Abstract: Methods are disclosed for monitoring operation integrity during hydrocarbon production or fluid injection operations. According to the methods, received microseismic data is processed to obtain a plurality of data panels corresponding to microseismic data measured over a predetermined time interval. For each data panel, trigger values are calculated for data traces corresponding to sensor receivers of the microseismic monitoring system. At least one data panel is selected as a triggered data panel that satisfies predetermined triggering criteria. A value is calculated for each of at least two event attributes of a plurality of event attributes of the event. An event is classified into at least one event category of a plurality of event categories based on the event score. Related non-transitory computer usable mediums are also disclosed.

Abstract: Methods and systems are disclosed for monitoring operation integrity during hydrocarbon production or fluid injection operations. According to the methods and systems, received microseismic data is processed to obtain a plurality of data panels corresponding to microseismic data measured over a predetermined time interval. For each data panel, trigger values are calculated for data traces corresponding to sensor receivers of the microseismic monitoring system. At least one data panel is selected as a triggered data panel that satisfies predetermined triggering criteria. At least one triggered data panel is selected as a non-trivial data panel that satisfies spectral density criteria. A value is calculated for each of at least two event attributes of a plurality of event attributes of the event. An event score is determined based on the values of the plurality of event attributes. An event is classified into at least one event category of a plurality of event categories based on the event score.

Abstract: The present disclosure describes computer-implemented methods, computer-program products, and computer systems, for providing parameters for successful automated fault patch extraction. Attributes are selected for annotating images generated from, and for interpretation of, seismic amplitude volume. Images are generated from layers of a seismic cube, each generated using a different attribute of the plural attributes. The plural images are blended using customized palettes and initial parameters to create a blended image illuminating discontinuities in the layers. Optimal parameters are iteratively determined for automatic derivation of fault discontinuities on an interpreter-selected edge-enhanced sub-volume. The iterations are controlled and terminated based on interpreter inputs. The optimal extraction parameters are applied to an entire edge-enhanced volume. Important extracted fault discontinuities are isolated using commercial filtering tools.

Abstract: The present disclosure describes computer-implemented methods, computer-program products, and computer systems, for providing parameters for successful automated fault patch extraction. Attributes are selected for annotating images generated from, and for interpretation of, seismic amplitude volume. Images are generated from layers of a seismic cube, each generated using a different attribute of the plural attributes. The plural images are blended using customized palettes and initial parameters to create a blended image illuminating discontinuities in the layers. Optimal parameters are iteratively determined for automatic derivation of fault discontinuities on an interpreter-selected edge-enhanced sub-volume. The iterations are controlled and terminated based on interpreter inputs. The optimal extraction parameters are applied to an entire edge-enhanced volume. Important extracted fault discontinuities are isolated using commercial filtering tools.

Abstract: The present disclosure describes computer-implemented methods, computer-program products, and computer systems, for providing parameters for successful automated fault patch extraction. Attributes are selected for annotating images generated from, and for interpretation of, seismic amplitude volume. Images are generated from layers of a seismic cube, each generated using a different attribute of the plural attributes. The plural images are blended using customized palettes and initial parameters to create a blended image illuminating discontinuities in the layers. Optimal parameters are iteratively determined for automatic derivation of fault discontinuities on an interpreter-selected edge-enhanced sub-volume. The iterations are controlled and terminated based on interpreter inputs. The optimal extraction parameters are applied to an entire edge-enhanced volume. Important extracted fault discontinuities are isolated using commercial filtering tools.

Abstract: Embodiments of non-uniformly spaced seismic receiver arrays and associated noise removal techniques are disclosed. In one embodiment of a method of seismic data acquisition, a plurality of seismic receivers may be positioned in an array having a plurality of regions, each region in the array having a respective average spacing between seismic receivers, with the average spacing in a second region of the plurality of regions being greater than the average spacing in a first region of the plurality of regions that is adjacent to the second region. Seismic data may be acquired utilizing the plurality of seismic receivers, and noise may be removed therefrom.

Abstract: The present application relates to a method for identifying events of digital signal. The method identifies the events of a digital signal by means of the characteristic that the events of a digital signal basically depend on the signal phase.

