Simplified phase-equilibrium calculations in integrated reservoir and surface-pipeline-network models

Effective procedures for the integrated reservoir and surface facility comp ositional simulations have been developed. Multiphase compositional fluid f low equations in reservoirs, well tubing strings, and surface pipeline netw ork 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 comp ositional simulations. The EOS interpolation procedure can be effectively a pplied for phase-equilibrium calculations in reservoirs, well tubing string s, pipelines, and/or separators. Saturation pressure, recovery factors of h ydrocarbon components, and compressibility factors are determined as tabula r functions of pressure, temperature, and fluid compositions. The equation of state is applied for the automatic generation of these functions in an i nitialization step of a reservoir simulation. The effectiveness and accuracy of the new simplified phase-equilibrium proc edure have been confirmed in many full-field compositional models and patte rn models. The new option significantly reduces the central processing unit time required for the simulations and it matches results of fully composit ional simulations in the tested models. The developed procedures for the integrated reservoir and facility composit ional simulations have been applied in many reservoir studies. Their applic ations in the integrated reservoir and surface facility model of the giant Prudhoe Bay oil field have been demonstrated.