S135钻杆内螺纹接头胀扣失效分析

本文对某油井发生的Ф127mmS135钻杆内螺纹接头胀扣失效事故进行了调研，并对其胀扣失效原因进行分析。结果表明，钻杆接头的材质符合行业标准要求；钻杆内螺纹接头胀扣失效的原因是外螺纹接头密封台肩面倒角直径过小，井下钻柱扭矩过大。内螺纹接头密封台肩面承受的接触压力超过材料屈服强度，导致内螺纹接头密封台肩面下陷，外螺纹接头密封台肩面进入内螺纹接头镗孔段，致使内螺纹接头发生胀扣失效。

Failure Analysis of S135 Box Swelling

A Ф127mm S135 box swelling accident was investigated. The failure analysis indicated that the box＇s material properties were in accordance with related standards; the bevel diameter of pin＇s make-up shoulder was too little and working torque of drilling pipes was too high, which leaded to that the compressive stress was in excess of box＇s yield strength and its make-up shoulder sagged; pin＇s makeup shoulder pressed into box＇s primitive hole; and at last the box swelled under the effect of working torque.