Laboratory tests for corrosion behaviors of Super 13Cr tubing and casing under sour downhole conditions
Li Qiongwei1,2,3,Xi Yuntao2,3,Dong Xiaohuan2,3,Cheng Bihai2,3,Li Hui2,3(1.Material Science and Engineering,Xi'an Jiaotong University,Xi'an,Shaanxi 710049,China;2.State Engineering Laboratory for Low-Permeability Oil & Gas Exploration and Development,Xi'an,Shaanxi 710018,China;3.Oil & Gas Technology Research Institute,Changqing Oilfield Company,PetroChina.Xi'an,Shaanxi 710018,China)
Over the past two decades,Super 13Cr(Super Martensitic Stainless Steel) tubing and casing have been widely applied for the equilibrium of a gas well's lifetime and tubular goods inputs in the H2S/CO2 coexistence environment or high Cl-deep wells or complex horizontal wells,However,the application conditions for Super 13Cr steel are strictly limited in the description of the international standards like ISO;especially concerning its resistance to sulfide stress cracking(SSC) and the related influencing factors,different scholars always dispute with each other.In view of this,simulating the corrosion environment of a H2S gas well in a block in north Shaanxi province,China,we conducted laboratory tests to evaluate the resistance of Super 13Cr tubular goods to electrochemical corrosion and SSC by using the electrochemical system and high-pressure corrosion testing system.Under such simulated corrosion environment,the electrochemical corrosion rate of Super 13Cr steel was 0.01 mm/a,while that of the conventional 13Cr steel was 0.26 mm/a;unlike that in the NACE's standard solution test,there is no SSC sensitivity found when the test pressure reached 80% or 90% of AYS(Applied Yielding Strength).This study provides reference for the application of Super 13Cr tubular goods in such a similar sour downhole environment.
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