Simulators / Computer Resources

Reservoir Simulators


GPAS is a three-dimensional multicomponent multiphase fully implicit finite difference and finite volume compositional simulator with the parallel processing capability. It includes both a cubic equation of state model for the hydrocarbon phase behavior and Hand's rule for the surfactant/oil/brine phase behavior. The Peng-Robinson EOS is used for hydrocarbon phase behavior calculations. The aqueous species in the chemical model include surfactant, polymer, and salt. The physical property models include surfactant/oil/brine phase behavior, interfacial tension, viscosity, adsorption, and relative permeability as a function of trapping number.


UTCHEM is a multicomponent, multiphase, three-dimensional chemical compositional reservoir simulation model. The flow and transport equations are as follows:

  • A mass conservation equation for each chemical species
  • An overall mass conservation equation that yields a pressure equation when combined with a generalized Darcy's law
  • An energy conservation equation


UTCOMP is an isothermal three-dimensional, EOS compositional reservoir simulator capable of modeling up to four-phase flow, namely, an aqueous phase, an oleic phase, a gaseous phase, and a second nonaqueous liquid phase. A finite-difference method that is third-order correct in space is used to reduce numerical dispersion and grid orientation effects when solving the material balance equations. We have dramatically improved the stability of the third-order method by adding a flux limiter that makes the scheme total variation diminish.

Simulator Comparison

GPAS (FIM, parallel) UTCHEM (IMPEC Chemical with Temperature Equation, Dual Porosity) UTCOMP (IMPEC EOS)
  • Unstructured Grid
  • Dual porosity
  • Discrete fracture
  • EOS gas
  • EOS surfactant
  • Polymer
  • Tracer
  • Geomechanics
  • Thermal
  • Tracer
  • Polymer (P)
  • Surfactant/polumer (SP)
  • Alkaline/surfactant/polymer (ASP)
  • Microbial EOR
  • Polymer-gel
  • Foam
  • Wettability alteration
  • Limited immiscible gas capability
  • Unstructured grid
  • Miscible gas flood
  • Asphaltene percipitation
  • Three phase flash
  • Tracer
  • Polymer
  • Dilute surfactant
  • Foam

Computer Resources

A specialized laboratory for parallel computing has been established to support parallel computational research. Through hardware grants from Dell Computers, the Reservoir Simulation JIP acquired a cluster of PCs. The cluster consists of eight nodes of dual processors at 3.02 GHz speed. This system has two TB of storage. The cluster runs a Linux operating system with GNU C/C++, Portland Group, and Intel Fortran compiler, MPICH version 1.2.4, which is a portable implementation of the Message Passing Interface (MPI) from Argonne National Laboratory for parallel; communication. We have access to the computational facilities at Texas Advanced Computing Center (TACC) of the University of Texas at Austin which has several clusters with total number of processors more than five thousands. Most of our code developments are performed on the in-house cluster, while larger production parallel runs as well as our benchmarking are done on the TACC's clusters.

[Alborz Cluster]