酸气回注井管柱剩余寿命预测及选材研究

Study on residual life prediction and material selection of acid gas reinjection well string

关键词:  H₂S/CO₂  温度  油管钢  腐蚀  寿命预测

Key words:  H₂S/CO₂  temperature  tubing steel  corrosion  life prediction

摘要:

为得出酸气回注环境下不同油管钢的腐蚀规律和安全服役寿命,利用高温高压釜模拟酸气回注井井下工况,在温度90~150 ℃、H₂S体积分数为55%、CO₂体积分数为45%的条件下开展了腐蚀失重实验,研究了不同温度下T95钢、P110SS钢、G3钢的腐蚀性能,并结合SEM与EDS对腐蚀产物进行了表征分析,最后基于均匀腐蚀速率对油管柱的腐蚀寿命进行了预测。结果 表明:随着温度的升高,T95钢及P110SS钢在液相中的腐蚀速率先增大后减小,120 ℃时达到最大值,T95钢的腐蚀速率为1.337 9 mm/a、P110SS钢为0.842 6 mm/a；在气相中,两种钢的腐蚀速率均随温度升高而增大,150 ℃时达到最大值,T95钢的腐蚀速率为0.249 0 mm/a、P110SS钢为0.233 9 mm/a；G3镍基合金钢表现出良好的抗腐蚀性能,各工况下均满足油田腐蚀控制指标0.076 mm/a。在120 ℃液相苛刻工况下,T95油管钢的安全服役年限为2.8年,P110SS油管钢为6年；在150 ℃气相苛刻工况下,T95油管钢的安全服役年限为14.9年,P110SS油管钢为21.3年。由于G3镍基合金钢在不同工况不同温度下均无明显腐蚀,则不对其作腐蚀寿命预测。明确了酸气回注环境中3种油管钢的腐蚀性与其安全服役年限,为酸气回注井的选材和针对性制定腐蚀防护对策提供了依据。 

Abstract:

In order to obtain the corrosion law and safe service life of different tubing steels in acid gas reinjection environment, the acid gas refilling well conditions were simulated by using high temperature autoclave. The corrosion weight loss experiment was carried out under the conditions of 90~150 ℃, H₂S content of 55 vol% and CO₂ content of 45 vol%. The corrosion properties of T95, P110SS and G3 steels were studied at different temperatures. The corrosion products were characterized by SEM and EDS. Finally, the corrosion life of the tubing columns was predicted basing on the uniform corrosion rate. The results show that the corrosion rate of T95 and P110SS steels increase first and then decrease in the liquid phase with the increase of temperature, reaching the maximum at 120 ℃, 1.3379 mm/a for T95 steel and 0.842 6 mm/a for P110SS steel. In the gas phase, the corrosion rate of two steels increase with the increase of temperature, reaching the maximum at 150 ℃, 0.2490 mm/a for T95 steel and 0.233 9 mm/a for P110SS steel. G3 nickel-based alloy steel exhibits good corrosion resistance and meets the oilfield corrosion control index of 0.076 mm/a under all working conditions. The service life of T95 tubing steel is 2.8 years and that of P110SS tubing steel is 6 years under the harsh working conditions of liquid phase at 120 ℃; the service life of T95 tubing steel is 14.9 years and that of P110SS tubing steel is 21.3 years under the severe conditions of gas phase at 150 ℃. This article clarifies the corrosiveness and safe service life of three tubing steels in acid gas reinjection environment, which provides a basis for selecting materials of acid gas reinjection wells and formulating the targeted corrosion protection measures.