Jurassic stratigraphic base-level cycle and subtle oil reservoir in Baijiahai-Wucaiwan,Junggar Basin,NW China

Baijiahai-Wucaiwan is located in the NE Junggar Basin,where the subtle oil reservoirs could be the major play targets.According to the stratigraphic base level,six mid-term base-level cycles and eleven shore-term base-level cycles can be recognized in the Jurassic.Based on the drilling,well logging,3-D seismic data,and the base-level cycle pattern of high-resolution sequence stratigraphy,eleven transfer levels of the base-level cycle are recognized,from which the high-resolution sequence stratigraphic framework is established,suggesting that the subtle oil reservoirs are mainly developed in the sand body in front of the delta in the descending half-cycles and channel-sand in the ascending half-cycles.