CHARACTERISTICS OF PROTOTYPE BASIN AND HYDROCARBON POTENTIAL EVALUATION OF THE LATE TRIASSIC IN THE WEST HE’NAN PROVINCE

Thick stratum was deposited in the west part of southern North China and the Ordos area during the Late Triassic,when the stable North China Craton turned into circum-Pacific tectonic tract.The Upper Triassic of Jiyuan-Luoyang area located in the south-east Ordos basin,with sedimentary facies ranging from lakeshore/shallow lake subfacies (Youfangzhuang,Chunshuyao formations)to bythyal lacustrine facies (Tanzhuang formation),and the source rock thickness and quality were not as good as those in the Ordos basin.During the Yanshan and Himalayan epoch,the Qingyang-Yan'an area of Ordos basin was relatively stable,which was an oil-rich zone with good condition of oil formation and preservation,while the Upper Triassic in Jiyuan-Luoyang area was eroded in the tremendous tectonic movement,and the earlier pool was destroyed.