Abstract: An improved method for gathering traces in a 3-D seismic survey is disclosed. In one configuration, receiver lines having equally spaced geophone receivers stations are run in one direction, and lines of equally spaced shotpoint stations run orthogonal to the receiver station lines. The station spacing in each shotpoint and receiver lines is selected to produce a desired spatial resolution, and the individual lines are spaced apart by a distance equal to at least two times the station intervals. In this method, a series of common mid point gathers centered about source/receiver line intersection, referred to as "hybrid gathers" is made, where each hybrid gather includes traces from a designated number of shots in the shotpoint line of the selected intersection that are directed into a designated number of geophone receivers in the receiver line of the selected intersection.

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: The invention relates to a device for exploring an underground formation crossed by a well, suited to work in well portions where the advance thereof under the effect of gravity is difficult, notably in horizontal well portions or in well portions greatly inclined to the vertical. A plurality of rigid exploration modules (Mi) are interconnected end to end, each one including a rigid pipe (1), a flexible leaf (11) fastened to each pipe (1) so as to press against the wall of the well at least one box (18) containing sensitive elements, a linking cable (32) connected to a surface central station (40), and a connecting block (26) comprising an acquisition system (37) connected to the various modules (M1-Mn) by a bundle of electric conductors running through the tubular elements (1), and a deferred electric connection useful in damp conditions between linking cable (32) and the acquisition system.

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: 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: 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: An object detector for detecting metallic or non-metallic objects is disclosed which comprises a sound source such as a speaker (12) for generating impulse short sound bursts. A tube (16) conducts the acoustic signal from the speaker to the ground and at least one microphone M1-M3 is utilised for detecting reflections from the ground. A reflection from a buried object is compared with a reference signal which may be obtained from another microphone M1, M2 or earlier in time from the same microphone M3. The reflected and reference signals are subtracted to provide a difference signal and a difference signal is correlated with the original acoustic signal to provide an indication of an object. Time windows may be set to enable analysis of different depths to be obtained.

Abstract: A method and system for using sonography to image the internal structure of geophysical and geologic models are disclosed. The sonography system includes a wand having a plurality of piezoelectric elements at an active surface thereof, each coupled to driver/receiver circuitry. Certain of the piezoelectric elements are selected as ultrasonic sources and receivers; the source/receiver designation may vary over time, as each of the elements may either generate or receive acoustic energy. A computer system, connected to the wand, receives signals from the receivers corresponding to reflected and refracted ultrasonic energy, and generates a zero offset trace image therefrom. In the geophysical case, the scale model is formed of materials such as plastics and rubbers having the desired properties for simulating the response of a portion or layer in the earth to ultrasonic vibrations.

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: A method for cascading or linking seismic vibrator sweeps to form a cascaded sweep sequence. According to the method, a first cascaded sweep sequence is generated containing N sweep segments linked end-to-end. The N sweep segments are substantially identical, except that the initial phase angle of each sweep segment within the sweep sequence is progressively rotated by a constant phase increment of about 360/N degrees. A second cascaded sweep sequence is generated consisting of (i) N consecutive sweep segments linked end-to-end which correspond to said first cascaded sweep sequence and (ii) an additional sweep segment linked to the N consecutive sweep segments which is positioned and phased so as to substantially suppress harmonic ghosts during correlation. One of these cascaded sweep sequences is used for the vibrator sweep sequence and the other is used for the correlation reference sequence.

Abstract: A method for processing seismic vibrator data. The method utilizes a deterministic signature deconvolution of the vibrator data to compress the impulse response of the data resulting in sharper, clearer seismic images than are possible using cross-correlation techniques. The method may be used in place of or in addition to cross-correlation. Further, the method may be implemented in either the time domain or the frequency domain.

Abstract: Acoustic energy is used to detect and identify objects buried in soil by imaging acoustic energy reflected from the soil and buried objects. Acoustic energy is injected into soil at an oblique angle relative to the surface of the soil, reflected and received. Signals representative of the reflected energy are processed to generate image signals used to generate images representative of the reflected energy. Objects buried within the soil are identified by viewing the images. In one embodiment, obliquely oriented acoustic energy signals are carried from a source to a soil sample by a first duct and reflections of that energy are carried to a receiver within an adjacent second duct. The ducts acoustically isolate the source from the receiver. A beveled end of the first duct and the second duct are supported above the soil sample for noncontact operations. In another embodiment, an acoustic energy source is obliquely supported upon and forced into engagement with soil in a reservoir.

Abstract: A seismic sensor platform comprises an open frame and a plurality of seismic motion sensors vertically positioned in a common horizontal plane in spaced relationship around the periphery of the open frame. A spike associated with each of the sensors extends beneath the open frame for anchoring each of the sensors in the earth. The frame includes a shield for protecting the sensors from physical damage and for shielding them from seismic noise. Second and third pluralities of horizontally positioned sensors may be provided on the frame, orthogonally positioned with respect to each other to sense orthogonal components of reflected seismic waves. The sensors may each be of a different natural frequency to optimize the multi frequency output of the sensor array.

