侧钻井弯曲段套管抗挤强度研究及应用

The Research and Application of Casing Extrusion Strength at Drilling Bending Section

为了确保侧钻井造斜段套管抗挤强度能够满足钻井作业过程中的安全要求,建立了套管在受到弯曲载荷状态下的力学模型,对其进行理论分析,并利用ANSYS有限元软件模拟验证,研究套管抗挤强度与弯曲曲率、径厚比及轴向载荷之间的关系。研究结果表明:套管的抗挤强度随套管弯曲率的增加而降低,且管壁越薄下降速度越快,当套管弯曲率到达套管极限时,套管抗挤强度几乎相等;在一定的曲率条件下,套管抗挤强度随着径厚比的增加而降低;同一套管规格和尺寸条件下,外径小的抗挤强度随径厚比下降速度趋势远大于外径较大的套管;随着曲率的增加,径厚比与套管抗挤强度关系变的越来越平缓,因此,径厚比对抗挤强度的影响不是固定的。在弯曲条件下,同时考虑弯曲载荷和综合轴向载荷时,随着套管弯曲率的增加,轴向载荷对套管抗挤强度的影响在逐渐减少。研究成果可以为侧钻井造斜段套管的抗挤强度的设计提供参考。

In order to guarantee the casing collapsing strength at the drilling deflection measurement section’s satisfaction of the safety requirements during drilling operation,the casing under bending load condition of mechanical force model was established and the theoretical analysis was carried out.The ANSYS finite element software simulation validation was applied on the casing collapsing strength,bending curvature,diameter-thick ratio and the relationship between the axial load.The results show that the casing compressive strength decreases exponentially with the increase of casing bending rate.The compressive strength of casing pipe with thinner wall decreases obviously compares with the thicker wall.when the bending rate reaches a certain degree,the compressive strength of casing pipe is almost equal.Under certain curvature conditions,the casing extrusion strength decreases with the increase of the diameter to thickness ratio.With the same casing size and specification,the decreasing speed of the compressive strength with small diameter is much greater than that with large diameter.With the increase of curvature,the relationship between the diameter-thickness ratio and the casing extrusion strength becomes more and more gentle and the effect of the diameter-thickness ratio on the extrusion strength is not fixed.With the increase of casing bending rate,the effect of axial load on casing extrusion strength decreases gradually under bending condition.