Estimation of Three-Phase Relative Permeability Isoperms in Heavy Oil/Water/Carbon Dioxide and Heavy Oil/Water/Methane Systems

摘要

Three-phase relative permeability data is an Achilles' heel in the field performance prediction of the enhanced heavy oil recovery processes with numerical simulation. Minor inaccuracy could lead to erroneous predictions and, in turn, considerable revenue losses. A technique is proposed to utilize two-and three-phase displacement experiments in order to estimate relative permeability isoperms for a fluid system of heavy oil/water/gas. Three-phase flow zone is determined in a ternary diagram with residual oil and irreducible water saturations obtained from two-phase heavy oil/water displacements experiments. A developed fully implicit three-phase simulator mimics three-phase displacement experiments in the form of gas (carbon dioxide and methane) injection into a consolidated Berea core saturated with heavy oil (1174cP at 28°C) and water. Threephase relative permeability data corresponds to a saturation path, drawn across the three-phase flow zone, is tuned to match simulated pressure drop, oil and water production with three-phase displacement experiment. Results have indicated, due to high residual oil saturation, a small three-phase flow zone can exist in presence of heavy oils. Although different curvatures have been obtained with relative permeability isoperms of oil, water, and gas phases; however, repeating experinemts with different gases (methane and carbon dioxide) indicates that relative permeability isoperms does not change siginificantly in presence of different gases. Comparison of the proposed procedure with the unsteady state technique indicates that unsteady state technique fails to provide reliable relative permeability data for numerical simulation purposes since it calculates three-phase relative permeability data at saturations out of the three-phase flow zone. In addition, in the case of water, unsteady state technique gives relative permeability values for a short range of water saturations. Proposed technique takes advantage of practicability of displacement experiments to estimate three-phase relative permeabilities it and, also, eliminates uncertainties with unsteady state method such as inaccurate derivative calculations. Although proposed method indirectly estimates three-phase relative permeabilities; sensitivity analysis shows a good margin of confidence with the relative permeability isoperms.