Abstract: An acoustic isolator for attenuating through-tool acoustic signals comprises a plurality of u-shaped link members, where each link member has two sets of ears. A plurality of yoke members are adapted to fit between cooperating sets of ears. A plurality of pins connect the plurality of u-shaped link members to the plurality of yoke members for providing limited flexural compliance. The isolator may be made from metallic and/or composite materials.

Abstract: A method for improving ROP and reducing hazards in drilling subterranean wells by using an acoustical system 15 to look ahead of the drill bit 14, detects and analyzes geologic features ahead of the bit 14 which may be qualified as drilling hazards 17. Detection of such hazards 17 may facilitate use of more aggressively penetrating bits 14 such as PDC bits as opposed to roller cone bits. In addition, other drilling parameters may be adjusted to improve ROP due to the ability to timely respond to identified hazards 17 before they may be detrimentally encountered by the bit 14. The acoustic system 15 may look ahead of the bit 14 by at least 100 meters, using propagated acoustic waves 19 to locate changes in acoustic impedance which may represent drilling hazards 17. In addition, bulk resistivity ahead of the bit 14 may also be measured and used to locate drilling hazards 17.

Abstract: Methods and apparatus for attenuating waves in a bore hole, and seismic surveying systems incorporating the same. In one embodiment, an attenuating device includes a soft compliant bladder coupled to a pressurized gas source. A pressure regulating system reduces the pressure of the gas from the gas source prior to entering the bladder and operates in conjunction with the hydrostatic pressure of the fluid in a bore hole to maintain the pressure of the bladder at a specified pressure relative to the surrounding bore hole pressure. Once the hydrostatic pressure of the bore hole fluid exceeds that of the gas source, bore hole fluid may be admitted into a vessel of the gas source to further compress and displace the gas contained therein. In another embodiment, a water-reactive material may be used to provide gas to the bladder wherein the amount of gas generated by the water-reactive material may depend on the hydrostatic pressure of the bore hole fluid.

Abstract: An acoustic system and method for monitoring a hydrocarbon reservoir. Wellbore tube wave energy may be created by natural or ambient sources or tube waves may be excited intentionally. Wellbore tube wave energy is converted to seismic body wave energy at minor borehole obstructions or irregularities. Each obstruction or discontinuity position along the borehole has an associated unique waveform source coda that may be measured for processing the body waves radiated into the earth formation surrounding the well bore. A plurality of sensors detects the radiated seismic energy after the seismic body wave energy has transited intervening earth formations. The system may be employed for permanent monitoring of mineral resources and resource management. Measurements of reservoir characteristics may be acquired at many different times over the productive life of a reservoir.

Abstract: A plurality of heavy mass irregularities attached to an inner wall of the drill collar attenuate waves traveling through the collar. The plurality of heavy mass irregularities are spaced and sized for the maximum attenuation of acoustic pulses in a predetermined frequency range. The mass irregularities may be rings secured to the inner surface of the collar by neck pieces, extending outwardly from the outer circumference of the ring. The mass irregularities may be made of steel or tungsten and are between six and ten in number. The spacing of the irregularities may lie between twelve and fourteen centimeters. A center pipe may be included to isolate the irregularities from the fluid flow associated with the drilling operation. The pipe may be of a soft material such as rubber to reduce transfer of acoustic noise along the drill string. The irregularities may be in an oil based fluid with the pipe fitting closely in the center of the rings.

Abstract: A sleeve for an acoustic logging tool has a structure with a window section having fewer bars than a conventional sleeve separated by a slotted region with thin circumferential slots which are stress-relieved at the ends (“dumb-bell” shaped). Steel receiver mounts are provided for hydrophone pressure sensors and this, together with the axially oriented hydrophones makes the tool less susceptible to interfering vibration.

Abstract: A system for sensing subterranean acoustic waves emitted from an acoustic source includes a plurality of laser sources, a plurality of subterranean optical sensors, at least one optical detector, and electronics. The laser sources each emit light at a different frequency. The subterranean optical sensors receive the light and alter the light in response to the acoustic waves. The optical detector receives the altered light and outputs an electrical signal. The electronics receives the electrical signal and converts it into seismic data format. The hydrophone for sensing the acoustic signals is able to operate at pressures of at least 5,000 psi and temperatures of at least 130 degrees Celsius. A hydrophone may be housed in a cable having a diameter of less than about 1.5 inches. The hydrophone's sensor preferably includes a reference mandrel, two sensing mandrels, and a telemetry can, all of which are aligned in a coaxial, end-to-end configuration to reduce the profile of the hydrophone.

