Evaluation of Fault Sealing in the No.2 Fault Zone of the Qiongdongnan Basin
The No.2 Fault is a key basement fault in the Qiongdongnan Basin,connecting the oil source and trap,and playing a crucial role in transport and distribution of oil and gas.This study aims to clarify the differ-ence in fault sealing across various sections of the No.2 Fault,providing a reliable theoretical basis for subse-quent exploration in this area and improving fault sealing evaluation methods through detailed seismic data inter-pretation.Based on fault activity calculations,the No.2 Fault Zone in the Qiongdongnan Basin can be divided into three sections:eastern,central,and western.Based on this,we quantitatively evaluated the fault sealing ability of different sections of the No.2 Fault Zone using the fuzzy mathematical evaluation method,by calcula-ting normal stress for section(F),mudstone cutting ratio(SGR),and mud filling index(Rm).Additionally,we qualitatively evaluated the sealing properties of fracture-related zones in different sections using fluid inclu-sions,thin section observation,and scanning electron microscopy,focusing on diagenetic cementation and oil thickening.The results indicate that the fault sealing characteristics of the No.2 Fault Zone exhibit regional variability,with the western section demonstrating superior fracture sealing and serving as an effective barrier for oil and gas migration,followed by the eastern section.The central section has the greatest need for enhanced fracture sealing.The western fracture zone is sealed by mineral cement,whereas the central and eastern sections are filled with thickened crude oil,with sealing occurring relatively later.Overall,the sealing of the No.2 Fault Zone is the result of multi-stage hydrothermal mineral crystallization and oil thickening,occurring on top of com-paction and filling processes.
万方数据
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