螺旋布孔射孔对套管强度的影响

射孔是造成套管损坏的重要原因之一,建立了射孔套管的有限元力学模型,采用弹塑性有限元法,分别对螺旋布孔射孔套管采用不同的射孔孔径、射孔密度和射孔相位给套管强度造成的影响进行了模拟和分析.分析了不同孔径、孔密及相位角的射孔套管在外挤压力作用下的孔眼应力集中系数的变化规律.结果表明,射孔后套管的极限承载能力均有不同程度的下降,下降幅度与射孔密度有关,射孔后套管内的应力随射孔孔径、射孔密度和射孔相位的增加而增大,并使套管的抗拉、抗压强度降低.因此,在套管柱设计时应该考虑射孔的影响.最后,通过对几种布孔方案进行对比分析,找出了射孔套管的优选布孔方案.为射孔完井优选设计提供了合理的模型,为射孔段套管柱的合理设计提供了承载能力计算的可靠依据.

Effect of helix distributing perforation on casing strength

One of important cause of casing damage is casing perforation. Finite element mechanical model of perforated casing is established, and effect of perforating on casing strength, especially influence of perforation diameter, perforation density and perforation phase angle on casing strength is studied by using elastic and plastic finite element numerical modeling method. Under outer pressure condition, finite element analysis of stress concentration co-efficient in perforated casing is studied with different perforation diameter, perforation density and phase angle. Results of numerical modeling show that strength of casing reduces with perforation density, and that stress in perforated casing increases with the increase of above - mentioned perforating parameters, resulting in decrease of tensile strength and compression strength. Thereform effect of perforation should be considered in design of casing string. Optimized scheme for holding perforation is identified by comparing different schemes for holding perforation. Analysis result provides reasonable model for optimization design of perforating well completion and reliable foundation of sustainability computation for reasonable design for perforating sections of casing.