Abstract: Method and apparatus for conducting seismic surveys from a single wellbore utilizing an array of seismic detectors and an seismic source suspended downhole from the detectors on a coiled tubing. Actuation of the airgun both generates a seismic signal penetrating the adjacent lateral geological formations and a plurality of air bubbles pass up the borehole to attenuate tube wave propagation in the borehole fluid.

Abstract: A process for preparing vertical seismic profiles (VSP) by bore drilling using, as the seismic source, the vibrations generated by the drilling bit. A cross-correlation between the bit signal and the signals collected by seismic geophone lines, is determined in which the bit signal is processed by arranging a plurality of several types of detectors on the bore drilling facility. A plurality of traces are recorded, in which the signal/noise components have different characteristics. These can be separated by means introducing filter functions by operating either on their Fourier Transforms or on the basis of their statistic distribution.

Abstract: A method for simulating crosswell seismic data between first and second spaced apart wells is disclosed. According to the invention, a surface seismic source is used to generate a seismic signal at a location on the surface of the earth substantially in line with, but not between, the wells and closer to the first well than to the second well. A plurality of downhole seismic receivers are located in the first well and at least one downhole seismic receiver is located in the second well. The actual arrival time of the seismic signal at each of the first well and second well seismic receivers is recorded. For each second well seismic receiver, the actual arrival time is then compared to an estimate of the seismic signal travel time calculated on the basis of an assumed interwell seismic velocity field.

Abstract: A marine seismic signal source apparatus and method that maximizes the usable acoustical (db) energy of the array signature in a lower frequency bandwidth. The apparatus forms a three dimensional 2.times.4.times.2 array having a plurality of 8 air guns of identical firing chamber size (10 cubic inch) operably arranged in pairs at different water depths. Firing of the guns in a top to bottom time delayed sequence shifts the frequency domain of the peak acoustical db signal to concentrate the usable seismic energy in the deeper earth formation penetrating range. The frequency boundaries of the bandwidth of the occurrence of the peak 6 db increment of acoustical power are lowered and compressed into a narrower bandwidth by the firing sequence.

Abstract: A method of acquiring and processing seismic data for repetitive monitoring of displacement of fluids impregnating a reservoir deep in the sub-surface below the surface weathered zone comprises the steps of: making at each point of a predetermined grid on the surface a vertical axis shallow borehole in the earth above the reservoir passing through the surface weathered zone; positioning in each borehole along its vertical axis a plurality of fixed receivers adapted to be connected separately to a seismic recorder on the surface; emitting near each borehole seismic waves into the earth by means of an emitter on the surface or close to the surface near the vertical axis of the borehole; recording for each borehole by means of receivers placed in the borehole the direct incident seismic waves and the seismic waves reflected at the interfaces of deep strata of the sub-surface, each receiver providing a separate record of an incident wave and a plurality of reflected waves; and carrying out the following processin

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

Abstract: A method for borehole compensation using a single transmitter measurement electromagnetic propagation tool is disclosed. Phase shift and attenuation are measured at each of three positions relative to a measurement depth. The measurements are used to calculate borehole compensation. The method may be used for other single transmitter tools and provides more accurate formation measurement in boreholes having high rugosity and washouts.

Abstract: Methods are provided for making use of an apparatus for generating vibrational energy in a borehole, the apparatus utilizes a mass and a rotary source for suspending the mass in a borehole or in casing in a borehole or in an instrument housing that may be positioned in an opened or cased borehole arranged to cause frictional contact with the surface of the rotating mass, the mass being rotatable about is rotational axis in one direction to cause it to backward whirl in the opposite direction, the centrifugal force of the whirling mass serving to generate vibrational energy that is used to obtain geophysical information as to the structure of the earth surrounding and adjacent to the borehole and for enhancing cementing and production enhancing techniques in oil or gas wells.

Abstract: A method of seismic surveying uses seismic waveguides in the earth. Seismic energy is transmitted from outside the waveguide and detected within the waveguide or vice-versa. Coupling of energy between the outside and the inside of the waveguide is effected by energy leakage at coupling sites where the waveguide departs from planarity. The method analyzes seismic signals to determine the position and nature of coupling sites and the propagation characteristics of the waveguide.