Abstract: A method of characterizing a fractured reservoir in a field includes measuring seismic reflection coefficient of the fractured reservoir as a function of angle of incidence and azimuth, predicting seismic reflection coefficient of the fractured reservoir as a function of angle of incidence and azimuth using an elastic stiffness tensor and an elastic compliance tensor of the fractured reservoir, determining components of an excess compliance tensor due to the presence of fractures in the fractured reservoir by matching the predicted seismic reflection coefficient to the measured seismic reflection coefficient, and characterizing one or more properties of the fractured reservoir using the excess compliance tensor.

Abstract: A method for simultaneously operating multiple seismic vibrators using continuous sweeps (little or no “listening” time between sweeps) for each vibrator, and recovering the separated seismic responses for each vibrator with the earth signature removed. Each vibrator is given a unique, continuous pilot signal. The earth response to the motion of each vibrator is measured or estimated. The vibrator motion records for each vibrator and the combined seismic data record for all the vibrators are parsed into separate shorter records. The shorter records are then used to form a system of simultaneous linear equations in the Fourier transform domain, following the HFVS method of Sallas and Allen. The equations are then solved for the separated earth responses.

Abstract: This invention is a method of separating induced microseismicity signals from seismic signals acquired within active seismic monitoring operations carried out in underground zones under development which has application for monitoring of underground hydrocarbon or fluid storage reservoirs. Seismic records are formed from signals emitted by one or more seismic sources controlled by orthogonal signals. In this case, the signals are processed to separate the respective contributions of the at least one seismic source to the signals received and to reconstruct the seismograms equivalent to those that would be obtained by actuating the at least one seismic source separately.

Abstract: A subterranean structure is characterized using composite seismic response data received from a plurality of sources. Phase encoding is applied to the data in which phase shifts are selected based on frequency variation of noise terms. The phase-encoded data is then migrated and a representation of the subterranean structure is produced according to the migrating.

Abstract: In accordance with the present invention, there is provided a method of determining whether a particular high fidelity vibratory seismic survey phase encoding is likely to be a good one based on an analysis of the eigenvalue structure (i.e., eigenvalues, eigenvalue separation, condition number, and model resolution matrix) of a matrix formed from the Fourier transforms of the sweep signals. Preferably, a singular value decomposition will be used to calculate the eigenvalues. Using this same approach, the condition number and eigenvalues of matrices that are associated with multiple proposed designs can be compared with each other to determine which is likely to be yield the best seismic data. This approach is preferably used either as a component of the advanced planning for a survey or in the field during pre-survey testing. The use of the instant approach to determine an optimal phase encoding scheme is also taught.

Abstract: Waveform data, such as reflection seismic data, is filtered by concurrently analyzing various phase angles of the data. The various phase angles of the data are compared to phase rotated background trends and the phase angle producing the maximum deviation from the equivalent background trend is selected as the optimum phase angle for predictive analysis or exclusion filtering.

Abstract: For determination of the laminar structure and other characteristics of a ground, oscillation sensors for detecting the vertical component or vertical and horizontal components of oscillations are disposed at three or more points within a comparatively small area at ground level to simultaneously measure microseisms at the respective points, if necessary with locations of said points being varied and measurements be performed at the respective locations and the vertical oscillation data or vertical and horizontal oscillation data thus generated are analyzed. This method not only permits an expedient, positive and accurate assessment of the laminar structure and other characteristics of the ground but also permits the measurement of ground structure even when the area available for measurement is small.

Abstract: For determination of the laminar structure and other characteristics of a ground, oscillation sensors for detecting the vertical component or vertical and horizontal components of oscillations are disposed at three or more points within a comparatively small area at ground level to simultaneously measure microseisms at the respective points, if necessary with locations of said points being varied and measurements be performed at the respective locations and the vertical oscillation data or vertical and horizontal oscillation data thus generated are analyzed. This method not only permits an expedient, positive and accurate assessment of the laminar structure and other characteristics of the ground but also permits the measurement of ground structure even when the area available for measurement is small.

