钻杆加厚过渡带几何结构对应力集中的影响

RESEARCH ON STRESS CONCENTRATION IN INTERMEDIATE BELT OF THICKENED DRILL PIPE

冯少波 林元华 施太和 骆发前 赵鹏

Feng Shaobo Lin Yuanhua Shi Taihe Luo Faqian Zhao Peng

西南石油学院石油管力学和环境行为重点实验室, 四川 成都 610500 塔里木油田公司, 新疆 库尔勒 841000 上海宝山钢铁股份有限公司, 上海 201900

油气井钻井过程中,钻杆主要失效部位是加厚过渡带处,该处容易形成应力集中,尤其在狗腿井段中的交变载荷作用下,表面易形成疲劳裂纹源,导致刺漏甚至断裂事故的发生。针对这一情况,应用有限元软件建立钻杆加厚过渡带力学模型。该模型公母接头共同建模,可以施加轴向拉力、内外压力、扭矩和弯矩,能很好地模拟狗腿井段的钻杆受力,为改进钻杆加厚过渡带结构设计提供理论依据。力学分析结果表明,最大应力出现在加厚过渡带内锥面消失处,且母接头端的应力比公接头端应力水平高;减小加厚过渡带内孔直径、增加内锥面长度、加大内锥面消失处圆角半径都可以减小钻杆应力集中系数。但在现有加厚过渡带结构的基础上改变加厚过渡带尺寸对减小钻杆应力集中效果并不明显,建议从改变加厚过渡带结构上入手来降低钻杆的应力集中系数。

Fore the stress concentration,the main failure while drilling is intermediate belt,especially in dog-leg section,with the change of load,it is easy to form of fatigue crack,and caused drill pipe damaged or even fault.Used finite-element software simulated the stress of drill pipe,and can direct the design for thicken of drill pipe.Mechanics analysis shows that decrease diameter of inner-bore,increase length of inner-cone area,increase radius of curvature of inner-cone are all can decrease index of stress concentration.But the available structure is not adequate to decrease stress,so it is feasible to decrease the stress concentration index by alter the structure of thickened intermediate belt.

10.3969/j.issn.1000-7393.2006.01.021