STRATIGRAPHIC-FORWARD MODELING OF A GROWTH-FAULTED SUBBASIN, FRIO FORMATION, CORPUS CHRISTI AREA, SOUTH TEXAS GULF COAST

A stratigraphic-forward model was built to simulate the stratigraphic response in growth-faulted subbasins of the Oligocene Frio Formation along the South Texas Gulf Coast. On the basis of high-resolution sequence stratigraphy, six third-order sequences were recognized in six growth-fault-bounded subbasins. Growth-fault activation created subbasin-confined sedimentation differentiation during sea-level lowstand and ceased its influence during subsequent transgression and highstand. The combination of eustasy and tectonic controls on available accommodation space and sediment accumulation created a strong volumetric partitioning between the lowstand slope and basin and the transgressive and highstand shelf. We studied the stratigraphic architecture of these seaward-stepping, progressively younger, basinward Frio subbasins by integrating sedimentological data, wireline-log response, and biostratigraphic data using a sequence-stratigraphic-based approach. Despite a large number of wells and 3D seismic, many uncertainties remain concerning the evolution of each of the subbasins. A 2D stratigraphic-forward model was created using Dionisos software to model the interaction of growth faulting and sedimentation in two subbasins of the Frio Formation. Input parameters were selected from an integrated study, including sediment supply, water discharge, eustasy oscillations, subsidence, growth-fault configuration, and low- and high-energy transport parameters. Synthetic well logs created from simulation results were compared with actual well log data in each of the subbasins to check the accuracy of results. The modeling resulted in a better understanding of (1) the influence of growth faulting on accommodation rates and architecture of the lowstand, transgressive, and highstand deposits and (2) the correct estimation of missing sediments, sequence boundaries, and maximum flooding surfaces due to growth-fault movement.