Chevron U.s.a. Inc.

Western Atlas International, Inc.

Bp Corporation North America Inc.

Westerngeco L.l.p.

Uwe Karsten Albertin

Chaoshun Hu

John Theodore Etgen

Joseph Paul Stefani

Sverre Brandsberg-Dahl

Andrey H Shabelansky

Mark A Meadows

Robert Ian Bloor

Goran Milan Stankovic

Ole Joran Askim

Peng Shen

Mariana Gherasim

Laurent Sirgue

Lin Zhang

A method is described for full waveform inversion using a b-spline projection that produces an earth model that can be used for seismic imaging. The method may be executed by a computer system.

System and method for improved full waveform inversion

A method is described for seismic imaging including determination of reservoir stresses. The method may include the use of elastic full waveform inversion (FWI), 3-order elasticity, and finite-difference strain calculations. The method may be executed by a computer system.

System and method for deriving reservoir stresses from 4D seismic data

A method is described for image-domain full waveform inversion. The method may include receiving, at a computer processor, a seismic dataset representative of the subsurface volume of interest and an initial earth model; performing, via the computer processor, an image domain full waveform inversion to generate an updated earth model; and performing, via the computer processor, seismic imaging of the seismic dataset using the updated earth model to generate a seismic image. The method may be executed by a computer system.

System and method for image-domain full waveform inversion

A method is described for improving subsalt seismic imaging using wavefield redatuming. The method redatums the source wavefield and receiver wavefield to the salt surface. It cross-correlates the redatumed wavefields and uses the time cross-correlations to update the salt surface. The method may be executed by a computer system.

System and method for salt surface updating via wavefield redatuming

A system and method for performing a target-oriented reverse time migration may include obtaining a seismic dataset and a geologic model representative of the subsurface volume of interest; identifying a target based on the seismic dataset and the geologic model; calculating a normal to represent a structural dip direction for at least one point on the target; upward propagating a cluster of beams from the at least one point on the target to a surface representing an acquisition surface of the seismic data; identifying valid source-receiver beam pairs based on coverage of the seismic dataset; accumulating coverage of the valid source-receiver beam pairs; identifying traces from the seismic dataset that fall within the accumulated beam pair coverage; and performing a target-oriented reverse time migration using the identified traces to produce a seismic image.

Systems and methods employing upward beam propagation for target-oriented seismic imaging

According to a preferred aspect of the instant invention, there is provided herein a system and method for extending zero-offset or stacked wave-equation illumination analysis into the angle-gather domain, where it becomes an appropriate tool for assessing the effects of complex overburden on AVA response. A preferred method for doing this involves first creating an angle gather that has a perfect AVA response (i.e. a constant amplitude as a function of angle). This gather is then preferably used as a reflectivity map that is fed into a demigration process which creates modeled data that by construction carries with it a completely flat reflectivity signature. Remigration of such a data set then results in a gather on which any amplitude variation is more likely to be a measure of illumination effects alone. The resulting AVA signature on the gather can then be used to assess the validity of the AVA response on modeled or actual data, resulting in a useful AVA risk analysis.

Migration-based illumination determination for AVA risk assessment

According to a first preferred aspect of the instant invention, there is provided an efficient method of computing a 3D frequency domain waveform inversion based on 3D time domain modeling. In the preferred arrangement, 3D frequency domain wavefields are computed using 3D time-domain modeling and a discrete Fourier transformation that is preferably computed 'on the fly' instead of solving the large systems of linear equations that have traditionally been required by direct frequency domain modeling. The instant invention makes use of the theory of gradient-based waveform inversion that estimates model parameters (for example velocities) by matching modeled data to field data sets. Preferably the modeled data are calculated using a forward modeling algorithm.

System and method for 3D frequency domain waveform inversion based on 3D time-domain forward modeling

This invention provides a method for analyzing and compensating for the deleterious effects of irregular illumination of the subsurface due to velocity variations in the subsurface and of irregular spatial sampling of seismic data. For a processing operator, like Kirchoff migration for seismic data, a conventional migration operation is carried out. The output points are analyzed for sampling artifacts caused by irregular surface sampling of the data and those due to ray path distortions. An inverse sampling operator or a filtering operator is determined that is related to dip dependent attributes at the image location. Application of the inverse sampling operator or filtering operator along with the migration or other processing operator to the seismic data compensates for the effects of irregular sampling and of raypath distortion.

Method for compensating for the effect of irregular spatial sampling and illumination of reflectors in seismic exploration

An array of output image points is distributed over a velocity model of a subsurface region of interest. A fan of rays is shot from each of a plurality of acoustic source points along the surface, the angular separation between the rays being equal to .pi./n, where n is the number of rays. A family of traveltime wavefronts is erected at selected time intervals, .DELTA.t, along the ray trajectories. The resulting wavefront map is superimposed over the array of output image points. Sub-arrays of output image points will lie within discrete traveltime cells, the widths of which are defined by the separation between adjacent rays paths and the heights are defined by the wavefront separation distance. Ray segments, wavefront segments and output image points are identified by a velocity layer index. A velocity interface that may cut across a traveltime cell, divides the cell into two parts, each having a different layer index. The traveltime to be assigned to a selected output image point is determined by projection from a nearby wavefront segment that has the same layer index as that of the output image point.

Traveltime generation in the presence of velocity discontinuities

An approximate method for imaging seismic data that originates from steeply dipping or overturned strata. The method provides a viable alternate approach to the generalized f-k migration that does not rely explicitly on some form of perturbation series expansion and thus avoids the steep-dip instability that is present in previously-known methods. This method is particularly useful in the presence of a moderate lateral velocity gradient, something that prior-art methods have trouble accommodating. An advantageous feature of the disclosed method is that the migration/imaging operators are composed of simple numerical coefficients.

Method for migrating seismic data

In areas where the velocity gradient is strong or exhibits a significant positive curvature, the usual phase shift f-k migration methods cannot properly image overtuned dips due to diving waves. In this disclosure, an Airy operator is substituted for the classical phase shift operator.

Growing community of inventors

Houston, TX, United States of America

Uwe Karsten Albertin