Abstract: A method and apparatus for placing acoustic devices in wellbores. The method comprises: providing a tubing with at least one anchoring device in the wellbore, where the anchoring device is extendable to the wellbore to exert a force on the wellbore; attaching at least one acoustic device to at least one anchoring device; placing the tubing in the least one acoustic device attached to the at least one anchoring device in the wellbore; and setting the anchoring device to extend to the wellbore to exert a force on the wellbore, thereby coupling the acoustic device to the wellbore. The wellbore system comprises a tubing that has an annular space between the tubing and the wellbore. At least one anchoring device is disposed on an outer surface of the tubing and extends to and exerts a force on the wellbore. An acoustic device is attached to the anchoring device.

Abstract: A regenerative combustion device having a combustion zone, and chemicals contained within the combustion zone, such as water, having a first equilibrium state, and a second combustible state. Means for transforming the chemicals from the first equilibrium state to the second combustible state, such as electrodes, are disposed within the chemicals. An igniter, such as a spark plug or similar device, is disposed within the combustion zone for igniting combustion of the chemicals in the second combustible state. The combustion products are contained within the combustion zone, and the chemicals are selected such that the combustion products naturally chemically revert into the chemicals in the first equilibrium state following combustion. The combustion device may thus be repeatedly reused, requiring only a brief wait after each ignition to allow the regeneration of combustible gasses within the head space.

Abstract: A method is disclosed for generating an image of earth formations penetrated by a wellbore. The method includes generating an initial model of the earth formations using formation resistivity measured by a direct current signal. A response to the initial model of an instrument used to make the direct current resistivity measurements is calculated. The calculated response is compared to the measurements of resistivity. The model is adjusted, and the calculating and comparing are repeated until a difference between the calculated response and measurements reaches a minimum. The adjusted model is refined based on resistivity measurements made using an electromagnetic measuring instrument, and the refined model is constrained using acoustic velocity measurements.

Abstract: One or more autonomous devices are deployed in the well to provide a moveable sensor source or obstruction for coupling a tube wave seismic signal into the formation adjacent the well bore. The autonomous devices move in the well and provide moveable obstructions or discontinuities which couple tube waves existing in the well bore or production tubing into the formation adjacent the well bore. Wellbore tube wave energy is converted to body wave energy at minor borehole obstructions or irregularities that become sources of seismic energy. A well bore may contain a plurality of minor obstructions or discontinuities. Each obstruction or discontinuity position along the borehole has an associated unique waveform source coda that may be measured for processing the wavefield radiated into the earth formation surrounding the well bore. A plurality of sensors detects the radiated seismic energy after the seismic energy has transited intervening earth formations.

Abstract: In one aspect, the invention involves an acoustic logging tool for performing acoustic investigations of subsurface geological formations. In one embodiment, the tool comprises a generally longitudinally extending tool body adapted for positioning in a borehole. At least one transmitter is mounted on the tool body to emit acoustic energy. At least one receiver is also mounted on the tool body at a location axially displaced from the at least one transmitter. The receiver is adapted to receive acoustic energy. An attenuator is also positioned along the body and includes at least one cavity having a plurality of particles disposed therein. The attenuator as disclosed herein may be applied to other logging tools for protecting tool components and enhancing measurement quality. Methods for attenuating acoustic energy transmitted through the body of an acoustic logging tool or other logging tools are also disclosed.

Abstract: A measuring device for measuring the elastic properties of a surface structure (3), comprising a probe (2) arranged within a housing (1), a transmitter and at least one receiver, the transmitter transmitting acoustic pulses and the receiver picking up the propagation behavior of the acoustic pulses in the surface structure (3), a control means (16) for generating acoustic pulses and an evaluating means (18) for the measuring signals received by the receiver, at least two adjacent measuring tips (4, 6) being connected as transmitting and receiving elements, the measuring tips being adapted to be set onto the surface structure (3) and having strip-shaped bi-morph elements (12, 14) carried by a holder (8, 10), wherein the measuring tips (4,6) are formed by the holders (8, 10) of the bi-morph elements (12, 14) and the strip-shaped elements (12, 14) have one side of one of their ends fastened to the holder (8, 10).

