鄂尔多斯盆地靖边气田气井油管腐蚀规律与防腐对策

Corrosion law of oil tubings and prevention countermeasures in gas wells of the Jingbian Gas Field,Ordos Basin

鄂尔多斯盆地靖边气田于1997年建成投产,天然气中携带H2S(平均691mg/m3)、CO2(5%)等酸性气体及高矿化度地层水等腐蚀性介质。为了掌握靖边气田气井油管腐蚀规律,利用多臂井径检测仪MIT、磁检测仪MTT、电磁探伤测井仪MID-K等仪器组合采取绳索作业方式,对60余口气井油管开展了不动管柱腐蚀检测作业,结合气井产水量、产水矿化度、氯离子、H2S和CO2含量等因素进行综合分析。结果表明:产水气井较其他气井的油管腐蚀更为严重,产水量越大、产水矿化度越高腐蚀就越严重,严重腐蚀井段主要集中在油管中下部;在0～2 000m油管腐蚀方式由外壁向内壁扩展,2 000m以下油管腐蚀主要由内壁向外壁扩展。针对靖边气田高产水气井油管的腐蚀状况,从使用新型缓蚀剂和"内涂外喷"涂层防腐油管两方面改进了防护措施,油管腐蚀情况大为减轻,局部最大腐蚀速率由3.67mm/a降至0.11mm/a,确保了产水气井正常、安全生产。

Corrosive media like Hz S （691 mg/m3 on average）, CO2 （5 %）, etc. , and high salt water have been carried with the natural gas produced from the Jingbian Gas Field, Ordos Basin, which was put into production in 1997. To master the corrosion law of oil tubings in the gas wells in this field, corrosion inspection has been done of oil tubings without pulling string in more than 60 gas wells, in which wireline operation work was completed by a combination of an multi-arm caliper logging tool, an magnetic testing （MTT） tool, an MID-K electromagnetic flaw detection tool, etc. On this basis, an integrated analysis was performed in combination with many factors such as chloride ion, H2 S and CO2 content in the produced gas, water mineralization degree, and water quantity in a gas well, and so forth. The results show that the corrosion phenomenon in oil tubings of gas wells with water production is much severer than that of other gas wells~ the higher the water production and water mineralization degree, the severer the corrosion will bet the severest corrosion occurs mainly in the middle and lower parts of production tubings~ and the corrosion extends from the out- side to inside wall of oil tubings at the strata up above 2000 m, conversely from inside to outside wall at the strata deeper than 2000 m. Accordingly, corrosion prevention and control countermeasures have been taken by adopting a new type of corrosion inhibitor and a new material of inner coating and out spray, and the maximum localized corrosion rate was reduced from 3.67 mm to 0.11 mm per year. In this way, normal safe production has been maintained in such gas wells with water production.