Continental shelf margin delta front sandstone reservoirs in the Zhujiang Formation, northern Baiyun depression, Zhujiangkou Basin: Characteristics and controlling factors

The characteristics and controlling factors are dealt with on the basis of thin section identification, scanning electron photomicrographs, mercury injection experiment and physical properties of the continental shelf margin delta front sandstone reservoirs in the Zhujiang Formation, northern Baiyun depression, Zhujiangkou Basin. The sandstone reservoirs dominated by grey medium-to fine-grained lithic sandstones are characterized by relatively low compositional and textural maturity, abundant secondary porosities with minor amount of residural primary intergranular porosity and primary porosity, relatively higher driving pressures and coordination numbers, relatively smaller pore throat sizes and poor sorting, and thus interpreted as the reservoir rocks with the medium to low porosity and medium to low permeability. The sandstone reservoirs are primarily constrained by sedimentary facies and diagenesis. The delta front subaqueous distributary channel microfacies is believed to be most favourable facies zone for the development of the sandstone reservoirs, followed by the delta front channel mouth bar microfacies. The destructive diagenesis such as mechanical compaction and cementation may reduce the porosity and permeability while the constructive diagenesis such as dissolution and cracking may facilitate the improvement of the porosity and permeability of the sandstone reservoirs.