Quantitative assessment of the tight gas reservoirs in the Obaiyed field, Shushan Basin, NW Egypt

ABSTRACT Obaiyed field lies in northern west Shushan Basin, which considers one of the largest Mesozoic coastal basins in northeast Africa, with high thickness sediment from the Jurassic to Palaeogene. The petrophysical parameters show difficulty in the development of the high gas reserve in the field, which led us to assess the geological systems that could constrain the formation and evolution of the basin concerning the study field. We simulated the tectonic evolution of the basin using a 1D-Airy isostasy backstripping technique with python coding and PetoMode® software. Also, we evaluated the current reservoir petrophysical parameters using TechLog® software. Based on integrating our results, we propose that the Shushan Basin represents a natural case of a Continuous Basin-Centred Gas accumulations model (CBCG) because of four main reasons: a) the vast extension of the Khatatba Formation, b) the coexistence of the source and the reservoir rocks in the Khatatba Formation, c) the low-permeability and gas saturation accumulations of the Lower Safa Member and d) the abnormal pressure of the Lower Safa reservoir because of its compartmentalization, where each compartment has its pressure peak. At a regional scale, this study highlights the effect of tectonics in the evolution of the basins.