The Research Of Casing Assembly With Different Materials And Anti-corrosion Completion Technology For The Gas Well With CO₂

Based on laboratory experiment, a study on the corrosion behavior of CO₂solutionin casing steel and casing combination is carried out for the specific condition ofXuShen Gas Filed.The corrosion assessment of P110、3Cr and13Cr is studied by inner experiment,the result display that13Cr shows better corrosion resistance. When temperature is80℃,CO₂partial pressure is2.5MPa,13Cr steel shows the highest corrosion rate. Whensystem temperature is lower100℃,the3Cr shows better corrosion resistance, whensystem is higher than100℃，3Cr steel corrosion rater is greater than P110corrosionrater. The corrosion factor is studied of gas well combination and inner experiment byGray theory, get the main control factor of corrosion if temperature and CO₂partialpressure. Based on the experimental results, the two-factor corrosion prediction modelis established,3D and2D corrosion forecast plates is also established.Galvanic corrosion characteristics of P110-3Cr、3Cr-13Cr and P110-13Cr isstudied by electrochemical experiment and HPHT simulation experiment. Thecorrosion potential measurements confirmed the tendency of materials coupledgalvanic corrosion. The HPHT experiment shows that galvanic corrosion tendency tofaint at high temperature, mainly because of the protective effect of specimen corrosionproduct film. More serious galvanic corrosion in the vicinity of80℃. The galvaniccorrosion acceleration factor of P110-13Cr combination is studied through theoretical,and establishment galvanic corrosion acceleration factor plate and galvanic corrosionrate plate. And get galvanic corrosion control method, as follows, first, select environmental to control galvanic corrosion rate, second, reduce the13Cr area, finally,inhibitor control.Identified3sets of production casing combination program by corrosion riskassessment of single well, and galvanic corrosion control. Gas well with low productiongas rate, low stable life, and limit the cost, select grogram one, as follows, carboncasing steel with inhibitor, lower initial investment costs. Gas HTHP well with high gasflow rate, corrosion seriously, and long production cycle, select the following twooptions, program two, use13Cr material casing at lower section, the upper of the packer,select carbon steel. To further reduce the cost of casing, select program three, usinganti-corrosion casing at the packer plugging section, other section select carbonsteel,and ensure the sealing packer and long-term safety. Group with technology toreduce completion costs, and to ensure that the purpose of gas well production.