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: An apparatus and method for detecting seismic waves traveling in an underground formation. The apparatus includes a hydraulic pressure source, preferably a downhole hydraulic pump; a plurality of small, light-weight, flexibly connected clamping detector units having hydraulically actuated clamps; conduit means connecting the hydraulic pressure source to the detector units so that the detector units may be hydraulically clamped to a wellbore with a large force by activation of the clamps; and means for conditioning signals from the detectors. The small, light-weight detector units are securely clamped to the side of the wellbore because of the high clamping force-to-weight ratio thereby allowing high frequency signals to be detected without interference.

Abstract: Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Logitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole relative to a stator that is clamped to the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements at a power level that causes heating to over 150.degree. C.

Abstract: A seismic signal receiving system is provided for use in boreholes to receive seismic waves in carrying out geophysical investigations. The system includes three pairs of opposed plates, each of the pairs of plates including oppositely facing outer surfaces for engagement with opposite sides of a borehole. A seismic receiver is mounted on the inner surface of each of the plates for receiving seismic signals. A double-acting, fluid-operated actuator selectively causes relative movement of the plates of the pairs of plates away from each other to provide expansion thereof so as to enable the plates to engage the walls of a borehole and selectively causes relative movement of the plates of the pairs of plates toward each other to provide retraction thereof so as to enable the system to be removed from a borehole. The pairs of plates each comprise a relatively long plate and a relatively short plate. An expandable linkage interconnects the long plates at the distal ends thereof.

Abstract: A method of seismic exploration uses recordings from both surface receivers and buried sensors to determine the full elastic effect of the near surface layer on an applied seismic wave. The surface receivers are arranged relative to the seismic source location so that rotational effects may be detected. Buried sensors are located so that vertical effects may be detected. This full elastic effect may be used in subsequent seismic data acquisition to reconcile the effect of the near surface so that the response of the underlying rock formations may be known.

Abstract: Coherent noise on seismic records is suppressed by reformatting the common shot gathers to common receiver gathers. Pairs of seismic traces from a common receiver gather are corrected for differential normal moveout, weighted in inverse relation to the RMS signal power, and combined to generate compressed common receiver gathers. The compressed common receiver gathers may be reformatted as common midpoint gathers for further processing.

Abstract: Air wave noise caused by a vibrating baseplate on a seismic vibrator is reduced or eliminated through active cancellation of sound. In active cancellation, the detection of acceleration of the baseplate is used to form a counterpart wave which is equal in amplitude but opposite in phase; a speaker produces an opposite air wave to cancel the baseplate air wave.

Abstract: An echographic technique based method for prospecting of the subsoil or sea bottom and the like, by means of acoustic waves and carried out by the use of an apparatus constitued, in combination of a known acoustic wave transmitting equipment (1) comprising of a body (6, 8) in the inside of which a chamber (9) is formed defined by an internal reflecting surface (7) shaped like a round paraboloid of axis (Y--Y), closed at the base by an elastic diaphragm (5) and filled with a proper liquid, into which acoustic waves are emitted produced by a pair of main electrodes (10a, 10b) associated with an auxiliary discharge priming electrode (11) put between the first ones.

Abstract: The invention comprises a method of geophysical exploration wherein a signal is generated at the lower end of a drill string and propagates into the earth and up said drill string. The signal is detected at the top of said drill string and at other locations substantially at the earth's surface. The signal detected at the top of the drill string is utilized to develop an operator to reduce the magnitude of drill string multiples in the signal detected by the field sensors.

Abstract: An acoustic borehole well logging method and apparatus for measuring azimuthal anisotropy of a formation traversed by a borehole using at least one multipole transducer. In a preferred embodiment, a dipole wave transmitter and at least one detector sensitive to dipole waves are employed. In an alternative preferred embodiment, a monopole transmitter and at least one multipole detector are employed. In the inventive method, two acoustic wave arrivals are detected, each associated with a different azimuthal orientation relative to the longitudinal axis of the borehole (i.e. each is transmitted by a multipole transmitter oriented at such angle, or is detected by a multipole detector oriented at such angle, or both). The inventive apparatus preferably includes at least one transducer unit including two or more multipole transmitters (or two or more multipole detectors) oriented at different azimuthal angles relative to the tool's longitudinal axis.

