Pore-Scale Simulation of Microcosmic Flow during Water-Alternating-Gas (WAG) in Porous Media
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摘要: 针对水气交替注入(water-alternating-gas, WAG)过程中, 油气水三相渗流的微观机理认识不足和油气水三相流体在多孔介质中分布规律认识不准确等问题, 基于三维孔隙网络模型, 应用孔隙级模拟方法, 从微观角度模拟了不同润湿性多孔介质中的WAG驱替过程.结果表明: 连通性较好的多孔介质中, 原油主要在前两轮的WAG循环中被驱替出来; 在前两轮WAG驱替之后, 流体饱和度和分布规律达到比较稳定的状态, 但在完全水湿模型中油相仍然在多孔介质中流动.得出的WAG驱替过程中各相流体饱和度的变化规律、各相流体分布规律和驱替类型, 较好地阐述和解释了多孔介质中的微观驱替机理.Abstract: In order to better understand the pore-scale physics of three phase flow during water-alternating-gas (WAG) injection, we simulate the WAG process in different wettability systems based on a 3-D pore-scale network model in this study, and the saturation paths, occupancy statistics and displacement statistics are obtained. The results show that oil is almost displaced during the first 2 WAG cycles; then, saturation and occupancy statistics of fluids reach a steady condition; the existence of double and multiple displacement chains enhances oil recovery. The obtained fluid saturation variation, fluid distribution and displacement type during WAG give good interpretation for the micro displacement mechanism in porous media.
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表 1 不同模型的油水接触角数值
Table 1. Contact angle of pores in the three models
模型方案 油水接触角(θow) 基本模型(Base Case,BC) 0 混合润湿模型A(MWL) 0, 140 混合润湿模型B(MWS) 0, 140 接触角分布模型(DCA) 0~30 MWL:水湿孔隙r≤15×10-6m,cosθow=1;油湿孔隙r≥15×10-6m,cosθow=-0.77.MWS:水湿孔隙r≤15×10-6m,cosθow=-0.77;油湿孔隙r≥15×10-6m,cosθow=1.油水接触角分布模型(DCA):接触角在所有孔隙中随机分布,0.5≤cosθow≤1.目标饱和度定义为每一次驱替后驱替相的饱和度,每次驱替的目标饱和度为1,其他3个模型每次驱替的目标饱和度根据BC模型设定. -
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