Characterization of dispersion, attenuation, and anisotropy at the Buena Vista Hills field, California

We create a log of intrinsic dispersion and attenuation for the Antelope Sh ale formation of the Buena Vista Hills field, San Joaquin Valley, Californi a. High dispersion (or low Q) values correlate with thin sand and carbonate beds within the Antelope Shale. These beds are at least ten times as perme able as the host shale formation, so this effect provides a possible avenue for seismic prediction of permeability. The dispersion log is formed throu gh comparison of crosswell seismic velocities (measured at approximately 1 kHz) and sonic log velocities (measured at approximately 10 kHz). In order to provide a proper basis for comparison, the sonic log must first be adjus ted fur field anisotropy, scaling effects, and resolution of measurement. W e estimate a local shale anisotropy of about 20% based on correlations gene rated from published measurements of other shale fields. We apply resolutio n enhancement to capture the thin sand and carbonate beds, and windowed Bac kus averaging to match the measurement scales. A modeling study verifies th e technique, and shows that beds of thickness greater than 30 cm have a mea surable signature. The actual resolution is on the order of the crosswell F resnel length, or about 7 m for the model study.