A note on IMPES and some IMPES-based simulation models

The generalized IMPES method applies to simulation models involving any number of conservation equations. The IMPES pressure equation is a linear combination of the linearized conservation equations. This article shows the generality, simplicity, uniqueness, and derivational brevity of that equation. The associated IMPES reduction vector leads directly to the value of total compressibility in a multiphase gridblock. That compressibility in turn gives several error checks on black oil pressure/volume/temperature (PVT) data. Three IMPES-type compositional models are compared and found to be very similar, with moderate differences in efficiencies and generality. An example problem serves two comparative purposes related to IMPES model efficiency.