AAPG Middle East Region, Shale Gas Evolution Symposium

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3-D Petroleum Systems Model of the Bighorn Basin, Wyoming

Abstract

This study developed a full 3-D petroleum system model of the oil- and gas-bearing Bighorn Basin of Wyoming from Precambrian to present day. The study identified thermally mature shale reservoirs that have characteristics favorable for establishing economic production and their location within the basin. These characteristics include drill depth. Previously published studies contain 1-D petroleum system models, which are limited to specific locations within the basin. This study utilized advanced 3-D modeling techniques to simulate the depositional history and thermal maturity throughout the entire basin. The project consisted of five phases – 1) structural framework construction, 2) geochemical data integration, 3) preliminary 1-D simulations, 4) 3-D predictive model simulation and 5) calibration. The results indicate a high degree of thermal maturity within the Permian petroleum system with high transformation ratio values. For the Cretaceous petroleum system, the results also indicate a high degree of thermal maturity and transformation ratios in the Lower Cretaceous with decreasing thermal maturity for the Upper Cretaceous formations. The cumulative erosion model indicates the majority of the erosion took place on the margins of the basin. The modeling indicates the Upper Cretaceous Frontier Formation and overlying Cody Shale are within the oil generation window over a large portion of the eastern side of the basin and are within economic drill depths.