Simplified Phase-Equilibrium Calculations in Integrated Reservoir and Surface-Pipeline-Network Models

Summary Effective procedures for the integrated reservoir and surface facility compositional simulations have been developed. Multiphase compositional fluid flow equations in reservoirs, well tubing strings, and surface pipeline network systems are solved simultaneously. The procedures have been implemented in the commercial compositional reservoir and surface facility simulator: VIP. The equation of state is applied for the phase-equilibrium calculations. A new equation-of-state (EOS) interpolation procedure has been developed (as an option) for simplified phase-equilibrium calculations in integrated compositional simulations. The EOS interpolation procedure can be effectively applied for phase-equilibrium calculations in reservoirs, well tubing strings, pipelines, and/or separators. Saturation pressure, recovery factors of hydrocarbon components, and compressibility factors are determined as tabular functions of pressure, temperature, and fluid compositions. The equation of state is applied for the automatic generation of these functions in an initialization step of a reservoir simulation. The effectiveness and accuracy of the new simplified phase-equilibrium procedure have been confirmed in many full-field compositional models and pattern models. The new option significantly reduces the central processing unit time required for the simulations and it matches results of fully compositional simulations in the tested models. The developed procedures for the integrated reservoir and facility compositional simulations have been applied in many reservoir studies. Their applications in the integrated reservoir and surface facility model of the giant Prudhoe Bay oil field have been demonstrated.