Abstract: A measuring device for a seismic profile within a well-bore includes resilient members such as springs which are flexible in at least two directions and are interposed between a geophone and a rigid arm connected to a measuring-tool body for applying the geophone against the wall of the well-bore during each detection of seismic waves generated at the ground surface. The elasticity of the resilient members is at least equal to the elasticity of the subsurface stratum through which the well-bore extends. The resonance frequency of the mass of the geophone with the resilient members is equal at a maximum to the resonance frequency defined by the geophone mass and elasticity of the subsurface stratum.

Abstract: The invention relates to a nondestructive downhole seismic source capable of generating S.sub.V -waves, S.sub.H -waves, and P-waves alone or in combination to determine information about a surrounding geologic formation. The invention also includes processes of performing crosswell tomography and reverse vertical seismic profiling. The invention also includes a means and process to carry out in hole seismic logging operations.

Abstract: A method of reducing Rayleigh waves (ground roll) in land seismic exploration employs a unique combination of amplitude output from and spacing of the vibrator sources making up a land seismic exploration system. The velocity of the Rayleigh wave for the prospect to be explored is determined. At least one receiver is used and is spaced from the vibrator sources a distance sufficient to establish the receiver as being in the far-field. The output of each of the vibrator sources is locked in phase and frequency and known separations between the vibrator sources are maintained. The frequency is varied and the individual output amplitude of each vibrator source is varied at each frequency so that the resultant Rayleigh waves traverse the known separations resulting in out-of-phase Rayleigh waves between the sources.

Abstract: The present invention is a downhole seismic source capable of generating seismic forces in excess of 1000 newtons. The source produces seismic waves for seismic applications, particularly cross borehole measurements and vertical seismic profiling. Coupled with motion sensing devices, the present invention also performs as a seismic logging tool. The source is comprised of an outer housing, a means for clamping the source securely to the wellbore, and a linear electromagnetic actuator which utilizes permanent magnetic material having remanent magnetic field exceeding about 0.9 T such as rare earth permanent magnetics. The source has a diameter of about 12.5 cm to fit within a typical wellbore and the actuator has a length of about 1 meter.

Abstract: A method for geophysical prospecting of complex orebodies, wherein elastic waves are excited at least two times in the rock mass containing orebodies and the radio-frequency electromagnetic pulses produced by said orebodies are recorded during each excitation to pinpoint the arrival time of the first and last pulses in each pulse train (1,2,3,4,5,6), then the difference is found between the maximum arrival time of the last pulse and the minimum arrival time of the first pulse in the pulse trains (1,3,5 and 2,4,6) representing one orebody, said differences being the basis for determination of the thickness of each orebody.

Abstract: Method and apparatus for downhole seismic exploration employing vibration emanating from a point deep in a well. An elastic steel column has an upper end extending above the top of the well. A reaction mass is attached vertically thereabove through a vertically mounted compression spring system, in parallel with it a vertically mounted servo-controlled hydraulic cylinder-piston assembly. The displacement of a spear or bit on the lower end of the column relative to earth develops a displacement signal. The piston in the hydraulic cylinder is under reciprocated servo control to apply vertical vibration to the upper end of the column and thereby to the spear, while developing an electrical, pressure-differential signal corresponding to the pressure across the cylinder-piston assembly.

Abstract: An apparatus and method for the measuring the transverse dimensions of a hole such as in an oil well including a sonde on which an electro-acoustic transducer is mounted in an offcentered position in relation to the axis of the sonde. This transducer has two opposite active faces so as to simultaneously transmit acoustic pulses in diametrically opposite diections from the sonde. When the sonde is centered in the hole, the transducer picks up the echoes retransmitted by the wall of the hole in the two directions, at different times. A recording is made of these times and preferably also of an indication of the amplitude of each of these echoes to obtain both a diameter measurement and an indication of the condition of the hole surface. Several transducers are provided, superposed and oriented along various diameters distributed around the axis of the sonde.

Abstract: The preferred embodiment of this invention includes a logging sonde, an elongated pair of oppositely polarized piezoelectric plates connected to each other by their flat surfaces, and an electrical pulse applying means for applying electrical pulses across the pair of plates so as to bend and vibrate the plates in a direction perpendicular to the length of the plates. Vibration of the plates in a fluid contained in a well creates in the fluid a positive compressional wave in one direction and simultaneously a negative compressional wave in the opposite direction. The two compressional waves will interfere to produce a dipole shear wave in the earth surrounding the well. The dipole shear wave arrival is detected at two locations in the fluid spaced longitudinally along the well from each other and from the plate.

Abstract: A method and apparatus for maintaining a second elongated hole axis substantially parallel to a previously bored horizontal hole axis which entails inserting a seismic signal generating apparatus into one hole and a seismic signal receiving apparatus into the other hole. The seismic receiver includes apparatus for moving it along the axis, for maintaining the receiver substantially parallel to the gravitational bottom of the hole, and for moving the receiver a predetermined distance from the borehole wall which is adjacent the borehole containing the seismic signal generating apparatus. Apparatus for observing the detected signal is located outside the borehole.

