Application of variational principles to cap and base rock heat losses

An approximate heat loss routine has been developed using variational principles. The heat loss has been incorporated into the energy balance of a numerical reservoir simulator for thermal recovery processes. The heat loss routine neglects horizontal conduction in the cap and base rock. However, acceptable accuracy is obtained on problems where the Peclet number is above 100. The accuracy of the calculated temperature distribution in the reservoir, when using the heat loss routine, is more sensitive to the Peclet number than to soak time in steam soak simulation problems. A large savings of computer storage and a moderate savings of computer time is possible by using the heat loss routine as compared to using an extended grid to model the cap and base rock.