A Field Experiment to Study Wave Propagation in Gas-Saturated and Fractured Rocks

P344 A FIELD EXPERIMENT TO STUDY WAVE PROPAGATION IN GAS-SATURATED AND FRACTURED ROCKS. Abstract 1 Six seismic tomography surveys between four boreholes have been acquired at a hydrogeological test site in the Cretaceous Chalk Yorkshire UK. Data were acquired before and after air injection into a fractured region of the geological sequence. Time-lapse velocity tomograms revealed that the air had migrated rapidly to the top of the sequence. Velocity anomalies of up to 14% were observed. Amplitude differences between the crosshole seismic data before and after air injection were attributed to small traces of air in 45 degree conjugate fractures