摘要
采用慢应变速率拉伸(SSRT)实验,并结合电化学噪声(ECN)、SEM与EIS等方法,研究了P110低合金油管钢在模拟井下环空液中的应力腐蚀开裂(SCC)行为,并探讨了S2-浓度对裂纹萌生和扩展过程的影响。结果表明,在P110钢的弹性形变阶段,环空液中低浓度S2-的加入加速了P110钢拉伸试样表面钝化膜的破坏,导致ECN曲线上出现许多由亚稳态点蚀引起的短时电流噪声峰。S2-的加入还显著缩短了亚稳态点蚀向稳定点蚀转变的时间,促使拉伸试样表面出现较大尺寸的蚀坑,这些蚀坑在拉应力作用下可以转变为裂纹萌生源。相比亚稳态点蚀,裂纹生长产生的噪声峰平均寿命更长(约400 s),且噪声幅值(约40 m A)和积分电量(约4000 m C)也更大。P110钢的SCC以阳极溶解为主,且裂纹生长速率随S2-浓度的增加而增大,但裂纹生长是断续而非连续进行的。
Stress corrosion cracking （SCC） is considered as the main risk of tubing steels during the exploitation of oil and gas fields, which could result in sudden and catastrophic failures of downhole tubing. Especially in annular downhole environment, P110 tubing steel is prone to sulfide stress corrosion cracking and hydrogen embrittlement （HE） where S2- could be originated from bio-reduction of SO42- inspired by sulfate-reducing bacteria （SRB）. Currently, extensive work have been performed to investigate the influence factors on SCC and mechanism of tubing steels, but limited researches have been conducted on the SCC of P110 tubing steel in annular downhole environment, particularly, on the early detection of SCC. In this work, the SCC behavior of P110 low alloy steel in simulating sulphur-containing annular fluid （SAF） and the effect of S2- concentration on the initiation and propagation of crack were investigated by slow stress rate test （SSRT）, non-destructive electrochemical noise （ECN）, SEM and EIS techniques. The results showed that, during the elastic stress stage, the addition of S2- accelerated the breakdown of passivation film on the surface of P110 steel tensile specimen. There are many short duration current transients caused by metastable pits on ECN curves. The transformation time of metastable to stable pits is shortened significantly by the addition of S2-, which not only promotes the growth of pits but the initiation of cracks from the stable pits under the action of tensile stress. Compared with the ECN spikes from metastable pits, the spikes associated to the advance of cracks are featured by longer average duration （about 400 s）, stronger amplitude （40 μA）, and higher charge （about 4000 μC）. As a result, the susceptibility of P110 steel to SCC increases with S2- concentration, and the propagation of SCC is dominated by anodic dissolution characteristic of discontinuous advance.
作者
余军
张德平
潘若生
董泽华
YU Jun;ZHANG Deping;PAN Ruosheng;DONG Zehua(School of Chemistry and Chemical Engineering,Huazhong University of Science and Technology,Wuhan 430074,China;Jilin Oilfield Company ofPetroChina,Songyuan 138000,China;R＆D Center of National Energy of CO_2 Flooding and Embedded Technology,Songyuan 138000,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第10期1399-1407,共9页
Acta Metallurgica Sinica
基金
国家自然科学基金项目No.51771079
国家油气重大专项项目No.2016ZX05016002-004~~
关键词
低合金钢
应力腐蚀开裂
电化学噪声
环空液
low alloy steel
stress corrosion cracking
electrochemical noise
annular fluid
