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.