射孔对套管抗挤强度的影响分析与试验

INFLUENCE OF PERFORATING ON CASING COLLAPSING STRENGTH AND ITS TEST

由于射孔孔眼改变了套管结构,当套管受外力后,孔眼周围出现应力集中而使套管的强度降低,套管发生损坏。射孔对套管的影响非常大,为明确射孔参数对套管抗挤强度的影响,利用ANSYS有限元软件建立了三维射孔套管有限元力学模型,并分别建立了不同射孔参数的有限元模型进行有限元分析。研究结果表明,孔眼附近的应力集中明显降低了射孔套管的抗挤强度,并且射孔套管的孔眼应力沿着布孔螺旋线发散,因此套管损坏最易沿螺旋线发展。基于有限元计算结果进一步进行了射孔套管的正交数值试验,明确了射孔参数中相位角对套管强度的影响最大,其次是孔密和孔径。通过回归拟合,结合正交数值试验,建立了射孔套管抗挤强度与射孔参数的关系,为套管综合强度校核提供了理论依据。

Due to the perforations of the casing,structure surrounding the perforations was changed.When the casing met external strength,stress concentration appeared and the casing intensity reduced,and then casing was damaged.The perforated casing was more vulnerable than common casing under external pressure.A 3D finite element model for analyzing the perforated casing was established by ANSYS in order to clear the effect of perforation parameters on the casing collapsing strength.The results showed that the stress concentrated near the performed hole,and the existence of plastic zone on the casing had an obvious effect on the casing collapsing strength especially along perforation distribution spiral line dissemination,so the casing damage was easiest along the spiral line direction.Based on the results,orthogonal numerical test of perforated casing was done,and the results showed that the phase angle was the biggest influential factor on casing collapsing strength,followed by pore density and pore size.By regression and the orthogonal numerical experiments,the relationship between perforated casing strength and the perforation parameters was obtained,which provided a theoretical basis for the casing strength check.