Abstract: A method for locating hydrocarbon reservoirs or other geological anomalies by determining lithological parameters including Poisson's ratio, density and seismic wave velocity. Such parameters are determined by quantitatively relating reflection wave amplitude to corrected source-detector offset data.

Abstract: A method for derivation of interval velocities from post-migration parts first includes the step of determining the apparent depth and slope of an event. The apparatus depth of an event is measured. The travel time of the recorded reflection for a particular offset is determined by ray-tracing through the old model and recorded. A trial velocity is assigned to the layer between events in the new model. The depth of the reflector is varied up or down until the computed travel time agrees with the measured travel time, keeping the source/receiver separation constant. A new velocity for the layer between reflectors is selected for which the depths at each offset are the same.

Abstract: A method of establishing a stratigraphic model of the subsurface from an acoustic impedance profile A.sub.o ={a.sub.o (n),n=1,N} corresponding to a series of reflection coefficients R.sub.o ={r.sub.o (n),n=1,N}, where n is an index relating to the depth sampled in time t, and from a seismic section comprising a plurality of seismic traces T.sub.i (t),i=0,I recorded in response to the emission of a seismic wave of signature W(t), the method comprising the following steps:successively determining each series of coefficients R.sub.i ={r.sub.i (n),n=1,N} by minimizing a cross-entropy function H(R.sub.i /R.sub.i) between firstly a series R.sub.i obtained from the series R.sub.i-1 and a set of one or more seismic traces {T.sub.i-j,T.sub.i+j }, and secondly the looked-for series R.sub.i, said minimization being performed under pre-established constraints; anddetermining the acoustic impedance profiles A.sub.i ={a.sub.i (n)} corresponding to the series R.sub.i.

Abstract: A method for generating a three dimensional velocity model makes use of two dimensional depth images, which are the result of two dimensional pre-stack depth migration, and corrects the out of plane distortion by ray tracing through a three dimensional model. The three dimensional model boundaries are iterated until the three dimensional effects are minimized. The final model can be used for a final three dimensional pre-stack depth migration, or as a three dimensional interpretation of all the two dimensional depth migration results.

Abstract: The present invention provides a three dimensional before stack depth migration of two dimensional or three dimensional seismic data. Ray tracing is used to move before stack trace segments to their approximate three dimensional position. The trace segments are scaled to depth, binned, stacked and compared to the model. The model can then be changed to match the depth trace segments which will be stacked better, moved closer to their correct three dimensional position and will compare better to the model.

Abstract: A method for seismic trace interpolation by dip range analysis is disclosed. In the preferred embodiment, a series of dip ranges are defined by a plurality of dips. A trace estimate for each of the dip ranges is generated by filtering with a mathematically integrated time shift in each frequency component of each seismic trace appearing in the dip range. These filtered frequency components are then passed through a low pass filter. The sum of the filtered frequency components is the trace estimate. The seismic traces are then demodulated to obtain the trace envelopes whose values along the above mentioned dips are examined for continuity. A continuity factor is developed for each dip and then each of the continuity factors is summed and the sum divided by the number of continuity factors to obtain a weighting function. The weighting functions are multiplied with the trace estimates, and the results summed to obtain the interpolated trace.

Abstract: An improved method for modeling the subterranean structure of the earth is disclosed. Assumed velocities are used in initially modeling the path of seismic energy through the subterranean structure. Arrays of travel times corresponding to upward and downward going energy from various locations in the subterranean structure are calculated using ray tracing techniques. Actual reflection points are located when the sum of the upward and downward going travel times calculated with respect to a particular point in the structure equals the actual travel times recorded. The velocity assumptions are verified by selecting common reflection point records and adjusting the assumed velocities, such that reflection events on displayed traces from the common reflection point are horizontal. A least squares fit is used to correct the common reflection point event data until it is optimally flat.

Abstract: A seismic record is enhanced through trace restoration and extrapolation. A set of traces surrounding a missing trace or adjacent an edge of the seismic record are transformed into the frequency domain using a fast Fourier transform. Each frequency of the resultant x-f representation a series of complex numbers, one corresponding to each trace, is selected. Autoregressive model coefficients are estimated for this complex series using a recursive least squares method. A complex number is estimated for trace restoration and extrapolation from the series of complex numbers and autoregressive coefficients. After all frequency components are thus processed restored or extrapolated traces are obtained by an inverse Fourier transform.

