西沙海域西琛1井生物礁性质及储层岩石学特征

西沙海域西琛1井生物礁主要是由红藻门壳状珊瑚藻、有节珊瑚藻和绿藻门仙掌藻等钙藻组成的植物礁，其次为珊瑚礁。礁相类型主要有礁核相和礁后泻湖相。岩石矿物成分单一，以碳酸盐矿物为主，包括低镁方解石和铁白云石；结构组分有生物骨架、粒屑、泥晶和亮晶；结构类型有生物格架结构、生物障积结构、生物节片结构、生物捆扎结构和生物粘结结构。岩石类型包括骨架石灰岩/白云岩、粘结石灰岩/白云岩、粒屑石灰岩/白云岩。储集空间类型有粒间孔、生物体腔孔和藻架孔等原生孔隙和铸模孔、裂缝、颗粒内溶蚀孔、藻类溶孔和扩大的粒间溶孔等次生孔隙。孔隙组合类型以粒间孔＋溶孔＋晶间孔最为发育，储集性能较好。

Biogenetic reefs and its petrological characteristics of well Xichen 1, Xisha sea area

Biogenetic reefs of well Xichen 1, Xisha sea area are mainly plant reefs which consist of calcareous alga, including Rhodophyta shell-like coralline algae, articulated coralline algae and Chlorophyta Halimeda, and secondly of coral reefs. Reef facies types are mostly reef core facies and back reef lagoon facies. Minerals in reef rocks is simplex, mainly consist of carbonate, involving low-magnesian calcite and ferroan dolomite. Textural components are organism framework, granular fragment, micrite and calcsparite. Rock types comprise framework limestone/dolostone, boundstone, grain limestone/dolostone, with organic framework texture, biology baffle texture, geniculum texture, binding texture, and cementitious texture. Reservoir pore space types are primary pore including intergranular pore and visceral foramen, and secondary pore including moldic pore, fissure, intragranular emposieu, enlarged intergranular pore, which mostly exist as intergranular pore-emposieu- intercrystal pore, with good storage capability.