Abstract: The present invention discloses an acoustic borehole source and method of using the source for generating elastic waves through an earth formation that may be used for logging or permanent installations. The acoustic source is comprised of a first motorized reaction mass and at least two pads, each pad connected to the sonde and the motorized reaction mass using pushing rods. In an alternate embodiment, the source has a first and second motorized reaction mass and at least two pads. The motorized reaction masses may be activated to allow the pads to move at an angle ? relative to the axis of the sonde. In a third embodiment, the acoustic borehole source includes additional pairs of motorized reaction masses so that pads may be independently activated.

Abstract: A marine vibrator that in a particular embodiment includes a substantially elliptically shaped outer shell, a driver having a first and second end, at least one outer spring connected between the first end and the second end of the driver, and at least one inner spring connected between the first end and the second end of the driver. One or more masses are attached to the inner spring. At least one transmission element connects the outer spring and the outer shell. The outer and inner springs and the masses attached to the inner spring are selected to generate a first resonance frequency and a second resonance within the frequency range between 1 Hz and 300 Hz.

Abstract: The invention relates to a device for emitting seismic vibration waves mountable on a movable platform (100) comprising a vibration system for transmitting the waves into the ground and a system for supporting a device (200) on the ground, wherein the system for supporting on the ground is fixable to the movable platform (100) and transfers a charge to a ground-mounted vibration system in a ground support direction (1). Said ground-mounted vibration system is fixable to the system for supporting on the ground by compensation means (251, 252, 253) for compensating perpendicularity defects between the ground general plane and the around support direction (1).

Abstract: An apparatus for generating a seismic signal in a wellbore includes an elongated housing configured to be disposed in the wellbore; a piston slidably disposed in an internal bore in the elongated housing; a strike plate fixed on the elongated housing proximate one end of the internal bore; and an energizing mechanism configured to move the piston to hit the strike plate. A downhole system for seismic survey of a formation penetrated by a wellbore includes at least one seismic receiver; a seismic source; and at least one inflatable packer configured to separate the seismic source and the at least one seismic receiver in different compartments in the wellbore when inflated.

Abstract: Methods and apparatus for generating a signal with a signal generator comprising a tool body disposed in a tubular member. A first and second electromagnets are disposed within the tool body such that the second electromagnet is opposite the first electromagnet. A power supply selectively provides electrical current to the first and second electromagnets so as to displace the tubular member and generate a signal in the surrounding formation.

Abstract: The method for exploring desired characteristics of a subsurface sector, having at least one resonant frequency, is based on selectively transmitting suitable narrowband energy waves into the subsurface sector, thereby producing narrowband signals reflected off the subsurface sector. The transmitted narrowband energy waves can be selectively and optimally adjusted in real time so as to provide optimum illumination of the desired characteristics from the explored sector.

Abstract: The invention relates to an apparatus and method for imparting a precise amount of impulse energy to be delivered to the ground. The apparatus includes an anvil for operative deployment against the earth a hammer operatively connected to the anvil for striking the anvil; and a control system operatively connected to the hammer for controlling the impulse energy of the hammer striking the anvil. The control system includes a linear feedback system for measuring the linear position of the hammer with respect to the anvil during a force stroke and a processor for receiving linear position data from the linear feedback system for controlling the relative speed of the hammer with respect to the anvil during a force stroke through an actuation system.

Abstract: A method of seismic surveying comprises emitting seismic energy at two or more different depths during a sweep. In one embodiment, the depth of a seismic source is varied during a sweep, by raising or lower the source while it is emitting seismic energy. In another embodiment, an array of two or more marine vibrators is used as the source of seismic energy, with the vibrators in the array being disposed at different depths. The invention allows notch frequencies in the amplitude spectrum to be eliminated, and allows improvements in both the spectral flatness and the amplitude at low frequencies.

