From Bureau of Economic Geology, The University of Texas at Austin (
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American Association of Petroleum Geologists Annual Meeting, Dallas, April 18-21, 2004

3D Cretaceous Rudist Reef Reservoir Model; Integration of

Jerome A. Bellian, Charles Kerans, Ted Playton, Xavier Janson, James Jennings, Jr., and Paul Dunn


A section of Red Bluff Creek in Medina County near Pipe Creek, Texas beautifully exposes parts of three high-frequency cycles of Cretaceous shallow water rudist buildups. Modern stream erosion along the creek-bed of Red Bluff Creek has exposed cycles that display lateral facies transitions from protected platform interior Toucasid patch reefs to higher-energy shelf-crest caprinid buildups and associated inter-buildup flanking debris and intermound channel-fill grainstone. RTK GPS (real-time kinematic global positioning systems), GPR (Ground Penetrating Radar) and LiDAR (Light Detection And Ranging) were coupled with data from 15 shallow outcrop cores to construct a new type of 3-D geological model. This model examined both high-resolution, laser mapped surfaces of exposed rudist mounds along the creek bed in conjunction with subsurface, radar-derived imagery. This part of a larger project is intended to better quantify fluid-flow potential through multi-scale touching vug, separate vug, and interparticle pore systems. The combination of GPR, RTK GPS, LiDAR, and core and petrographic facies analysis allows mapping in three dimensions at the cm scale and develops a more comprehensive understanding of sweep efficiency in this common Cretaceous reservoir analog system.