Despite the significance of coral reefs as resources for development and research, only a limited amount of drilling surveys have been done on coral reefs, and obtaining comprehensive geological information remains difficultly to obtained. In the Chenhang Island survey, the digital borehole camera technology was utilized for the first time in China to provide guidance and acquire firsthand information of coral reefs, including anomalies in the rock body (e.g. fissures, cavities, traces of biological activities, interfaces, foreign strata and substances, color variations, etc), which also helped determine the causes of low or zero coring rates. In addition, data acquired by borehole camera can be used to evaluate the integrity of coral reefs. It can be concluded that:
the borehole camera system is an accurate and effective tool for determining the geological characteristics of coral reefs;
the system can serve important purposes in the geological survey of coral reefs.
The coral reefs are soil and rock structures formed from the remains of scleractinian corals, shaped by geological forces over a long period (Wei et al. 2008). Their great potential as a natural and military resource lends importance to the geological survey of coral reefs. In the drilling of Chenhang Island in Xisha (Paracel) Islands, we used deep boreholes to obtain rock cores from coral reefs and model their geological structures. The data can be used in the research of climate and environmental changes on a million-year time scale, the study of coral reefs' development and their interaction with the environment, as well as the exploitation of coral reefs for military purposes. The scientific and engineering values of such data would be significant.