超高强度抽油杆腐蚀疲劳损伤机理研究与耐久性设计

Corrosion fatigue failure of sucker rod has become increasingly common in the later period of onshore oil fields and turned into an important factor restricting the development of oil fields. So the in-depth study of corrosion fatigue damage mechanism is very urgent..In this research, based on the theoretical framework of corrosion electrochemical and damage mechanics, the corrosion-fatigue coupling mechanics of ultra-high strength sucker rod is studied. The contents in detail are shown as follows: The corrosion fatigue tests are designed to analyze the corrosion fatigue characteristics of ultra-high strength sucker rod in the well liquid with a single or variety of corrosive media. Combined with surface treatment layer dissection techniques, corrosion fatigue damage coupling mechanisms are revealed. On this basis, the evolution law of corrosion fatigue damage is deduced and the corrosion fatigue life prediction model is established. The surface treatment technology is introduced to assist the durability mechanism analysis under corrosion fatigue condition and then refined into an environment-friendly durability design. This research is of great significance in theoretical basis and technical support for parameters optimization and accident evaluation of oil production.

随着陆上油田进入开发后期，抽油杆柱的腐蚀疲劳断裂现象日益突出，成为制约油田开发的重要因素，因此深化抽油杆柱的腐蚀疲劳损伤机理研究非常迫切。本课题基于腐蚀电化学、损伤力学理论，开展了超高强度抽油杆材料的腐蚀、疲劳耦合机理研究。具体内容包括：设计超高强度抽油杆腐蚀疲劳实验，分析材料在单一及多种腐蚀性介质共存井液中的腐蚀疲劳特性；利用表面处理层解剖技术，探索材料在腐蚀介质、交变载荷耦合作用下的损伤及演化机制，建立腐蚀疲劳损伤演化律，形成腐蚀疲劳寿命预测模型；结合表面处理技术，进行超高强度抽油杆材料的腐蚀疲劳耐久性机理研究，开发一套环境友好的耐久性设计方案，为有杆采油方案优化及事故预测评价等提供理论基础及技术支持。

超高强度抽油杆在腐蚀性井液中的腐蚀疲劳失效及应力、腐蚀耦合损伤机制是当前油田开发领域中亟待解决的重要基础性课题。本研究从热力学、腐蚀电化学、损伤力学入手，开展了超高强度抽油杆材料FG20、30CrMoA的腐蚀电化学、腐蚀疲劳实验，获得了材料在腐蚀性井液中的电化学特性和腐蚀机理；建立了腐蚀疲劳的裂纹成核以及裂纹扩展过程的热力学体系，分析了腐蚀疲劳裂纹成核机制和腐蚀疲劳裂纹成核寿命预测模型。根据SEM、EPMA分析腐蚀疲劳损伤机理，并利用连续损伤力学提出腐蚀疲劳损伤模型，形成一种基于损伤演化律的腐蚀疲劳寿命预测工程方法。开展了FG20、30CrMo材料的表面喷丸等耐久性技术研究，实验验证表面喷丸提高腐蚀疲劳裂纹成核寿命，同时对腐蚀疲劳裂纹扩展电化学过程起到抑制作用。