Abstract: A model-based iterative method of depth-processing seismic data. An estimate of a geologic horizon is entered into a three-dimensional seismic model and synthetic shot records are determined from the model. Reflection tracks are estimated from the modeling results. The actual seismic traces are sorted into bins according to common reflection points determined from the reflection tracks and are stacked. The sorted and stacked data are used to estimate the difference between the seismic travel time and the model travel time, and the model is changed in order to match the seismic data. The process is repeated until the margin of error is acceptable. Lower horizons of interest are modeled in the same way until all the horizons of interest in a geological area are determined.

Abstract: A Monte Carlo statistical method for combining discrete geological measurements of rock properties with continuous measurements of seismic attributes and for converting those combined measurements into a display of the best estimate of subsurface rock classes.

Abstract: A method for classifying seismic data which uses a pattern recognition approach to comparing and equating data characteristics. Data is processed for a selected training area of such as a seismic section wherein a stochastic model of the data establishes data characteristics of either non-causal or causal type for selective comparison to similar data characteristics for other test areas of the data thereby to establish or classify similarities and/or distinctions between given training and test areas.

Abstract: Method of interpolating additional seismic traces between existing seismic traces obtained during the exploration of a subsurface formation. Seismic traces are recorded upon a datum surface in accordance with standard seismic data acquistion methods. Forward and backward wave equation datuming of the data set at the same velocity estimates new measurements for originally acquired data deemed unsatisfactory by propagating measured seismic traces to a fictitious datum plane using wave theory to create a second set of seismic traces and datuming the second set of seismic traces, again using wave theory, back to the original datum plane to create a third set of seismic traces. The third set of seismic traces will include new seismic traces to be used in place of the originally acquired unsatisfactory data.

Abstract: A method of removing multiple surface reflection events from seismic data is disclosed. Pairs of real seismic traces having end points in common with a trace being analyzed are convolved with one another to yield synthetic multiple traces having real components. All possible combinations of real traces are thus convolved. These are then stacked to yield the synthetic multiple trace having the shortest total travel time, which is the synthetic multiple trace corresponding to the actual multiple reflection event recorded as part of the real trace being analyzed. The stacked synthetic multiple trace can then be subtracted from the real trace under analysis to yield a multiple-free seismic record for further processing.

Abstract: Method for restoring seismic data to missing or severely noise contaminated traces included in a seismic section. The seismic section is transformed into a data localizing space and muted to retain only the localized data components of the seismic section. The muted transform space is inverse-transformed into the x-t domain to produce first estimates of the seismic data to be restored. The first estimates of the restored data are substituted for the corresponding traces in the original seismic section. Fully restored traces corresponding to the missing or severly noise contaminated traces are determined from the single estimate of the restored traces.

Abstract: A method is disclosed for converting seismic data obtained at known points to synthesized seismic traces obtainable at arbitrarily selected points. Two dimensional seismic data are converted to dense three dimensional data with the aid of a programmed computer to permit generation of arbitrary views of a particular geologic structure as well as a mathematical representation of the structure. The data is used to locate potential drilling and mining locations for drilling oil or other minerals. In order to provide accurate interpolation from the sparse two dimensional data, both apparent and true dip characteristics are obtained for the surveyed structure, and seismic trace data for a desired point are synthesized as a function of the dip of the surveyed structure. The dip characteristics are obtained from partial derivatives of the two dimensional data in specified coordinate directions. A three dimensional surface corresponding to the dip characteristics is obtained by a least squares fitting technique.

Abstract: Method of restoring null traces in seismic records. The seismic record is transformed from the x-t domain to the f-k domain by a series of fast Fourier transforms. The f-k transform of the seismic record is filtered to retain only coherent events and the filtered f-k transform is inverse-transformed back to the x-t domain. A first determination of the restored trace corresponding to the null trace is selected and substituted for the null trace. The first determination of the restored trace is used to determine a fully restored trace.

