TOMOGRAPHIC IMAGING OF VELOCITY AND Q WITH APPLICATION TO CROSSWELL SEISMIC DATA FROM THE GYPSY PILOT SITE, OKLAHOMA

The centroid frequency shift method is implemented, tested with synthe tic data, and applied to held data from three contiguous crosswell sei smic experiments at the Gypsy Pilot Site in northern Oklahoma. The sim ultaneous iterative reconstruction technique is used for tomographic e stimations of both P-wave velocity and Q. No amplitude corrections or spreading loss corrections are needed for the Q estimation. The estima ted in-situ velocity and Q distributions correlate well with log data and local lithology. The Q/velocity ratio appears to correlate with th e sand/shale ratio (ranging from an average of similar to 15 s/km for the sand-dominated lithologies to an average of similar to 8.5 s/km fo r the shale-dominated ones), with the result that new information is p rovided on interwell connectivity.