Structure evolution and hydrocarbon accumulation the Beisantai uplift in Junggar Basin
Wu Xiaozhi1, Zhou Lu2, Yang Disheng3, Qi Xuefeng1, Li Bohua1
1. Research Institute of Petroleum Exploration & Development,PetroChina,Beijing 100083;
2. Southwest Petroleum University,Chengdu 610500;
3. Research Institute of Petroleum Exploration & Development, Xinjiang Oilfield Company, PetroChina, Kelamayi,Xinjiang 834000
Beisantai uplift located at the eastern part of Junggar is a relic palaeohigh.Because of the special location,Fukang had been separated from Jimusaer in the west-east direction,and Shazhang fault-fold belt separated from fukang fault north-south direction.Its evolvement has undergone Hercynian movement,Indo-China movement,Yanshan tectonic movements and Himalayan movement.The whole impress can be described as a northeast uplift descented to the west part,and fault systems developed around the palaeohigh.Compressional faulting developed at deep zone such as Carboniferous-Triassic,and down throw faulting at Jurassic-cretaceous,all this fault systems formed early and closed late.It was cut by latitudinal and longitudinal faults,Beisantai uplift presented as two uplifts,two slopes and six fault structure belts combination.When in middle-late Yanshan epoch,affected by the increased tectonic loading owing to Bogeda piedmont depression transforming into accretionary wedge,the faults on the north part thrusted up for a long way,as a result,Beisantai area uplifted strongly and fall into the uplifting pattern.From Permian to Jurassic,the core of the uplift moved to the north,with the impact of longitudinal compressinal stress,when at early Jurassic,it start to move to Beisantai.The strata onlapped from the Fukang sag to the bump,and become thinner layer by layer.The above structural evolution matched well with Permian main hydrocarbon generating process,so Beisantai uplift was always the converging place of hydrocarbon from Fukang sag.When the uplift lifted constantly,strata on high point had been denuded and the accumulation was destroyed,but the hydrocarbon supplied frequently as the hydrocarbon source was abundant.Therefore,it guaranteed full injection into structure belts such as uplifts,faults and slopes.The Triassic and Lower-Middle Jurassic layer of low uplift,footwall of fault belts and slope preserved well,the accumulation formed early can be preserved intact till now.Medium and small sized hydrocarbon accumulations are dominant,which surrounded Beisantai uplift.Slopes of Triassic-Jurassic and deep Carboniferous-Permian is the potential exploration domain.