Abstract: The invention is a method for facilitating discrimination and identification of seismic or microseismic events by means of permanent pickups in an underground zone under development. The method comprises permanent installation of, in one or more wells, elastic wave receivers, geophones and hydrophones leaving the wells clear for development of the zone, at least one reference pickup with direct acoustic coupling with the technical zone development equipment (pickup pressed against a production string for example) for detection of events directly connected with the operation of the wells (valve opening and closure, etc.

Abstract: The present invention relates to a time-lapse or 4-D seismic data processing method in which cross-correlation of trace information in a series of time-lapse seismic images is used to distinguish one source of noise from another source of noise. After a source of noise has been identified, an appropriate filter is constructed to provide a correction to the noise produced by this particular source of noise. The data from one of the time-lapse seismic images is then applied to the filter to produce a corrected image. Differences between the corrected image and an uncorrected image are then used to determine time-lapse changes in the underlying geological structure. By being able to provide filters specifically tailored to correct each of the different types of noise present in a series of time-lapse seismic images, an accurate image of the time-lapse changes in the underlying geological structure is attained.

Abstract: A method is disclosed for borehole compensation of measurements of earth formations penetrated by a borehole including differential time (.DELTA.t) measurements obtained from a borehole tool in the formation. The borehole tool includes at least one transmitter and a plurality of receivers spaced apart from each transmitter. Each transmitter generates a waveform, and the receivers are responsive to the waveform. A receiver array .DELTA.t measurement is generated for a depth interval spanned by the receivers by cross-correlating receiver array waveforms relevant to the spanned depth interval. A synthesized transmitter array .DELTA.t measurement corresponding to the spanned depth interval is generated by cross-correlating selected transmitter array waveforms.

Abstract: A method for enhancing zero-phase seismic data traces so that subtle geologic features are easier to identify and interpret. In a first embodiment, the method comprises enhancing the amplitudes of at least the peaks and troughs in the zero-phase seismic data traces. This enhancement can be accomplished in a variety of ways. In a second embodiment, the negative second difference is calculated at each sample point along the zero-phase seismic data trace to enhance bends or kinks in the data, as well as peaks and troughs.

Abstract: A discrete, minimally-equipped standard seismic calibration system is permanently installed over a subsurface reservoir structure that contains fluids of economic interest. Changes in the fluid content as a function of long-term time lapse may introduce changes in the acoustical characteristics of the reservoir rock layers, producing a corresponding change in the seismic signature recorded by the calibration system. The difference between two signatures over a selected time epoch defines a time-lapse calibration signature. The time lapse calibration signature can be applied to reduce the results of different conventional seismic data-acquisition systems of different vintages and technologies to a common standard.

Abstract: A method and computer system for deriving and applying normal moveout phase and time shift corrections to seismic survey traces is disclosed. Normal moveout time-shift corrections are first applied to traces in a common midpoint (CMP) or common depth point (CDP) gather, based upon stacking velocity analysis applied to envelopes of the traces. One offset in the survey, preferably the maximum offset, is selected as the reference point; the NMO time shift at this reference offset is then selected as a reference NMO time-shift. The traces in the gather are each phase-shifted based upon iterated reference phase dispersion values at the reference offset, times the ratio of the normal moveout time-shifts for the trace in the gather to that of the reference offset (raised to a power). Semblance analysis is performed to identify, for each point in normal incidence time and thus for each reflective event, the optimum reference phase dispersion value.

Abstract: A method for eliminating the influence of multiple reflections in seismic data by determining an up going and down going vector wave-field from the vector wave-field, determining a product of the free surface refection coefficient and the down going vector wave-field, and adding the product to the up going vector wave-field. Also provided is a method for eliminating the effects of receiver coupling from seismic data taken in a survey by describing a first cross-equalization filter as a function of the reverberation period, describing a second cross equalization filter as a function of the seismic data, deriving an inverse coupling filter as a function of the first cross-equalization filter and the second-equalization filter, and applying the coupling filter to the seismic data.

Abstract: A method for separating and pre-processing vibratory source data includes varying the phase of vibratory sources according to two patterns. A first pattern is used for odd numbered sources while a second pattern is used for even numbered sources. Each pattern begins with a zero phase shift, the zero phase shift occurring at the sweep number corresponding to the position number of the source. The first pattern is one of zero phase shift, ninety degree phase shift, ninety degree phase shift and one hundred eighty degree phase shift. The second pattern is one of zero phase shift, one hundred eighty degree phase shift, ninety degree phase shift and ninety degree phase shift. The patterns are alternated for each source, the beginning of the pattern corresponds to the position of the source in a line. The first source begins with the first pattern. The second source begins with the second pattern, with zero starting at the second sweep.