Abstract: Apparatus for shear wave logging of a fluid-filled borehole which consist of an elongated housing defining an air cavity and containing first and second spaced geophone housing each having an orthogonal pair of horizontal motion detectors secured therein for detection of horizontal shear waves along said borehole as generated from a seismic source in a frequency range having wavelengths that are long relative to the length of housing.

Abstract: Seismic sources and detectors are each positioned in a series of shotholes along a course to be explored. The sources in the shotholes are activated in a sequence along the course and caused to emit seismic waves. The detectors remaining along the course sense or detect the seismic waves which are then recorded. Since the detector at each shothole has performed its function, that of sensing signals from earlier shots in the sequence, its disposal by destruction when the source in the shothole with it is activated does not impair further surveying efforts.

Abstract: Illustrative embodiments of the present invention include a transducer for acoustic well logging, comprising a cylindrical hollow body which is capable of vibrating radially and longitudinally with respect to its axis, and an hemispherical cap coupled to one end of the hollow body. A transducer of this type has a directivity pattern in the range of angles of about 15.degree. to 75.degree. to its axis. This range includes substantially all the acoustic waves whose angles of incidence at the interface between the drilling mud and the formations fall in the range of limit refraction angles typically encountered for the drilling mud commonly used and the various different kinds of formations usually investigated.

Abstract: A hollow, projectile-shaped body containing an acoustical transducer is rased into the sea such that the body descends in free fall until it strikes and penetrates the sea floor, coming to a rest therein. Acoustic signals emanating from the acoustic transducer are processed to generate a direct current analog signal which is a function of the acoustical attenuation of the acoustic signals from a time immediately preceding the body striking the sea floor surface until the body comes to rest in the sea floor, thereby obtaining an indication of the physical characteristics of the sea floor.

Abstract: Electroacoustical transmitting or receiving transducer comprising a flat disc piezoelectric transducer element aligned with a conical reflector. The disc transducer element is positioned to transmit acoustic energy in a direction parallel with a borehole axis and this energy is reflected by the conical reflector so that it impinges upon a borehole wall near the critical angle to provide maximum propagation of energy in the rock in one direction parallel to the borehole. The same transducer arrangement also functions as an efficient directional receiver of acoustic energy.

Abstract: In areal seismic exploration, seismic impulses are generated successively at locations spaced along a centrally located, asymmetic sawtooth shot-point line which regularly crosses a median line coincident with the line of survey. Seismic waves resulting from each impulse are detected at at least a pair of detector spreads each parallel to the median line, but offset from each other a distance equal to an integral multiple of the vertical offset of the shot-point line. Preferably the detected signals are summed on a cross-steered basis, such that the resulting traces associated with crossed sets of centerpoints normal to the survey line provide directional ("dip") information to better indicate areal subsurface structure. Additionally, the dectected signal can be stacked on a common depth point bases (CDPS).

Abstract: A highly directional acoustic source for use in a well logging system wherein a fluid-filled tube is provided with a transducer at one end and an acoustic reflector at the other end to reflect the acoustic beam into the formation. The transducer is excited at two frequencies whose difference is the desired frequency and the tube is made sufficiently long to produce parametric generation of the difference frequency.

Abstract: A method of seismic exploration is disclosed wherein an explosive charge is placed in a hole in the ground and wherein a detector is placed in a second hole spaced away from the first hole. The detector is mounted in the bottom of the hole by using an adherent base. The mouth of the hole is sealed to form a quiescent volume in the hole for the detector. Thereafter, the explosive charge is discharged and the output of the detector is recorded.

Abstract: This invention relates to a land seismic exploration method and apparatus employing a plurality of elongated tubes each having a flexible wall for containing a volume of liquid explosive therein. Each tube is adapted to be detachably connected to either a detonating device for exploding the liquid explosive therein thereby creating a seismic explosion, or to a pressure transducer for monitoring the pressure changes in the liquid explosive caused by the detected seismic pressure waves.

Abstract: A sonic generator sends a collimated acoustical wave into the section of earth under test and resonance conditions are established depending upon the nature and depth of discontinuities in the path of the acoustical wave. These resonance conditions are monitored by observing and recording electrical relationship in the power supply section of the sonic generator.

Abstract: A method and apparatus are disclosed for detecting seismic waves and electromagnetic waves at the same location in making geophysical measurements. A seismic wave is generated at a first location and the seismic wave and electromagnetic waves generated by said seismic wave are detected at a spaced-apart second location. The seismic wave may be detected by a single apparatus that also detects the magnetic field. Alternatively, the seismic wave may be detected by two spaced-apart apparatus that also measures the magnetic field at the two spaced-apart locations as well as measuring the electric field between the two apparatus.