Petrologic Characteristics of Quaternary Reef-Carbonate Rocks in Well Xike-1, Xisha Area

The reef-carbonate rock types and reef types are described based on the core observation and petrologic characteristic analysis of reef-carbonate rocks in well Xike-1. Analyses of 543 casting lamellas and observation of 214.89 m core samples indicate that the reef-carbonate rock types are composed mainly of wackstone, packstone and framestone, and secondly of bindstone, grainstone, floatstone and rudstone. Vertical variations of rock types are characterized by dominant grain stone at a depth of 0-10 m, bioclastic calcarenite at a depth of 10-22 m, and wackstone, packstone and framestone at a depth of 22-214.89 m, respectively. It is concluded that the reef types are frame reefs and main reef-building organisms consisting of corals and a few coralline algae by the quantitative analysis results. Frame reefs develop at the depth of 0-214.89 m, and cluster and segment reefs only develop at the depth of 83-98 m.