Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Techniques for Subseismic Fault Prediction: Filling the White Space
(1) Shell International E&P, Houston, TX.
Faults occur over a wide spectrum of sizes, from tiny cm-scale fractures and deformation bands to major tectonic faults along plate boundaries. Faults from any portion of this spectrum may be present in or influence well and reservoir performance. However, faults with throws of less than a few tens of meters are generally invisible to seismic imaging. These smaller faults are generically termed ‘subseismic,’ and in some cases can compartmentalize or baffle flow within the reservoir. Methods for extrapolating from borehole observations to larger seismically visible structures are needed to properly account for this in the reservoir appraisal stage. This effectively amounts to filling the structural ‘white space’ created by the limitations of seismic resolution. We review several cases where reservoir performance has been impacted by such subseismic faults. Techniques to characterize the subseismic fault population are then presented. Fault size distribution analysis can be used to predict the numbers of ‘missing’ subseismic faults, but we find that these are limited by dependence on mechanical stratigraphy. Some techniques such as seismic curvature analysis can detect ‘subtle faults,’ which are at the larger end member of the subseismic fault population. However, such tools are still limited by seismic resolution. Kinematic forward modeling techniques can be applied to estimate areas of high strain which may correspond to locally abundant of subseismic faults. To be fully successful as a predictive tool, such forward modeling must also account for rock properties.