At this point, I have discussed several seismic features visible in the time-lapse images and suggested correlations to the presence of steam, hot water and a high-pressure front. Furthermore, I have postulated an idealized steamflood fluid-flow model, and combined the basic physics of that model with rock physics lab measurements made on cores taken from the Duri site. This process gave rise to predictions that the steam zone should be seismically visible due to velocity decreases of 40%, large time delays, and strong impedance contrasts (reflections and diffractions). The hot water zone should show a 10% increase in velocity, while the hot oil zone should be seismically transparent. The high-pressure front should be visible from 20% velocity increases causing large time pull-ups and possible reflectivity changes along boundary layers. The seismogram modeling section demonstrated all of these predicted seismic responses qualitatively from a simple steamflood velocity model based on the core data and the idealized steamflood physics.
In this section, I present a detailed traveltime and velocity analysis of the reservoir zone to estimate traveltime and velocity changes directly from the six time-lapse data sets. Because this is a time consuming effort, I concentrate only on the east-west inline section that connects the steam injector with the two temperature monitor wells of Figure 1.