Influence of Chlorite on Siliceous Cement under Control of Reservoir Lithology

In the background of low-permeability reservoir in Huagang Formation, Xihu depression, high-quality reservoir is often associated with the enrichment of chlorite and siliceous cement, which is inconsistent with the view that chlorite can restrain siliceous cement. The classification and formation of chlorite were analyzed by X-ray, casting thin section, fluid inclusion test and scanning electron microscopy with spectrum. And the influence of chlorite on siliceous cement was studied through the comparison of the distribution of chlorite and siliceous cement in different reservoirs and the evolution of formation condition and reservoir quality. The results show that chlorite presents as pore-linking and pore-filling occurrences. Pore-linking chlorite is formed by the recrystallization of early clay coating or crystallization of pore fluid, and pore-filling chlorite is closely related to the dissolution of volcanic debris and feldspar. Chlorite and siliceous cement are both abundant in coarse reservoir (except sandy conglomerate and muddy gravel reservoir). Chlorite can hinder siliceous cement effectively during shallow burial and low geotemperature, and siliceous cement only grows above discontinuity chlorite or broken particle as isolated columnar quartz. Siliceous cement cannot be prevented during deeply buried and high geotemperature, and it develops as quartz overgrowth. The pores of coarse reservoir are more abundant than fine reservoir and conglomerate and muddy gravel reservoir, and the pores provide necessary space for quartz overgrowth, which is the main reason why chlorite and siliceous cement are both plentiful in high-quality coarse reservoir.