硫化氢环境下常用油井管材质腐蚀规律研究

Corrosion Rules of Commonly Used Oil Well Pipes in Hydrogen Sulfide Environment

目的通过失重法测定L80、N80、1Cr、3Cr、9Cr、13Cr等油井管材质在硫化氢分压为0.001、0.01、0.1、0.5、1.26、2 MPa环境条件下的腐蚀速率。方法采用高温高压反应釜对L80、N80、1Cr、3Cr、9Cr、13Cr等材料在模拟工况下的腐蚀行为进行研究。用扫描电子显微镜对所得样品的腐蚀产物种类、微观形貌进行分析。结果在硫化氢分压为2 MPa以下时,各种材料的腐蚀速率均低于0.125 mm/a,属于中度腐蚀。而硫化氢分压为2MPa时,除9Cr外,其余材料的腐蚀速率均达到了重度腐蚀以上。不锈钢的腐蚀速率要明显低于低合金钢,且加入少量Cr元素并未对耐蚀性能有显著的提升,且某些条件下,腐蚀速率要高于普通低合金钢。对于低合金钢及含Cr量较低的钢,硫化氢压力不高于0.1 MPa时,腐蚀速率差异不大,基本保持在0.025 mm/a附近,属于轻微腐蚀,但当硫化氢压力达到0.5 MPa时,L80、N80和1Cr的腐蚀速率显著增高。在硫化氢分压0.001～0.1 MPa之间,常用油井管材质的点蚀严重程度随硫化氢分压增大而逐渐增加;在硫化氢分压0.1～0.5 MPa之间,常用油井管材质点蚀程度随硫化氢分压增大而逐渐降低;在0.5～2 MPa之间,点蚀程度又逐渐增加。结论对于不锈钢,当硫化氢压力不高于0.1 MPa时,虽然腐蚀速率随硫化氢压力升高,呈现一定的上升趋势,但腐蚀速率均维持在较低的水平;当硫化氢压力达到0.5 MPa时,不锈钢的腐蚀速率显著增大。不锈钢的耐蚀性能要远优于低合金钢,尤其是在硫化氢压力较低的环境中。

The work aims to measure the corrosion rates of L80,N80,1Cr,3Cr,9Cr and 13Cr oil well pipes under the conditions of hydrogen sulfide partial pressure of 0.001,0.01,0.1,0.5,1.26 and 2 MPa by the method of weight loss.The corrosion behavior of L80,N80,1Cr,3Cr,9Cr,13Cr and other materials under simulated conditions was studied by high temperature and high pressure reactor.Scanning electron microscope(SEM)was used to analyze the types and microstructure of corrosion products.The corrosion rate of all materials was lower than 0.125 mm/a when the partial pressure of hydrogen sulfide was less than 2 MPa,so the corrosion was moderate.When the partial pressure of hydrogen sulfide was 2 MPa,the corrosion rate of all the materials except 9Cr was higher than that of severe corrosion.The corrosion rate of stainless steel was significantly lower than that of low alloy steel,and addition of a small amount of Cr element could not significantly improve the corrosion resistance.Under certain conditions,the corrosion rate was higher than that of ordinary low alloy steels.For low alloy steel and low Cr steel,the corrosion rate was not much different when the hydrogen sulfide pressure was not higher than 0.1 MPa,and the corrosion rate was basically kept near 0.025 mm/a,so the corrosion was slight.However,when the hydrogen sulfide pressure reached 0.5 MPa,the corrosion rates of L80,N80 and 1Cr increased significantly.The severity of pitting on commonly used oil well pipes gradually increased with the increase of partial pressure of hydrogen sulfide when the partial pressure of hydrogen sulfide was from 0.001~0.1 MPa.When the partial pressure of hydrogen sulfide was 0.1~0.5 MPa,the pitting degree of commonly used oil well pipes decreased with the increase of partial pressure of hydrogen sulfide.The degree of pitting gradually increased again when the partial pressure of hydrogen sulfide was from 0.5~2 MPa.For stainless steel,when hydrogen sulfide pressure is not higher than 0.1 MPa,the corrosion rate of stainless steel increases with the increase of hydrogen sulfide pressure,but the corrosion rate remains at a low level.When the hydrogen sulfide pressure reaches 0.5 MPa,the corrosion rate of stainless steel increases significantly.The corrosion resistance of stainless steel is much better than that of low alloy steel,especially in the environment of low hydrogen sulfide pressure.