摘要:
元坝地区高压气层天然气中普遍含有H2S,影响固井质量和气井的寿命。为此,借鉴其他地区应用胶乳水泥浆的经验,结合元坝地区的特点,确定了胶乳水泥浆的基本配方。通过室内试验分析了影响胶乳水泥浆性能的敏感因素,结果表明,剪切速率、水质和密度等因素对其性能影响不大,虽然水泥浆的稠化时间随温度升高而缩短,但能满足元坝地区固井施工要求。采用扫描电镜观察水泥石腐蚀前后的结构变化、对比水泥石腐蚀前后的抗压强度和渗透率、测试水泥石的腐蚀率,评价了胶乳防腐水泥浆抗H2S腐蚀的性能,分析了胶乳防腐水泥浆抗H2S腐蚀的机理。试验结果表明,胶乳防腐水泥浆形成的水泥石具有较好的抗H2S腐蚀性能,在H2S体积分数为4.0%环境中的腐蚀率不到16%,远低于常规水泥石的腐蚀率。34井次的现场应用表明,胶乳防腐水泥浆可提高元坝地区气井固井质量。
Abstract:
In Yuanba Area where high-pressure gas zones are commonly encountered in exploratory wells,and hydrogen sulfide (H2S) is contained in the natural gas,it is of crucial importance to employ latex cement slurry that can prevent gas channeling and corrosion to increase life span of wells.In view of the formation characteristics of Yuanba Area and combined with the application experience of latex cement slurry in other regions,the fundamental formula of latex cement slurry was worked out.Lab experiments prove that all the sensitive factors,such as shear rate,water quality and density had little effect on the properties of latex cement slurry,which is suitable for the sophisticated circumstances in Yuanba Area.Although the thickening time shortens with the rise in temperature,it fulfills the requirements of cementing operation in Yuanba Area.The corrosion resistivity of the latex cement slurry was evaluated by observing the structure changes of cement stones under scanning electron microscope (SEM) before and after corrosion,and comparing the strength and permeablity measured before and after corrosion by H2S,and the tested rates of corrosion,and the corrosion resistant mechanism of latex cement slurry was investigated as well.The cement stone formed by latex cement slurry exhibited preferable corrosion resistant performance to H2S.In the environment with a 4.0% volume fraction of H2S,its rate of corrosion was less than 16%,which was much lower than that of the cement stone formed by conventional cement slurry.Field application results indicated that utilization of corrosion resistant latex cement slurry in Yuanba Area could improve cementing quality and prevent the corrosion of H2S on cementing quality.
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