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油井出砂机制的研究是提高油藏产能和石油开采成本减小的关键课题,而常规的宏观力学理论和方法不能全面反映油藏开采过程中油井出砂的发生和发展。鉴于砂岩储层的物理性质和射孔试验特征,从岩土力学的角度建立基于柱坐标系的三维颗粒流数值模型,与理论分析成果进行比较,以说明该细观数值模型可行性,有效地模拟出砂过程中的渗流及流-固耦合效应。在该基础上,综合考虑流体压力梯度力和拖曳力,基于PFC3D模型模拟流体不同运动时的砂岩性态。数值分析得到的模型宏观应力图形说明流体运动对砂岩力学特性的影响不可忽略,且在相同条件下,流量越大,砂岩的塑性区越大,形成砂岩破坏出砂的几率也越大。同时,不同工况的砂岩黏结分布和颗粒转动图形表明,相同条件下流量越大,颗粒间平行黏结破坏越多,颗粒转动越大,失去黏结约束的颗粒也越多,出砂量就越大,可见两种细观特征图形与宏观应力图形变化规律一致,该模型可用于油井出砂机制的研究,可为出砂量预测及出砂控制提供新的研究思路。
The research on sand production mechanism of oil well is the key issue to improve the reservoir productivity and reduce the cost of oil exploration. However, the conventional macroscopic mechanics theory and method can not fully reflect the occurrence and development of oil well sand production during the process of oil recovery. In view of the physical properties of sandstone reservoirs and the characteristics of perforation test, a three-dimensional particle flow numerical model based on cylindrical coordinate system is established from the perspective of geomechanics and compared with theoretical analysis results to illustrate the feasibility of the numerical model, effectively Simulation of seepage and flow-solid coupling effects in sand production. On this basis, considering the fluid pressure gradient force and the drag force, the sandstone behavior under different motions of the fluid is simulated based on the PFC3D model. The macroscopic stress diagram of the model obtained by numerical analysis shows that the influence of fluid motion on the mechanical properties of the sandstone can not be neglected. Under the same conditions, the greater the flow rate, the larger the plastic zone of the sandstone, and the greater the probability of sanding the sands. At the same time, the sandstone cohesion distribution and the particle rotation pattern under different conditions show that the greater the flow rate under the same conditions, the more the parallel particles are broken and the more the particles rotate, the more particles lose the binding constraint and the larger the sand production It can be seen that the patterns of the two kinds of mesoscopic features are consistent with the changes of macroscopic stress patterns. This model can be used to study the sand production mechanism in oil wells and provide a new research idea for sand production prediction and sand production control.