Abstract: A method of seismic exploration is disclosed wherein a signal recording obtained from subsurface geophone receivers placed below the weathered layer is used to characterize the waveform of the downgoing signal generated in the earth by a surface seismic source. The reflections of the source signal measured at the earth's surface at a point remote from this source are then deconvolved with an operator derived from the subsurface waveform in order to eliminate or compensate for the filtering effect of the weathered layer. Successive measurements of the downgoing source signal are taken at the earth's surface as the source is advanced along a seismic line. One of such surface signals can be combined with the subsurface signal recording in order to derive a transfer function indicative of such filtering effect for the intervening weathered layer.

Abstract: A technique is disclosed for determining properties of an anisotropic elastic medium, such as earth formations. Acoustic waves are established in the medium. At several spaced locations in the medium, there are measured at least two orthogonal components of acoustic waves which have propagated through the medium. For positions corresponding to a plurality of adjacent ones of the spaced locations, there are computed model composite waves which would result from the superposition of a plurality of model acoustic waves, each having selected model parameters. The model acoustic waves include a plurality of model acoustic shear waves and the model parameters include model velocities and model polarizations for each of the model acoustic shear waves. An error value is determined, the error value depending on the differences, at each of the plurality of adjacent ones of the locations, between measured wave components and the model composite wave. The model parameters are then modified.

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: A method for using mode converted P- or S- wave data to delineate the surface of an anomalous geologic structure such as a salt dome is disclosed. Seismic wavefields are propagated from near the surface, through the earth, and through the anomalous geologic unit, so that a wavefield encounters the geologic unit at a non-normal incidence angle to generate a converted S- wave. Incidence angles of the direct arrival and converted waves are then determined. The intersection point of each converted S- wave raypath with each direct arrival raypath is determined, to provide a length of the raypaths. Travel times along the raypaths are determined, and a point on the interface of the anomalous geologic unit with the surrounding earth is determined by comparing raypath travel time differences with the recorded arrival time differences.

Abstract: An apparatus (10) for providing while drilling information on a subterranean geologic formation (28) includes a drilling rig (12) and a rotary drill bit (18) attached to the drilling rig (12) for providing seismic waves as it drills in the earth (16). Geophones (20) are spaced from the rotary drill bit (18) in the earth (16) and receive in direct seismic wave paths (26) and seismic wave paths (30) reflected from the subterranean geologic formation (28) the seismic waves provided by the drill bit (18). A reference sensor (24) is located on the drilling rig (12). The seismic signals sensed by the reference sensor (24) and by the geophones (20) are cross-correlated to separate the drill bit generated signals from interference signals by combining the reference signals and the signals received by the geophones (20).

Abstract: Method of vertical seismic profiling in drilling operations utilizing the drill bit for a source of seismic energy without any break in drilling operations. The noise of the drill bit and reflections of the noise in the formation are recorded with the aid of a geometrically extended array of receivers which are provided in a predetermined matrix group. The received signals are analyzed according to velocity and migration principles per se on the basis of differences in reception times, by which the noise signature of the drill bit can be determined at any desired location during drilling operations and extracted from the traces. The remaining received signal frequencies and signal amplitudes are analyzed in relation to their deviation in time, the signals being grouped according to time differences corresponding to focusing on certain areas in the formation.

Abstract: Continuity of subsurface formations or beds in the earth between existing wells is investigated. Seismic energy is sent from a seismic source in one of the wells at various selected fixed depths. A number of sensing geophones deployed at selected fixed depths in one or more adjacent wells detect the seismic energy as data. A frequency domain decomposition process is performed on the data in order to determine if any of the formations located between the wells function as waveguides for seismic energy within the frequencies of interest. Those formations exhibiting waveguide properties are indicated as continuous between the wells.

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

Abstract: A metallic down hole seismic sensor cable for operating at temperatures up to about 400.degree. F. and pressures up to about 5000 psig is provided. The seismic sensor cable includes a flexible metallic conduit sized for receiving a seismic sensor, and means for transmitting output generated by the seismic sensor. The cable is preferably constructed of stainless steel. An inert curable heat resistant material substantially fills the unoccupied spaces of the assembled seismic sensor cable.

Abstract: A drill string in a fluid-filled borehole acts as a waveguide for an extensional wavefield that is generated in the drill string when it is excited by the vibrations of a drill bit secured to the lower end of the drill string. The waveguide acts as a distributed acoustic energy source which initiates head waves in the surrounding formation. The head waves are detected at one or more discrete locations near the surface of the earth. The extensional wavefield is detected by a sensing means mounted at the top of the drill string. The detected head waves are cross-correlated with the detected extensional waves to create a cross-correlogram which may be displayed.

