Pressure front

Table 2 shows that the leading pressure front from the injector has a pore pressure increase of at least 50 psia, with no change in temperature. Since the reservoir pore pressure is initially at 100 psia, and the bubble point is estimated to be about 110 psia, large regions of the pressure front could easily be above bubble point. In this case, the initial 10% free gas in pore space would be dissolved into liquid oil. If that happens, a V_p increase on the order of 20-25% could occur. This may be slightly counterbalanced by a 5% decrease in V_p from pore pressure softening of the rock matrix. However, the net result would be a 20% increase in V_p in regions of the pressure front which are above bubble point. Density variations would be negligible. The combined rock property changes in the pressure front should be seismically apparent by significant time pull-ups and potential reflection polarity changes.

The velocity and density changes in each steamflood zone, compared to the initial reservoir conditions, are summarized in Table 3.

 

$$\Delta V_p \Delta \rho$$ ZONE

steam -40% -15%

hot water +10% 0%

hot oil 0% 0%

pressure front +20% 0%