新疆阜康深层煤层气井腐蚀机理与防护研究

Corrosion Mechanisms and Precision Protection Technologies for Deep Coalbed Methane Wells in Fukang, Xinjiang

摘要: 新疆阜康深层煤层气井因高矿化度、高CO₂分压与复杂流场的协同作用，面临严峻的管柱腐蚀与套损挑战。本文通过现场大规模调研(73口井)、系统流体分析(30口井)、井下挂片实验(5口井)及多尺度室内表征，明确了腐蚀失效的时空规律。结果表明，产出水高矿化度(7278.66~18922.74 mg/L)与高CO₂分压(0.16~0.99 MPa)是驱动电化学腐蚀的核心环境因素。通过腐蚀产物膜微观分析，揭示了Cl⁻与$HC{O}_3^{-}$ 协同破坏FeCO₃膜完整性的“竞争吸附–化学溶解”机制，并阐明了井筒780 m以下射孔/造斜段“冲蚀–腐蚀–结垢”三重动态耦合的宏观失效模式。基于灰色关联度分析，量化了各影响因素权重：流场剪切力(~40%) > Cl-浓度(~35%) > CO₂分压(~15%) > 垢层不均度(~10%)。结合腐蚀速率、点蚀深度与电化学参数($I_{corr}$ , $R_p$ )的强关联性，建立了腐蚀风险四级评价模型及“材料–药剂–监测–管控”四位一体的精准防护体系，其工程有效性与经济性显著。

Abstract: Deep coalbed methane (CBM) wells in the Fukang area of Xinjiang face severe tubing corrosion and casing damage due to the synergistic effects of high salinity, high CO₂ partial pressure, and complex flow fields. Through extensive field surveys (73 wells), systematic fluid analyses (30 wells), downhole coupon testing (5 wells), and multi-scale laboratory characterization, this study identifies the spatio-temporal patterns of corrosion failure. The results indicate that high produced-water salinity (7278.66~18,922.74 mg/L) and elevated CO₂ partial pressure (0.16~0.99 MPa) are the primary environmental drivers of electrochemical corrosion. Microscopic analysis of the corrosion product film reveals a “competitive adsorption-chemical dissolution” mechanism, where Cl⁻ and $HC{O}_3^{-}$ synergistically compromise the integrity of the FeCO₃ scale. Furthermore, a macro-failure mode characterized by a “erosion-corrosion-scaling” triple dynamic coupling was elucidated for the perforated and deviated sections below 780 m. Using Gray Relational Analysis (GRA), the influence of various factors was quantified: flow field shear stress (~40%) > Cl^- concentration (~35%) > CO₂ partial pressure (~15%) > scale layer inhomogeneity (~10%). By correlating corrosion rates and pitting depth with electrochemical parameters ($I_{corr}$ , $R_p$ ), a four-tier corrosion risk assessment model was established and an integrated “Material-Chemical-Monitoring-Management” precision protection system was developed. The system’s engineering efficacy and economic viability is obvious.