Abstract: The Chang 7 member of the Triassic Yanchang Formation in the Ordos Basin contains wealthy of oil shale resources. It is mostly distributed in the southern part of the basin and the thickness of these layers is from 15 to 30 meters (with the thickest exceeds 40 meters) with 5% to 10% oil yield. The development of the Ordos Basin reached its culmination in the sedimentary period of the Yanchang Formation and the lake basin was largest in area during the Chang 7 epoch. Based on the research on the relationship between the distribution of oil shale and the character of sedimentary facies during Chang 7 epoch, we suggest that the distribution of oil shale is remarkably controlled by the depositional environment then. The oil shale of the Chang 7 member formed under deep lake to half deep lake environment are of higher oil yield and of thicker and wider distribution range. The Chang 7 member in the Ordos Basin is very rich in oil shale resource and the volume of the shale oil resources is 10 476×10⁸t. Moreover, because the structure of the Ordos Basin is simple, their exploitation conditions are good. So the Chang 7 member of the Yanchang Formation in the Ordos Basin is potential for prospecting and exploitation.

Key words: Ordos Basin, Chang 7 member, oil shale, depositional environment, resources potential