable at the surface. De-energizing the motor driving the pilot valve results in re-adjustment of internal fluid pressures, causing the main valve to reopen, thereby terminating the pressure pulse.

Abstract: Systems are disclosed for securing near vertically deployed seismic detector systems in a cased well borehole from oscillatory motion during a seismic survey. In one embodiment a generally cylindrical body member of an unsymmetrical shape having one flat side is used opposite a selectably extensible backup locking arm. In a second embodiment a generally symmetrical cylindrical body member having sets of four essentially coplanar contacting feet disposed at 90 degree circumferential spacing an opposite ends is provided. The sets of locking feet on opposite ends of the tool body member are phased 45 degrees apart circumferentially with respect to each other. Locking edges and feet may be magnetically assisted if desired.

Abstract: A downhole tool containing instruments and a pulser is landed within a string of drill pipe. The pulser has a pulser body and an orifice on a lower end. A piston slides within a bore in the body and has a signal poppet on a lower end. In an extended position, the signal poppet extends into and obstructs the orifice to reduce the flow of drilling fluid. In an open position, the signal poppet does not obstruct the orifice to increase the flow of drilling fluid. A bidirectional solenoid valve is located above the piston and has upper and lower electromagnetic coils and an axially moveable rod. The rod is movable between a closed position in an opening in the body and an open position away from the opening. The rod is moved to both positions in response to the instruments which sends signals to the coils. The mud pulser also has an on/off flow switch which is actuated by the commencement of mud circulation. Initially, the rod is in the closed position.

Abstract: A method for monitoring production mineral reservoirs, the method comprising: permanently installing a geophone in a borehole; generating a first set of seismic waves; receiving a first set of seismic data with the geophone; recording the first set of data of said receiving a first set of seismic data; generating a second set of seismic waves after sufficient time has passed for conditions in the reservoir to have changed from the generating a first set of seismic waves; receiving a second set of seismic data with the geophone; and recording the second set of seismic data of said receiving a second set of seismic data. A method for installing instruments below the surface of the earth, the method comprising: drilling a borehole with a drill apparatus; inserting an instrument in the borehole; and permanently fixing the instrument in the borehole.

Abstract: A clamped receiver array using coiled tubing conveyed packer elements is disclosed and described. The receiver array is adapted to be received within a borehole and is therefore particularly useful for borehole seismology. The receiver array has a plurality of receivers connected together by a signal cable. The receivers include sensors which can be 3-component geophones. The apparatus is further provided with a fluid conduit running essentially parallel to the signal cable, the fluid conduit having expansible sections located adjacent to the receivers. The expansible sections expand in response to an increase of fluid pressure within the fluid conduit, contacting the associated receiver and thereby pushing the receiver into a coupled or clamped contact with the casing in the wellbore.

Abstract: A receiver section for an acoustic oil well logging tool comprised of a plurality of receiver sub-units connected longitudinally within a rigid tubular member. Each receiver sub-unit has a series of acoustic wave sensors located for receiving and detecting monopole, dipole, quadrupole and unipole waveforms. Separate channels are provided for conveying waveforms data from each receiver sub-unit to an above ground data processing unit. Each receiver sub-unit also includes a compensating sensor for detecting tool vibrations and for producing signals which are combined with waveform data in the processing unit to eliminate the effects of tool vibration.

Abstract: A magnetic coupling for substantially synchronously transferring linear motion through a non magnetic barrier from a first movable element to a second movable element. The coupling comprises magnets disposed at spaced apart locations along the first element. The magnets each have a magnetization direction substantially perpendicular to a direction of motion of the first element along the non magnetic barrier. The coupling includes magnets disposed at spaced apart locations along the second element at locations corresponding to locations of the magnets op the first element. Each of the magnets on the second element has a magnetization direction inclined at an oblique angle with respect to the magnetization direction of the corresponding magnet so as to capture magnetic flux from the magnets on the first element when either of the elements is moved along the barrier.

Abstract: An acoustic logging tool having an acoustic transmitter and at least one acoustic receiver longitudinally spaced from the transmitter is lowered into a borehole fluid within a tubular member having a known resonant frequency. A pulse of acoustic energy is then transmitted into the tubular member, and acoustic energy traversing the tubular member and formation is detected at the acoustic receiver. A frequency domain transformation is performed on the detected acoustic energy and a cement bond evaluation is performed by comparing transformed detected acoustic energy amplitudes within a predetermined range of the resonant frequency of the tubular member, effectively filtering out acoustic energy which traverses the formation surrounding the tubular member.

