考虑裂缝诱导应力场的水平井裸眼完整性分析

Integrity Analysis of Open-hole Horizontal Well under Fracture-induced Stress Field

井筒完整性不仅关系到油气井安全生产,还影响着水平井水力压裂增产作业效果。水平井裸眼封隔器分段压裂过程中,在高内压和裂缝诱导应力的作用下,裸眼井筒可能发生破坏,造成封割器隔离层段失效和压裂液窜流,影响水平井分段压裂效果。为此,建立了考虑水力裂缝诱导应力作用下的水平井井筒剪切破坏宽度、拉伸裂缝深度的计算模型。利用所建模型分析了裂缝长度、裂缝距离对水平井井筒破坏程度的影响规律。分析结果表明,水平井分段压裂过程中,正压裂段容易形成纵向拉伸裂缝,且在靠近裸眼封隔器处裂缝深度较大;已压裂段容易发生剪切破坏,且在靠近裸眼封隔器处剪切破坏程度最大。随着水力裂缝增长,剪切破坏程度和拉伸裂缝深度都逐渐增加。所建模型和分析结果可为水平井裸眼分段压裂设计提供理论指导,以提高裸眼封隔器的层段隔离性和分段压裂效果。

The wellbore integrity is not only related to the safe production of oil and gas,but also affects the performance of horizontal after hydraulic fracturing. The high wellbore pressure and fracturing induced stress may cause wellbore failure during the open-hole packer staged fracturing,and result in an invalid isolation and water channeling between adjacent stages,affecting the effect of staged fracturing in horizontal well. The calculation models of shear fracture width and tensile crack depth of horizontal well are established considering the stress induced by hydraulic fracture. The influences of hydraulic fracture length and the distance from hydraulic fracture on the failure of horizontal wellbore are analyzed by using these models. The results show that the fracturing section is easy to form longitudinally tensile cracks and the depth of cracks is great near the packer. The fractured section is prone to shear failure and the degree of shear failure will reach the maximum near the packer. With the increase of hydraulic fractures,both the degree of shear failure and the depth of tensile cracks increase. The model and analysis results can provide a theoretical guidance for the design of multistage fracturing in horizontal well in order to improve the packer isolation and fracturing performance.