P- and S-wave migration of while drilling data

I investigate some aspects of multicomponent processing in seismic while drilling (SWD) acquisitions. I start from the consideration that a working roller cone is a good source of either P- and S-waves. Then, by examining the radiation pattern of the bit, I evaluate the subsurface illumination in simple models and for different geophones directivity. It results that S-waves can increase the lateral extent of the imaged area, while P-waves obtain a higher illumination in the vicinity of the borehole. By using the appropriate velocity model it is possible to produce separately a migrated gather for P-waves and one for S-waves. In addition, migration gathers can be observed in the aperture angle domain. I show the results on SWD synthetic and real data. The information that can be recovered about both compressional and shear properties of the subsurface, especially during the drilling process, can be crucial to predict overpressured zones and to reduce the ambiguity between variations in pore pressure and variations in lithology.