Densification mechanism of deep low-permeability sandstone reservoir in deltaic depositional setting and its implications for resource development: A case study of the Paleogene reservoirs in Gaoshangpu area of Nanpu sag, China

A better understanding of reservoir densification mechanisms is very important for petroleum exploration and controlling the quality distribution in low-permeability reservoirs. Low porosity low permeability, difficult reconstruction, economic infeasibility are factors restricting its efficient production. Systematic analysis was performed to study evolution different microfacies deltaic depositional setting Paleogene deep Gaoshangpu reservoir, define their genetic mechanisms, delineate dominant facies belts, favorable diagenetic sequences that high-quality To understand tight genesis reservoirs, we analyzed sedimentological characteristics various (i.e., underwater distributary channel, bay, mouth bar, front sheet sand) using core data physical property sand body. The results show channel estuary bar body with medium-to fine-grained poor–medium sorting. diagenesis dominated by strong compaction, calcareous, argillaceous cementation, dissolution during stage B early middle diagenesis. In fan delta environment, weak anti-compaction resistance reservoirs mainly due large content plastic particles, finer grain size, medium–poor sorting, an average reduction rate 65%. This a key factor above 3000 m. Comparison among sandstone shows shale has slightly stronger compaction resistance. not obvious at depth 3,000–4,000 m, but loss permeability this section significant, improvement from later most section. Calcareous cementation cause some bars channels late stage. Under influence calcareous-filling pore throat, been basically densified 3,000 resulting limited transformation dissolution. main densification, calcareous secondary cause, another enhancement. research can provide reference direction development search sweet spot reservoir.