Abstract: Method and system for creating a vertical seismic profile (VSP) whereby the spacing interval between units, either seismic sources or receivers, in a borehole increase exponentially as their distance from the surface increases, and the spacing interval between units, either seismic sources or receivers, along the surface of the earth decreases exponentially as their distance from the surface intercept of the wellbore increases. In a preferred embodiment of this invention, the common depth point (CDP) fold of the data gathered is substantially flattened across the reflectors surveyed.

Abstract: A method for high-resolution seismic recording with increased bandwidth using detectors planted at shallow depths below the earth's surface. In one embodiment, an optimum depth where the amplitudes of high frequency signals increase relative to that of the noise during high-resolution recording is determined, geophones are then planted at that optimum depth and signals are recorded at that depth. To find this optimum depth, detectors are planted at various depths below the earth's surface in order to record the signals at those various depths. The frequency spectra for each detected signal is generated and a velocity profile of the depths covered by the detectors is also generated from the signals. The bandwidth of the frequency spectra and the velocity profile are used to determine a depth for planting the detectors that is closer to the earth's surface than the depths previously considered.

Abstract: A method and apparatus for acquiring acoustical data from a borehole and is especially useful in carrying out tomogrphy surveys. The borehole digital geophone (BDG) tool of the present invention is capable of operating from a standard, 7-conductor logging cable with no special cables being required since the individual digital geophone modules (DGM) which form the BDG tool are connected together by short, separate lengths of the same 7-conductor cable. Each DGM acquires, digitizes, stacks, and stores data generated by its own three-component geophone assembly prior to transmitting these signals to the surface over a dedicated conductor in the cable thereby substantially increasing the sample rate of the tool which, in turn, substantially reduces the field time to run a tomography survey.

Abstract: A vertical gradient estimation technique is used to separate downgoing seismic ghost wavefields. The upgoing reflected seismic wavefield, allows the ghost wavefield to be attenuated to improve signal-to-noise ratio. The vertical gradient estimation technique is applicable to both marine seismic surveying using towed hydrophones, and to land seismic surveying using buried geophones. The technique allows the vertical signal gradient to be estimated from seismic signals measured at a single depth, and is based on a relationship between the measured seismic signals, and the source signature and the Green's function for the survey media. The technique involves determning (20) the source signature for the seismic source, and determining (21) the Green's function for the survey media. Seismic signals are then measured (22). These data are then processed to estimate (24) the vertical signal gradient as a function of source signature, Green's function and the measured seismic signals.

Abstract: An apparatus (10) for providing while drilling information on a subterranean geologic formation (28) includes a drilling rig (12) and a rotary drill bit (18) attached to the drilling rig (12) for providing seismic waves as it drills in the earth (16). Geophones (20) are spaced from the rotary drill bit (18) in the earth (16) and receive indirect seismic wave paths (26) and seismic wave paths (30) reflected from the subterranean geologic formation (28) the seismic waves provided by the drill bit (18). A reference sensor (24) is located on the drilling rig (12). The seismic signals sensed by the reference sensor (24) and by the geophones (20) are cross-correlated to separate the drill bit generated signals from interference signals by combining the reference signals and the signals received by the geophones (20).

Abstract: A method for producing an inverse vertical seismic profile using a seismic source place down a borehole has been invented. The directly transmitted waves from the seismic source and the secondary reflectances thereof are detected by a sensor(s) on the earth's surface. The method depends only on knowing the relative arrival times at the sensor of the direct waves and the secondary reflectance waves.

Abstract: An apparatus is disclosed for use within a borehole for seismic surveying that has a vertical array of seismic receivers connected to a cable, a top inflatable bladder connected to the cable above the top seismic receiver, and a bottom inflatable bladder connected to the cable below the bottom seismic receiver. The top bladder acoustically isolates all seismic receivers from the borehole environment above the top bladder. The bottom bladder acoustically isolates all seismic receivers from the borehole environment below the bottom bladder. Additional inflatable bladders are placed between each separate seismic receiver in the array.

Abstract: A method of determining the continuity of a lithographic layer located between two vertical boreholes is disclosed. A seismic source is lowered in the first borehole while simultaneously a receiver pair, preferably a pair of "vertical" geophones spaced apart by about two feet, are lowered in the second borehole to develop a "differenced signal". The recording of high amplitude signals within a layer is an indication of a continuous, low velocity layer. The middle of a layer can also be discovered using a single vertical receiver and finding the place of phase reversal.

