Application of an automatic differentiation tool in the development of a compositional reservoir simulator

Automatic differentiation is an approach to numerically compute derivatives both accurately and efficiently. This can be quite valuable, for example, in the fully implicit solution of compositional reservoir equations. We des cribe the procedures necessary to apply the ADIFOR (Automatic Differentiati on of Fortran) tool to the IPARS (Integrated Parallel Accurate Reservoir Si mulator) compositional reservoir simulator and the approaches used to explo it the sparsity in the required Jacobian matrix. Values and execution times of the ADIFOR-generated derivatives are compared with a handwritten code t hat implements analytically derived expressions for the derivatives. Copyri ght (C) 1999 John Wiley & Sons, Ltd.