FAULT SYSTEMS AND THEIR TECTONIC EVOLUTION IN XUANHAN-DAXIAN AREA, THE NORTHEASTERN SICHUAN BASIN

Faults and fault related folds are the most important and typical structure in Xuanhan-Daxian area,the northeastern Sichuan Basin.They decided the primary reservoirs' preservation and the secondary reservoirs' reconstruction.Based on the detailed interpretation of about 500 km² of 3-demension seismic data,the fault systems in Xuanhan-Daxian area have been divided into three systems:the fault system of Silurian bottom,the fault system of the middle structural stratigraphic and the fault system of the upper structural stratigraphic.The later two fault systems are the most important fault systems in this area.The fault system of Silurian bottom is very abnormal and it may be formatted in Indosinian Movements epoch.The fault system of the middle structural stratigraphic is the most important one in this area,it has good heredity and formatted the main structure traps in this area,the main system of NE direction formed in Yanshanian Movement epoch and controlled the primary reservoirs' formation and preservation.The fault system of the upper structural stratigraphic formed in the two periods of the early and later Himalayan Movement epoch.The main fault system in NW direction superposited on the fault system of the middle structural stratigraphic and reconstructed it in vertical direction.It also play a significant role in the secondary re-servoirs' formation,preservation and reconstruction in Puguang and Maoba chang areas.