Imaging blended VSP data using full wavefield migration

Blended source and/or simultaneous source acquisition for multi-offset and multi-azimuth VSP measurements can prove significantly beneficial in saving expensive borehole down-time. In the last few years, for the case of surface seismic data, it was proposed to redefine imaging and inversion of the blended data to handle the data directly without any need to separate the blended sources. Recently, we proposed the concept of full wavefield migration (FWM) to image VSP data, where using all the multiples - both surface and internal multiples - in the imaging provides better illumination, especially away from the well. Using the above mentioned two concepts, in this paper, we will show the potential of FWM to directly image blended VSP data, without the need for intermediate deblending. We can see FWM imaging as a deblending algorithm itself that transforms the blended data into the reflectivity image space by an inversion process. The concept of FWM formulated in terms of a constrained least-squares inversion scheme indeed enables us to use any kind of complex source wavefield to explain the subsurface reflectivity. The method is illustrated successfully for some synthetic blended VSP examples.IST/Imaging Science and TechnologyApplied Science