GRAVITY FLOW SEDIMENTARY CHARACTERISTICS AND THE SIGNIFICANCE OF PETROLEUM EXPLORATION IN THE CHALUHE FAULT DEPRESSION, THE YITONG BASIN

Lots of subaqueous gravity flow sedimentary bodies were developed in the Eocene strata of Chaluhe Fault Depression,the Yitong Basin.Based on the study of distribution and sedimentary character of gravity flow,four sedimentary types can be recognized: shallow-water and deep-water turbidity current deposits,underwater slide deposits and underwater debris flow deposits.Through the comprehensive analysis of regional geological background,drilling lithology,well loggings and seismic data,it is suggest that underwater slide deposits and underwater debris flow deposits were formed in re-transported and redeposition,which were usually associated with faults.Shallow-water and deepwater turbidity current deposits were developed in the pre-fan delta,and mostly related to the paroxysmal water flow event due to subaqueous distributary channel,and partially to the slump turbidity current redeposition.Based on the oil-gas exploration results,it shows that the turbidity sand-body has developed well reservoir capability and has a successful oil-gas exploration.It has been proved that shallow-water and deep-water turbidite sand bodies have good potentials for oil and gas exploration in this region,which are in Liangjia structural belt of the down-thrown side of the No.2 fault and in the periphery of Wanchang structural belt.