Abstract: A formation surrounding a borehole is traversed with a logging tool employing an acoustic transmitter and a pair of spaced-apart acoustic receivers. Acoustic energy traveling through the formation from the transmitter to the receivers are detected. The energy of tube waves contained within the detected acoustic energy is measured. Such measured tube wave energy is calibrated in response to measurements of tube wave energy ratio carried out in a zone of the formation having zero permeability. This calibrated tube wave energy is transformed into formation permeability in accordance with a measured relationship between permeability and tube wave energy ratio.

Abstract: The present invention provides methods for processing converted wave seismic data which includes, fractional point gathering of the data in a manner consistent with a selected velocity model, dynamic correction of the data using parameters measured from the data to account for the asymmetric travel path of the converted wave rays and stacking the dynamically corrected data. Methods are also provided for updating the velocity model.

Abstract: Depositional reconstruction for petroleum location is a new exploration-development technique for delineating hydrocarbon accumulations and prospect development. The technique uses existing information and establishes a relationship between present day subsurface structure and stratigraphic prehistoric reservoir development for determination and projection of relative reservoir development, definition and grading of combination structural-stratigraphic type traps, determination of permeability barriers, migration paths, accumulation areas, prospect grading, pressure cells and prediction of fluid movement. Depositional reconstruction results in a summary map which outlines productive areas, shows potential extensions, graded prospects, relative reservoir developments, and the other stratigraphic conditions which control the successful economic exploitation of a potential horizon.

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: The growth of a hydraulic fracture increases the period of free oscillations in the well connected to the fracture. Simultaneously, the decay rate of free oscillations decreases. The properties of forced oscillations in a well also change during fracture growth. All of these effects result from the changing impedance of the hydraulic fracture that intersects the well. Hydraulic fracture impedance can be defined in terms of the hydraulic resistance and the hydraulic capacitance of a fracture. Fracture impedance can be determined directly by measuring the ratio of down hole pressure and flow oscillation or indirectly from well head impedance measurements using impedance transfere functions. Well head pressure measurements can also be used to evaluate fracture impedance by comparing them to pressure oscillations computed with hydraulic models that include fractures with different impedances.

Abstract: Method and apparatus for producing improved synthetic velocity logs from seismic traces. The seismic traces are processed to enhance high frequency content by converting each trace to a spike trace, then filtering the spike trace with a function designed to reduce side lobes and enhance high frequency content. The processed trace is then operated on by a conventional summation process to produce a synthetic velocity log. Due to the enhanced high frequency content of the processed trace, the resulting synthetic log tends to show sharp discontinuities in the geology, much like a log taken from a well.

Abstract: The present invention provides a method of seismic exploration for obtaining a measure of the subterranean formation rock properties. Incident angle ordered gathers of seismic signal are processed to obtain a measure of the reflection coefficient as well as attributes descriptive of variations in amplitude of the seismic signal as a function of incident angle. Such attributes, when plotted on an angle dependent amplitude diagram, are transformed into a most probable estimate of the subterranean formation rock properties as well as a diagnostic of relative lithology and pore fluid contrast.

Abstract: Disclosed are a method and a system for discrete transformation of measurements such as seismic data into and out of tau-p space which is both exact and practical in terms of processing time. The measurements can be filtered or otherwise processed in tau-p space in ways which are not practical or possible in their original space. Since the transformations into and out of tau-p space are exact, the filtered and transformed measurements are free of errors and distortions that perturb known approximate transforms which can be performed in a reasonable time. When the transformation process is carried out in frequency space, it is done frequency-by-frequency, and when it is carried out in the spatial domain, it can utilize a transformation matrix having a block-circulant structure. In each case, the transformation process and matrix have a structure which substantially reduces storage and processing requirements as compared with known prior art.