Abstract: A marine seismic reflection prospecting system reduces coherent noise by applying a scale factor to the output of a pressure transducer and a particle velocity transducer positioned substantially adjacent one another in the water. The transducers can be positioned at a point in the water above the bottom and, thereby, eliminate downgoing components of reverberation, or they can be positioned on the water's bottom and, thereby, eliminate both upgoing and downgoing components of the reverberation. The scale factor, which derives from the acoustical impedance of the water or water-bottom material, can be determined both deterministically and statistically. The former involves measuring and comparing the responses of the pressure and velocity transducers to a pressure wave induced in the water.

Abstract: Walkaway vertical seismic profiling is conducted in a body of water. A marine seismic cable is positioned substantially vertically in a body of water. The cable has a number of hydrophones spaced along its length. A seismic source is moved along a line of traverse past the seismic cable and is periodically activated to emit acoustic waves. The response of the hydrophones to reflection of the acoustic waves from subsurface formations is then recorded for processing and analysis.

Abstract: A source array useful in vertical seismic profiling is disclosed wherein a first set of source elements having horizontal extent is spaced to have at least a first direction and a second direction, and a second set of source elements having vertical extent are spaced below the first set of source elements. The source elements in the source array are sequentially activated to focus the seismic energy along selected radial paths through the earth's subsurface.

Abstract: The invention is a method for improving quality of seismic data generatd with a source positioned substantially at the lower end of a drill string within a wellbore. A pilot signal is detected at the upper end of the drill string for cross-correlation with signals detected by field sensors positioned at the earth's surface displaced from the wellbore. Noise is reduced in the pilot signal by detecting the noise wih a sensor positioned to be sensitive to the noise but substantially insensitive to the acoustic signal transmitted up the drill string from the source. The frequency band within which there is high coherence between the energy in the noise signal and the pilot signal is determined. The noise signal is then amplified by a factor equal to the average ratio of the energy amplitude of the pilot signal to the noise signal within this frequency band, and this weighted noise signal is substracted from the pilot signal to reduce the noise in the pilot signal.

Abstract: A seismic layout technique and a processing technique for providing better data acquisition relative to salt domes which utilizes a line of sources in a selected pattern opposite a salt flank from a well bore, and a plurality of spaced receivers are disposed along the well bore for coaction with energy from said plural source location to record an array of multi-fold data. The data is then processed to establish a pseudo-source point along the well bore in relation to each of the receiver points to enable subsequent CDP processing of the data thereby to establish a vertical common reflection point outline of the vertical flank of the salt dome.

Abstract: An apparatus (10) for providing while drilling information on a subterranean geologic formation (28) includes a drilling rig (12) and a rotary drill bit (18) attached to the drilling rig (12) for providing seismic waves as it drills in the earth (16). Geophones (20) are spaced from the rotary drill bit (18) in the earth (16) and receive in direct seismic wave paths (26) and seismic wave paths (30) reflected from the subterranean geologic formation (28) the seismic waves provided by the drill bit (18). A reference sensor (24) is located on the drilling rig (12). The seismic signals sensed by the reference sensor (24) and by the geophones (20) are cross-correlated to separate the drill bit generated signals from interference signals by combining the reference signals and the signals received by the geophones (20).

Abstract: A method for the determination and deconvolution of the signature of an unknown, non-impulsive source signal. The method supposes that that an array of receivers is positioned at the earth's surface to detect and record the seismic signals resulting from the interaction of the source with the earth's subsurface. The traces of data recorded are time-shifted by an amount determined by a coherency analysis of the data. The signal is estimated from the time-shifted data with a weighting factor applied at each trace. A deconvolution filter is determined from the estimate and is weighted at each frequency according to the strength of the source at that frequency. The filter is then applied to the time-shifted data.

Abstract: A system is provided for acquiring and recording signals delivered by a set of sensors disposed in one or more probes lowered into a well at the end of a multi-function cable.The different signals to be transmitted are multiplexed before being applied to an acquisition chain adapted for amplifying them, digitizing them and coding them before applying them to a transmission channel in the form of blocks of digitized words. The multiplexing means may comprise several multiplexing units. The sampling frequency of each signal and the formation of the blocks of words are adapted to the number of units effectively used. In the surface installation, the blocks of words are dissociated and stored in a memory in a single mode suitable for all the blocks whatever their formation.

