Volume Based Curvature Calculations Show Effects of Stress Fields on Varying Lithologies

BLUMENTRITT, CHARLES, University of Houston, Houston, Texas

    Structural geologists use curvature analysis to identify stress fields acting in an area and the fracture orientations which result. Several articles in the recent literature deal with such analysis on surfaces constructed from interpretation of 3-D seismic data and the attendant problems caused by errors in picking and the effects of scale dependence. We resolve some of these problems by computing various curvatures directly from the uninterpreted seismic volume using a very small subvolume to minimize the effects of small scale variations in data quality and a scale factor to adjust the spatial frequency of the analysis. Once the curvatures are computed, they may be extracted from the resultant volume along time slices or horizon slices, without the effects of the picking process altering the basic calculation.
    We apply these techniques to a data set from the Central Basin Platform of West Texas and compare horizon slices through the Devonian Thirtyone Formation Carbonate to slices through the Devonian Woodford Shale to find that the shale is less intensely deformed. We selected these formations as being relatively uniform in their respective lithologies and nearly contemporaneous and therefore affected by the same stress fields. We further compare the results to Permian age carbonates that have not been subjected to the stress fields of the Early to Middle Paleozoic to identify Late Paleozoic stress fields and remove their effects from the deeper section.