Abstract: A plurality of heavy mass irregularities attached to an inner wall of the drill collar attenuate waves traveling through the collar. The plurality of heavy mass irregularities are spaced and sized for the maximum attenuation of acoustic pulses in a predetermined frequency range. The mass irregularities may be rings secured to the inner surface of the collar by neck pieces, extending outwardly from the outer circumference of the ring. The mass irregularities may be made of steel or tungsten and are between six and ten in number. The spacing of the irregularities may lie between twelve and fourteen centimeters. A center pipe may be included to isolate the irregularities from the fluid flow associated with the drilling operation. The pipe may be of a soft material such as rubber to reduce transfer of acoustic noise along the drill string. The irregularities may be in an oil based fluid with the pipe fitting closely in the center of the rings.

Abstract: An isolator bar of acoustic instruments used in downhole applications is made of a substantially cylindrical tube of metal of the type from which downhole instrument housing is usually made. A plurality of slots are placed in the tube at angles which are between 10 to 80° angle relative to the longitudinal axis of the tube. The isolator bar is equipped with traditional mechanical means with which it is incorporated in the acoustic instrument, placed between an acoustic transducer and an acoustic sensor or sensors utilized in the instrument. The angled slots cause sound waves traveling through the isolator bar to travel through multiple and extended path to the acoustic sensor, without significantly weakening the structural strength of the isolator bar.

Abstract: A borehole tool including a tool body having and an anchoring mechanism, the anchoring mechanism having a drive mechanism including a motor, drive shaft, and clutch; an anchor arm moveable between first and second positions relative to the tool body; a push rod connecting the anchor arm to the drive mechanism; and a spring acting to bias the arm into a first position relative to the tool body. The push rod extends through the clutch mechanism and is engaged by the spring to bias the arm into the first position, and is also driven by the drive mechanism through the clutch to move the arm between the first and second position. The push rod may be connected to the anchor arm by a link. Measurement devices may be used to determine the position of the anchor arm or the tool body.

Abstract: A clamped receiver array using tubing conveyed packer elements is disclosed and described. The receiver array can be used for borehole seismology as well as marine bottom surface seismology. The receiver array has a plurality of receivers connected together by a signal cable. The apparatus is further provided with a fluid conduit running essentially parallel to the signal cable. The fluid conduit has a plurality of receiver deployment sections which are located proximate to respective receivers. The receiver deployment sections are responsive to an increase in pressure within the fluid conduit, causing the receiver deployment sections to operate to press the receiver against the inside of a wellbore or to a marine bottom surface. In one example the receiver deployment section uses pistons disposed in openings in the fluid conduit to push the receivers away from the conduit as pressure in the conduit is increased.

Abstract: An acoustic logging tool including an elongated body, one or more acoustic transmitters, one or more acoustic receivers, and a broadband acoustic absorption region. A substantial portion of the broadband acoustic absorption region is between the transmitter and the receiver. The acoustic energy absorber includes a first absorber for absorbing a first mode of acoustic energy and a second absorber for absorbing a second mode of acoustic energy. The acoustic absorption material used to make the acoustic absorbers has an acoustic impedance between 20% and 120% of the material used to construct the acoustic logging tool. The acoustic logging tool includes an elongated hollow tool body, an insert configured to be inserted into the tool body, and a ring configured to be inserted onto the insert. A first element is supported by the ring and exposed to a pressure field, and a second element is supported by the ring and exposed to a pressure field.

Abstract: In one embodiment the invention comprises a system for generating an image of an Earth formation surrounding a borehole penetrating the formation. Resistivity of the formation is measured using a DC measurement, and conductivity and resistivity of the formations is measured with a time domain signal or AC measurement. Acoustic velocity of the formation is also measured. The DC resistivity measurement, the conductivity measurement made with a time domain electromagnetic signal, the resistivity measurement made with a time domain electromagnetic signal and the acoustic velocity measurements are combined to generate the image of the Earth formation.

Abstract: Apparatus and methods are described for isolating in a drillstring a device from acoustic noise by introducing between the device and a source of acoustic vibration an noise isolating apparatus, wherein the noise isolating apparatus has adjacent zones of different acoustic impedance. The zones are preferably created by zones of different thickness and designed such that noise suppression occurs in a predetermined range of acoustic frequencies. In a preferred application the apparatus and method is used in combination with drillstring telemetry.

