Simultaneous estimation of relative permeability and capillary pressure for non-Darcy flow-steady state
An inverse interpretation method has been developed to determine the relative permeability and capillary pressure curves from steady-state core flood experiments with or without the non-Darcy effect included. The Forchheimer equation has been incorporated for multiphase non-Darcy flow and the forward model has been solved numerically by the finite difference method. The simulated annealing method has been applied as the non-linear global optimization technique for history matching. The flow functions were generated by automatic history matching of the saturation and pressure profiles along the core. Different steady state experimental methods have been introduced in the literature to eliminate or minimize the influence of capillary end effects. However, in this study, capillary end effect has been used as an asset to determine the relative permeability and capillary pressure curves. Because the capillary end effect is strongly related to the properties of the multiphase fluid in porous core, it can be best incorporated by using the saturation profiles as the in-situ measurement. Thus, instead of repeating various tests at many different gas/water ratio and for flow rates for covering a full saturation range, experiments for two or three different gas/water ratio, which give different saturation ranges, will be sufficient to capture the characteristic flow functions. The main difficulty in this method is the requirement of accurate saturation profiles by high resolution X-ray computer tomography, specifically at the ends of the core. Relative permeability of gas for non-Darcy flow has a higher curvature than Darcy`s flow. Due to greater pressure dissipation, the gas saturation develops more rapidly under non-Darcy flow conditions. Results indicate that non-Darcy flow is not negligible for estimation of relative permeability and capillary pressure curves, particularly for the gas/brine system.
- OSTI ID:
- 272873
- Report Number(s):
- CONF-960441--
- Country of Publication:
- United States
- Language:
- English
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