Application of Automatic Differentiation for the Simulation of Nonisothermal, Multiphase Flow in Geothermal Reservoirs

Simulation of nonisothermal, multiphase flow through fractured geothermal reservoirs involves the solution of a system of strongly nonlinear algebraic equations. The Newton-Raphson method used to solve such a nonlinear system of equations requires the evaluation of a Jacobian matrix. In this paper we discuss automatic differentiation (AD) as a method for analytically computing the Jacobian matrix of derivatives. Robustness and efficiency of the ADgenerated derivative codes are compared with a conventional derivative computation approach based on first-order finite differences.