Abstract: A logging system has a sonde in a borehole, which transmits sonic waves with one or more dipole sources to optimally excite dipole flexural mode sonic waves in the borehole. The system first determines the Airy frequency of the borehole. Then, the dipole sources are fired at a dipole firing frequency selected based on the Airy frequency.

Abstract: A sleeve for an acoustic logging tool having a structure with a window section having fewer bars than a conventional sleeve separated by a slotted region with thin circumferential slots which are stress-relieved at the ends (“dumb-bell” shaped). Steel receiver mounts are provided for hydrophone pressure sensors and this, together with the axially oriented hydrophones, makes the tool less susceptible to interfering vibration.

Abstract: A dynamic force transducer for generating vertically oriented compressional forces and motions at the surface of a solid medium. A frame is rigidly coupled in direct contact with the solid medium surface. At least one pair of identical driver units are mounted to the frame to impart vertically oriented forces to the medium. Compliant springs support the drivers and introduce mechanical resonances. The driver units are excited to produce the vertically oriented pushing and pulling forces along a common collinear vertical direction. The driver units also impart either continuous or pulsed oscillatory forces to produce prescribed seismic compressional waves in the medium.

Abstract: A method for improving ROP and reducing hazards in drilling subterranean wells by using an acoustical system 15 to look ahead of the drill bit 14, detects and analyzes geologic features ahead of the bit 14 which may be qualified as drilling hazards 17. Detection of such hazards 17 may facilitate use of more aggressively penetrating bits 14 such as PDC bits as opposed to roller cone bits. In addition, other drilling parameters may be adjusted to improve ROP due to the ability to timely respond to identified hazards 17 before they may be detrimentally encountered by the bit 14. The acoustic system 15 may look ahead of the bit 14 by at least 100 meters, using propagated acoustic waves 19 to locate changes in acoustic impedance which may represent drilling hazards 17. In addition, bulk resistivity ahead of the bit 14 may also be measured and used to locate drilling hazards 17.

Abstract: A logging tool having a tool body, which can be positioned in a fluid-filled borehole, including a receiver section and a dipole transmitter; wherein the dipole transmitter includes a transducer with a shell having a reaction mass and a motor located therein, the motor operatively connecting the shell and the reaction mass such that only an outer surface of the shell is in contact with the fluid in the borehole. This new type of dipole source for well logging involves shaking all or part (axially) of a dipole tool body to produce a pure, broadband acoustic dipole signal while at the same time coupling as little energy as possible into the tool body. Important variations on this idea include a linear phased array of shaker sources, and active cancellation of tool borne noise.

Abstract: A plurality of heavy mass irregularities attached to an inner wall of the drill collar attenuate waves traveling through the collar. The plurality of heavy mass irregularities are spaced and sized for the maximum attenuation of acoustic pulses in a predetermined frequency range. The mass irregularities may be rings firmly coupled to the outer surface of the collar. Alternatively, the mass irregularities may be rings firmly coupled to the outer collar surface by neck pieces, extending inwardly from the inner circumference of the ring. The mass irregularities may be made of steel or tungsten. In another preferred embodiment, the mass irregularities are asymmetrically coupled to an outer collar wall for providing preferential directional attenuation.

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: One or more autonomous devices are deployed in the well to provide a moveable sensor source or obstruction for coupling a tube wave seismic signal into the formation adjacent the well bore. The autonomous devices move in the well and provide moveable obstructions or discontinuities which couple tube waves existing in the well bore or production tubing into the formation adjacent the well bore. Wellbore tube wave energy is converted to body wave energy at minor borehole obstructions or irregularities that become sources of seismic energy. A well bore may contain a plurality of minor obstructions or discontinuities. Each obstruction or discontinuity position along the borehole has an associated unique waveform source coda that may be measured for processing the wavefield radiated into the earth formation surrounding the well bore. A plurality of sensors detects the radiated seismic energy after the seismic energy has transited intervening earth formations.

Abstract: The invention is a method and apparatus for acoustic logging including one or more acoustic transmitters and one or more acoustic receivers. One or more of the elements of a set made up of the acoustic receivers and acoustic transmitters are spaced radially apart from one or more of the remaining elements of the set. The acoustic receivers and acoustic transmitters are configured along with electronics and software incorporated in the tool to allow the acoustic receivers and acoustic transmitters to act as multi-pole receivers and multi-pole transmitters, respectively. The tool is configured to compute one or more acoustic velocities and to provide storage for unprocessed and processed, compressed and error correction coded data. The tool is configured to provide the data for transmission to the surface.