Abstract: In the oil industry, the acoustic sounding method is a well-known technique for taking the depth measurements of particular attributes of an oil well or borehole. The method involves sending a short, sharp, clear, loud bang sound down a borehole, normally between the inside wall of the borehole casing, commonly referred to as the annulus and the outside of the production tubing string, and recording the echoes generated. One device for generating the sound needed in the acoustic sounding method is an air or gas pressurized chamber which is discharged at or near the wellhead of the borehole. The sound being generated by this device, commonly known as an acoustic generator, comes from the energy released by the equilibration of the different gas pressures.

Abstract: A method for generating acoustic waves, the method having the steps of: extending a tine from a support structure so that a proximal end of the tine is attached to the support structure and a distal end of the tine is uninhibited; positioning an oscillator so as to be supported by the support structure and to mechanically communicate with the tine; and oscillating the tine with the oscillator.

Abstract: Apparatus and methods for acoustically isolating logging tool receiver and transmitter sections. One or more modular isolators is arranged between the receiver and transmitter sections. The modular isolators comprise a high tensile strength while also providing for a high wave attenuation level. The modular isolators are mechanical mass-spring systems capable of absorbing acoustic waves propagating along the logging tool. The mass is a swinging sleeve, and the spring includes a Belleville spring stack. The use of the strong modular isolators provides acoustic isolation between the transmitters and receivers for the complete sonic frequency band at multiple modes.

Abstract: An apparatus for generating acoustic waves, the apparatus having: a support structure; two tines extending from the support structure so that proximal ends of the two tines are attached to the support structure so that distal ends of the two tines are positioned with standoffs relative to a dimension of the support structure and the distal ends of the two tines are uninhibited, wherein the two tines each comprise a moment arm; and an oscillator in mechanical communication with the two tines.

Abstract: An acoustic attenuator includes a housing having an inner side surface which defines an interior chamber and at least one dampening member both physically and acoustically coupled to the housing and projecting into the interior chamber. Acoustic energy propagating within the housing is deflected into the dampening members for acoustically dispersal within the interior chamber. In various aspects thereof, the dampening members may include one or a group of two or more generally cylindrical sleeves having one end both physically and acoustically coupled to the housing and a second end projecting into the interior chamber. Preferably, when a group of two or more cylindrical sleeves are employed, the sleeves are nested within one another. The dampening members may further include a second, oppositely disposed, group of two or more acoustic attenuators nested within one another and interdigitated with the first group of cylindrical sleeves.

Abstract: A gerotor and bearing apparatus for a whirling mass orbital vibrator which generates vibration in a borehole. The apparatus includes a gerotor with an inner gear rotated by a shaft having one less lobe than an outer gear. A whirling mass is attached to the shaft. At least one bearing is attached to the shaft so that the bearing engages at least one sleeve. A mechanism is provided to rotate the inner gear, the mass and the bearing in a selected rotational direction in order to cause the mass, the inner gear, and the bearing to backwards whirl in an opposite rotational direction. The backwards whirling mass creates seismic vibrations.

Abstract: A method of conducting seismic evaluation of a subterranean formation wherein a rigid, elongate member having a first end and a second end is positioned such that the first end of the elongate member is at a point on the earth's surface, imparting an impulsive force to the elongate member to urge the member into the earth, the positioning of the rigid member and the impulsive force being sufficient to generate and propagate primary seismic waves into the subterranean formation and positioning one or more seismic wave detectors on the surface of the earth to detect and receive reflected seismic waves from the subterranean formation.

Abstract: A vibration generator can be used for seismic applications, producing vibrations for exploration of near-surface subsoils up to 150 meters. Containing two coils activated with AC current or other electrical pulses, the generator is coupled to the object to be investigated by suitable elements. Inside is an inner housing, the outer housing movably supporting, on opposing sides, two coils connected through the inner housing. One coil is activated continuously and alternates with a positive wave component of an AC current control signal; at the same time the other coil alternates with a negative wave component. The result, a controlled vibratory motion, is also achieved with DC voltage. Because of the law of action and reaction, the vibratory motion passed to the coupling elements allows motion into the object being investigated. In contrast to conventional moving coil systems for electromechanical vibration transduction, this generator is based on a soft-metal magnetic instrument.

