Southwest Section AAPG Annual Convention

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Carbonate Facies in the Good Field, Borden County, Texas


3 cores were logged in the Pennsylvanian Strawn to Missourian Canyon-B Good Field bioherm in Borden County, TX. The TJ Good #22, #24, and #27 for analysis of facies distribution, thickness, and lateral variations. It was colonized by non-rigid reef forming organisms including: phylloid-algae, binding algae, and pelmatozoans. The bioherm amalgamated during Midland Basin subsidence and eustatic sea level change. Bioherm growth was followed by repeated subaerial exposure indicated by karst surfaces, breccias, reworked bio-debris, and transported clasts. Facies include: 1) crinoid-bivalve-bryozoan-bioclastic mudstone, 2) crinoid-algal-foraminifer-bioclastic mudstone to wackestone, 3) crinoid-bivalve-fusulinid-foraminifer-bioclastic wackestone with rare mudstone-wackestone lithoclasts, 4) crinoid-bivalve-fusulinid-bryozoan wackestone to mud-dominated packstone, 5) crinoid-bivalve-fusulinid-bryozoan mud-dominated packstone with lithoclasts, 6) crinoid-ooid-bioclastic mud-dominated packstone, 7) crinoid-fusulinid-bivalve-foraminifer-bioclastic mud-to grain-dominated packstone, 8) crinoid-fusulinid-bivalve-ooid bioclastic grain-dominated packstone with rare mudstone-wackestone lithoclasts, 9) crinoid-fusulinid-echinoderm-ooid bioclastic grain-dominated packstone to grainstone, 10) crinoid-fusulinid-bivalve-echinoderm-ooid bioclastic grainstone with rare mud-dominated packstone lithoclasts, 11) algal boundstone, and 12) karst breccia. Porosity types include: fracture, vug, and moldic followed by intergrain, intragrain, intrafossil, and intercrystalline. Calcite cementation is apparent along fractures, between breccia clasts, in vugs, and pores. Reviewing cores to maximize geologic understanding of carbonate bioherm reservoirs, their lithofacies distribution, depositional environment, paleogeography, sea level fluctuations, and porosity and permeability systems provides insight into hydrocarbon emplacement, barriers to flow, and hydrocarbon recovery efficiency. Insight into the exact nature of a carbonate bioherm has implications for geologic modeling and proper well placement for primary, secondary, and tertiary recovery. With numerous carbonate bioherms having already been depleted across the Permian Basin they are excellent candidates for future CO2 EOR recovery or permanent CO2 sequestration. A thorough geologic understanding extracted from cores is essential to the economic success of any CO2 based operation.