Abstract: A VSP or reversed VSP type seismic prospecting method according to the invention allows disturbances contained in seismic recordings produced by tube waves propagating along wells and refracted in zones close to the surface to be minimized. The method disperses a gas under pressure, having preferably a high compressibility, capable of absorbing these tube waves. The gas may be generated by an explosive chemical reaction set off in situ, at a certain depth of the well (which may constitute the seismic wave source). The method has an application for seismic prospecting or drilling noise monitoring.

Abstract: A borehole tool, such as a seismic shuttle-type logging tool, including a tool body having at least one sensor package and an anchoring mechanism, the anchoring mechanism having a drive mechanism including a motor, a drive shaft and a clutch; an anchoring arm moveable between first (extended)and second (retracted) positions relative to the tool body; a push rod connecting the anchoring arm to the drive mechanism; and a spring acting to bias the arm into a first position relative to the tool body. The push rod extends through the clutch mechanism and is engaged by the spring to bias the arm into the first position, and is also driven by the drive mechanism through the clutch to move the arm between the first and second positions. The spring is a coil spring surrounding the drive mechanism and acting on the push rod directly.

Abstract: A clamped receiver array using tubing conveyed packer elements is disclosed and described. The receiver array can be used for borehole seismology as well as marine bottom surface seismology. The receiver array has a plurality of receivers connected together by a signal cable. The apparatus is further provided with a fluid conduit running essentially parallel to the signal cable. The fluid conduit has a plurality of receiver deployment sections which are located proximate to respective receivers. The receiver deployment sections are responsive to an increase in pressure within the fluid conduit, causing the receiver deployment sections to operate to press the receiver against the inside of a wellbore or to a marine bottom surface. In one example the receiver deployment section uses pistons disposed in openings in the fluid conduit to push the receivers away from the conduit as pressure in the conduit is increased.

Abstract: A borehole tool including a tool body having and an anchoring mechanism, the anchoring mechanism having a drive mechanism including a motor, drive shaft, and clutch; an anchor arm moveable between first and second positions relative to the tool body; a push rod connecting the anchor arm to the drive mechanism; and a spring acting to bias the arm into a first position relative to the tool body. The push rod extends through the clutch mechanism and is engaged by the spring to bias the arm into the first position, and is also driven by the drive mechanism through the clutch to move the arm between the first and second position. The push rod may be connected to the anchor arm by a link. Measurement devices may be used to determine the position of the anchor arm or the tool body.

Abstract: A system for sensing subterranean acoustic waves emitted from an acoustic source includes a plurality of laser sources, a plurality of subterranean optical sensors, at least one optical detector, and electronics. The laser sources each emit light at a different frequency. The subterranean optical sensors receive the light and alter the light in response to the acoustic waves. The optical detector receives the altered light and outputs an electrical signal. The electronics receives the electrical signal and converts it into seismic data format. Preferably, the light emitted from the optical sources is modulated at a plurality of modulation frequencies. The electronics can be used to demodulate the signal. The electronics may demodulate the electrical signal by mixing the signal with periodic waveforms having frequencies corresponding to the modulation frequencies and twice the modulation frequencies.

Abstract: A non-destructive method of measuring physical characteristics of a medium, such as uncemented sediment, sandstone, or limestone. A pseudo-random code is generated and is used to generate a pseudo-random acoustic signal. This signal is transmitted into the medium to be measured through the use of a transducer, such as a piezoelectric element, and is received by a plurality of hydrophones. The received signal is then processed to obtain an image of its velocity and attenuation. A universal geoacoustic model of the medium for a given set of measured data is determined, and the model is solved to obtain a pair of permeability-porosity results for the medium. The one of this pair of permeability-porosity results which is correctly indicative of the physical characteristics of the medium is then determined.

Abstract: This invention is a method of conducting seismic prospecting operations using a drilling tool (1) acting at the bottom of a well (2), which creates very powerful seismic vibrations, transmitting reference signals representing the vibrations of the tool in real time or later, and correlating the seismic signals picked up by a receiving assembly (12) with the reference signals. The reference signals are furnished by sensors (7) in contact with the drill string and at a distance from the down-hole assembly constituted by tool (1) and associated drill collars (4). In order for these reference signals to be truly representative, a damping means (8, 19) and at least one filtering element (20) designed to attenuate to a great degree the multiple reflections in a frequency range useful for seismic prospecting are interposed into the drill string. The invention has application to the making of seismic recordings.

