Structural constrain to hydrocarbon accumulation in the Wulungu depression of the Junggar Basin
Yang Zhao1,2, Zhao Shujuan1,2, Li Sanzhong1,2, Yu Shan1,2, Sun Wenjun1,2, Xu Liqing1,2, Liu Xin1,2, Lou Da3, Wang Xuebin1,2, Li Tao1,2
1. College of Marine Geosciences, Ocean University of China, Qingdao, Shandong 266100;
2. The Key Lab of Submarine Geosciences and Exploration Techniques, Ministry of Education, Qingdao, Shandong 266100;
3. Dagang Oil-Gas Company, CNPC, Tianjin 300280
As geological investigation of the Wulungu depression in the Northeast Junggar Basin goes on in recent years, rich oil and gas resources are founded in the depression. But compared with the other part of the basin, the investigative level of oil and gas in the Wulungu depression is still low. This article systematically explores the law of oil and gas accumulation based on the structural characteristics and fault evolution. The Wulungu depression developed three sets of source rocks. The Dishuiquan Group and Batamayineishan group of Carboniferous dark mudstone is the most important source rock. According to the structural characteristics and evolution, the piedmont of Kelameili Mountain is the favorable oil and gas accumulation areas. The Wulungu depression is the oil-gas accumulation zone controlled by thrust faults, the oil and gas reservoirs in this area are characterized by zonal distribution along the NW-striking faults. The active deep-seated faults are the major hydrocarbon migration paths, the shallow faults mostly distributed in the Kalasayi fault, may damaged the early oil and gas reservoirs but benefit to the formation of secondary reservoirs in some degree. As the tectonic migration from north to south, the fault intensely active period matched well with the hydrocarbon generation. Structural traps in the root zone in the north developed from Late Indocinian stage to Early Yanshan stage, the main hydrocarbon reservoir types are faulted noses and faulted blocks related to the thrusting and secondary lithofacies reservoirs. Structural traps in the front zone in the south formed at Middle-Late Yanshan stage, the main hydrocarbon reservoir types are fault-related bends, fault-propagation folds, angular unconformity reservoirs and lithofacies reservoirs, but most of them are damaged by normal faulting during Himalayan period.