碳酸盐胶结物对深层优质碎屑岩储层影响研究OACSTPCD

The Paleogene Shahejie Formation is a significant oil-bearing series in Bohai Bay Basin.However,in the northern part of Bozhong Depression in the Bohai Sea,the Shahejie Formation exhibits poor reservoir properties due to deep burial and complex diagenetic evolution.In order to explore deep high-quality reservoir,this paper focuses on the newly drilled LD25-AE structure well in the southern segment of the Liaoxi Uplift,which has shown promising oil and gas indications.The research,utilizing various experimental techniques,elucidates the impact of carbonate cements on deep clastic rock reservoirs within the medium-porosity and medium-permeability reservoir within the 1st and 2nd members of Shahejie Formation.The results indicate the presence of three distinct stages of carbonate cements in reservoirs,characterized by different compositions,origin and occurrence:syngenetic bioclastic carbonate,early basement cemented carbonate and late metasomatic iron-rich carbonate.Additionally,the calcite in the reservoir underwent two stages of dolomitization which are evaporative pump dolomitization and late hydrothermal dolomitization.The intense wave washing during the syngenetic period resulted in relatively clean intergranular pores,favorable for cement development.The early carbonates were cemented in a basal manner,preserving the primary pore space.Organic acids dissolved early carbonate minerals and feldspar particles,forming a large number of seconday pores.The discovery of this type of reservoir further reveals the exploration potential below 3 500 m depth in the Bohai Sea,providing a basis for identifying high-quality deep Paleogene reservoirs in offshore areas with limited wells.