Abstract: There exist multiple unconformities developed in Beisantai area of Junggar basin. They can be divided into truncation unconformity, onlap unconformity,fault-fold unconformity and parallel unconformity in terms of their forming mechanisms and section configurations. They are of typical laminar textures due to uneven weathering and denudation processes,including basal conglomerate,transgres-sive sand body,weathered claystone and semi-weathering leached zone. It is such unconformable types that control the dips and intersecting extent of unconformities, followed by controlling the hydrocarbon migration and patterns of hydrocarbon accumulation here.

Key words: Junggar basin, Beisantai oilfield, unconformity, hydrocarbon accumulation, hydrocarbon migration