SEGJ Technical Conference

Monitoring seismic attenuation change associated with vapor-liquid phase transition using time-lapse reflection seismic data in the Kakkonda geothermal field, Japan.

Abstract We conducted time-lapse attenuation estimation using three reflection seismic surveys with different timings acquired in the Kakkonda geothermal field during a 12-day period spanning a well shut-in period. To investigate geothermal fluid changes associated with increased pore pressure, careful preprocessing was carried out to enhance the repeatability of time-lapse seismic data, focusing on the frequency content, which is indirectly related to seismic attenuation. Time-lapse attenuation was evaluated for two of the three PSTM sections using the spectral ratio method and the centroid frequency shift method. We demonstrated an increase in attenuation associated with an increase in pore pressure in and around the known super-shallow vapor-dominated reservoir. A possible cause of this short-period attenuation increase is the vapor-liquid phase transition in the reservoir.