气田封隔液高温高压条件下CO_2腐蚀研究

The CO_2 Corrosion Packing Fluid for Gas Fields at HTHP

建立了室内高温高压CO2腐蚀评价方法及应力腐蚀评价方法,分析了现场油管、套管及井下工具使用钢材材质的主要化学成分,并对现场使用的封隔液进行了腐蚀性研究。研究结果表明,在现场使用的3种不锈钢材料耐蚀性顺序依次为13CrS、13CrM、13Cr,封隔液的腐蚀性随着温度、CO2分压、密度的降低而减小;对比甲酸钾,使用焦磷酸钾作为封隔液体系的加重基液大幅度降低了封隔液对钢片的腐蚀,腐蚀速率相对减小了4倍多;通过提高缓蚀剂的加量和采用焦磷酸钾和甲酸钾复合盐水加重,使封隔液分别在温度60~150℃中CO2分压12.36MPa及温度150℃中CO2分压6.20~12.3MPa时,对13Cr钢的腐蚀速率小于0.076mm/a,并提高了13Cr和13CrS钢试片在温度150℃,CO2分压12.36MPa条件下抗应力腐蚀性。

The evaluation method of high temperature and high pressure CO2 corrosion and stress corrosion evaluation method are established in laboratory,the main chemical composition of steeltubing,casing and downhole tools used in the oilfield are analyzed,and the corrosion of field used packer fluid is studied.The results show that the corrosion resistance of three kinds of stainless steels is 13 CrS,13CrM and 13 Cr in order.The corrosion resistance of packing fluid reduces with the decrease of temperature,CO2 partial pressure and its density.Compared with potassium formate,the corrosion of steel is reduced greatly as potassium pyrophosphate is used as weighting base fluid of the packing fluid,the corrosion rate is relatively reduced more than four times.By raising the adding amount of corrosion inhibitor and a compound of potassium pyrophosphate and formic acid potassium salt water is used for aggravating,CO2 partial pressure is 12.36 MPa at the packer liquid temperature60~150℃ and the CO2 partial pressure is 6.20~12.36 MPa at temperature of 150 ℃,the corrosion rate of steel for 13 Cr is less than 0.076mm/a.And it improves the stress corrosion resistance of 13 Cr and13CrS steel specimens under the condition of temperature 150℃and the CO2 partial pressure 12.36 MPa.