Modeling Compositional Flows

Abstract

Porous-media flows that are strongly influenced by the effects of changing fluid compositions are considerably more complicated than the flows examined in Chapter Three, and solving the equations governing such compositional flows is a correspondingly complex task. There are two main reasons for this increase in difficulty. To begin with, the transport laws for a system of N components give rise to a system of N coupled partial differential equations, which require more effort simply because of the larger number of unknowns to be solved for. In addition, the flow coefficients and fluid densities in the equations vary in response to pressure and composition in complicated ways governed by the thermodynamic constraints, as Chapter Two discusses. Thus the nonlinearity of the system imposes another level of hardship. Indeed, the complexity of compositional flows is the prime motivation for modeling them numerically.