Integration of diagenesis, porosity evolution, and oil emplacement in lacustrine tight sandstone reservoirs: A review with illustrative cases from the major oil-bearing basins in China

Tight sandstone oil is currently one of the most important unconventional hydrocarbon resources in China. The coupling relationship between porosity evolution and oil emplacement determines the reservoir effectiveness and oil exploration potential in tight sandstones. Complex diagenetic alterations, however, make research on porosity evolution much more difficult than that on conventional sandstone reservoirs. This study examines the typical lacustrine tight sandstones from western to eastern China. The reservoir lithologies, characteristics, and paragenetic sequences of the diagenesis are reviewed, and an integrated analysis of diagenesis, porosity evolution, and oil emplacement is proposed.Results demonstrate that diagenesis is influenced by rock composition and lithological associations. For example, calcite cementation is primarily controlled by the distance to the sandstone–mudstone interface, whereas zeolite cements are related to volcanic rock fragments. Furthermore, we established a porosity evolution recovery method with respect to the paleoburial depth (or time) of major diagenetic events, including the evaluation of the relationship between the thin section and helium porosity and oil emplacement. We clarified the formation time and the underlying mechanisms. Three typical examples from the major oil-bearing basins in China were chosen to analyze the integration process of diagenesis, the porosity evolution of tight sandstones, as well as the coupling relationship between porosity evolution and oil emplacement. Tight sandstones characterized by different diagenetic alterations exhibit different coupling relationships between porosity evolution and oil emplacement. Our study can provide important guidance for reservoir quality prediction and oil exploration potential evaluation.