--> Abstract: Geological Patterns and Rock Physics for a New Seismic Inversion Method; #90063 (2007)

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Geological Patterns and Rock Physics for a New Seismic Inversion Method

 

Gonzalez, Ezequiel F.1, Tapan Mukerji2, Gary Mavko2 (1) Shell International Exploration and Production, Houston, TX (2) Stanford University, Stanford, CA

 

We present a novel inversion technique that constructs solutions based on expected geological patterns in a study area and honors local rock physics transformations. The inversion is posed as an inference problem, with prior geological and rock physics knowledge, represented as probability densities (pdfs), being updated by seismic data to obtain solutions. Using probabilities is a way to accept and account for imperfect and limited data as well as imperfect models. The technique can be extended to invert different types of geophysical data. Solutions from this inversion are realizations of predefined groups with common lithology, fluids, or other reservoir property of interest. Thus, e.g., shales, oil sands, and brine sands might constitute three different groups in a particular study. Rock physics principles help to establish the link between multivariate pdfs of elastic properties and the reservoir characteristics defining the groups. Multiple-point geostatistics (MPG) is used to define and explore the space of geological patterns. The pattern-based MPG algorithm (a modified version of SIMPAT, i.e. sequential simulation with patterns) first extracts geologically consistent spatial patterns of groups from a geological model (“training image”). Then, using sequential simulation principles, candidate local solutions are proposed that are accepted only if, on applying the forward modeling operator, they generate synthetic data reproducing the observed seismic data within acceptable tolerances. The concept and implementation of the inversion were validated using a synthetic reservoir (Stanford VI), consisting of a system of fluvial channels. Moreover, applicability to real problems was demonstrated by inverting a field seismic section. We believe that this technique lays the foundation for innovative inversions of geophysical data tied to geological patterns.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California