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酸性气井井下防腐是石油工程学界的技术难题之一,对于“井筒第一屏障”——固井水泥环的腐蚀研究更是备受重视。针对目前井下固井水泥环腐蚀研究中存在的问题,采用界面腐蚀的试验方法,利用X射线衍射、扫描电镜等实验分析手段,对川渝地区含硫气井固井水泥环腐蚀机理进行了探索。结果表明:①水泥石的腐蚀深度和H2S分压值、腐蚀时间成正比;②腐蚀后水泥石抗压强度值和H2S分压值、腐蚀时间成反比;③由于水泥石受酸性气体腐蚀后的产物逐渐富集、堆积及运移,使水泥石形成一个较为稳定的致密层或腐蚀过渡带,腐蚀后水泥石的孔隙度和渗透率随腐蚀时间的增加呈现先增加后降低的特点,并最终使腐蚀介质进入水泥石内部变得更加困难;④确保水泥环在保持一定腐蚀深度的情况下,尽快形成较为稳定的腐蚀过渡带或降低水泥环的腐蚀速率,是含硫气井固井水泥环在酸性环境下保持长期密封性及化学完整性的重要基础条件。
Downhole corrosion of acid gas well is one of the technical problems in the field of petroleum engineering. For the first barrier of wellbore, the corrosion research of cementing cement ring has drawn more attention. Aiming at the problems existing in the study of cement ring corrosion in downhole cementing wells, the corrosion mechanism of cement slurry in sulfur gas wells in Sichuan and Chongqing wells was explored by means of interfacial corrosion test and X-ray diffraction and scanning electron microscopy. The results show that: (1) The corrosion depth of cement stone is proportional to the partial pressure of H2S and the corrosion time; (2) The compressive strength of cement stone is inversely proportional to the partial pressure of H2S and the corrosion time; (3) The products gradually enriched, accumulated and migrated, resulting in a more stable compact layer or corrosion transition zone of cement stone. The porosity and permeability of cement stone after corrosion increased first and then decreased with the increase of corrosion time, and finally So that the corrosive medium into the interior of the cement becomes more difficult; ④ to ensure that the cement ring to maintain a certain depth of corrosion, as soon as possible to form a more stable corrosion transition zone or reduce the corrosion rate of the cement ring, cementing the sulfur gas well cementing ring Acidic environment to maintain long-term sealing and chemical integrity of the important basic conditions.