Abstract:

The determination of relative permeability curve for complex multiphase system while flowing through porous media is very important to understand the percolation mechanism，a basical and necessary information is provided for numerical modeling and prediction of production performance in oil &gas reservoirs.In this paper，the unsteady-state displacement method is employed to model the real scenarios of complex multiphase flowing in sandstones，and the pressure and flowrate data for each phase during the displacement process are used to estimate the relative permeability characteristic parameters through nonlinear system parameter identification technology.The self-adaptive step of the relative permeability characteristic parameters during iteration is based on the LMF method and optimal control theory.It is shown that the relative permeabilities obtained by parameter estimation are in good accordance with experimental results，and it provides a fast and reliable method to attain relative permeabilities with full-range of saturation and avoidance the limitations of conventional method.

Key words: parameter identification, optimal control, relative permeability, oil &, gas reservoir, nonlinear