Analysis of reservoir characteristics and controlling factors in the Enping Formation, Panyu 4 Sag, Pearl River Mouth Basin

This study focuses on the clastic rocks of the Paleogene Enping Formation in the Panyu 4 Sag of the Pearl River Mouth Basin. Within a low-porosity and medium-to low-permeability background, the reservoir permeability shows significant variation, with a geometric coefficient of variation reaching up to 2.36, and some wells developing medium-to high-permeability quality reservoirs or locally occurring medium-permeability sweet spot reservoirs. By comprehensively utilizing core observation, cast thin sections, scanning electron microscopy, physical property tests, and mercury injection capillary pressure analysis, systematic research was conducted on the petrological characteristics, diagenesis, and their controlling mechanisms on reservoir quality. The results indicate that the Enping Formation reservoirs overall exhibit low porosity (average 10.5%) and low permeability (average 41.0 mD). The formation of high-quality reservoirs is primarily controlled by sedimentary microfacies, rock fabric, and diagenesis types. The subaqueous distributary channel microfacies of braided river delta fronts, relatively high quartz content, and coarse-grained deposits provide the material foundation for forming quality reservoirs. Based on differences in diagenetic intensity, four types can be identified: moderate compaction-weak cementation, moderate to strong compaction-moderate cementation, strong cementation, and moderate to weak compaction-moderate cementation. This effectively reveals the differential response mechanisms of reservoir physical properties under different diagenetic evolution pathways. The research findings provide critical geological evidence for high-precision exploration and development of mid-deep oil and gas reservoirs, directly guiding the optimization of exploration targets and minimization of deep exploration risks.