Abstract: An apparatus and method are disclosed for eliminating a noise signal from at least one source during an acoustic measurement of a subsurface geological formation or borehole. The apparatus includes a longitudinal body for positioning in the borehole and a transmitter supported by the body for transmitting acoustic signals into the formation and borehole. A sensor, substantially isolated within the body, is used to detect one or more noise signals and a receiver is carried by the body for receiving acoustic signals traversing the formation and borehole, and for receiving one or more noise signals. A processor is connected to the sensor and receiver for processing the acoustic signals and noise signals coupled from the receiver and the noise signal coupled from the sensor into a preferred formation or borehole signal by determining the noise signal received at the receiver using the noise signal received in the sensor and a propagation factor for the noise signal between the sensor and receiver.

Abstract: A device for coupling a receiver system with the wall of a well (1) bored in the ground comprises at least one sensor (11;12) sensitive to vibrations, structure (14,15) for applying the system against the wall of said well at the two ends of the system. A surface for supporting the system against the wall, arranged between the applying structure, has a radius of curvature essentially identical to the radius of curvature of a transverse section of the well so that this contact surface (MN) between said system and the wall follows a portion of a cylinder contained within an arc equal to at least 90.degree..

Abstract: A method for monitoring production mineral reservoirs, the method comprising: permanently installing a geophone in a borehole; generating a first set of seismic waves; receiving a first set of seismic data with the geophone; recording the first set of data of said receiving a first set of seismic data; generating a second set of seismic waves after sufficient time has passed for conditions in the reservoir to have changed from the generating a first set of seismic waves; receiving a second set of seismic data with the geophone; and recording the second set of seismic data of said receiving a second set of seismic data. A method for installing instruments below the surface of the earth, the method comprising: drilling a borehole with a drill apparatus; inserting an instrument in the borehole; and permanently fixing the instrument in the borehole.

Abstract: The present invention is directed to sonic logging while drilling. A transmitter and at least one receiver are mounted on a drill collar for performing sonic investigations of the formation traversing a borehole. It has been discovered that a drill collar has a natural stop band or notch where acoustic energy propagating in this frequency range is severely attenuated. Thus, to reduce drill collar acoustic coupling, the transmitter is operated within this natural stop band of the drill collar. An imperforate stop band filter is also included between the transmitter and receiver to amplify the natural stop band. The transmitter is mounted transvere to the longitudinal axis of the drill collar, and is preferably mounted within means that reduce drill collar acoustic coupling.

Abstract: An acoustic formation logging tool includes a transmitter, a receiver, a tube wave absorber, and a digital signal processing section. The transmitter includes an electromagnetic actuator based on capacitive discharge through a coil, producing an intense magnetic pressure which causes an actuator to move into an oil-filled acoustic waveguide. The actuator includes a pusher plate with holes that reduces cavitation and is capable of operation at great depths commonly encountered in oil well logging. Pulse power and spectrum of the acoustic transmitter are sufficient to measure either reflections from distant geological structures or waves propagating through the formation near the borehole. A positive acoustic pulse and a symmetric negative acoustic pulse are generated by action of the actuator on the acoustic waveguide.

Abstract: A method for estimating porosity of an earth formation from measurements of acoustic energy traversing the earth formation and from measurements of seismoelectric voltages generated in the formation in response to the acoustic energy. The method includes the steps of measuring the acoustic energy traversing the earth formation and measuring said seismoelectric voltages generated in response to the acoustic energy traversing the formation. A seismoelectric signal is synthesized from the measurements of the acoustic energy using an initial value of the porosity. A difference is determined between the synthesized seismoelectric voltages and the measured seismoelectric voltages. The initial value of porosity is adjusted, and the steps of synthesizing the seismoelectric voltages from the acoustic signal, determining the difference, and adjusting the value of porosity are repeated until the difference drops below a predetermined threshold or the difference reaches a minimum value.

