JIANG Kai-xi1, HE Wen-xiang2, PENG Li3, CHEN Zu-lin2, ZHU Jun-zhang4, GUO Qing-zheng1, XIANG Nian1
1. CNOOC Energy Technology & Services Technical Institute of Unconventional Hydrocarbon, Tianjin 300452, China;
2. School of Earth Environment and Water Resources, Yangtze University, Wuhan Hubei 430100, China;
3. Bohai Experimental Center of CNOOC, Tianjin 300452, China;
4. Technology Department, CNOOC China Limited-Shenzhen, Guangzhou 510240, China
Abstract: This paper discussed the origin and source of acid fluids under burial condition, brought forward the new understanding of chalky limestones and the scheme model of burial dissolution by using GC and GC/MS to analyze extracts from Zhujiang carbonates, and investigated the regional tectonics and the dynamic characteristics of the formation water. We concluded that the acid fluids originated mainly from ① pyrolysis of source rock from Huizhou depression ② biodegradation of crude oil ③ CO2 and other acid fluids released from magmatism.The forming of chalky limestone was related to the continuous corrosion,soaking and washing by organic acid fluids.The burial acid fluids took the faults and complex fracture networks caused by the Dongsha movement as the migration channel and space for mass exchange, the strong acid-carbonate rock reaction took place under the active ground water condition of the Liuhua area, and then carbonate strata collapsed and the distribution of sink holes of the Liuhua area were formed. In addition,the possible causes of sinkholes-meteoric corrosion and dolomitization corrosion had been excluded after a systematic discussion.
Keywords: acid fluids burial dissolution carbonate rock Liuhua area Pearl River Mouth Basin
Bulletin of Mineralogy, Petrology and Geochemistry Vol. 34, No.3, 2015, page 592-600