Abstract: A method for recording and pre-processing vertical seismic profile high fidelity vibratory seismic data includes the steps of measuring the motion of the vibrator which is related to the vibrator applied force times a transfer function of minimum phase, causal, linear system relating the actual vibrator output with the measured vibrator motion, separating signals according to the generating source of each, determining a ratio by dividing the vibratory seismic data by the measured motion of the vibrator to remove the unknown applied force leaving the earth reflectivity times a time derivative divided by a minimum phase function, minimum phase band pass filtering the resulting ratio and performing minimum phase deconvolution to remove the time derivative divided by the transfer function of minimum phase.

Abstract: A method for attenuating source-generated surface wavetrains in a set of seismic data traces. According to the method, the seismic data traces are Fourier transformed with respect to time to determine the frequency components of the surface wavetrain. A phase matching operation is then performed using estimates of the wavenumbers for each of the frequency components to approximately align the surface wavetrain in the seismic data traces. Next, a spatial low-pass filter is used to remove the approximately aligned surface wavetrain. Finally, the phase matching is removed and an inverse Fourier transformation is performed to return the seismic data traces to the time domain.

Abstract: A method for utilizing instantaneous phase and the derivatives of instantaneous phase as display and/or plot attributes for seismic reflection data processing and interpretation for two-dimensional and three-dimensional seismic data. The spatial frequency, dip magnitude and dip azimuth attributes of the seismic events are calculated using the rate of change of instantaneous phase with space, instantaneous frequency and velocity, and displayed or plotted to assist interpreters in identifying fault breaks and stratigraphic features in the earth's subsurface.

Abstract: A method for recording and pre-processing high fidelity vibratory seismic data includes the steps of measuring the motion of the vibrator which is related to the vibrator applied force times a transfer function of minimum phase, causal, linear system relating the actual vibrator output with the measured vibrator motion, separation of signals according to generating source, determining a ratio by dividing the vibratory seismic data by the measured motion of the vibrator to remove the unknown applied force leaving the earth reflectivity times a time derivative divided by a minimum phase function, minimum phase band pass filtering the resulting ratio and performing minimum phase deconvolution to remove the time derivative divided by the transfer function of minimum phase. The method may also include shot ensemble deconvolution, receiver ensemble deconvolution, statics correction, F-K filtering for noise, zero phase spiking deconvolution and model dephasing.

Abstract: A phase locked loop circuit having a voltage controlled oscillator for generating a clock signal with a frequency determined by a voltage control signal supplied to the voltage controlled oscillator, an AD-conversion circuit for sampling a target signal with a timing determined by the clock signal and for converting sampled values into digital data, a phase locked loop control circuit for generating control data with values representing values of the digital data, and a DA-conversion circuit having an adjustable conversion characteristic for converting the control data into an analog signal and for outputting the analog signal to the voltage controlled oscillator as the voltage control signal.

Abstract: A method for recording and pre-processing high fidelity vibratory seismic data includes measuring the motion of the vibrator which is related to the vibrator applied force times a transfer function of minimum phase, causal, linear system relating the actual vibrator output with the measured vibrator motion, determining a ratio by dividing the vibratory seismic data by the measured motion of the vibrator to remove the unknown applied force leaving the earth reflectivity times a time derivative divided by a minimum phase function, minimum phase band pass filtering the resulting ratio and performing minimum phase deconvolution to remove the time derivative divided by the transfer function of minimum phase. The method may also include the steps of receiver ensemble deconvolution, statics correction, F-K filtering for noise, zero phase spiking deconvolution and model dephasing. The actual signal that the vibrator is sending into the ground is used in pre-processing.