Abstract: Scaling may be reduced during oil and gas production using a device having a sound transducer. The device can be used downhole and functions independently of an external power supply. Use of the device allows for the reduction or elimination of anti-scaling chemical additives during the production phase of an oil and gas well.

Abstract: One embodiment of the invention provides for an apparatus for detecting geophysical energy. The apparatus includes a receiver configured to receive geophysical energy and to convert the geophysical energy into a signal. The apparatus further includes a signal transport device configured to accept the signal and relay the signal to a remote location. The apparatus also includes a fluid conduit configured to contain a pressurized fluid, a production tubing, and an expansible section disposed inline in the fluid conduit. The expansible section is positioned between the production tubing and the receiver, and is configured to expand in response to an increase of fluid pressure within said conduit. When expanded, the expansible section presses against the production tubing and the receiver and thereby causes the receiver to be moved from a first position to a second position.

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: An acoustic logging tool includes external baffle assemblies forming a waveguide structure at the acoustic source. The logging tool is designed for acoustic logging of earth formation surrounding a borehole. The external baffle assemblies form a waveguide structure that is designed to increase signal to noise ratio in an acoustic logging tool using dipole or other acoustic waves. In a preferred embodiment, the acoustic logging tool includes an elongated transmitter module, and a receiver sonde having a linear array of acoustic receivers. The transmitter module includes first and second cylindrical masses spaced apart along the axis by first and second spacers. The first cylindrical mass defines a first circular facing surface and a first cylindrical outer surface. The second cylindrical mass defines a second circular facing surface and a second cylindrical outer surface.

Abstract: The present invention provides a system for, and method of determining an azimuth of a seismic energy source. In one embodiment, the system includes a directional assembly having a mount configured to be coupled to a seismic energy source, a rotatable mass assembly coupled to the mount, a compass rose coupled to one of the mount or the rotatable mass assembly and a direction reference coupled to the other of the mount or the rotatable mass assembly. The compass rose is registered with the direction reference to provide a direction orientation of the rotatable mass assembly with respect to the mount.

Abstract: A boomer for generating acoustic signals in a marine seismic survey has a frame towed by a survey vessel. A coil is mounted to the frame and a conductive plate is adjacent to the coil. A capacitor is mounted to the frame, and control electronics system delivers an electric charge stored in the capacitor to the coil. The invention obviates the need for heavy conductive cables between the survey vessel and the boomer in conventional systems where the capacitors are carried by the vessel, while maintaining the desirable acoustic properties of the boomer.

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: In one embodiment of the present invention, a drive assembly for a seismic land vibrator is provided. The drive assembly comprises at least a first spring element. The first spring element operates in at least two vibration modes in a seismic frequency band of interest. The drive assembly also comprises a baseplate, a driver, and a reaction mass. The driver interacts with the reaction mass and the first spring element to transfer energy to the baseplate.

Abstract: The present invention discloses a shaftless acoustic source having a solenoid, a bullet and driving electronics. The bullet, which is positioned inside the solenoid's coil, can be accelerated by a magnetic force generated when a current pulse is applied to the coil. Acoustic energies are generated upon the impact of the bullet with an object, such as a borehole wall. This impact force can be described by the Hertzian Contact Theory (also referred to herein as Hertzian Theory) as a point of normal force with a time function similar to a half period sine function. A retraction means may be used to retract the bullet back into the solenoid after firing.

Abstract: A seismic source array 15 comprises a plurality of seismic source 26 arranged about a central point of the source array 15 in such a way that an imaginary circle drawn with said central point at its centre, and containing all of said seismic sources 26, can be divided into at least three whole sectors each of which contains a substantially identical arrangement of seismic sources 26.

