Shale alteration calibration in shallow formations of Qikou depression
Guo Shu-wen1,3, Xiao Dun-qing1, Fu Dong-li11, Wang Yu1, Zhai Li-jun2
1. Research Institute of Exploration and Development,Dagang Oilfield,PetroChina, Tianjin, 300280, China;
2. Production Management Department,Dagang Oilfield,PetroChina, Tianjin, 300280, China
Abstract：Water base mud in Qikou depression invades shales in the shallow formation,which leads to shale alteration and errors in acoustic logs that cannot reflect velocities of origin formations.So synthetic seismogram calibration and well-constrain inversion cannot be accurate.Statistics show that shale velocity decreases with the soak time.After dividing the sand and shale profile,mean and variance methods can be used to calibrate shale alteration basing on short time soak well as a reference.Applications reveal that synthetic seismogram calibration and reservoir inversion of thin sands are better with shale alteration corrected acoustic log.
