Analysis on hydrocarbon accumulation system in Wulungu depression of Junggar basin

Wulungu depression is located in the north part of Junggar basin.Based on the theory of petroleum system,the depression was analyzed according to basic petroleum characters as the feature of basin evolution,source rocks,cap rocks and reservoir-seal associations and trap types,and hydrocarbon accumulation systems was established.The results showed that the mudstone of late Carboniferous and Triassic and the coal rocks of Jurassic are major source rocks.The main reservoir-seal associations in Jurassic and Cretaceous were developed in Badaowan formation,Sangonghe formation,Xishanyao formation and Shishugou groups in the depression with the good configures of trap conditions,oil migration and accumulations.Late Jurassic and Cretaceous are the main periods of hydrocarbon accumulation.In Wulungu depression,secondary hydrocarbon reservoirs may exist and the south slope and footfall of Hongyan fault step zones were the exploration potential areas.