The depositional evolution and associated controls on the reservoir property in the Permian Upper Urho Formation, southern Zhongguai Rise, Junggar Basin, northwest China

Abstract

The Permian strata in southern Zhongguai Rise are famous for their abundant petroleum reservoirs. The depositional evolution of the Upper Urho Formation has been studied by analyzing the interactions between the sedimentary environments and the diagenetic evolution based on the comprehensive analysis of geologic and geophysical data sets. The obtained results have shown that fan delta deposits, overlain by lacustrine deposits, are deposited. Proceeding upward, the fan delta succession is characterized by retrogradational patterns, such as sandstone facies and conglomeratic facies. These facies have shown different clay mineralogic compositions, porosity, and physical properties. The sandstone facies indicate well-sorted and well-rounded sedimentological textures with good physical properties. In contrast, the conglomeratic facies indicate poorly sorted and poorly rounded sedimentological textures with poor physical properties. All of these characteristics lead to reservoir heterogeneity resulting from sedimentary facies and diagenesis.