Deriving the Oil-Water Seepage Pressure Distribution from Two-Phase Oil-Water Flow Stress Gradient
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The characteristics of oil-water two-phase flow in low-permeability reservoirs have been insufficiently studied. In the present article, we estimate the oil-water seepage parameters using a flow stress gradient model with a nonuniform radial distribution of the water saturation coefficient in a low-permeability reservoir. We apply the oil-water relative permeability curves and the Buckley-Leverett equation to determine the oil-water mobility ratio and the functional relationship between the two-phase flow stress gradient, the radial distribution, and the oil saturation. In this way, we construct an oil-water radial flow model based on the oil-water two-phase flow stress to derive the pressure distribution equation. Calculation results show that there is a linear relationship between the oil-water two-phase flow stress gradient and the oil saturation and a quadratic relationship between the oil-water two-phase mobility ratio and the oil saturation. The strata/ pressure distribution for low-permeability reservoirs is highly sensitive to the oil-water two-phase flow stress gradient, and the effect is more noticeable near the wellbore.
Keywordslow-permeability oil-water reservoir two-phase flow stress gradient radial flow pressure distribution model
The authors wish to express their appreciation to the National Innovation and Entrepreneurship Training Program for College Students (Grant 201510710064), The Yan'an Municipal Bureau of Science and Technology Project: Research and Demonstration Extension of Key Technologies for Improving Oil Recovery ( Project No. 2017WZZ - 01 - 02 ), Project of Yan'an University for Support of Young Scientists: Optimization of Air-Foam Flooding Parameters for Low-Permeability and High Water Content Reservoirs (Grant YDQ2017 - 21).
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