油藏渗流过程中孔隙弹性模型的分析与修正

Analysis and modification of Biot poro-elastic theory for application in flow modeling of oil reservoirs

将油藏宏观渗流场与弹性波场耦合,改进孔隙弹性模型控制方程,揭示低频波动采油技术的动力学作用原理。基于低频波动采油试验机制、Biot理论模型,通过区分低渗开发储层波动采油应用时的流体渗流状态、弹性波传播方向与经典孔隙介质弹性波传播理论模型的差异,并考虑持续变化的压力对耦合物性参数的影响,建立饱和单相渗流流体孔隙介质弹性波传播理论模型,对孔隙介质弹性波传播理论模型的流体耦合运动方程、状态方程(包括骨架孔隙度和流体黏度变化)、边界初始条件进行修正,给出修正模型的计算流程,并利用算例分析验证修正模型的适用性。结果表明,低渗储层低频波作用关于孔渗的敏感性变化规律与常规试验认识一致,低频波动采油效果在低孔、低渗储层中具有较好的适用性,增渗、增压效果明显,说明修正模型揭示低频波动采油机制具有有效性。

A poro-elastic model can be derived for flow modeling in porous media of oil reser oirs, in which the Darcy flow in porous media and the elastic wave theor^^ are considered in the process of oil production assisted by a low frequency vibration technique. A general poro-elastic model for fluid flow and wave propagation in porous media saturated with single-phase fluid was established in combining different mechanisms and considering various factors,including the oil extraction mechanism via low frequency vibration technology and the Biot poro-elastic model. In the new model the coupling flow equation, the state e-quation of porosity and oil viscosity under low-frequency vibration, and specifi conditions were improved. The solution of the new poro-elastic model was described and the use of the model was verified in a case study. The simulation results show that an increase of pressure in the middle of the rock and the flow rate at the inlet induced by vibration can be identified,which is in line with the observation in laboratory experiments. The low frequency vibration oil extraction technology can improve oil recovery in low porosity and permeability reservoirs. The modified model can lay foundation for the establishment of a general poro-elastic model for multi-phase flows.