基于相场法的非等温气-水两相驱替特征研究
CHARACTERISATION OF NON-ISOTHERMAL GAS-WATER TWO-PHASE DISPLACEMENT BASED ON THE PHASE FIELD METHOD
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摘要: 为了阐明在非等温条件下多孔介质中气-水两相动态驱替特征, 使用一种基于Navier-Stokes方程、Cahn-Hilliard方程耦合下的两相流数值方法, 与表面张力模型、传热模型相结合, 完成了对流体动力学和传热的定量计算, 同时利用表征真实孔隙特征下的非均质模型, 实现了多孔介质内非等温热-流耦合下两相流动过程的精准表征. 通过求解Cahn-Hilliard方程精准模拟相分离的演化特征, 利用Navier-Stokes方程完成对流体速度及压力的相关计算, 结合传热方程获取各个时刻的温度分布; 联合流动耦合和温度耦合的节点, 实现质量、动量及能量方面的全耦合; 算法使用自适应网格法, 使网格点分布始终与物理解耦合, 提高了解的高精度性. 研究表明: 大孔中流体压力变化态势平稳, 孔喉狭窄处流体速度较大且波动剧烈; 注气压力增加, 气体突破时间缩短, 温度的热传导速率加快, 驱替效率在气体突破后呈下降趋势; 注气压力较高会加剧水对气体流动能力的干扰, 当注气压差满足气相可进入细小孔隙, 同时受流动干扰相对较小时, 驱水效果最好.Abstract: This paper employs a two-phase flow numerical method based on the coupling of Navier-Stokes and Cahn-Hilliard equations, coupled with a surface tension model and a heat transfer model, to complete the quantitative calculations of fluid dynamics and heat transfer while also using a non-homogenous approach to clarify the dynamic replacement characteristics of gas-water two-phase flow in porous media under non-isothermal conditions. At the same time, we accurately characterize the two-phase flow process under the non-isothermal heat-fluid coupling in the porous medium by using the non-homogeneous model to characterize the true pore space characteristics. The fluid's velocity and pressure are calculated using the Navier-Stokes equation, and the temperature distribution at each instant is obtained by combining the heat transfer equation and the Cahn-Hilliard equation to accurately simulate the evolutionary characteristics of phase separation; The nodes of the temperature coupling and joint flow coupling are used to realize the full coupling in terms of mass, momentum, and energy; The algorithms employ an adaptive mesh method, so that the distribution of mesh points is the grid point distribution is always associated with the physical solution thanks to the algorithm's adaptive grid technique, which increases the solution's high accuracy. The study reveals that: the fluid pressure change trend in the large hole is smooth, while the fluid velocity in the narrow hole throat is larger and fluctuates sharply; the gas injection pressure increases, the time it takes for the gas to breakthrough is shortened, the temperature's heat conduction rate is accelerated, and the repellent efficiency decreases after the gas breakthrough; the higher the gas injection pressure, the more the water interferes with the gas flow capacity; The best water-repellent effect is obtained when the injection pressure difference allows the gas phase to penetrate the fine pore space while also being relatively less disturbed by the flow, higher injection pressures make the interference of water with the gas flow capacity worse.