低含H2S工况下110SS的超临界CO2腐蚀行为

Corrosion Behavior of 110SS Steel in Supercritical CO2 Phase under Environment with Low H2S

目的明确低含H2S工况下,110SS钢在超临界CO2相中的适用性及腐蚀行为。方法利用高温高压反应釜对高温高压低含H2S气井的井底腐蚀工况进行模拟,采用腐蚀失重法获取腐蚀速率,结合激光共聚焦显微镜、扫描电子显微镜(SEM)、能谱仪(EDS)及X射线衍射仪(XRD)对腐蚀行为进行分析研究。结果在141℃、13.3 MPa CO2分压、1.33 kPa H2S分压工况下,110SS在含饱和水的超临界中均呈现均匀腐蚀特征,腐蚀速率为0.017 mm/a,腐蚀轻微,CO2腐蚀占主导地位。基体表面腐蚀产物膜分布并不均匀,呈水珠状分布,产物膜为单层结构,腐蚀产物以碳酸亚铁为主,含少量H2S腐蚀产物,且H2S腐蚀多集中于水珠状区域内部。腐蚀产物膜由不连续的晶粒构成,部分部位基体直接暴露于腐蚀性介质中,对基体的保护有限。结论以0.125 mm/a作为油套管选材标准,对于仅含凝析水,无积水问题的气井,可选用110SS管材作为油套管材质(温度≤141℃,CO2分压≤13.3 MPa,H2S分压≤1.33 kPa,Cl^–质量浓度≤4646 mg/L)。

To clarify the applicability and corrosion mechanism of 110SS steel in supercritical CO2 phase under environment with low H2S,HTHP reactor was adopted to simulate the HTHP low H2S environment at the bottom of gas well.The corrosion rate was measured by weight loss methods;the corrosion behavior was analyzed by the laser scanning confocal microscope(LSCM),the scanning electron microscope(SEM),energy spectrum(EDS),and X-ray diffraction(XRD).The results show that 110 SS steel presents uniform corrosion characteristics in the supercritical CO2 phase containing saturated water,with corrosion rates of 0.017 mm/a at 141℃,13.3 MPa CO2 partial pressure,and 1.33 kPa H2S partial pressure.CO2 controls the corrosion.The corrosion film is distributed unevenly in the shape of water beads and has a monolayer structure.The corrosion products are mainly FeCO3,containing a small amount of H2S,and H2S corrosion is mostly concentrated in the interior of the water-bead area.The corrosion film is composed of discontinuous grains,and some parts of the matrix are directly exposed to the corrosive medium,so the protection of the matrix is limited.Taking 0.125 mm/a as the casing and tubing material selection standard,110 SS steel can be selected as casing and tubing material for gas wells with only condensate water and without water accumulation(T≤141℃,PCO2≤13.3 MPa,PH2S≤1.33 kPa,Cl^–≤4646 mg/L).