Abstract: An inventive method for simultaneously collecting depth-of-focus vertical seismic profiling (VSP) data and three-dimensional surface seismic data is disclosed. At least one seismic sensor is deployed at a predetermined depth of a borehole and raised in increments determined by the survey. A seismic source and a plurality of seismic sensor may be deployed at the surface along a partial arc offset from the top of the borehole by a distance inversely proportional to the depth of the sensor in the borehole. The seismic source generates a seismic signal at a plurality of points in a circular path around the borehole. Once a circle has been completed, the borehole sensor is raised, and the seismic signal generator and sensors are moved to the next largest circular path and the process is repeated. The seismic signals are simultaneously recorded by the borehole sensor and the sensors deployed in the arcuate path.

Abstract: Seismic energy is generated at a multiplicity of source offsets from a borehole and offset VSP data is collected by an acoustic detector at a multiplicity of geophone depths for each source offset. The recorded data is sorted into Zero Source-Receiver (ZSR), common reflection point bins. Data from each offset VSP, ZSR common reflection point gather are dynamically moveout corrected with data adaptive parameters including reduced direct arrival times, dip, borehole deviation and stacking velocities. The moveout corrected VSP data are then stacked.

Abstract: VSP-based method for tieing surface data shot with different types of seismic sources together. VSP data is acquired using the same types of seismic sources utilized to acquire the surface data. The acquired VSP data is used to produce a correction operator for application to the surface data.

Abstract: A method and apparatus are disclosed for carrying out the seismic exploration of the strata which surrounds a borehole during the drilling of that borehole. A compressional mode jar mechanism is disposed in a drill string above a drill bit. Sufficient weights to cock and actuate the jar are disposed both below and above the jar mechanism respectively. A telescoping joint above the jar prevents the impact on the drill bit from propagating up the drill string and multiple geophones at the surface are utilized to receive the seismic waves generated by the impact of the drill bit within the borehole. In a preferred mode of the present invention, an additional geophone is disposed within the drill string proximate to the drill bit to detect the "first break" of the impact thus generated.

Abstract: An endfire seismic array comprises one or more marine seismic cables having a plurality of acoustic-to-electrical hydrophone receivers spaced therealong, each being operatively connected in combination so that as a unit an endfire receiving beam pattern with respect to any frequency across the seismic band is formed by causing the signals from the individual hydrophone receivers to be additive for that frequency. A plurality of cables results in a more narrow beam than a single cable. A geologic or lithologic formation that is a dip change from the norm may be detected either as an extra strong increase or decrease in signal, depending on the mode of use.

Abstract: Methods and apparatus are described utilizing low frequency tube waves in determining characteristics of formations traversed by a borehole. Data received from three spaced receiving transducers are utilized in formulating quantities representative of complex compressibility of formations as well as loss parameters attributed to formation characteristics. When these two factors are recorded as a function of depth, interpretation is made readily available as to the permeability and rigidity of subsurface earth formations. Data is also provided by way of the present invention to enable interpretation concerning the presence of fractures or cracks in the earth formations. The methods and apparatus may also be utilized to examine the condition of casing in a borehole.

Abstract: A method of velocity filtering seismic signals and an installation for implementing the method. A two-dimensional signal g(z,t) is available built up from a set of signals .sub.i (t) for I>i>n as produced by sound wave detectors located at different depths z.sub.1, . . . z.sub.n in a borehole in response to sound waves being emitted from a source as seismic waves, with said detected signals including upgoing waves and downgoing waves. In order to reinforce the upgoing waves (or conversely the downgoing waves) in the signal g(z,t), an operator A is applied recursively to said signal, where: A=1/2[Id+.epsilon..B.H.sub.t.D.sub.z ] where: Id is the identity operator; .epsilon.=+1(or -1); B is normalization factor whose value depends on the signal g(z,t) to which the operator A is applied; H.sub.t is the one-dimensional Hilbert operator relating to the variable t; and D.sub.z is a differentiation operator relating to the variable z.

Abstract: In a VSP survey, the subsurface coverage of the bounce points of primary reflections is limited to one-half the offset between a borehole and a seismic-source point. The subsurface coverage may be extended by use of selected multiply-reflected wavefield arrivals.

