Abstract FISHES, otherwise known as Fully Implicit Hydrothermal Event Simulator, simulates two-phase fluid flow in a porous matrix saturated with NaCl-H₂0. We discuss the addition of MUMPS, Multifrontal Massively Parallel sparse direct Solver, to FISHES. MUMPS is a tool that offers solutions to large linear systems that present complex arithmetic to achieve parallel factorization. We address the use of MPI (Message Passing Interface) and its implmentation with MUMPS to offer a parallel computing...