Tight Carbonates: Development of an Early-Stage Multidisciplinary Predictive Reservoir Model for the Buda, Georgetown and Edwards Formations East of the San Marcos Arch

Abstract

After decades of denial and thousands of well-bore penetrations, naturally-fractured tight carbonate reservoirs have attained new life through recent technological and regulatory breakthroughs. An explosion of vertically comingled economic wells in East Texas are being developed on the heels of the prolific Austin Chalk fracture play. De-risking these complex reservoirs hinges on our ability to integrate multi-disciplinary reservoir-scale predictive models using whole core as a base calibration. This study details an early-stage collaboration of academia and industry to develop a high resolution core-based reservoir model combining petrography, litho-typing, fracture characterization, geo-mechanical properties, wire-line log analysis, and regional basin modeling. Data for this study includes 342 feet (104 m) of detailed (0.1 ft./3 cm. resolution) slabbed whole-core description, Rebound Hammer Unconfined Compressional Strength (UCS), Core Gamma Ray, and a basic open-hole wire-line log suite through the Buda, Georgetown, Kiamichi, and Edwards formations. These data were obtained from the Flora Johnson #1 well drilled by Shell Oil in Grimes County in East Texas. Regional correlations were attained through extensive digital and raster log archives, drill-cuttings analyses, side-wall core evaluations, and applicable literature. Five distinct facies were identified in core and correlated to wire-line log character: (1) Argillaceous Globigerinid Mud-Dominated Packestone/Wackestone, (2) Thalassinoides Globigerinid Mud-Dominated Packestone, (3) Argillaceous Bivalve Wackestone, (4) Calcareous Mudstone/Shale, and (5) Bivalve Fragment Gastropod Wackestone/Rudstone. Facies 1, the most prospective litho-type, exhibits high fracture intensity, low UCS values, relatively low velocities, and significant SP deflection. A preliminary basin model has been developed through regional correlation and interpretation of these properties to predict the distribution of the most fractured, thus most prospective vertical sections throughout the basin.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015