Do no harm! - Seismic petrophysical aspects of time-lapse monitoring

© 2000 Society of Exploration Geophysicists. Time-lapse seismic studies of oil and gas reservoirs depend on understanding the seismic response to changing reservoir conditions. By providing erroneous predictions, however, geophysicists have the ability to actually harm future production. The steps involved in time-lapse seismic petrophysical modeling are simple; the details, however, are imposing. To predict future reservoir seismic response accurately, one must know the future reservoir conditions that may be encountered, including: changes in fluid saturation; changes in the properties of the fluids themselves; changes in the dry-frame moduli; and changes in the whole-rock response (usually modeled by Gassmann theory). Simple applications of the modeling procedure described above can lead to highly misleading interpretations of timelapse seismic observations; extreme care must be taken to include all appropriate parameters and to model the response correctly