Crosscorrelogram migration of IVSPWD data

Drill-bit seismic data can provide valuable information about reflector characteristics above or below the drill bit. In this paper, an interferometric migration method is developed and applied to synthetic data and Union Pacific Resources Corporation (UPRC) drill-bit data. UPRC data are recorded on the earth's free surface while a tricone drill bit and down hole motor were used to drill along a horizontal trajectory at a depth of 9188 ft in the Austin Chalk formation. Crosscorrelograms were migrated based on the primary-ghost imaging condition. The merit of interferometric or crosscorrelogram migration is that both drill-bit position and pilot signal do not need to be known and is applicable to deviated wells. Synthetic results verify the validity of the reflectivity image obtained by migrating crosscorrelated drill-bit traces generated by a drill bit moving along a horizontal hole. The resulting migration images obtained from the UPRC data are compared with a surface-CDP section adjacent to the well rig. The results show that the crosscorrelogram ghost-migration image roughly correlates with the CDP section. But we also note that there is some spurious noise in the images. Our results suggest that crosscorrelogram migration can be used to image the reflectivity distribution with Inverse Vertical Seismic Profiling While Drilling (IVSPWD) data, but caution is needed so as to not image virtual multiples as actual reflectors.