Application of multioffset vertical seismic profiling in fracture mapping

Abstract

Multioffset vertical seismic profiling (VSP) combines the improved vertical resolution of VSP with the lateral resolution of the conventional seismic method. In this study, the multioffset VSP technique was employed to map the fracture zones in a granite batholith in which the Atomic Energy of Canada Ltd.’s Underground Research Laboratory (URL) is located. With shotpoints along a vertical shaft and receiver arrays on the surface (cemented to outcrops), six 2-D seismic sections were obtained. The upcoming and downgoing events were separated using a Radon transform wave‐field separation method. For the given multioffset experimental configuration, the VSP-CDP transformation converted the VSP section into conventional type seismic sections. The results indicate that the multioffset configuration is an effective method for mapping deep fracture zones, in this case with respect to the URL shaft. However, the VSP-CDP transformation method used in this study tends to stretch the shallow reflection events, resulting in reduced resolution.