基于FEMM-Fracflow研究缝洞型油藏中裂缝扩展问题

Investigation on fracture propagation in fractured-cavity reservoirs based on FEMM-fracflow modelling

在缝洞型油藏中,水力裂缝的偏转路径对石油的开采量有重要的影响。Hybrid Finite-element and Mesh-free Method-Fracflow(FEMM-Fracflow)数值模拟平台,通过数值实验,文章分析了缝洞型油藏中自然溶洞、水平地应力以及注水流速三种因素对水力裂缝偏转路径的影响。结果表明,在存在溶洞时,裂缝明显向溶洞方向偏转;在改变水平围压时,不施加水平围压条件下,裂缝明显偏向溶洞方向扩展,并且最终与溶洞连通;而在施加50 MPa水平围压时,水力裂缝偏向溶洞的趋势明显减弱;在改变流速时,当流速为0.05 kg/s,裂缝明显向溶洞方向偏转,而当流速为0.2 kg/s,裂缝向溶洞方向偏转的趋势则减弱。

The propagation path of hydraulic fractures is critical to oil recovery in fractured-cavity reservoirs.Based on Hybrid Finite-element and Mesh-free Method-Fracflow(FEMM-Fracflow)numerical simulation platform,this paper explores the influence of natural caves,in-situ stress and injection velocity on the propagation path of hydraulic fractures in reservoirs.The simulation results show that when there are caves,the fracture propagates toward the cave.When the horizontal confining pressure is changed,the fracture propagates toward the cave obviously without applying horizontal confining pressure,and eventually connects with the cave;when the horizontal confining pressure of 50 MPa is applied,the trend of hydraulic fracture propagating toward the cave is obviously weakened;when injection velocity is changed,the fracture propagates toward the cave with the injection velocity of 0.05 kg/s,while the tendency of fracture propagating toward the cave is weakened with the injection velocity of 0.2 kg/s.