

Overview 


We use mathematical and computational methods to solve challenging problems in numerical analysis of geophysical data and in seismic imaging of the Earth's interior (upper crust for petroleum exploration).
Our work is funded by research grants from industrial partners. A typical research project addresses a problem that is both practically important and scientifically challenging.
Prospective sponsors should contact sergey.fomel@beg.utexas.edu 


Currently Funded Projects at Texas Consortium of Computational Geophysics 

Examples of previous projects




Attenuation of diffraction multiples
We develop new technology for seismic multiple attenuation based on separation of diffraction and reflection events and using diffraction events for predicting corresponding multiple reflections. Diffraction waves are caused by small subsurface features (such as faults, fractures, channels, etc.) or by small changes in seismic reflectivity.
Our criterion for separating reflection and diffraction events is smoothness and continuity of the local event slopes. 



Seismic Data Regularization and Noise Attenuation Using Novel
Transform Methods
We develop a new technology for 3D seismic data regularization and noise attenuation. The technology is based on a family of data transform methods called ``the seislet transform''. The seislet transform shares the scalability and efficiency properties of the digital wavelet transform but is tuned specifically to represent seismic data and to explore the multidimensional predictability of seismic reflection events. A powerful combination is the integration of the seislet transform with differential azimuth moveout with application to 3D data regularization of multiazimuth data (both land and marine).


Improving Wave Equation Fidelity of Gaussian Beams
We develop new numerical methods and algorithms for improving the wave equation fidelity of Gaussian beams. The Gaussian beam technology has been used successfully for seismic imaging and seismic data analysis in complex areas. The classical Gaussian beam method is based on the paraxial ray approximation, which requires a large number of beams in order to approximate the wave equation solution accurately. Using recent developments in Eulerian multiplearrival traveltime computations and complex eikonal solvers, we develop new solutions that improve both the accuracy and efficiency of the Gaussian beam method by minimizing the required number of beams.


Differential Azimuth Moveout
Differential azimuth moveout (AMO) is a new powerful method for regularizing 3D seismic reflection data. In theory, differential AMO is represented by a partial differential equation, whose role with respect to integral (Kirchhoff) azimuth moveout is similar to the role of the wave equation with respect to Kirchhoff migration. In practice, differential azimuth moveout behaves as a compact, local, accurate, and efficiently computed regularization operator. The operator is applied iteratively to produce regular output from irregular input.




Narrow Azimuth Migration
Narrowazimuth migration takes advantage of the narrowazimuth character of the data acquired by marine streamers to increase the efficiency of seismic imaging by wavefield extrapolation methods. New theory is developed to account for inadequate approximation in commonazimuth migration and correct for small rotation in the offset azimuth of propagating wavefield. This theory leads to a noticeably improvement in the current seismic imaging technology. An additional increase in efficiency comes from implementing the narrowazimuth algorithm on parallel computer clusters.




Petrophysical Analysis of Multicomponent Seismic Data
A new technology for improved multicomponent seismic data analysis is based on creating angle gathers for both Pwave and Swave amplitudeversusangle (AVA) analysis using new powerful waveequation imaging approaches. Unlike traditional amplitudeversusoffset (AVO) gathers, AVA gathers operate directly in the true reflection angle coordinates, providing a direct assessment for inverting Pwave and Swave reflectivity for seismic lithology, porosity, and pore fluid content. A joint inversion of multicomponent data in the true angle coordinates opens new possibilities for direct detection of natural gas resources by discriminating between oil, water, and gas content in complex reservoirs during both exploration and production. This technology facilitates exploration in complex geologic areas, improves oilandgas reservoir characterization, increases the accuracy of petrophysical attributes estimation, and decreases the much higher costs of exploratory drilling and failed secondary recovery injection projects.




Multiple Elimination Using PlaneWave Construction
A new method of multiple elimination is based on planewaveconstruction and shaping regularization. It is applicable to both prestack unmigrated gathers and to depthmigrated common image gathers. The algorithm is designed to cleanly separate primary and multiple events by identifying and discriminating local event slopes. It is able to input multiple models generated by different methods, such as surfacerelated (SRME) or waveequation (WE) approaches, and to handle a situation of several multiple sets, such as differentorder multiples in SRME or receiverside and sourceside multiples in WE.




Seismic Imaging by Riemannian Wavefield Extrapolation
Riemannian wavefield extrapolation (RWE) was proposed by Sava and Fomel (2004) for imaging steeply dipping and overturning reflections in geologically complex exploration areas, such as deep subsalt structures in the Gulf of Mexico. RWE belongs to the class of waveequation extrapolation methods that are known to handle accurately largevelocity contrasts, multipathing, and bandlimited wave propagation effects. Instead of conventional downward extrapolation, RWE employs a coordinate transformation to extrapolate waves numerically in a direction close to the preferential direction of natural wave propagation. As a result, one can accurately image large propagation angles, including overturning saltflank reflections, using inexpensive extrapolation operators.




Multicomponent Seismic Data Analysis
Multicomponent seismic exploration opens a world of new possibilities for improving seismic imaging by providing valuable additional information about subsurface physical properties. However, extracting this information is not an easy task. Conventional multicomponent data processing often falls short of delivering the expected additional value. The goal of this study was to provide a scientific validation of the multicomponent data analysis methods and to explore possible ways of improving the current multicomponent data processing flows. The focus of the project is the highquality Coronation dataset acquired by Apache in West Canada.




Estimating Petrophysical Properties of Hydrocarbon Reservoirs Using Full Waveform Inversion of Angle Gathers from WaveEquation Migration
A new technology for estimating petrophysical properties of hydrocarbon reservoirs is based on using inversion of seismic reflection data. The key idea is the use of reflection angle gathers computed from the output of 3D prestack wave equation migration. The petrophysical information contained in waveequation angle gathers is extracted by full waveform inversion using global and hybrid optimization methods and stochastic uncertainty analysis.




Seismic Reservoir Characterization Using Diffraction Imaging
Diffraction imaging is a new technology for seismic imaging of small subsurface objects such as salt edges, channels, fractures, and fluid flows. The technology is based on extracting and optimal focusing of diffraction wave energy. Our criterion for separating reflection and diffraction events is the smoothness and continuity of local event slopes. Our criterion for optimal focusing is the local varimax measure. This technology is especially attractive for addressing the problem of feature identification in complex reservoirs using seismic data.


