ABSTRACT
In the past few years there has been increased interest in modeling miscible and thermal recovery processes by the use of reservoir simulation models. The prediction of sharp saturation or temperature fronts resulting from these processes has shown that these simulators can in many cases be very sensitive to grid orientation. One method for minimizing the effect of grid sensitivity is to describe the difference equations with a nine-point rather than the standard five-point finite difference approximations. Inherent in the use of the nine-point approximations is the necessity for calculating consistent transmissibility coefficients. Previously published methods for calculating these coefficients do not have general applicability to heterogeneous reservoirs and/or various irregular grid spacings. This paper presents a method for calculating nine-point transmissibilities for a general heterogeneous system with unequal grid spacing.