Abstract: The present invention is directed to a method of inverting seismic traces Sk by determining the series R={r.sub.i } representative of the seismic reflection coefficients from geological strata. The method includes the steps of determining an approximate solution to R.degree. by minimizing an entropy type function H(R)=.SIGMA.f(r.sub.i) under constraints related to the upgoing wavefield Uk and the downgoing wavefield Dk; determining a correction value .DELTA.R by minimizing a linear function J(.DELTA.R) under linear constraints related to the noise in the traces and to the time-depth curve extracted from the traces; and calculating R=R.degree.+.DELTA.R, representative of the reflection coefficients. In a variant, the selection of the approximate solution R.degree. is guided by taking into account information contained in one or more logs, and determining .DELTA.R so that the series R satisfies the stacking velocities which result from surface seismic processing.

Abstract: The instant invention is a method for accurately estimating the subsurface porosity and porosity-thickness of an interval of interest. A seismic acoustic model is constructed from data collected in a seismic survey. The acoustic model provides information from which predicted porosity values may be calculated. The predicted porosity valves are then cross-plotted with actual porosity valves obtained from well information, providing an accurate estimate of porosity away from the well locations. Porosity thickness is determined using the thickness information provided by the well data.

Abstract: Three-axis vertical seismic profile measurements are analyzed to derive values for the velocity v.sub.p and angel of incidence .PSI..sub.p of a plane compressional wave at the borehole and for the shear wave velocity v.sub.s and angle of incidence .PSI..sub.s of a plane shear wave at the borehole. In the described embodiment this is accomplished by finding values for these parameters which maximize the expression.SIGMA..sub..omega. .vertline.(a.sub.p +a.sub.s).sup.H u(.omega.).vertline..sup.2 /.parallel.a.sub.p +a.sub.5 .parallel..sup.2 +.vertline.(a.sub.p -a.sub.s).sup.H u(.omega.).vertline..sup.2 /.parallel.a.sub.p -a.sub.s .parallel..sup.2where.omega. is angular frequency;a.sub.p and a.sub.s are column vectors representing compressional and shear wave particle motions at frequency .omega. at a multiplicity of locations in the borehole;u(.omega.) represents components in a plane of waveform measurements obtained at these locations;.parallel. .parallel.

Abstract: A method for segregating and stacking vertical seismic profile data is disclosed wherein the offset difference between the well location and the position of the source is divided into equal segments, VSP moveout corrected data are placed in common reflection point bins and stacked.

Abstract: A process for separating upgoing and downgoing seismic wave events in a vertical seismic profile, and particularly for vertical seismic profiles wherein the seismic energy source is offset from the borehole in which seismic detectors are located in vertical spaced array. The process operates on two detector signals at a time (as S.sub.1 and S.sub.2) and is based on the concept that waves traveling in opposite directions have spatial derivatives of opposite sign. The derivative is approximated by the difference of the two signals which is time integrated to recover the phase. The resulting integrated difference signal I is then amplitude scale corrected and combined by addition or substraction with a signal S.sub.0 representing the sum of the two detector signals to form a succession of filtered signals which, when recorded in alignment in order of detector depths to form a vertical seismic profile preserves either the upgoing or the downgoing seismic events.

Abstract: What is disclosed is an improvement in a multi-level geophone sonde installation for VSP which includes a well penetrating subterranean formations; surface source for generating and inputting vibrational wave energy; a plurality of geophone sondes with a plurality of detachable geophone sondes disposed in the well with an uppermost sonde and at least a plurality of other lower sondes at predetermined spacings for receiving vibrational wave energy arrival and generating the data indicative thereof; and conductors for getting to the earth's surface a record of the vibrational wave energy arrival data. The cable has a greater width than thickness and is rigid because it is formed in a plurality of vertebrae type formations so that it is self supporting or load bearing. Moreover, the rectangular cable reduces the twist of the cable.

Abstract: A drill bit drilling a borehole is used as a strong high frequency, subsurface seismic source in combination with at least one receiver in a preexisting borehole to determine the continuity of a subsurface formation layer extending between the borehole being drilled by the drill bit and the borehole in which the receiver is located. The receiver(s) in the preexisting borehole may be any conventional seismic receiver or receivers, such as hydrophones or geophones. The receiver or receivers are positioned in the preexisting borehole at a depth adjacent the formation layer whose continuity is to be determined. The depth (position), velocity and thickness of the layer is determined from a conventional well log of the preexisting borehole. A frequency power spectrum for a preselected frequency range (the range is selected based on the logging data) may be computed from the signals recorded by the receiver(s).