Abstract: A gas gun is provided for generation of an acoustic pulse and subsequent detection of return reflections from the annulus of a well. The system includes a gas gun and a hand-held gas source. The hand-held gas source comprises: a two-part housing forming a chamber for receipt of a small CO.sub.2 gas cartridge commonly used for CO.sub.2 target pistols; means for piercing the gas cartridge and pressurizing the chamber; a coupling for releasable connection to a delivery assembly; a passageway leading from the chamber to the coupling; and a first valve in the passageway for controlling release of gas from the chamber.

Abstract: The invention relates to a device for exploring an underground formation crossed by a well inclined significantly to the vertical.

Abstract: An acoustic sensor for use as part of a drill string in a borehole has an acoustic transducer which vibrates the drill bit in contact with the rock at the end of the borehole to generate acoustic signals in the rock. These acoustic signals propogate through the rocks ahead of the drill bit and are reflected and scattered to return to an acoustic sensor contained within the drill string.

Abstract: The present invention is directed to sonic logging while drilling. A transmitter and at least one receiver are mounted on a drill collar for performing sonic investigations of the formation traversed by a borehole. It has been discovered that a drill collar has a natural stop band or notch where acoustic energy propagating in this frequency range is severely attenuated. Thus, to reduce drill collar acoustic coupling, the transmitter is operated within this natural stop band of the drill collar. An imperforate stop band filter is also included between the transmitter and receiver to enhance the natural stop band. The transmitter is mounted transverse to the longitudinal axis of the drill collar, and is preferably mounted within means that reduce drill collar acoustic coupling.

Abstract: A system for eliminating the tool mode signal from a received combined signal comprising both tool mode and formation mode components, comprising: a formation receiver for receiving said combined signal, a reference receiver for receiving a tool mode reference signal, a filter for processing said tool mode reference signal and generating a predicted tool mode component of the combined signal, and a summation element for subtracting said predicted tool mode component from said combined signal and generating a predicted formation mode component. The filter preferably incorporates a portion of the output of the summation element as an error signal, enabling the filter to adapt to changing conditions and update the algorithm on which it makes its predictions. According to an alternative system, an average value for the tool mode signal is updated according to a moving average to which new data points are added as they become available.

Abstract: A method and apparatus is disclosed to identify fluid hydrocarbon flow rates in a flow line such as a pipeline or a producing oil well having a unidirectional fluid flow including moving an acoustic tool through a flow line. Acoustic energy is transmitted into the fluid flow. The acoustic energy is then received when it is reflected back by interfaces within the fluid flow. The reflected acoustic energy is transformed into electrical signals. The electrical signals are rectified. The amplitude peaks of the rectified electrical signals are determined. The travel times of the amplitude peaks are also determined. The amplitude peaks and the time values are used to determine hydrocarbon gas and the hydrocarbon liquid in the hydrocarbon fluid flow in the oil well. A transducer within the acoustic tool rotates three hundred sixty degrees six times per second. This enables us to obtain holdup and velocities for the total flow around the tool even in non ideal operating conditions such as deviated wells.

Abstract: An acoustic wave transducer useful in sonic logging while drilling a borehole through an adjacent earth formation includes an array of transducer elements mounted circumferentially around a drill collar. The elements are bonded in an elastomer ring that is received in an external groove in the collar and are protected by a shield having windows. The elements are electrically connected in parallel so that when excited by an electrical pulse, the elements generate a monopole acoustic wave that propagates out into the formation. When used as a receiver, the electrically connected array of elements detect averaged acoustic waves from the formation around the circumference of the drill collar and have minimum sensitivity to acoustic multipole waves traveling through the drill collar.

Abstract: A method and apparatus for determining the various components of a multi-phase fluid flow in a defined area includes using an acoustic transceiver tool to direct a beam of acoustic energy toward the fluid flow in a producing well or a horizontal line. A signal is generated when the reflection of the beam of acoustic energy returns and is detected. The signal is rectified and recorded as a measure of oil flow rate within the well. The amplitude peaks are identified and areas around each peak are determined. Two areas of the rectified signal are defined relating to the determined amplitude peaks. The rectified signal under each area is integrated to provide an indication of fluid flow and the strength of the signal reaching the casing. A ratio is determined from the integration results of the two areas. The magnitude of this ratio provides an indication of the extent of the presence of gas in the fluid flow.

