For slightly unstable situations steam tends to override the oil. The model proposed by van Lookeren has been extended to describe this override behaviour, by using a semi-steady state approximation for the heat transfer at the steam condensation front (SCF). In the absence of heat losses the ensuing equations are completely analogous to the equations for oil-water flow. We have also incorporated heat losses and thus developed the first simple steamdrive model which combines fluid flow and heat losses without empirical assumptions. The interface model comprises Marx-Langen heim and complete override models as limiting cases. The ensuing equations are solved with the method of characteristics.
In order to validate the theoretical model we used a scaled laboratory model. The model is transparent and experiments are performed at subatmospheric pressures. An advanced infrared scanner technique was used, together with thermocouples, to measure temperature distributions in the model. Fluid distributions and interface positions are observed visually.
The interface model describes both the convex (short term) and concave (long term) shape of the SCF and shows excellent agreement with the experimental results.