基于Comsol Multiphysics的十字状裂隙中流体运动特征分析

地震波在岩石中传播时,在微观尺度下的十字状裂隙中,压力梯度会引起垂直于波传播方向的扁平裂隙中流体流动到临近的平行于波传播方向的裂隙中,这个流动过程具有特征尺度小和持续时间非常短的特征,被称之为微观喷射流。针对喷射流机制提出一种新的数值方法,认为多孔介质的固液两相分别遵循不同的物理方程,并为了深入了解在地震波的作用下裂隙中流体的流动特征及压力分布情况,应用COMSOL Multiphysics多物理场仿真软件对平面波入射导致的喷射流的发生过程进行数值模拟,分析不同时刻水平及垂直裂隙轴向上流体流动速度和压力状态。结果表明:在水平裂隙中,越靠近中心位置,流体的流速越大,压力越小,在中心位置处达到其最大值和最小值;在垂直裂隙中,越靠近中心位置,流速也是逐渐增大,在中心位置处流体速度达到最大值,由于压缩波的传播方向与垂直裂隙的轴向一直,在波传播方向上使流体强制运动,其次水平裂隙中流体在壁面压力作用下流入到垂直裂隙中,造成垂直裂隙流体压力不规则变化的现象。

Analysis on Fluid Flow Properties In interconnected Fractures Base On Comsol Multiphysics

The pressure gradient causes fluid in the horizontal fractures perpendicular to the wave propagation direction to flow into the adjacent vertical fractures when seismic waves propagating in interconnected fractures medium at microscopic scales, the flow process is characterized by a small scale and a very short duration, known as the Squirt-Flow type. We proposed a new hydromechanical numerical approach to describe the process of Squirt-Flow type,according to this method, solids and liquids follow different equations, respectively.In order to recognize the flow characteristics,in other words, we should know the velocities and pressures distribution of fluids in fractures under the influence of seismic waves,therefore,we use Comsol Multiphysics to simulate the process of Squirt-Flow caused by plane wave in this paper, and analyze the fluid flow velocities and pressures in the axial direction of horizontal and vertical cracks at different moments.The results show that in the horizontal fracture, the closer to the center position, the greater the flow velocity of the fluid, in contrast,the smaller the pressure, the extreme values will appear at the center position; in the vertical fracture, the flow rate is gradually increased as it approaches the center position. The fluid velocity reaches a maximum at the center position. Since the propagation direction of the compression wave is always perpendicular to the axial direction of the vertical fracture, the fluid is forced to move in the wave propagation direction, and the fluid in the horizontal fracture flows into the vertical fracture under the pressure,causing irregular pressure change in the vertical fracture fluid.