“三高”气田固井水泥体系研究

Cement systems for well cementation in gas fields with high pressure,high gas production rate and high sulfur concent

针对高压、高产、高含硫化氢(H2S)气体('三高')气田在固井过程中面临的难点,探讨'三高'气田对固井水泥浆的要求,在分析水泥腐蚀机制的基础上,提出'三高'气田水泥防腐策略;采用水泥浆不同配料组分的颗粒粒径合理级配原理优化设计水泥,通过正交试验筛选出可形成致密水泥石、防腐性能优良的低密度高强度水泥和纤维-胶乳-微膨胀水泥2种体系4个配方,对其形成的水泥石进行抗硫化氢和二氧化碳(H2S/CO2)腐蚀性能评价试验,包括水泥石强度、渗透率、质量损失、腐蚀深度和腐蚀前后内部结构的变化情况,依据试验数据从理论上预测水泥石的抗腐蚀寿命。龙岗气田现场应用表明,所筛选的水泥浆的固井质量得到明显提高,可用于'三高'气田固井,并能延长气井寿命。

In view of the cementing difficulties in high production gas wells with high pressure and high sulfur content（three high）,related requirements for cement slurry were discussed.On the basis of the analysis of the cement corrosion mechanism,the antiseptic strategy for cement system in ＂three high＂ gas fields was proposed.An appropriate particle size distribution philosophy was used for different blending component of cement slurry to optimize the design of cement slurry formulation.Orthogonal experiments were conducted,and four kinds of formulation for two cement systems,the light-weight high-strength cement system and the fiber-latex-microdilatancy cement system,were screened out with densely packed cement sheath and favorable corrosion prevention capability.In addition,evaluation tests on the corrosion resistance of set cement against H2S and CO2 were carried out,including the strength,permeability,loss in weight,corrosion depth and internal structure alteration before and after corrosion.The life span of set cement under corrosion was predicted in the light of the experimental data.The application results of Longgan gas field show that the qualification for cementing can be obviously improved by using the technology.Research results can be used to provide guidance for cementing in ＂three high＂ gas fields,and to prolong the life span of gas well.