Based on the simple steamflood model of Figure 9, and the core measurements taken by Wang and Cates, some rock physics analysis can be made to give approximate estimates of seismic velocity changes that may occur in the reservoir during the steamflood. These rock physics predictions give an indication as to what might be observed in time-lapse 3-D surface seismic monitor surveys. The effects of pressure, temperature, gas/fluid saturation, and the hydrocarbon P-T phase diagram are considered for each of the four steamflood fluid-flow zones described previously.