VSP velocity extraction using wave field extrapolation
Sun Zan-dong1,4, Xie Chun-hui1,2, Hao Hui-min3, Xue-shan2
1. Lab for Integration of Geology and Geophysics, China University of Petroleum(Beijing), Beijing, 102249, China;
2. Northwest Branch,Research Institute of Petroleum Exploration & Development,PetroChina, Lanzhou, Gansu, 730020, China;
3. BGP Inc.,CNPC, Zhuozhou, Hebei, 072751, China
Abstract：We extrapolate the sources of VSP common receiver gathers to the same level as receivers by phase shift algorithm.The gathers after extrapolating is similar with the surface seismic data,then the root mean square velocity of layers below the receivers can be extracted using stack velocity analysis.Finally we figure out the interval velocity.This method solves the limit that the VSP travel-time inversion can only calculate interval velocity of layers between the receivers.Applying this method in Lungu 38 field VSP data,we obtain the 3D velocity volume for zone of interest.
