川东鄂西长兴期海绵礁的特征和形成条件

CHARACTERISTICS, FORMATION CONDITION AND RESERVOIR POTENTIAL OF UPPER PERMIAN CHANGXING FORMATION CALCISPONGE REEFS IN EAST SICHUAN AND WEST HUBEI

晚二叠世长兴期川东、鄂西碳酸盐岩台地的海绵礁主要有三种类型:台缘镶边骨架礁、台内线状或点状骨架礁和台内点状障积礁。第一成礁带发育在台地的东缘,第二成礁带位于断陷型淹没台地与开阔台地的交界带,第三成礁带发育在台地西部的缓坡上。礁体的形成、分布主要受断裂构造的控制。

The calcisponge reefs of the Upper Permian Changxing carbonate platform in EasternSichuan and Western Hubei Provinces can be divided into three types: rimming frame-work reefs developed on the eastern margin of the platform, linear or point frameworkreefs located within the platform and baffling point reefs on the ramp of the western plat-form, the framework reef complexes of which, both rimming and linear or point, arefavourable oil and gas reservoirs. The formation and distribution of reef bodies are mainlycontrolled by faulting, especially synsedimentary faulting. The reef bodies developedthroughout the whole Changxing stage, the best of which are middle and late stages. Fromthe end of Changxing to Early Triassic, a rapid rising of sea--level took place, resulted indrowning out of the entire platform and all the reef bodies.