Abstract: The shear velocity of a formation traversed by a fluid-filled open or cased borehole is obtained directly. Waveforms are obtained from a dipole acoustic investigation of the formation relative to a common location in the borehole. In this investigation, the bandwidth of the waveforms is substantially bounded by an upper frequency f.sub.u at and below which energy traveling at the shear velocity is dominant. Moreover, the bandwidth of the waveforms is concentrated near the frequency f.sub.u. The shear velocity of said earth formation is determined from these waveforms. In one embodiment, the waveforms are obtained from a broadband dipole acoustic investigation. The waveforms are low-pass filtered, and an interim shear velocity v.sub.s is determined from the filtered waveforms. The filtering and determining of v.sub.s are done first for an initial f.sub.cut, and subsequently for additional decreasing values of f.sub.cut, until a preselected relationship between f.sub.cut and v.sub.s is satisfied.

Abstract: The shear velocity of a formation traversed by a fluid-filled borehole is determined in the presence of a significant flexural mode arrival. A plurality of waveforms are obtained from a dipole acoustic investigation of the formation relative to a common location in the borehole. The flexural mode phase velocity as a function of frequency is determined. If a low frequency asymptote is identifiable, it is reported as the shear velocity. If a low frequency asymptote is not identifiable, however, a plurality of additional curves of the flexural mode phase velocity as a function of frequency are theoretically determined, based on respective estimated shear velocities. These theoretically determined curves are respectively fitted to the curve determined from the waveforms, until a satisfactory least error fit is achieved. The last-estimated shear velocity is reported as the shear velocity of the formation.

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 method of seismic exploration of the subsurface of the earth. Seismic reflection data are gathered in a selected area. The seismic data are combined with available non-seismic data to define an initial two-dimensional lithologic model. Based upon the initial model, a set of synthetic seismic data is generated. The degree of correspondence between the set of synthetic reflection data and the gathered seismic data is determined. The initial model-parameters are systematically perturbed during a series of iterations until a desired degree of correspondence has been achieved, resulting in a final lithologic model.

Abstract: Method and apparatus are disclosed for converting seismic data obtained at known points to synthesized seismic traces obtainable at arbitrarily selected points. Two dimensional seismic data are converted to three dimensional data with the aid of a programmed computer to permit generation of arbitrary views of a particular geologic structure as well as a mathematical representation of the structure. In order to provide accurate interpolation from the known data, both apparent and true dip characteristics are obtained for the surveyed structure, and seismic trace data for a desired point are synthesized as a function of the dip of the surveyed structure. The dip characteristics are obtained from partial derivatives of the two dimensional data in specified coordinate directions. A three dimensional surface corresponding to the dip characteristics is obtained by a least squares fitting technique.

Abstract: A method is disclosed for estimating the impulse response of the earth from Vibroseis data. Based on a time domain system identification approach, the earth's impulse response is estimated by operating on the seismic trace data and the vibrator pilot. Two implementations are discussed. The first is an adaptive method using a sliding data window and the uncorrelated trace data. Preferably, the process used to control the adaptation is the fast Kalman estimation (FKE) technique. This technique, based on recursive least squares, has a fast convergence rate and desirable computational requirements. The second implementation is non-adaptive. It uses the Levinson recursion technique to compute the Wiener filter solution based on the pilot autocorrelation function and the correlated trace data. Simulations demonstrate the capability of the system identification model to resolve reflection events.

Abstract: A method for avoiding aliasing in .tau.-p transformation or "slant stacking" of seismic data is disclosed which features identification of frequency components of the data likely to be aliased during correlative summation steps and removal thereof from the data prior to summing.

Abstract: In vertical seismic profiling (VSP), VSP seismic data is transformed into surface seismic data by mapping segments of the VSP seismic data into surface seismic data time. The transformation results in data which is more easily interpreted with respect to determining subsurface structure because the data is stacked and because the data is in a more conventional form.

Abstract: Seismic signals are processed to determine relative location error. In a further aspect, the relative location errors are corrected and the corrected seismic signals are processed to give information on subsurface structure.

Abstract: Methods and apparatus are described for estimating parameters, such as slowness and attenuation, of composite acoustic waves obtained in the course of sonic logging of formations traversed by a borehole. Sonic energy is sensed arriving at a plurality of points spaced vertically along the borehole after refraction, reflection and direct transmission through and along the formations. A window is established of predetermined length and moveout and the composite waves are multiplied by the window. A Fourier transform is obtained of the windowed data and the data are simultaneously analyzed to obtain an estimate of the parameters. The procedure is repeated for different window moveouts and index positions along the composite waves. The analysis is performed at each window position and moveout to obtain the best estimate of the parameters.

