Reservoir Characteristics and Controls on High-Quality Deep Clastic Reservoirs in the Huangliu Formation, Ledong Area, Yinggehai Basin

Key words: 
• Yinggehai Basin /
• Huangliu Formation /
• deep reservoirs /
• reservoir quality /
• lithofacies /
• diagenesis /
• overpressure

Abstract: Abstract：[Objective] The primary controls on high-quality deep clastic reservoirs in the Huangliu Formation (Ledong area, Yinggehai Basin) remain poorly constrained, limiting deep gas exploration. [Methods] We integrate core description, blue-epoxy petrography, SEM, cathodoluminescence, fluid-inclusion homogenization temperatures, PVTx- and equation-based paleo-pressure reconstructions, and compaction simulation to characterize lithology, diagenesis, pore systems, and formation pressure, and to establish a genetic model. [Results and Discussions] Reservoirs are dominated by feldspathic quartz sandstones. Diagenesis is marked by moderate–strong compaction, weak dissolution (local leaching of feldspar grains and bioclasts), and predominantly calcite cementation with subordinate silica. Pore systems are chiefly primary intergranular pores with minor feldspar-dissolution pores. Lithofacies set the baseline porosity and compaction resistance, whereas diagenesis drives petrophysical differentiation: compaction and cementation govern tightness, while dissolution mainly modulates pore type and connectivity with limited net porosity gain. Since ~6 Ma, medium–strong overpressure—generated by undercompaction and hydrocarbon generation and transmitted upward from ~2300 m—suppressed compaction and cementation, preserving early primary porosity. Porosity declines with burial but the rate diminishes below ~3300 m; even at >4000 m, sandstones remain primary-pore dominated, indicating substantial deep-reservoir potential. [Conclusions] We propose a “facies foundation–diagenetic differentiation–overpressure preservation” model, identifying overpressure conditions, medium- to coarse-grained lithofacies, and moderate compaction/cementation as the principal controls. These findings provide a basis for predicting high-quality deep gas reservoirs and support efficient exploration in the deep-water South China Sea. Keywords: Yinggehai Basin; Huangliu Formation; deep reservoirs; reservoir quality; lithofacies; diagenesis; overpressure