Abstract: A dipole acoustic well logging instrument including an acoustic transmitter. Receiver sections are disposed at axially spaced apart locations from the acoustic transmitter. Each receiver section includes an outer shoulder at each end adapted to be placed in acoustically isolated contact with an internal shoulder of a connector coupling when the instrument is in tension. The outer shoulders have an acoustically isolating material disposed on their surfaces. The receiver sections include an inner shoulder at each end adapted to be placed in direct contact with an external shoulder of the connector coupling when the instrument is in compression. The instrument includes one connector couplings disposed at each end of each receiver section to couple the receiver sections to each other and to the remainder of the instrument. At least one receiver element is disposed in a passage formed into each of the receiver sections.

Abstract: An acoustic well logging tool is shown having a transmitter section and a receiver section spaced apart by a semi-rigid housing. The semi-rigid housing includes a number of rigid tubular members which are joined by interlocking lobes which permit relative movement between the tubular members but which prevent the separation thereof. Gaps between the interlocking lobes are filled with a connecting material which differs significantly in acoustic impedance from the material of the remainder of the housing, whereby acoustic energy passing from the transmitter section along the body of the tool is delayed and attenuated.

Abstract: A standoff compensation system is disclosed for use in an acoustic LWD system. An acoustic transducer is provided to measure the standoff distance between the logging tool and the borehole wall. The present invention includes a downhole processor for determining an index value which is used to align received acoustic formation signal measurements based upon the measured standoff distance. The index value can either be calculated by the downhole processor or can be retrieved from a pre-calculated look-up table in ROM. The processor then shifts the received acoustic formation signals based upon the index value assigned to each formation signal. The aligned acoustic formation signals are stacked, so that a single acoustic formation signal can be obtained for each firing period and either stored in downhole memory, used immediately, or transmitted by telemetry to the surface. The firing of the acoustic formation transmitters occurs in a rapid firing mode, followed by a relatively long idle.

Abstract: Method for measuring the propagation velocities of ultrasonic acoustic waves through rock fragments which includes the steps of (a) introducing the fragment in a coupling fluid between a pair of piezoelectric transducers capable of generating highly damped ultrasonic acoustic waves; (b) passing highly damped ultrasonic acoustic waves through the fragment, said waves being generated by a pulse generator with a pulse width varying from 0.1 .mu.s to 20 .mu.s; (c) visualizing the obtained electric signals by an oscilloscope with a resolution of at least 10.sup.-2 .mu.s; and (d) measuring the transit time of the waves themselves. The ultrasonic acoustic waves may be compressional or shear waves. In one embodiment the coupling fluid has a viscosity varying be 200 and 800 poises.

Abstract: Disclosed is a sonic well tool for performing acoustic investigations of subsurface geological formations penetrated by a borehole, and a method of logging formation data. The well tool generally includes a longitudinally extending body for positioning in said borehole. The tool also includes a transmitter supported by the body for transmitting acoustic energy, and at least two receivers. One of the receivers is positioned on the interior of the sonic tool to receive the acoustic signals that traverse the sonic well tool. The second receiver is positioned on the exterior of the sonic tool and receive sonic signals that traverse the sonic tool and those that traverse the formation. The apparatus further includes a processor for subtracting the well tool signal of the first receiver from the combined well tool and formation signal of the second receiver.

Abstract: A poppet and orifice mud pulser assembly is disclosed for use in an MWD system. The mud pulser is capable of generating pressure pulses in the column of drilling mud of various amplitudes to increase the data rate of the mud pulse telemetry system. The mud pulser includes a piston assembly that positions the poppet with respect to the orifice. The piston assembly comprises part of a by-pass conduit which defines a mud flow path around the orifice. Mud flow in the piston assembly generates a force tending to shut the poppet, because the surface area of the piston A.sub.2 is greater than the surface area of the poppet A.sub.1. Mud flow through the conduit (and thus through the piston) tends to force the poppet into a closed position because the force on the piston is greater than the force on the poppet, because of the greater surface area of the piston. A pilot valve is provided to enable and disable flow through the conduit, thus allowing the poppet to open and close.

