高钢级油井管在高温高压气井全生命周期环境中的腐蚀行为及寿命预测

Corrosion Behavior and Life Prediction of High Grade OCTG in Full-life-cycle Environment of High Temperature High Pressure Gas Well

采用高温高压腐蚀测试系统研究了140ksi高钢级油井管在高温高压气井全生命周期单环境和连续多环境中的腐蚀行为。结果表明,140ksi高钢级油井管在全生命周期单环境和连续多环境中的腐蚀速率均呈现为CR鲜酸>CR残酸>CR地层水>CR凝析水的趋势,其中连续多环境中腐蚀行为表现出一定的"遗传效应"。地层水腐蚀介质中,140ksi高钢级油井管在单环境和连续多环境的腐蚀速率均随实验周期增加而减小,60 d后腐蚀速率趋于稳定。基于点蚀速率结果,采用有限元方法计算得到不同腐蚀状态下140ksi高钢级油井管的服役寿命。

The corrosion behavior of 140 ksi high grade steels, namely the so-called oil country tubular goods(OCTG), in the single environment and multi-consecutive environment in the full-life-cycle of high pressure and high temperature gas wells was systematically studied via high pressure and high temperature corrosion testing system. The results showed that the decreasing trend of corrosion rates of140 ksi high grade OCTG steels in both single environment tests and multi-consecutive environment tests could be ranked as follows: CRfresh acid>CRused acid>CRformation water>CRcondensate water, and some"genetic effects"were also observed in the multi-consecutive environment tests. The corrosion rates of 140 ksi high grade OCTG steels decreased with the increase of test time in the formation water for both single environment tests and multi-consecutive environment tests, which tended to be stable after 60 d exposure. Based on the pitting rates, the service life of 140 ksi high grade OCTG steels under different corrosion conditions was calculated using the finite element method.