Abstract: This invention provides near real-time systems and methods for acquiring seismic data in reservoirs at very high resolution such that advancing fluid fronts can be mapped substantially in real time. In one system, one or more autonomous devices are deployed in the well to detect seismic data. Each device includes at least one seismic receiver. An acoustic energy source, preferably at the surface, induces acoustic waves into the subsurface formations. The autonomous devices move in the well and detect seismic waves at selected discrete locations in the well. The seismic data is stored in on-board memory. After the data acquisition, the devices dock at a receiver stations in the well. The receiver stations download the stored data from the memory and transmit such data to a surface control unit via a two-way data link between the receiver and the surface control unit. The surface computer system also sends command signals to the downhole receiver to control the operation of the individual devices.

Abstract: A clamped receiver array using 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. The expansible sections have a resilient outer sleeve which fits over a fluid conduit element adjacent to the receiver.

Abstract: The invention is an apparatus for generating a seismic signal in a fluid filled borehole which includes an elongated housing formed from a gas impermeable material and a controlled frequency energy source within said housing. The housing has an external shape which expands and contracts in response to variations in pressure within said housing to enhance the transmission of said seismic signal to the borehole fluid, such as pressure variations resulting from fluid resonance within said housing.

Abstract: A system intended for permanent installation of measuring sondes against the inner wall of a pipe (1) such as a well or a tube. Measuring sondes (7) are respectively associated with coupling devices (2) that are brought to their respective coupling points in the pipe by means of a tube (3) positioned by off-centering devices (4) for example. Each coupling device (2) comprises a flexible element (6) carrying sonde (7), that is deformed to a set back position where it is immobilized by a lock (9) so as to allow displacement thereof along pipe (1). In order to release flexible blades (6), a sufficient overpressure allowing to push back the piston of a jack (10) whose cylinder communicates at one end with the inside of pipe (1) is established. In this expanded position, it immobilizes coupling device (2) and presses sonde (7) against pipe (1) while mechanically decoupling it from tube (3). Tube (3) can possibly be withdrawn if it does not serve another purpose.

Abstract: A method and device for generating a high amplitude sound wave is provided. The device includes a housing having an open end. A piston is slidably disposed in the open end of the housing and forms a chamber for holding a pressurized liquid. The pressurized liquid acts on the piston to move the piston relative to the housing. A latch is operable to fix the piston relative to the housing and to release the piston. Upon release of the latch, the piston moves relative to the housing to generate the sound wave. In the method of the present invention, a piston is fixed relative to a housing to form a chamber between the housing and the piston. The chamber is filled with a pressurized fluid and the piston is released to allow the pressurized fluid move the piston relative to the housing and generate the sound wave.

Abstract: A borehole seismic shuttle tool includes (a) a tool body having a cavity with an opening in the wall of the tool body; (b) an anchoring arm attached to the tool body and operable to anchor the tool body to the borehole wall; (c) a sensor package positioned in the cavity and mounted on resilient mounts which act to urge the sensor package in the direction of the opening, such that when the tool body is anchored to the borehole wall, the sensor package projects part way through the opening and is held against the borehole wall by the action of the resilient mounts. The tool is characterised in that when the tool body is not in contact with the borehole wall, peripheral portions of the sensor package is urged into contact with the tool body wall surrounding the opening.

Abstract: A drill string assembly containing a section of tube with a first end. The first end directly, mechanically links a drill pipe to a drill bit and transmits rotational forces from the drill pipe to the drill bit during drilling. A spring is connected to the section of tube at a point remote from the first end of the section of tube. A mass is connected to the spring such that the mass can vibrate on the spring in an axial direction relative to the section of tube and drill string. The value of the mass and the stiffness of the spring being selected such as to cause them to act as a mechanical filter and damp longitudinal compression waves at a predetermined frequency of frequency band and received at the first end of the section of tube.