Abstract: Controlled-polarization marine seismic shear-wave source has a base suitable for positioning on a seafloor, beneath a water body. Twin water-blast tubes (seismic-impulse-generation thrusters) are mounted on the base, aimed upwardly, outwardly in opposite directions at equal acute angles &bgr; relative to the base. These blast tubes are positioned symmetrically on opposite sides of vertical centerline CL of the source. When submerged, water enters open mouths at upper ends of the tubes. The base has multiple downwardly projecting blade-like teeth for penetrating into the seafloor. Firing a compressed-air discharger mounted in a lower end of a water-blast tube hurls a powerful slug of water upwardly along the tube, producing a powerful reaction impulse acting downwardly generally parallel with the tube axis.

Abstract: An underwater acoustic projector comprising a pair of spaced apart end plates with an acoustic driver positioned between the end plates, the driver having smaller cross-sectional dimensions than the end plates. Each end plate close one end of an open ended tubular pipe waveguide and that plate is mechanically connected to one end of a piezoelectric drive unit with a tubular waveguide extending inwards and surrounding the end portion of the acoustic driver.

Abstract: A sound mitigation system and method reduce the transmission of acoustic output from explosions underwater. The system is submerged to bottom terrain of a body of water and has at a series of gas-generating devices providing volumes of gas that are fed to refractory heat resistant tubing assemblies and flexible general tubing assemblies. The heat resistant and general tubing assemblies extend between adjacent gas generating devices and are provided with at least one row of holes to vent bubbles of gas and form a virtually continuous curtain of bubbles rising to the surface of the water between detonating explosives and areas of interest. The curtain of bubbles mitigates the effects of the explosions on marine mammals and endangered, threatened, or protected species within an area adjacent to the explosions.

Abstract: A reusable low frequency projector system that is capable of producing coherent broadband, high power, low frequency acoustic pressure waves underwater. The projector has two halves each with a spiral wound insulated wire core. The spiral wound wires are separately encapsulated and then joined flexibly in a contiguous parallel orientation. When energized by a voltage source the encapsulated spiral wound wires are repelled from one another and then come back together when not energized, imparting a pressure wave to the water at a desired frequency. The projector requires no pressure compensation devices for operation.

Abstract: A non-contact vibrometer is employed to measure seismic energy imparted to the earth by a land vibrator. The non-contact vibrometer can be a laser vibrometer operable to measure the motion of a baseplate of the land vibrator. A computing device can be used to record both the imparted seismic energy detected by the non-contact vibrometer and reflected seismic energy sensed with geophones.

Abstract: An improved seismic method comprises the steps of generating seismic waves by exploding an explosive device in a subterranean formation, wherein the explosive device comprises a plurality of explosive elements whereby there is a time delay between the detonations of the individual explosive elements, and detecting the seismic waves and/or reflections thereof with seismic detectors. Also disclosed are geophysical survey systems that comprise a seismic energy source comprising an explosive device that comprises a plurality of explosive elements, the seismic energy source being located in a subterranean formation, and a plurality of seismic detectors that are adapted to detect seismic waves and/or reflections generated when the seismic energy source explodes.

Abstract: A system and method for utilizing a surface located oscillator to generate seismic signals at a downhole location. The system includes a vibratory source for generating axial vibrational energy in a tubular string anchored in the borehole at a suitable location. The vibratory source may be operated at a predetermined frequency or may generate a swept frequency signal. The axial vibrations are transmitted through the tubular string and impart a seismic signal through the anchor to the formation.. In different configurations, the system imparts broadband seismic signals into the formation. Sensors are mounted on the vibratory source and downhole anchor for monitoring the system operation. Seismic receivers are deployed on the surface, in offset wells, or in the source well. Signals from the receivers are transmitted to a control unit. The control unit utilizes the sensor and receiver signals to control the operation of the vibratory source.

