Figure 8 shows a 3-D migration time slice before and after steam injection, at a pseudodepth of 208 ms, which is right at the base of the P reservoir (upper steam zone), and just above the top of the K reservoir (lower steam zone), as shown in Figure 2. The inline sections described above pass through Figure 8 from west to east through the center of the time-slice image. Comparing time slices before and after steam injection, some obvious seismic anomalies are visible around the injector location.
The bright white disk labeled ``S'' is almost certainly steam, not just heated fluid, as will be explained in later sections of this paper. The dark annulus to the east labeled ``Pr'' is the polarity reversal along the east base of the P formation, as observed in the inline sections. However, the time slice shows that the polarity reversal actually forms a semi-circular annulus around the well on the east and south side. I will later describe why I think this feature is related to a pressure front propagating slowly towards the southeast. On the west, the region where the base of the P formation apparently vanished is labeled ``Z''. I will later explain why I think that a pressure front has already propagated out of the picture to the northwest, leaving behind an impedance match that causes the base P reflector to vanish to the west. Finally, a thin dark annulus is visible in the time slice very close to the injector, labeled ``W''. I believe this may be the seismic image of a thin ring of hot water that is created by steam condensing in the reservoir close to the injector.