北黄海盆地东部坳陷下白垩统砂岩成岩作用及其储层意义

Sandstone diagenesis and its reservoir significance of Lower Cretaceous in North Yellow Sea Basin

通过对取芯井砂岩镜下特征及孔隙度渗透率变化的分析,研究了北黄海盆地东部坳陷下白垩统砂岩的成岩作用及其储层意义。结果显示,储层砂岩类型以长石砂岩、长石石英砂岩和岩屑石英砂岩为主,处于中成岩作用阶段的A亚期末期至B亚期早期。主要的成岩作用类型有压实作用、压溶作用、胶结作用、交代作用、蚀变作用、溶蚀作用和重结晶作用,主要孔隙类型有粒间孔隙、粒内孔隙、填隙物内孔隙和次生裂缝。长石砂岩是主要储层。压实作用、压溶作用、胶结作用和重结晶作用使砂岩孔隙度减小,降低了储层物性,起到破坏性作用;交代作用、蚀变作用和溶蚀作用使砂岩孔隙度增大,改善了储层物性,起到建设性作用。孔隙度和渗透率整体上由浅变深而呈现由大到小趋势,在深度为3 000~3 020 m和3 140~3 250 m时出现异常高值,孔隙度与渗透率的异常高值带是次生孔隙发育带。

The sandstone diagenesis and its reservoir significance of Lower Cretaceous in North Yellow Sea Basin are studied by the analysis of the thin sections of sandstone and variation of porosity and permeability.The research shows that the reservoir sandstones are mainly composed of feldspar sandstone,feldspar quartz sandstone and lithic quartz sandstone.The sandstone reservoirs are in the late stage of the A-sub-period to early stage of B-sub-period in the middle diagenesis stage.The main types of diagenesis in studied area are compaction,pressure dissolution,cementation,metasomatism,alteration,dissolution and recrystallization.The main types of porosity are intergranular pores,intracellular pores,interstitial pores and secondary cracks.Feldspar sandstone is the main reservoir.Compaction,pressure dissolution,cementation and recrystallization decrease the porosity of sandstone and reduce the physical properties of the reservoir and play a destructive effect.Metasomatism,alteration and dissolution increase sand porosity,improve the physical properties of the reservoir,and play a constructive role.The porosity and permeability of the coring section decrease with depth and are abnormally high at depths of 3 000~3 020 m and 3 140~3 250 m,which are the secondary pore development zone.