Abstract: An axially extended downhole seismic source is disclosed. In one embodiment, the seismic source includes multiple pressure storage chambers, each having an inlet valve and an outlet valve. The inlet valve is coupled between the pressure storage chamber and the interior of the drill string, and the outlet valve is similarly coupled between the pressure storage chamber and the annular space around the drill string. A compressible fluid may be provided in the pressure storage chambers, and pistons may be positioned to contact the compressible fluid. For each pressure storage chamber, an inlet piston contacts the compressible fluid and fluid inside the drill string, while an outlet piston contacts the compressible fluid and fluid in the annular space around the drill string. When the outlet valve is closed, the inlet valve can be opened to allow pressure inside the drill string to compress the compressible fluid inside the pressure storage chamber.

Abstract: A seismic acquisition system includes one or more perforating shaped charge modules activable to generate seismic signals into an earth sub-surface. The seismic signals are created by perforating jets formed by the perforating shaped charge modules when activated. The perforating jets produce directional seismic signals that reduce the amount of lateral noise. One or more detectors are employed to receive signals reflected from the earth sub-surface in response to the seismic signals.

Abstract: A method of seismic investigation using the swept impact seismic technique involves measuring the response of a site to be investigated to a series of controlled impact sequences applied at different points of the site, each sequence using impacts generating pulses of energy at 100-2500 Hz., the impacts of the sequence having a repetition frequency swept between frequencies in the range of 10 to 500 Hz., the end frequencies having a ratio of at least 1.5 to 1, and the number of impacts in the sequence being at least 100 (and preferably at least 500). The invention also extends to apparatus for implementing such a method, comprising an electrically-actuated hammer having an impact frequency variable through a range of at least 1.5:1 within the range 10 to 500 Hz., and generating impacts characterized by substantial energy within a frequency range of 100-5000 Hz.

Abstract: Compact vibrator for emitting elastic waves in a material medium such as the subsoil. The vibrator comprises a baseplate (3) intended to be coupled in operation with a surface of this medium, an inertia mass (5) and at least a pair of electromechanical transducers (1, 2) comprising each one or more pillars (A, B) made for example of a piezoelectric or magnetostrictive material. Pillars (A) of first transducer (1) are interposed between baseplate (3) and a relay plate (4). Pillars (B) of the second transducer are interposed between relay plate (4) and inertia mass (5), on the same side of relay plate (4) as pillars (A) preferably, so that inertia mass (5) is positioned in the vicinity of baseplate (3), which contributes to the compactness and to the stability of the vibrator that can therefore be used on slightly sloping surfaces.

Abstract: A method and apparatus for in-situ characterization of downhole fluids in a wellbore using ultrasonic acoustic signals. Measurements of the speed of sound, attenuation of the signal, and acoustic back-scattering are used to provide qualitative and quantitative data as to the composition, nature of solid particulates, compressibility, bubble point, and the oil/water ratio of the fluid. The tool generally comprises three sets of acoustic transducers mounted perpendicular to the direction of the flow. These transducers are capable of operating at different frequencies so that the spectrum of the acoustic signal can be optimized. The apparatus is capable of operating downhole to provide real time information as to conditions in the well.

Abstract: A marine vibrator has a hollow body formed of one shell or of two opposed shells defining an inner space therein with vibrator apparatus within the hollow body. At least one shell has a curved shape, and the shell can have a streamlined shape with relatively low hydrodynamic drag. Certain embodiments include one or more exterior control members to facilitate positioning of the vibrator in water. Other than their mating ends, when two shells are used the two shells may be different in shape and volume or they may be identical. In preferred two-shell embodiments, there is a flexible seal between and connecting the two opposed shells. In certain aspects the inner space is filled with gas. A vibrator apparatus in one aspect applies equal and opposite forces to the shells of a two-shell vibrator or to opposed sides of a single shell vibrator.