Abstract: A production logging tool for use in deviated wellbores is provided having an elongate tool body and an elongate sensor probe that is capable of lateral movement relative to the tool body. The sensor probe is connected to the tool body by a mechanism serving to deploy the sensor probe such that it is oriented across the wellbore. The tool body has a defined weight and the probe has a weight less than the defined weight, thus causing gravity induced orientation of the sensor probe so as to extend from top to bottom of the fluid passage for sensing all phases of the fluid present therein. The sensor probe is typically of elongate configuration and may support a single elongate sensor or a plurality of independent similar or dissimilar sensors arranged in spaced relation along the length of the probe. Orientation of the sensor probe across the borehole is accomplished mechanically by coil or leaf springs or by a hydraulically or pneumatically powered mechanism or by an electric motor driven mechanism.

Abstract: A surfactant composition is used to repel down-hole fluids such as crude oil and water to prevent their adherence to a down-hole instrument for an extended period of time. A down-hole fluid repelling surfactant, preferably in the form of a liquid solution, is applied to an exterior surface of the instrument, dried, and polished to prevent down-hole fluids from adhering to the surface. A preferred liquid surfactant solution contains as an active ingredient an amount of tricresyl phosphate effective to repel down-hole fluids such as oil and water.

Abstract: The mobile seismic system according to the invention is made up by interconnecting reception sections (T1) and of anchoring sections (T2), and possibly emission sections, the assembly being suspended in the well by means of an electro-carrying cable (3). The first sections (T1), which are filled with liquid, are delimited at least partly by a wall transparent to acoustic waves. They contain each one or several hydrophones and an electronic module of acquisition of the signals picked up. The second sections (T2) comprise a body provided with retractable anchoring means (13) and with motor means, either autonomous, or connected, by a hydraulic line running along the reception system, to common motor means located preferably in a lower section so as to be used as a ballast weight. The reception system may be continuous or made up of several parts connected to each other by electric or electro-hydraulic linking means. The system is suitable for seismic prospecting in wells for example.

Abstract: The signal-to-noise ratio of televiewer signals from a rotary sidewall acoustic-beam scanner is improved by replacing the volume of borehole drill fluid that lies in the path of the acoustic beam with a solid medium characterized by a lower coefficient of attenuation than that of the drill fluid.

Abstract: The invention concern a combination well logging device adapted to be moved inside a borehole to measure the properties of geological formations through which the borehole passes.The device according to the invention comprises a series of elongate logging sections mounted end to end, including a first section adapted to be maintained with a generatrix applied against the wall of the borehole, a second section comprising a body and a measurement pad adapted to be spaced radially from the body for application against said wall, a third section adapted to be kept space from said wall, and first and second hinges connecting the second section to the first and third sections respectively in order to allow respective angles of inclination between the second section and the first and third sections.

Abstract: A seismic profiling tool is moveable on a wireline in a well bore for exploring subsurface formations adjacent the well bore at various source-receiver spacings. The tool includes at least one acoustic source, an acoustic receiver assembly, and a spacing system for providing variable spacing and relative movement between the source and receiver assembly.

Abstract: Disclosed is a sonic well tool for performing acoustic investigations of subsurface geological formations penetrated by a borehole. The well tool generally includes a longitudinally extending body for positioning in said borehole. The tool also includes a transmitter supported by the body for transmitting acoustic energy, and a receiver supported by the body for receiving acoustic energy. Finally, the tool includes an acoustic attenuation section positioned on the body between the transmitter and the receiver. This section includes one or more cavities defined by the body, inertial mass members positioned inside the cavities in a suitable manner to form a gap between the wall of the cavity and the inertial mass members, and an acoustical attenuation fluid in the gap. The method for attenuating sonic waves generally includes transmitting a sonic wave from the transmitter to the tool, passing the sonic wave through the acoustic attenuation section, and receiving attenuated wave at the receivers.

Abstract: A string of sondes is designed to be lowered down a borehole by means of a cable in order to detect the arrival of seismic waves therein, the sondes including retractable anchor means that are hydraulically actuateable and that are connected by a hydraulic circuit to a common source of hydraulic pressure. The string includes means for putting said hydraulic circuit to ambient pressure, said means being connected to said cable and being adapted to act on said hydraulic circuit in order to cause said anchor means to be retracted when a traction force exceeding a selected value is exerted on said cable.