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 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: A method to adjust a common subsurface feature on seismic traces associated with line misties is provided so that the seismic traces are consistent about the common subsurface feature. The method uses traces which are uniquely located in an x-y coordinate system to reflect the actual location of the traces with respect to an intersection. In this method traces can be associated with a line of seismic data or can be isolated traces such as well-log synthetics or vertical seismic profiles. The traces make up sets of data. An intersection is selected and representative traces from two sets of data are initially selected and form trace pairs. A time gate is determined about a common subsurface features of interest on the representative traces. The time gate isolates a trace gate about the common subsurface feature on each trace leaving only the trace gates in the trace pairs. A time delay is determined for each trace pair.

Abstract: A gas thermometer has a case with a case end section (10) made of metal of good thermal conductivity and a main case section (14) made of material of poor thermal conductivity. By means of separating walls (46, 48, 62, 64, 70) and reflector walls (66, 68), two sound paths are created in the interior of the thermometer case, which differ by twice the distance between the reflector walls (66, 68). The phase difference of partial sound wave fields which are obtained by splitting a sound wave field produced by a common sound generator (40) between the two paths is converted to an electrical signal corresponding to the temperature in the case end section (10) by using microphones (26, 28) and an analyzing circuit (92) connected with them.

Abstract: The present invention offers methods and apparatus for sonic borehole logging of formation shear using discrete frequency measurements. A multipole source transducer emits sonic energy at a location in a borehole of at least one discrete frequency which induces propagation of multipole sonic waves in the borehole; sonic energy of the multipole sonic waves is detected at multiple receiver locations in the borehole by multipole receivers to produce a received sonic signal for each location, the multiple receiver locations being spaced apart from one another and from the source transducer location. For each receiver location, the complex values of the received sonic signal are detected relative to a predetermined phase reference. The detected complex values of the received sonic signal may be processed to determine multipole sonic wave velocity and shear attenuation at discrete frequencies and to calculate velocity and attenuation as a function of frequency.

Abstract: When a record mark portion arranged on the upstream side of a data area is reproduced, the peak value of a reproduction signal of the record mark portion is compared with a reference level. An overwrite preventing circuit is arranged so as to output an inhibiting signal for inhibiting data writing when the comparison output exceeds a predetermined level. With this preventing circuit, a data portion need not be checked in a read mode prior to a write mode.

Abstract: A method is disclosed for acquiring and processing logs obtained by a well-logging tool moved in a well, providing better discrimination between the discontinuities of the sub-soil oriented substantially in the same direction as the well and situated on each side thereof, and particularly in a substantially horizontal well. The method includes the displacement of the tool along the well and the provision of at least two series of signal transmission, reception and logging cycles, the position of the signal transmission and/or reception means relatively to the axis of the well being different from one series to another, so as to cause the distance from the transmission and/or reception means to the discontinuities on each side of the well to vary. Combining the logs from these series of cycles makes it possible to distinguish the reflections on the side of the well from which they come.

Abstract: A method is provided for significantly reducing the distortion and crossfeed from any selected order harmonic for any number of vibratory seismic sources operated concurrently, at the same time providing for separation of the signals from the different sources and for improving the signal-to-noise ratio. After determining the highest order harmonic likely to cause distortion, a number of sweeps of each source in each position is selected. This number depends upon the number of sources and the highest order harmonic to be suppressed. Initial phase angles for each sweep of each source are then selected to permit signal separation while suppressing harmonics up to and including that highest order harmonic.

Abstract: A method is provided for enhancing processing and evaluating seismic data. More particularly, a novel method is described for enhancing and evaluating common depth point seismic data. Common depth point (CDP) gathers of seismic signals are processed to suppress random noise and coherent noise and to enhance primary reflection events while preserving geologically-induced amplitude variations as a function of range for the primary reflection events. The processed CDP gathers of seismic signals can then be processed to obtain attributes descriptive of amplitude variations as a function of range for the selected primary reflection event whereby formation lithology and fluid content can be evaluated.

Abstract: A geophysical method of exploration including processing and displaying seismic data so as to enhance geophysicists' ability to evaluate and interpret subtle variations in the earth's geological and lithological structure. In particular, an exponentiated phase signal is obtained for a complex signal formed from seismic data exponentiated to a selected power. Displays of the exponentiated phase signal can be produced which visually highlight subtle variations in the earth's geological and lithological structure.

