Bridging the Scale Gap: Geological and Seismic Forward Modeling of Outcrop Data

Mark Tomasso¹, Renaud Bouroullec², and David R. Pyles^2
1Enhanced Oil Recovery Institute, The University of Wyoming, Laramie, WY
²Chevron Center of Research Excellence, Dept. of Geology and Geological Engineering, Colorado School of Mines, Golden, CO

Reservoir stratigraphy is commonly interpreted from seismic images. Exploration-grade seismic data is typically acquired with peak frequencies varying from 30 to 60 Hz, giving average vertical stratigraphic resolution of between ~23 to ~11 m in siliciclastic sediments. Many stratigraphic bodies, for example architectural elements and beds, cannot be resolved with those data. Seismic forward modeling of outcrop analogs provides a method to address those uncertainties. Seismic forward modeling is a process by which a seismic image is constructed from outcrops, where architectural elements, bedding, and facies are known.

One of the key strengths of this technique is the ability to bridge the gap between concepts learned about high-resolution stratigraphic architecture in outcrop analogs and lower resolution seismic data sets. Ground-based lidar acquisition of outcrops has influenced a step-change in the way outcrops are modeled. Previous techniques utilized classic cliff exposures to derive 2D and pseudo-3D geological models. With lidar technology, complex three-dimensional exposures can be captured and interrogated in the digital realm. Combining these capabilities with traditional outcrop data enables rigorous three-dimensional geological models of outcrops to be constructed which honor the architectures that are observed in the field. Models are presented from a series of 3D outcrops covering several siliciclastic depositional environments. High-resolution interpretations of the outcrops were combined with the lidar data to build detailed geological framework and facies models. Petrophysical parameters from analog subsurface reservoirs were assigned to the facies. The resulting seismic forward models, acquired at several different frequencies, can be compared to outcrop interpretations, allowing a direct comparison between outcrop and seismic architecture.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery