Measurement and simulation of one-dimensional transient three phase flow for monotonic liquid drainage
Simultaneous movement of oil, water, and air in a sandy porous medium was investigated experimentally under transient flow conditions and results were compared to numerical simulations employing a finite element multiphase flow code. The liquid hydrocarbon was Soltrol 170, a low-density branched alkane mixture. Liquid saturations were measured using a collinear dual-energy gamma radiation apparatus and liquid pressures were measured using hydrophilic (untreated) and hydrophobic (treated) ceramic tensiometers connected to pressure transducers. The experimental regime was selected to impose monotonically draining water and total liquid saturation paths to avoid hysteretic effects. Measured saturations and pressures are compared to values obtained from numerical simulations of the experiment using a finite element solution of the governing multiphase flow equations assuming negligible gas pressure gradients. Functional relationships between permeabilitiesk, saturations S, and capillary pressures P employed in the numerical model were estimated by two calibration methods which require different degrees of experimental effort. Measured transient water saturation versus oil-water capillary head data agreed well with predictions from static air-water S-P relations and interfacial tension data. Transient total liquid saturation versus air-oil capillary head data deviated more severely from the scaled air-water S-P data, possibly reflecting noncompliance with the assumption of negligible gas pressure gradients. Reasonably good agreement was observed between measured and numerically simulated water and oil saturations and pressures in space and time. Sensitivity of the numerical results to calibration method was not great.