蜡沉积凝析气-液-固变相态复杂渗流数学模型

Porous flow mathematical model of multiphase complex flow with phase change and wax deposition

含蜡凝析气藏开采过程中伴有凝析液、蜡析出呈气-液-固变相态多相复杂流动.在渗流机理的实验研究基础上,对气-液-固复杂渗流的数学模型进行描述,以期揭示伴有蜡沉积的凝析气-液-固变相态复杂渗流规律.根据相的变化受析蜡线、露点线的相态变化规律控制,分析相变特性会导致储层内油气饱和度的变化,揭示蜡沉积在多孔介质表面引起孔隙性质改变和气、液、固在储集层中的微观空间分布会影响凝析气的流动特征.在蜡沉积变相态渗流实验和渗流数学模型的研究基础上,引入蜡沉积数学模型、考虑毛管力和表面张力的相对渗透率模型等,建立了相应的多孔介质中气-液-固变相态多相流-固耦合渗流数学模型.数值模拟结果表明,蜡沉积可使部分区域孔隙减少,流动阻力增大.不考虑蜡沉积会对产量预测明显偏大,蜡沉积可使产量下降.该模型较好地反映了凝析气-液-固变相态复杂渗流的物理实质.

Gas-liquid-solid complex flow was complicated in the production of a condensate gas reservoir with wax deposition. Under experiment research results on the porous flow mechanism, the porous flow model was described to reveal the complex flow law. According to the phase change law for wax deposition and dew point line curves, and the change of the saturation of condensate gas with phase properties, gas-liquid-solid was transformed with phase change, which would result in the change of distribution of fluid pressure and influence or alter the characteristic and the process of condensate gas percolation flow. Under experimental results of wax deposition and phase change, the mechanical characteristics of fluids flowing through porous media and the relevant physicochemical problem were all summed up as solving the gas-liquid-solid coupling mathematical model. After considering the phase change action between condensate gas and condensate liquid, wax deposition interlarded with interracial drag force and capillary pressure engendered in the process of phase change. Numerical simulation results proved that the flow resistance increased and the production output decreased owing to wax deposition. The model could reveal the physical essence of porous flow.