泡沫压裂液的两相欧拉颗粒流数值模拟

Two-Phase Fluid Numerical Simulation on Foam Fracturing Fluid with Gas Phase Being Treated as Granular

从两相流的角度出发,将泡沫压裂液的气相处理成气泡相并建立两相欧拉颗粒流模型来研究泡沫压裂液的流变性.研究发现:气泡尺寸随剪切速率增加而减小是泡沫压裂液呈剪切稀化的重要原因,泡沫压裂液的黏度及非牛顿流体性质主要由气泡相黏度产生;气泡间的摩擦和碰撞是泡沫压裂液黏度急剧上升的主要因素,摩擦产生的黏度在高气相体积分数时占主要地位;两相之间基本没有相间滑移速度存在,两相的湍流脉动动能随气相体积分数的增加而增加,管壁附近的湍流脉动动能最大;有效黏度的模拟值与实验结果基本吻合,但模拟值稍微偏大,这可能是因为实际泡沫压裂液中的气泡在剪切场中发生了破碎和变形.但是,该两相流模型不能用于气相体积分数大于65%以上的泡沫压裂液.

The rheology mechanism of foam fracturing fluid was studied by Eulerian-Eulerian two-phase fluid method with the gas phase being treated as ‘granular’. The results show that the decrease in bubble size with rising shear rate was the primary reason of shear thinning behavior of foam fracturing fluid, and the viscosity and non-Newtonian fluid characteristic of foam fracturing fluid were influenced by the bubble phase. Moreover, the increase in viscosity of foam fracturing fluid was mainly caused by the collision and friction between liquid phase and bubbles. The viscosity yielded by friction was dominant at large gas volume. Further, there was almost no slip velocity between liquid phase and bubbles. The turbulent kinetic energy of each phase augmented with increasing volume fraction had the largest value at the wall adjacent region. In addition, the simulation result of effective viscosity agrees with the experiments data. The error between them may be caused by the breaking up and distortion of bubbles in practical fracturing fluid. However, this two-phase fluid model is not suitable for foam fracturing fluid with gas volume fraction higher than 65 %.