The sedimentological reservoir characteristics of the Jurassic Sangonghe Formation, Southern Mahu Slope, Junggar Basin, Northwestern China

Abstract

The hydrocarbon discoveries are increasing in deltaic systems in Jurassic Sangonghe Formation in southern Mahu Slope of Junggar Basin in recent years. However, different scales of sedimentological heterogeneities influence reservoir quality and architecture. Consequently, the study aims to employ thin sections, core logs and wireline logs to conduct research to address the issues. The results show that the integrated analysis of conventional cores reveals three facies groups in Sangonghe Formation which are deposited in braided deltaic and lacustrine environment. Each facies group contains several lithofacies given their grain size, sedimentary structures. In addition, the lithofacies types, associations, and wireline responses indicates that Lower, Middle, and Upper Sangonghe Formation is deposited in braided delta plain, braided delta front, and pro‐delta respectively. Moreover, the Sangonghe Formation is characterized by variations regarding sandbody, thickness, geometry, and architecture. The facies distribution and sedimentary environment indicate that accommodation space plays essential controls. The sedimentological heterogeneity controls reservoir quality and architecture from macro‐ to micro‐scale. The macro‐scale insights reflect that the lower and middle Sangonghe Formation shows high connectivity of sandbodies while the upper Sangonghe Formation shows low connectivity of sandbodies. The micro‐scale insights indicate that sandstone types, texture, composition all plays significantly role in controlling reservoir porosity and permeability. Finally, the understandings and insights of reservoir sedimentological heterogeneities assist in better prediction and assessment of reservoir quality and architecture. Finally, it will make contributions to reservoir development, recovery, and productivity for areas with similar sedimentological settings.