Comparative Anatomy of Cretaceous Carbonate Ramps - An Outcrop-Driven Interpretation for a Sirte Basin Field

The use of outcrop analogs for constraining stratigraphic interpretations has often been presented for mature fields with seemingly inexhaustible data and tight well spacing. In contrast, a viable fourth-order stratigraphic interpretation of a mixed carbonate siliciclastic system is proposed for a Sirte Basin field with only twenty wells on 640-acre spacing. The objective was to squeeze as much information regarding the depositional environments from scarce well data, integrate observations within an outcrop analog, and develop a play concept to prioritize a potential field acquisition candidate. The result is an outcrop-driven depositional model and stratigraphic framework that honors observations made from core, thin sections, accommodation trends, and paleogeographic setting. A “best fit” analog was identified from Albian outcrops along the Lower Canyons of the Rio Grande in the Big Bend region of Texas. Lithofacies, fossil assemblages, and accommodation trends were analyzed for comparison and were found to be remarkably similar. Actual and comparative evidence suggests this field was situated atop a shallow, current-swept, intrabasin platform, characterized by localized ramps onlapping basement highs. Clastic-rich, radiolitid buildups and associated grainstones developed along the inner ramp, onlapping basement highs, and grade offstructure into chalky Inoceramus-globigerinid wackestones and shales.