Abstract
The Daanzhai section of the Lower Jurassic Ziliujing Formation in the central Sichuan Basin hosts substantial tight oil resources; however, strong reservoir heterogeneity and low resource abundance result in significant production variability among individual wells, severely limiting large-scale efficient development. This study aims to identify the main controlling factors and physical mechanisms of tight oil accumulation by analyzing the geological characteristics of typical high-yield wells. Integrating production data from over a thousand wells with microscopic rock physics experiments, multi-scale fracture characterization, and two-dimensional filling physical simulation, the control effects of source-reservoir configuration, sedimentary facies belts, and formation pressure systems on well productivity were quantitatively evaluated. Results indicate that high production in the Daanzhai tight oil is governed by a “facies-reservoir-driving” trinity coupling mechanism: the high-energy littoral bioclastic shoal facies provide the foundation for quality reservoir development; the multi-scale fracture network significantly improves fluid conductivity in ultra-low permeability matrix and enhances hydrocarbon charging efficiency by regulating the pressure gradient at the source-reservoir interface; additionally, the elastic energy release from associated gas within the system is a key driving force for sustaining long-term stable well production. The study concludes that effective exploration in the Daanzhai section should focus on the spatial superposition of closely coupled source-reservoir zones, high-energy facies belts, and fracture networks forming the “physical sweet spots.” The proposed “ternary coupling” accumulation model advances the theory of low-abundance continental tight oil accumulation and provides important theoretical guidance and practical reference for oil and gas exploration in the Sichuan Basin and analogous continental lacustrine basins.