Abstract: An acoustic formation apparatus is set forth. It utilizes the drill bit on a drill stem as the acoustic source. At a common azimuth and spaced vertically along the drill stem, first and second acoustic transducers are installed. They connect to first and second amplifiers, first and second band pass filters, first and second clipping circuits, a single delay circuit and a cross correlating circuit. The signals are received, filtered, amplified, clipped, one delayed, and then cross correlation is made utilizing variable time delays. The resulting cross correlation function is analyzed using a microprocessor which removes stationary correlation peaks and ignores very short correlation delay times.

Abstract: A surfactant composition is used to repel down-hole fluids such as crude oil and water to prevent remote viewing cameras from being obscured by such fluids, for extended periods of time. An effective amount of a down-hole fluid repelling surfactant, preferably in the form of a liquid solution, is applied to an exterior surface of an optical element of the viewing instrument, dried, and polished to prevent down-hole fluids from adhering to the surface of the optical element. A preferred liquid surfactant solution contains as an active ingredient an amount of tricresyl phosphate effective to repel down-hole fluids such as oil and water.

Abstract: The invention is a method and apparatus for measuring the quality of acoustic coupling between a wellbore wall and a borehole seismic sensor system. The system includes the steps of positioning the system at a desired depth in the wellbore and activating a locking mechanism powered by a DC motor. The motor then has broadband AC applied to it to cause vibration of the system. The output of at least one seismic sensor in the system is processed in a spectrum analyzer, and the result is checked for the presence or absence of natural resonance of the system. In a particular embodiment, the system response to the broadband AC is used to generate an inverse filter operator to compensate the system response to a geophysical survey for partial acoustic coupling.

Abstract: A non-destructive method of measuring physical characteristics of sediments to obtain a cross-sectional distribution of porosity and permeability values and variations, and of shear modulus and shear strength. A pair of boreholes have borehole entries spaced apart from each other at a predetermined distance, and a plurality of hydrophones are spaced at predetermined known positions. A pseudo-random binary sequence code generator as a source of seismic energy is placed into another borehole and activated to transmit pseudo-random wave energy from the source to the hydrophones. Seismic wave characteristics are measured in a multiplicity of paths extending from the source to the hydrophones, using cross-bore tomography.

Abstract: The orientation of vertical fractures in subsurface rock formations is determined. A cross-dipole logging tool collects four-component shear-wave seismic data through a formation interval of interest in a subsurface formation adjacent a well bore. A gyroscope is typically provided to indicate compass orientation of the logging tool. The collected seismic data are then transformed within a time window containing arrivals of the shear waves to a new coordinate system within which the motion of the shear waves becomes linear. In the new coordinate system, the shear wave data are processed to determine the presence and orientation of fractures in the formation.

Abstract: A sonic transmitter assembly for use in logging-while-drilling includes stacks of piezoelectric crystals that extend outwardly from a nodal plate member, and a generally tubular assembly that contains such stacks and has end portions that are sealingly mounted in diametrically opposed holes in a pipe member that forms a pan of the drill string. Spring mass isolator systems are employed to inhibit transmission of acoustic waves to the pipe member. Balanced mounting forces and the bilateral symmetry of the construction also inhibit transmission of acoustic waves to the pipe member, particularly waves which are asymmetric with respect to the longitudinal axis of the pipe member.

Abstract: A multi-mode receiver sonde having individual receiver stations within a semi-rigid receiver array. The semi-rigid receiver array is adapted to decouple noise (tool-mode noise and/or road-noise) at one location within the receiver array from other locations within the receiver array by using compliant spacers between the receiver stations to absorb and scatter the noise.In preferred embodiments, multi-mode receiver stations are presented which provide a common ground for output signals detected by the receiver stations. Additional embodiments provide for combining the output signals into composite signals which represent a selected borehole propagation mode.In one highly preferred embodiment, the use of transducer detectors which have a flat frequency response over a selected bandwidth allows for accurate comparisons between composite signals so that changes in phase and amplitude over distance and time can be determined.

