深井油管CO2腐蚀规律及其应用研究

 采用高温高压水介质,测试研究了模拟现场工况环境中几种材料在不同井况环境下的动态腐蚀特征,对腐蚀产物和速率变化特征进行了分析.结果表明,不同井况环境下,腐蚀产物特征和速率存在较大差异,腐蚀速率最高值与最低值差别可达5倍以上;在同一口井中的不同井段,同种材料的腐蚀特征表现出极大的差异,腐蚀产物形貌、与基体结合力以及腐蚀速率等方面各不相同,其中以1500—3500m井段腐蚀较为严重,1500m以上腐蚀较轻,而井底部位试样表面基本都形成具有较好结合力的腐蚀产物膜,阻碍了腐蚀的发展;模拟环境下,同一口井中不同材料和不同井段间的耐蚀性也存在差别,这种差别是多种影响因素共同作用的结果,各影响因素的作用大小有所不同.可见,深井或超深井中油管的CO₂腐蚀,需要针对各油井的具体状况以及CO₂腐蚀的发生、发展规律和趋势,对每一口具体井的不同井段进行有关温度、压力及流速的测试和计算,找出可能发生严重CO₂腐蚀的井段;在研究油管的CO₂腐蚀规律时,需要综合考虑各种因素的协同作用.

CO2 Corrosion Law and Its Application to Analysis of Tubing in Deep and Super Deep Wells

The corrosion rate and characteristics of several kinds materials are studied under the in situ conditions of high pressure and high temperature in the stirring aqueous solution in a nickel-based alloy autoclave. The test results show that the corrosion rate and characteristics under different well conditions are different, the highest corrosion rate is 5 times greater than the lowest one. And in the same well, the corrosion rates of different materials and sections of a well are also different under the simulating test conditions. The differences come from the joint effects of multi-factors in different degrees. In different sections of a well, different corrosion characteristics of the same material are observed. As can be seen from the topography of the corrosion scales, the binding force of the corrosion scales with the base metal and the corrosion rate itself, the most serious corrosive section is at a depth from 1500m to 3500m, with the top 1500m part slightly corroded. At the bottom of the well, the corrosion is also gentle according to the formation of corrosion scales and the excellent binding force which would obstruct the corrosion process. Therefore, many factors should be considered when studying the CO₂ corrosion characteristics of tubing materials in deep or super deep wells, such as the tendency of the corrosion rate, and the conditions of the well. The temperature, the pressure and the flow rate of each well in different sections should also be tested and calculated to find out the most serious section under the corrosion, conditions and the effects of different factors are not the same on the corrosion rate. Therefore, the joint effects of all factors should be considered when studying the CO₂ corrosion of tubing.