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本文采用力学有限元方法分析油层套管射孔后套管的剩余强度。为提高数值计算精度,以适应射孔套管孔边存在的高倍应力集中问题,构造了新型高精度三角单元,并论述了射孔套管应力场分布的数值计算方法;文中还根据套管上相邻孔间区域强度相对较弱时的破坏模式概念,建立起以强度理论为基础的射孔套管强度折减系数的计算方法。运用上述理论和方法,以N80钢级?139.7mm套管为算例,阐述了在单一载荷作用下射孔孔径、孔距及布孔螺旋角等多种因素对射孔套管强度的影响。文内首次研究了不同形式的组合载荷和不同组合载荷比对射孔管强度的特殊影响,给出了在常规射孔密度下不同组合载荷形式和不同组合载荷比的强度折减系数值与布孔螺旋角关系曲线族,指出选择布孔方式与组合载荷形式以及组合载荷比值有密切关系。最后本文还讨论了不同载荷工况下射孔套管优化布孔方案。
In this paper, finite element method is used to analyze the residual strength of casing after perforation of casing. In order to improve the accuracy of numerical calculation, a new type of high-precision triangular element was constructed to adapt to the problem of high magnification stress concentration at the perforation edge of the perforated casing. The numerical calculation method of the stress field distribution of perforation casing was discussed. The concept of failure mode when the strength of adjacent holes is relatively weak is established and the calculation method of the strength reduction coefficient of perforation casing based on the strength theory is established. With the above theory and method, taking N80 steel grade 139.7mm casing as an example, the effects of perforation aperture, hole pitch and hole helix angle on the strength of perforation casing are illustrated. In this paper, the special effects of different types of combined loads and different combinations of load ratios on the perforating tube strength are studied for the first time. The relationship between the strength reduction coefficient values of different combinations of loading forms and different combinations of loading ratios and cloths Hole helix angle relationship curve family, pointed out that the choice of the hole mode and the combination of load forms and combination load ratio are closely related. Finally, this paper also discusses the perforating casing perforated optimization program under different load conditions.