外应力对套管腐蚀速率的影响

Effect of external stress to casing corrosion rate

高德利 赵增新

GAO Deli ZHAO Zengxin

中国石油大学石油工程教育部重点实验室，北京　102249

MOE Key Lab of Petroleum Engineering, China University of Petroleum, Beijing 102249, China

受腐蚀性油气介质的影响，油气井套管在生产过程中将发生腐蚀，从而导致服役管柱的损坏，除化学腐蚀外，管体中由于流体压力而产生的应力也将影响管柱的腐蚀。针对管体所受外部应力会加速腐蚀速率、严重缩短管柱服役寿命这一现象，结合化学力学效应理论，分二向应力和三向应力2 种情况，建立了外应力影响套管腐蚀速率的解析模型，给出了计算应力影响管柱寿命衰减的解析公式。算例计算结果显示，该模型所得结果与目前文献中应力对腐蚀速率的影响实验研究结果相符；管柱所受应力越大，管柱实际寿命衰减得越快。该结论对精确确定管柱的寿命具有重要的参考意义。

Casing will be damaged by corrosion with the corrosive oil and gas fluid during the process of oil and gas production.The stress caused by high pressure production fluid will affect the rate of casing corrosion. This paper focuses on the phenomenon thatthe external stress which loads on the corrosive casing will accelerate corrosion rate and shorten the casing service life significantly.Combining the theory of mechanochemical effect, the analytical model is established for casing corrosion accelerating rate by externalstress with two dimensions stress and three dimensions stress, and the analytical formula for calculating the stress effect on casing servicelife is put forward. According to the sample result, the result obtained from the model is consistent with the literature result achieved byexperimental research. It is concluded that the higher the stress on casing, the faster the actual casing service life gets shorter. The modeland the calculating result can work as reference for exact determination of casing servicing life.