Fluid Charging and Paleo-pressure Evolution in the Ledong Slope Zone of the Yinggehai Basin,South China Sea

作     者：ZHAO Jing HUANG Zhilong MA Jian WANG Rui YANG Yizhuo FAN Caiwei ZHOU Ying XU Maguang ZHAO Jing;HUANG Zhilong;MA Jian;WANG Rui;YANG Yizhuo;FAN Caiwei;ZHOU Ying;XU Maguang

作者机构：College of GeosciencesChina University of Petroleum(Beijing)Beijing 102249China State Key Laboratory of Petroleum Resources and ProspectingChina University of Petroleum(Beijing)Beijing102249China Beijing Research Institute of Uranium GeologyBeijing 100029China Hainan Branch of the China National Offshore Oil Corporation Ltd.HaikouHainan 570100China Zhanjiang Branch of the China National Offshore Oil Corporation Ltd.ZhanjiangGuangdong 524057China University of AlbertaAlberta T6G2R3Canada 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2023年第97卷第3期

页      面：796-815页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 0708[理学-地球物理学] 

基　　金：supported by the‘Research on Exploration and Development Technology and New Exploration Fields of high Temperature and High-pressure Gas Reservoirs in the West of the South China Sea’,a subject of the key technology projects of the CNOOC‘Key Technologies for Producing 20 million m~3 of Oil in the Western South China Sea Oilfield’(No.CNOOC-KJ 135 ZDXM 38 ZJ 02 ZJ) The financial support from CNOOC(Hainan)。 

主　　题：fluid inclusions fluid charging overpressure Ledong slope zone Yinggehai Basin 

摘      要：Large numbers of gas reservoirs have been discovered in overpressure basins.Fluid charging has a close relationship with paleo-pressure evolution,affecting the migration of gas reservoirs.To study fluid charging and the related pressure system,we analyzed burial histories and fluid inclusion(PVTx)simulations and conducted basin modeling of the Ledong Slope Zone in the Yinggehai Basin as an example.On the basis of fluid-inclusion assemblages(FIAs),homogenization temperature(Th),final melting temperature(Tm,ice)and Raman spectroscopy in fluid inclusions,there are three stages of fluid charging:during the first and second stage,methane-dominated fluid was charged at 2.2–1.7 Ma and 1.7–0.9 Ma,respectively.In the third stage,CO_(2)-rich hydrothermal fluid was charged since 0.9 Ma.It could be concluded from the well-logging data that the disequilibrium compaction in the Yinggehai Fm.,along with the fluid expansion and clay diagenesis in the Huangliu and Meishan formations,resulted in the overpressure in the Ledong slope zone.The evolution of paleo-pressure was affected by the sedimentation rate of the Yinggehai Fm.,as well as the hydrocarbon generation rate.Additionally,the Ledong Slope Zone is less affected by diapir activity than the nearby diapir area.Based on fluid inclusions,paleo-pressure,basin modeling and geological background,the gas migration history of the Ledong Slope Zone can be divided into four stages:in the first stage,excess pressure was formed around 5 Ma;from 2.2 to 1.7 Ma,there was a reduction in the charging of hydrocarbon fluid and steadily increasing excess pressure;during the 1.7–0.9 Ma period a large amount of hydrocarbon was generated,excess pressure increasing significantly and hydraulic fractures forming in mudstones,With gas reservoirs developing in structural highs;since 0.9 Ma,CO_(2)-rich hydrothermal fluid accumulated in reservoirs adjacent to faults and the pressure coefficient remained stable.The research results are helpful in the study of fluid migration and accumulation mechanisms in overpressure basins.