渤海湾盆地饶阳凹陷河间洼槽古近系砂岩储层成岩—成藏耦合关系

饶阳凹陷河间洼槽古近系沙河街组砂岩储层具有典型的低孔低渗特征，为揭示储层致密化过程，并分析其与油气成藏的关系，通过岩心观察、铸体薄片鉴定、流体包裹体分析等手段，结合地层埋藏史和热演化史模拟，分析储层成岩演化过程，同时利用“反演回剥”的原理，以铸体薄片资料为基础，定量恢复地质历史时期的储层孔隙度演化，与油气充注史相结合确定研究区砂岩储层成岩演化与成藏之间的耦合关系。结果表明，经历酸碱交替的流体演化，储层成岩演化呈多期溶解多期胶结的特征；成岩早期缺乏抗压实的碳酸盐胶结物、塑形矿物的压实作用、硅质和碳酸盐胶结作用是造成储层致密化的主要因素；储层致密化前后有2期油气充注，第1期油气充注于储层致密化之前，即油气在浮力作用下进入储层的“先成藏后致密”的过程，第2期油气充注于储层致密化之后，即油气在超压作用下进入储层的“先致密后成藏”的过程。

Coupling relationship between diagenetic evolution of sandstone reservoirs and hydrocarbon accumulation in Palaeogene in Hejian trough,Raoyang Depression,Bohai Bay Basin,China

Sandstone reservoirs of Shahejie Formation in Palaeogene in Hejian trough has typical characteristic of low permeability and low porosity.To reveal the densification process of reservoirs and analyze the relationship between the evolution of sandstone reservoirs and hydrocarbon accumulation,the diagenetic evolution process of the reservoirs was studied on the base of core observation,thin section examination,fluid inclusion analysis,simulation of stratigraphic burial history and organic matter thermal evolution.According to the principle of inversion and back-stripping,the evolution history of actual porosity was established quantitatively on the base of casting thin sections in the study area.Combined with hydrocarbon charging history,the coupling relationship between diagenetic evolution and hydrocarbon accumulation period was studied.The result proves that the densification factors include lacking of early carbonate cement,mechanical compaction of plastic mineral,late silicic and carbonate cementation.With acid and alkali fluid alternating evolution,the diagenetic evolution has the characteristic of multi-period dissolution and cementation.The first phase of oil charges before densification of reservoirs by buoyancy,which belongs to the type of densification after hydrocarbon accumulation.The second phase of oil and gas charge after densification of reservoirs by overpressure,which belongs to the type of densification before the hydrocarbon accumulation.