Head-wave Excitation with Virtual Source

The original applications of the Virtual Source Method (VSM) concentrated on reflected waves and demonstrated that imaging and monitoring through complex and changing overburdens can be accomplished at the expense of using downhole geophones in horizontal wells. There is number of reasons to expect even better results when head waves are restored and used for reservoir imaging and monitoring purposes. Being compared with a reflection survey, the head waves have less strict requirements for surface sources placements providing data for high resolution tomographic image for substantially larger areas. Head waves show high sensitivity to changes in the reservoir and look promising for monitoring applications. The drawback of this VSM application is in requirement of receiver lines placement close to reservoir depths. Application of VSM to realistic 3D model with complex near surface heterogeneous components has demonstrated many similarities in real and restored wavefields. Summation over limited number of surface shots in the vicinity of stationary point for head waves has demonstrated a better restoration of virtual source wavefield.