【摘要】 通过ABAQUS扩展有限元法(XFEM)建立基于地层流-固耦合方程的储层模型,以最大主应力准则、最大能量释放率准则为损伤机制,模拟分析单径向井、垂向多径向井、水平多径向井情况下的裂缝形态,并通过大型真三维物理模拟试验在一定程度上验证数值模拟结果的正确性。在多径向井压裂裂缝形态研究的基础上,对径向钻孔的布孔方案进行优化。结果表明:压裂时沿径向井分布的诱导应力场是压裂裂缝沿径向井定向扩展的根本原因,其有效引导距离可达40 m;垂向多径向井可有效强化压裂裂缝的定向扩展效果,且具备降低起裂压力的能力;水平多径向井在远井带形成沿各径向井独立扩展的主裂缝,近井带形成沟通相邻两径向井的次级裂缝,两者协同可有效提高泄油面积、降低近井带油流阻力。更多还原

【Abstract】 The technology of radial well fracturing has been applied in various oil fields and proved to be effective,and the crack morphology needs an intensive investigation.In this study,a formation fracturing model was built using the extended finite element method(XFEM) based on fluid-solid coupling equations,and the maximum principal stress criterion and maximum energy release rate criterion were both used as the damage mechanisms of rock materials.The simulation results of three types of well models(i.e.the single radial well,vertical multiple radial wells and horizontal multiple radial wells) were analyzed,and verified by 3D physical experiments in the laboratory.It has concluded that an induced stress field along the radial well during fracturing is the main reason for the propagation major fractures.The distance of orientated fracture can extend to 40 meters.The effect of crack orientated propagation can be improved under vertical multi radial wells fracturing.An interference stress field can be induced at near wellbore under horizontal multi radial well fracturing,and secondary cracks connected with nearby radial wells can be generated in the interference stress field.Also the major fracture propagating along the radial well can be still generated in the zone far away from the wellbore.The combination of the two kinds of fractures can effectively improve the oil drainage area and also can reduce the oil flow resistance near the wellbore.At last the perforation scheme of radial wells is optimized.更多还原