Abstract: The present invention relates to an acoustic logging system having a sonde for arranging in a borehole of a well such as an oil well. The sonde has at least one transmitter for providing at least one transmitter acoustic signal, and has receivers for responding to the at least one transmitter acoustic signal, for providing receiver signals containing information about properties of earth formations in the borehole. The acoustic logging system features one or more transducers, a light source, an optical fiber and a detection and management unit. The one or more transducers responds to the receiver signals from the receiver of the sonde, for providing one or more mechanical transducer forces containing information about the receiver signals. At least one transducer may be a piezoelectric or magnetostrictive transducer. The light source provides an optical signal.

Abstract: A well tool in accordance with the invention comprises an attenuation device which attenuates tube waves associated with an elastic wave emission and/or reception set (1, 12). The attenuation device comprises a bubble generator (2) which releases into the well a gas not readily soluble in the well fluid, slightly overpressured in relation to the hydrostatic pressure, in the form of calibrated bubbles which greatly attenuate the parasitic tube waves. The attenuation device is placed above or below the elastic wave emission and/or reception set having a plurality of pickups whose signals are acquired by a local electronic module (14) and/or a source of elastic waves such as a vibrator. A bubble trap (17) is preferably associated with the bubble generator (2) in order to limit the volume of gas to be generated in situ. The invention is applicable to VSP type seismic prospecting and acoustic logging.

Abstract: An acoustic attenuator suppresses acoustic signals traveling along the body of a measurement-while-drilling (MWD) tool, making it possible to obtain acoustic measurements relating to underground formations. Shaped cavities (spherical or cylindrical) filled with a fluid have a resonance frequency that is tuned to be within the band of interest thereby attenuating acoustic signals traveling through the body at these resonance frequencies. The staggered arrangement of the cavities increases the path length for the acoustic signals and provides further attenuation. Attenuation may also be accomplished by use of a composite consisting of cylindrical layers of two different materials with thicknesses that attenuate selected frequencies. Additional attenuation is provided by lengthening the path length of a seismic signal passing through the more competent of the two materials of the composite.

Abstract: This invention is directed toward apparatus and methods for obtaining acoustic measurements or "logs" of earth formations penetrated by a borehole. More particularly, the invention is directed toward obtaining the acoustic measurements while the borehole is being drilled. The downhole apparatus comprises a plurality of segmented transmitters and receivers which allows the transmitted acoustic energy to be directionally focused at an angle ranging from essentially 0 degrees to essentially 180 degrees with respect to the axis of the borehole. Downhole computational means and methods are used to process the full acoustic wave forms recorded by a plurality of receivers. A two way communication system is also used in the preferred embodiment of the invention.

Abstract: There is provided an acoustic source especially for use in seismic studies at sea. The acoustic source has a longitudinal axis and sound emitting surfaces adapted to be put into sound emitting movements towards and away from each other by use of a drive unit. The sound emitting surfaces comprise two curved plate members having upper and lower ends essentially symmetrically positioned in relation to the longitudinal axis of the acoustic source, and forming a convex cross section with their respective upper and lower edges converging towards each other. The upper and lower edges of the sound emitting surfaces, respectively, are connected to each other with two corresponding side elements, the side elements each being connected to at least one hinge stretching along at least a part of the length of the source.

Abstract: A non-destructive method of measuring physical characteristics of a medium, such as uncemented sediment, sandstone, or limestone. A pseudo-random code is generated and is used to generate a pseudo-random acoustic signal. This signal is transmitted into the medium to be measured through the use of a transducer, such as a piezoelectric element, and is received by a plurality of hydrophones. The received signal is then processed to obtain an image of its velocity and attenuation. A universal geoacoustic model of the medium for a given set of measured data is determined, and the model is solved to obtain a pair of permeability-porosity results for the medium. The one of this pair of permeability-porosity results which is correctly indicative of the physical characteristics of the medium is then determined.

Abstract: Acoustic source, especially for use in seismic studies at sea, with sound emitting surfaces adapted to be put into sound emitting movements toward and away from each other by use of a drive unit in a known manner, in which the sound emitting surfaces comprise two curved plate members essentially symmetrically positioned in relation to the longitudinal axis of the source, forming a convex cross section with their respective upper and lower edges converging towards each other, and the respective upper and lower edges of the sound emitting surfaces are flexibly connected to two corresponding side elements positioned between them, and that the source comprises a rigid frame for supporting the drive unit, comprising at least two rigid slide rods stretching through the side elements, and that rigid covers are mounted on the slide rods, covering at least the whole side elements, thus forming rigid, covering surfaces with a constant distance between the covers.