Systematic Restoration of Eroded Thickness by Unconformity in Cretaceous of Xujiaweizi in the North of Songliao Basin

By using the deposition-erosion process analysis,we analyzed and forecasted the deposition-erosion process including a total of 15typical wells and special the Xushen 3well in Xujiaweizi in the north of Songliao basin,then quantitatively resumed the thickness by the unconformity in Cretaceous.Decomposed four high-frequency wave periods containing 18Ma,8Ma,4Ma and 1Ma,which reflects the deposition-erosion process in different sags and different structural parts of the same sag in basin.The curves of two high-frequency wave periods of 8Ma and 4Ma correspond to the 4times of the uplift-erosion process,respectively at the late Shahezi Group of early Cretaceous,the medium-term of Yingcheng Group,the late Yingcheng period-the early Denglouku period and the late Quantou Group.During this study,the medium-term of Yingcheng Group and the early Denglouku period this two uplift-erosion process'thickness were calculated.The thickness was between 14mand 156min the medium-term of Yingcheng Group and between 121mand 287min the early Denglouku period,leading to the lack of the second layer of the Yingcheng Group and the first layer of the Denglouku Group in Xujiaweizi.The five relative small-scale structure uplift movements were determined and predicted in Yingcheng period from the characteristics of wave curves belonging to the 1Ma high-frequency,leading to the multi-period volcanic features in the Yingcheng period,which also determined the multi-stage gas accumulation in the Yingcheng period.We quantitatively resumed the thickness of the horizontal distribution in unconformity by the late Huoshiling period,the late Shahezi period in the Early Cretaceous and the Late Yingcheng period,which was regional distribution of the uplift and erosion areas was showed in crucial gas accumulation.The layers of the structure uplift were predicted and the thickness of the unconformity was calculated in Mesozoic and Cenozoic in study area.From the prediction and calculation we find that the time of structure uplift-erosion occurred in the early of mid-Yanshan movement and its thickness was about 633m.The average thickness was about 1 279min the late-Yanshan movement and was about 1 414 m in the early Himalayan movement.By comparing a variety methods of erosion thickness,we find the deposition-erosion process analysis owns characteristics including systemic,predictability and small restrictions from the information,and relatively more effective used in the erosion thickness recovery by unconformity which experienced multi-structure and volcanic activity.