Abstract: Earthquake simulator making it possible to produce seismic waves and apply them to a sample, wherein it comprises a generator able to produce shock waves, whose frequencies are similar to the shock wave frequencies produced in a natural earthquake, the ratio of similitude being equal to 1/.lambda. in which .lambda. is a positive integer, said generator being formed by a cylinder, sealed at one of its ends by one of the walls of a cell containing the sample and at the other end by a thick wall to which are fixed means making it possible to produce shock waves within the cylinder, said waves being transmitted from the interior of the cylinder to the interior of the cell by means of openings made in the wall of the latter causing movements of the sample similar to those encountered during natural earthquakes.

Abstract: In seismic exploration, an improved synthetic acoustic log is produced from seismograms by combining band limited reflectivity and velocity functions, both of which are obtained from the seismograms. The reflectivity function is obtained by deconvolving the field seismograms, transforming the reflectivity function so obtained into the frequency domain, and filtering the frequency domain representation to suppress frequencies below the seismic band. The velocity functions is obtained by applying a velocity spectra technique to the field seismograms to produce an acoustic log, transforming the acoustic log into the frequency domain, filtering to suppress all frequencies in the seismic pass band and converting back into the time domain.

Abstract: An improved method of generating synthetic seismograms for use in determining the accuracy of hypothesized subterranean structures is disclosed. The method features defining hypothesized detector locations corresponding to real detector locations rather than interpolating from arbitrary detector locations generated by specifying of initial ray path angles as input data. The accuracy of the results is improved by elimination of interpolation.

Abstract: The present invention indicates that acoustic characteristics associated with a first well penetrating a gas/oil-containing strata such as a sandstone, limestone or dolostone, can be normalized (and favorably compared) with similar characteristics of a second, contiguous well of known hydrocarbon potential, such characteristics being calculated and displayed by means of a machine-implemented data processing method in which well logging and geologic data are fed thereto to calculate such characteristics without the need for shear-wave velocities.In more detail, in accordance with the invention brine-saturated bulk and shear moduli, (i.e., Kw* and Gw*) of a sandstone, limestone or dolostone penetrated by the second well can be predicted as a function of, say, brine-saturated P-wave modulus (Pw*) alone (independent of shear-wave velocity). In that way, resulting acoustic values including distinct velocity and amplitude values as a function of a saturation operator can ultimately be provided.

Abstract: The present invention indicates that acoustic characteristics associated with gas/oil-containing strata of an earth formation, including reflectivity coefficients can be normalized (and favorably compared) with similar characteristics calculated and displayed by means of a machine-implemented data processing method in which well logging and geologic data are fed thereto to calculate such characteristics without the need for shear-wave velocities.In more detail, in accordance with the invention brine-saturated bulk and shear moduli, (i.e., Kw* and Gw*) of the strata of interest can be predicted as a function of, say, brine-saturated P-wave modulus (Pw*) alone (independent of shear-wave velocity). In that way, resulting acoustic values including seismic velocities and amplitudes (also, reflectivities) as a function of saturation can ultimately be provided.

Abstract: The present invention indicates that acoustic characteristics associated with a first well penetrating a gas/oil-containing strata such as a sandstone, limestone or dolostone, can be normalized (and favorably compared) with similar characteristics of a second, contiguous well of known hydrocarbon potential, such characteristics being calculated and displayed by means of a machine-implemented data processing method in which well logging and geologic data are fed thereto to calculate such characteristics without the need for shear-wave velocities.In more detail, in accordance with the invention brine-saturated bulk and shear moduli, (i.e., Kw* and Gw*) of a sandstone, limestone or dolostone penetrated by the second well can be predicted as a function of, say, brine-saturated P-wave modulus (Pw*) alone (independent of shear-wave velocity). In that way, resulting acoustic values including distinct velocity and amplitude values as a function of a saturation operator can ultimately be provided.

