Abstract
During the exploitation of bottom water oil reservoir, bottom water coning influences the breakthrough of bottom water significantly. Because water cut rises quickly after the breakthrough of bottom water, measures should be taken before the breakthrough to postpone production period without water, thus improving oil recovery. So accurate prediction of water coning profile and breakthrough time is very essential. Through mathematical derivation, this paper proposed a prediction method of bottom water coning profile and bottom water breakthrough time in bottom water reservoir without barrier. Based on theory of fluids flow in porous media, this paper assumes that the flow models are plane radial flow in opened intervals and spherical radial flow in unopened intervals. Further, factors of fluid viscosity, irreducible water saturation, residual oil saturation, and oil-water contact (OWC) movement are also taken into account. Compared with other prediction equations, this method achieves more precise bottom water breakthrough time, and the relative deviation is only 1.14 percent.
Highlights
Sandstone reservoir with bottom water is a common kind of oil reservoir
This paper proposed a prediction method of bottom water coning profile and bottom water breakthrough time in bottom water reservoir without barrier
Based on theory of fluids flow in porous media, this paper assumes that the flow models are plane radial flow in opened intervals and spherical radial flow in unopened intervals
Summary
Sandstone reservoir with bottom water is a common kind of oil reservoir. During the recovery of this kind of reservoir, bottom water provides energy to drive oil. It is essential to obtain bottom water coning profile and control the breakthrough time. Zhu [1] developed his prediction method using a conic bottom water body with straight generatrix; the generatrix should be curved. Tang [2] concluded the prediction equations for breakthrough time and geometrical function of water cone height, postulating that there are plane radial flow and spherical flow but disregarding the impact of residual oil saturation, irreducible water saturation, and oil/water viscosity. Providing curved generatrix of the bottom water cone, Li [3] and Xiong et al [4] presented their prediction equations of breakthrough time, respectively. Neither of them took account of the OWC movement and nor do they consider the bottom water coning profile
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