Abstract: Methods and apparatus for processing vibrative seismic data. Baseplate phaselock vibrative energy, reaction mass phaselock vibrative energy and ground force phaselock vibrative energy are transmitted into the earth using a land vibrator and the reflections of the transmitted waves recorded. The source signature of the land vibrator is computed for each type of vibrative energy and the source signature is correlated with the corresponding recorded data to produce an image of the subsurface. Regardless of the type of phaselock vibrative energy generated into the subsurface, the images of the subsurface produced by the correlation of the source signature and the recorded data are substantially the same. The correlated data may be then analyzed to yield useful information related to the characteristics of the subsurface.

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: The invention is a method of performing a plurality of vibratory seismic surveys simultaneously. A plurality of vibratory sources transmit signals into the earth. Each vibratory source successively transmits the same signal, except that an offset phase of the signal is selectively shifted for successive transmissions. The offset phase of the signal transmitted by each vibratory source is selected to enable the signal from each of the vibratory sources to be recovered by data processing.

Abstract: Disclosed are a process and a system for improving seismic returns and other signals representative of non-time varying series which have been degraded by interaction with unknown wavelets. Use is made of a sequence of two-term operators, each derived from the most recent version of the signal and each applied thereto to obtain the next version. The operators are selected such that their application tends to increase the entropy of the signal, and to remove the effects of the unknown wavelets and change the observed signal in a manner which tends to reveal the signal of interest.

Abstract: A variable amplitude/phase color seismic display is provided which increases the ease with which interpreters can locate peaks, troughs and other information of interest.

Abstract: A vibrator seismic source has a hydraulic system, including a pad, for applying reciprocating forces to the ground and sensor means for generating a feedback signal representative of the force applied to the ground. Circuitry is provided for generating a pilot signal representative of the desired force to be applied to the ground. The pilot and feedback signals are single sideband shifted to increase both frequencies by a predetermined frequency. The high frequency pilot and feedback signals have their phase difference conventionally detected and provided to a digital computer for phase shifting the signal for controlling the vibrator so that the feedback signal is in phase with the pilot signal. In another embodiment, the instantaneous phase of each signal is computed continuously by a digital computer. The control signal digital representation is corrected to correspond with the pilot digital representation and an analog output signal is generated to provide the proper analog control signal.

Abstract: Data points for a sinusoidal waveform are assigned 2 bit values which indicate the state of the amplitude (positive or negative) and the slope of the sinusoidal signal at the particular data point (positive or negative). The 2 bit values for a plurality of sinusoidal waveforms are compared to determine the phase misalignment between the plurality of sinusoidal waveforms.

Abstract: A method for developing a novel seismic data attribute enables improvements in seismic data processing and interpretation. Seismic signals or trace data are first rectified and then Hilbert transformed and processed with the arc tangent function to develop a new instantaneous phase parameter referred to as phase of rectified trace (PORT). Output data may be further enhanced with tri-modal, interactive color display.

Abstract: A method of processing geophysical seismic data so as to enhance its evaluation and interpretation. A plurality of response waveform characteristics are developed from a seismic signal. The response waveform characteristics can provide empirical basis for correlating a seismic signal fo formation geology and lithology. In accordance with the present invention, the response waveform characteristics are chromatically quantified and the intensity of which can be modulated so as to enhance the signal-to-noise ratio of the displayed response waveform characteristics.

Abstract: Seismic pulse waveforms are generated for travel through subsurface formations. Both normally-reflected and obliquely-reflected waveforms from subsurface interfaces are recorded. The differential phase change between the normally-reflected and obliquely-reflected waveforms are determined for each interface. The fluid characteristics of the porous subsurface layers are identified as gas-saturated or water-saturated in response to the relative amounts of phase change, a gas-saturated layer providing a larger phase change than a water-saturated phase change.

Abstract: Apparatus for shear wave logging of formations adjacent a borehole wherein a tubular apparatus is specifically constructed for sympathetic movement with the borehole in response to low frequency horizontal shear waves. The apparatus consists of tubular frame structure with end members including housings for rigid seating of orthogonal pairs of horizontal wave detectors. Outer sleeve structure may be utilized for buoyancy adjustment.