Abstract: A sidewall contact parameter tool, adapted to be disposed in a mud-filled wellbore, includes a pad assembly, in accordance with the present invention, which is adapted to cut through mudcake and measure a parameter of a formation disposed under the mudcake. The wellbore wall includes a mudcake and an earth formation disposed under the mudcake. The pad assembly includes at least one formation parameter sensor, and the formation parameter sensor includes a base portion and a knife edge portion integrally connected to the base portion. The base portion of each formation parameter sensor is adapted to contact a surface of the mudcake but the knife edge portion is adapted to cut into the mudcake and contact or penetrate a surface of the earth formation disposed under the mudcake. The knife edge portion of each sensor includes an internal space or pinhole aperture, and a parameter sensing apparatus disposed within the internal space or aperture.

Abstract: A multi-mode receiver sonde having individual receiver stations. The receiver stations have transducers which have a flat frequency response over a selected bandwidth so that there is an approximately constant ratio in amplitude and substantially little phase difference between the response signal and an input acoustic signal from a liquid containing borehole.The wide-band output response signals are combined to form composite signals which represent selected borehole propagation modes. Accurate comparisons can then be made between the composite signals obtained by separate receiver stations so that changes in phase and amplitude over distance and time can be determined.In one highly preferred embodiment, the receiver sonde has a semi-rigid receiver array. The semi-rigid receiver array is adapted to decouple noise (tool-mode noise and/or road-noise) in one location within the array from other locations within the array by using compliant spacers between the receiver stations to absorb and scatter the noise.

Abstract: Method and apparatus for generating resonant broad band pressure waves in a fluid-filled wellbore for seismic exploration. In the preferred embodiment, a device is provided in a borehole; the device comprises a cylindrical choke body and a means at each end of the choke body for partially or completely blocking off the borehole and creating a fluid-filled borehole cavity. The fluid inside the cavity is oscillated to establish a standing pressure wave of a desired bandwidth in the fluid. The standing wave is radiated through the wellbore into the earth formation and is received by seismic detectors. The fluid is oscillated over a range of frequencies to generate more information about the earth formation.

Abstract: The invention relates to the principle of a probe to improve the quality of imaging logs in excavations, providing especially a good coverage of the wall 2 of the excavation by the beam of sensors 4 or electrodes. The basic component is constituted by a casing 6 moulded from a material of the elastomer type and made to allow it to be unfolded in the working position for the helically implanted zones of measurements 7, and applied against the wall 2.The material of the zones 7 of measurements is selected as a function of the parameter to be measured, the immediate but non-limiting applications concerning microresistive and acoustic imaging.The helical arrangement of the sensors 4 improves the coverage of the measurements with respect to conventional probes. Moreover, by eliminating the drilling mud 3 between the sensors 4 and the formation, this probe improves, in certain cases such as acoustic imaging for example, the response thereof and the quality of the measurements.

Abstract: The invention concerns an apparatus for the acquisition of a seismic signal transmitted by a drill bit, placed at the end of a drill pipe rotating about an axis of rotation.

Abstract: A method and apparatus by which elastic properties of rock formations are determined includes a downhole logging device which has two internal accelerometers mounted within to measure the acceleration of the device. A reference displacement of the device is determined by measuring the acceleration outside the borehole while the device is suspended in air. The output of the accelerometers is measured in the borehole. Integrating the acceleration outputs of these accelerometers twice yields the displacement in the borehole. Changes in the displacement of the device are indicative of various elastic properties of formations surrounding the borehole. Using two accelerometers to determine displacement allows the continuous logging of Young's modulus and other elastic properties of rocks surrounding a well bore. In an alternate embodiment, geophones are used to measure the velocity of the device and their outputs are integrated once to yield displacement.

Abstract: Pulse echo apparatus and methods are disclosed for measuring characteristics of a borehole while it is being drilled. A component of a bottomhole assembly, preferably a drilling collar, is provided with one or more ultra-sonic transceivers. A pulse echo sensor of the transceiver is preferably placed in a stabilizer fin of the collar, but may also be placed in the wall of the collar, preferably close to a stabilizing fin. Electronic processing and control circuitry for the pulse-echo sensor is provided in an electronic module placed within such collar. Such pulse echo apparatus, which preferably includes two diametrically opposed transceivers, generates signals from which standoff from a borehole wall may be determined. A method and apparatus are provided for measuring standoff and borehole diameter in the presence of drilling cuttings entrained in the drilling fluid. In a preferred embodiment, such signals are assessed by the electronic processing and control circuity to determine if gas has entered borehole.