Abstract: Chepaizi swell in western margin of Junggar basin is a favorable area with composite hydrocarbon accumulation. In recent years, a number of prolific lithologic reservoirs have been discovered in the Sha-II member of Neogene Shawan formation, representing an important breakthrough in shallow-depth exploration. This paper analyzes the hydrocarbon distribution and typical reservoir characteristics of the Sha-II member, discusses its main factors controlling hydrocarbon accumulation and reservoir pattern, and proposes four main elements to control hydrocarbon accumulation such as lake-enlarged beach bar sands, hydrocarbon conduit system, lateral barrier conditions and paleostructural crest, and the reservoir pattern controlled by multi-factors of distal source and late accumulation. The beach bar sands parallel to the paleo-lake strandline could be the key target for further exploration.

Key words: Junggar basin, Chepaizi field, Neogene, control, factor, reservoir pattern