Fan Deltas and Diagenesis Control on the Reservoir Capacity of Tight Sandstone: Shahezi Formation, Lishu Fault Depression, Songliao Basin, China

High-quality reservoirs are the main places where oil and gas reservoirs are located, and their distribution is crucial for the efficient exploration of tight gas reservoirs. However, the formation of reservoirs is affected by a number of elements, including depositional conditions and diagenesis, making it challenging to identify high-quality reservoirs in the formation. In this paper, our aim is to establish a development model of sandstone reservoirs in the fan delta depositional system by analyzing the control of depositional facies and diagenesis on reservoir quality. The research methods include core descriptions, drilling and logging data, rock thin sections, scanning electron microscopy (SEM), porosity and permeability testing, and X-ray diffraction. The results show that the Shahezi Formation of the Lishu Fault Depresssion developed a fan delta depositional system with localized development of lacustrine facies. The sandstones of the Shahezi Formation are mainly made up of fine- to coarse-grained, poorly sorted litharenite and feldspathic litharenite. The reservoir has undergone three major diagenetic stages: compaction and cementation in early burial, dissolution in midburial, and cementation in late burial, and is currently in the Mesodiagenesis B. Due to differences in sandstone composition, structure, and diagenesis, the subaqueous distributary channel sand bodies have the best storage properties, moderate in mouth bars and sheet sands, with subaerial distributary channel microfacies having the poorest reservoir quality. Based on the above analysis, the differences in diagenetic types and intensities corresponding to different depositional facies are the controlling factors for reservoir quality.