Abstract: The Huwan area in the northwestern margin of Junggar basin is a highly prospected area for more than 50 years. Since 1998 several new oil reservoirs have been discovered in this area including KQ-10 and KQ-109 reservoirs. In this paper, 835 old well logging data and observations of cores from 8 wells and microfacies analysis were used to finely study the reservoirs. It is concluded that the Qigu Formation and Badaowan Formation belong to the braided river sedimentation. The high permeable reservoirs mainly belong to the batture and channel sedimentary microfacies. They are distributed in a wide banded shape. By using two quantitative oil identifying models, 56 oil layers were determined from the old drilled wells for Qigu Formation. The types, controlling factors and distribution of hydrocarbon accumulations in the Badaowan Formation and Qigu Formation were summarized. It is shown that the reservoir of Qigu Formation belongs to the lithologic oil pool and the reservoir of BadaowanFormation belongs to the stratigraphic oil pool. The latter reservoir has a further exploration potential and the former reservoir may have a continuous distribution.