普光高酸性气田井筒管材及完井方案优选

Optimal selection of downhole tubular goods and well completion programs for the Puguang Sour gas Field

四川盆地普光气田属于高含H2S和CO2的碳酸盐岩过成熟酸性气田,存在气藏压力高、埋藏深度大、地质构造复杂、腐蚀严重、易喷易漏、安全风险高等开发难题。为解决上述难题,实现气田的安全高效开发,在深入调研国内外高含硫气田完井技术现状的基础上,分析了硫化氢、二氧化碳以及氯离子等对井下管材的腐蚀方式,提出了管柱腐蚀的防治措施:①采用防腐蚀管材;②注入缓蚀剂;③将上述两种方式综合应用。进而设计了3种完井方案:①高镍基合金完井;②高镍基合金与高抗硫材质组合完井;③高抗硫材质完井。经分析对比,最终确定采用镍基合金和高抗硫钢套管组合,配合镍基合金油管和永久式封隔器的完井方案;射孔后下酸压—生产一体化完井管柱,酸化压裂后投产。该方案成功解决了气井酸压、生产、防腐蚀等问题,具有防腐性能优越、后期维护成本低、管柱有效生产时间长、安全系数高等特点。

During the development of the over-matured carbonate sour gas reservoirs in the Puguang Gas Field,Sichuan Basin,great challenges are encountered like high contents of H2S and CO2,high reservoir pressures,great burial depths,complicated geological structures,serious corrosion,and frequent potential kicks and lost circulations,and high safety risks,etc.In order to solve the above problems and to achieve the safe and efficient gas field development,an in-depth investigation is conducted into the state-of-the-art technologies of well completion in sour gas wells at home and abroad,and the corrosion of H2S,CO2 and chloride ions on downhole pipe strings is analyzed respectively.On the basis of this,the following preventive measures are put forward:(1)adopting anti-corrosion tubular goods,(2)injecting corrosion inhibitors,(3)applying the above(1)and(2).Ultimately,the optimal well completion tools in 3 combination modes of tubular goods are presented:(1)high nickel-based alloy completion string,(2)completion string of high nickel-based alloy and high H2S-resistance material combination,(3)high H2S-resistance material completion string.Through a comparative study,the perfect well completion program is thus determined:using the first combination with nickel-based alloy and high H2S-resistance steel casing string plus the second one with nickel alloy tubing and permanent packer,then running the integrated acid frac and production completion string after perforation,and finally putting the well into production after acid frac.This program can successfully help realize the goals of acid frac,gas recovery and corrosion control,with many advantages of good corrosion control performance,low intervention operation cost,long service lives of completion strings,and a high safety factor.