Abstract: The present invention indicates that acoustic characteristics associated with gas/oil-containing strata such as a sandstone, limestone or dolostone, including reflectivity coefficients can be normalized (and favorably compared) with similar characteristics calculated and displayed by means of a machine-implemented data processing method in which well logging and geologic data are fed thereto to calculate such characteristics without the need for shear-wave velocities.In more detail, in accordance with the invention brine-saturated bulk and shear moduli, (i.e., Kw* and Gw*) of a sandstone, limestone or dolostone can be predicted as a function of, say, brine-saturated P-wave modulus (Pw*) alone (independent of shear-wave velocity). In that way, resulting acoustic values including seismic velocities and amplitudes (also, reflectivities) as a function of a saturation operator can ultimately be provided.

Abstract: The present invention provides for the accurate mapping of shallow crustal earth formations by means for refractive seismic waves to identify structure, elastic parameters and lithology of the strata undergoing survey to indicate deposits of ore, marker rock, economic minerals and the like. After a "roll-along" technique has been used in the field to collect the refraction data and preliminary processing steps undertaken in which there are provisions for (i) accurate separation and determination of seismic shear and compressional responses; (ii) stacking displays that allow for accurate identification of shape of the surveyed strata; and (iii) final depth displays of the refracting bed segments associated with seismic shear and compressional wave velocities as well as Poisson's ratios, in accordance with the present invention, additional processing then occurs.

Abstract: A method for deriving seismic information of more generalized nature over a relatively large and previously unexplored expanse of land to determine relevant strike, dip, velocity and related information. The method consists of the placing of a plurality of seismic sources and receivers in respective lines arranged in a cross pattern, each line being generally at right angles each to the other, and thereafter exciting the sources and recording the received energy for further processing to derive the strike, dip and velocity information for selected strata by using travel times of signal return.

Abstract: Faults in an underground coal seam are located by firing a shot at one point in the seam and detecting the seismic reflections in an array of geophones. Signals from the geophones are recompressed and analyzed according to an exponential formula to give a holograph of the seam and to predict the fault pattern.

Abstract: A method is disclosed for improving the signal-to-noise ratio of low level seismic signals resulting from weak acoustic sources. The method has application to the summation of signals from swept-frequency sources. A reference model of the level of a valid seismic signal is built for each of a number of time windows during a seismic-data recording cycle. The model is selected by obtaining the average of the absolute magnitudes for each time window from a number of sweeps to form a set of averages. The median of each set is selected and is padded by a suitable coefficient to provide the reference model for each time window. Subsequently, a normal recording is made. Each data sample amplitude of the recording is compared with the reference model corresponding to the time window that includes the data sample. If the amplitude level of the data sample exceeds the reference model level, that sample is suppressed prior to summing.

Abstract: This invention utilizes data collected in the course of reflection seismic prospecting methods to produce a map, such as a vertical profile or a three-dimensional picture, of subterranean earth formations. This is accomplished by aplanatic mapping of received seismic wave trains in the memory unit of a computer taking into account the travel times of waves, the location of the source, the location of the receiver, and the velocity with which the waves travel from the source point to the deflecting point in the earth and from then to the receiver. The data recorded by each source receiver doublet is digitalized and stored aplanatically in the memory unit, taking into account both signs and amplitudes of the signals. The accumulated data represents a map of the earth formations. Sections of this map are plotted to provide desired views of the formations.

Abstract: A borehole investigating device takes measurements of a subsurface earth formation and provides signals forming sonic, formation density or similar logs of the borehole. Additionally, the investigating device measures the dip of seismic signal reflectors traversed by the borehole and provides corresponding dip signals. A seismic section which may or may not include the borehole is selected, and the log and dip signals are combined with signals defining the location of the seismic section with respect to the borehole, to thereby provide synthetic logs for each of a number of virtual boreholes which coincide with selected virtual and/or actual shotpoints of the seismic section. The synthetic log signals are then combined to form a truly two-dimensional synthetic seismogram for the selected seismic section. The synthetically derived signals may be corrected in accordance with a selected geological model of the formation.