Abstract: A dynamic force transducer for generating horizontally oriented shear forces and motion at a surface of a solid medium. A rigid frame is placed in direct contact with the surface of the solid medium. At least one pair of identical dynamic-force driver units is mounted on the frame to impart horizontally oriented forces to the frame. Symmetrical pairs of compliant springs support the force drivers, but the compliances of each pair of springs may be adjusted or interchanged with other similar springs to introduce different predetermined mechanical resonances. The driver units are excited to produce the horizontally oriented forces with one or more driver units imparting a pushing force and one or more driver units simultaneously imparting a pulling force.

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: 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 marine seismic source for generating acoustic source energy. A housing has a continuous exterior perimeter which is moveable to displace water. Movement of the housing can be accomplished by providing alternating convex and concave exterior surfaces connected with inflection points. The composite shape provides movement inwardly or outwardly, and can be moved with different types of actuators. Piezoelectric elements can be activated to move the housing surfaces and to change the internal housing volume. The resulting pressure pulse provides acoustic source energy useful for the evaluation of subterranean geologic formations and for other purposes.

Abstract: A marine seismic source for generating acoustic source energy from electrical power. A slotted housing has an exterior surface engaged with an electrically activated transducer such as a piezoelectric transducer. One or more piezoelectric components can be adhered or otherwise attached to the exterior surface of the housing. A case can cover all or part of the piezoelectric components, and the case can be waterproof to prevent contact between the transducer and the water. The case can be integrated with the slotted housing to form a composite structure, or a cavity, for containing a transducer such as piezoelectric components.

Abstract: A seismic vibrator system for imparting compressional and shear wave vibrations into the earth has an earth contacting base with a vertical post. A tubular hub is slidably received on the post in a piston/cylinder relationship. Spaced apart horizontal top and bottom plates are secured to the hub. A mass is slidably supported between the plates. Pistons interconnect the hub and the mass. Hydraulic energy is used to reciprocate the mass vertically on the post and horizontally between the plates.

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.

Abstract: A system for seismic prospecting by using reflections of acoustic waves and an operation method thereof. Unprocessed raw data from a plurality geophone sensors and other processed data are stored in a storage unit further processing and analysis. The preferred operation comprises four stages, performing test sweeps no and analyzing results thereof (testing stage), determination of control parameters for the spatial distribution of sensor array and data-collection sweeps based on the analysis of test sweeps (parameter-determination stage), performing data-collection sweeps (data collecting stage), and analysis and processing of the data-collection sweeps (data processing stage). Test sweeps and availability of unprocessed raw data allow optimization of the system to achieve maximal resolution and signal-to-noise ratios.

Abstract: An apparatus for generating signals and energy for transmission to a large mass. The apparatus incorporates a pulsed generator such as a compensated pulsed alternator for storing and for discharging large amounts of energy in a controlled manner for transmission through a vibrator or similar electromechanical device. In the field of seismic exploration, the apparatus discharges seismic source energy into a land mass or water to generate seismic waves which are reflected from the interface between subsurface geologic formations. The pulsed generator permits the seismic source energy to be discharged in a controlled manner to shape the energy signal, and permits large quantities of energy to be discharged to increase the penetration depth and strength of the reflected signals.

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: Seismic exploration for hydrocarbons may use an eccentric-mass (or "swinging-weight") vibrator as the seismic source. According to the invention, a vibrator undergoes alternate periods of acceleration and deceleration, during one of which the vibration may be annulled. For example, the rotating mass may be formed in a plurality of parts; then the several parts are disposed in a manner that rapidly and automatically balances their vibratory forces during the period when the vibration is to be annulled, and that adds their vibratory forces during the other period. The invention further provides for modulation of the frequency-time relation during deceleration, for synchronization of several vibrators, and for modulation of the effective output force by controllable variation of the mass, eccentric radius or relative phase of the several parts of the rotating mass; in such modulation, only resultant forces are applied to the vibrator bearings.