普光气田气体钻井钻具失效原因分析及预防措施

气体钻井技术虽然大幅度提高了普光气田上部陆相地层钻井速度，但屡次出现钻具失效事故，不仅影响钻井速度，而且威胁井下安全。分析了钻具失效规律，并通过宏观分析判断钻杆为疲劳和腐蚀疲劳断裂，钻铤为疲劳断裂。从气体钻井自身因素、钻柱运动（包括公转和纵向共振）、钻具腐蚀、钻井方式、钻铤弯曲强度比不足等方面分析钻具失效原因，提出使用空气锤钻井技术、加强钻具探伤、优化钻具组合和钻井参数、缓解钻具腐蚀、加强钻柱振动监测等预防措施。指出应加强气体钻井钻具失效的微观机理、钻柱运动与动力学、岩屑对钻具的冲蚀磨损、钻具腐蚀、消除钻柱公转等方面的研究以预防钻具失效。

Cause analysis of drill pipe fracture in air drilling

Several drilling tool fracture accidents took place during air drilling in one oil field. In order to know the cause of the accidents, an investigation is taken and the failure analysis is carried out for one broken drill pipe. The fracture analysis includes the macro-fractography and micro-fractography, the experimental analysis of the chemical components, the mechanical properties, and the metallography of drill pipes, and the stress conditions analysis of drill pipes in air drilling. It is considered that fatigue crack is early produced on drill pipes, because the vibration load of drilling tools in air drilling is more severe than that in mud drilling. Fatigue cracks easily occur under alternating vibration. Because the current wellhead detecting instruments can not be used to reflect the change of pump pressure produced after drill pipe piercement timely and accurately, effective measures can not be taken in time to prevent the expansion of fatigue cracks. As a result, drill pipe fracture accidents occur.