This study examined the composition and characteristics of scales formed at different depths in an oil production well, which had developed over years of well operation, workovers, and interventions, by the combined use of optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction. The iron-rich scales consist of several mineral phases, including a dominant portion of akagneite and hibbingite, some barite, silicon dioxide, copper sulfide, and small amounts of iron oxide and calcium carbonate. The scales typically have a layered structure consisting of five to six distinct layers, which impacts steel corrosion processes. The type of corrosion beneath the scale surface was found to be diversified. Pitting morphology corresponding to different stages in the development of scales was observed. The relation between pitting density and the extent of corrosion was analyzed. The effects of environmental factors, including calcium, chlorine, oxygen content, steel microstructure, and multiphase flow, on scale formation and corrosion mechanisms, were discussed. The results provide important insights into the formation of scales and the under-deposit corrosion processes in the oil production tubes.

中文翻译：

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某采油井结垢特征及其对沉积下腐蚀的影响

本研究结合光学显微镜、扫描电子显微镜、能量色散 X-射线光谱、透射电子显微镜和 X 射线衍射。富含铁的鳞片由几种矿物相组成，包括主要部分的赤霞石和辉沸石、一些重晶石、二氧化硅、硫化铜以及少量的氧化铁和碳酸钙。鳞片通常具有由五到六个不同层组成的分层结构，这会影响钢的腐蚀过程。发现水垢表面下的腐蚀类型多种多样。观察了鳞片发育不同阶段对应的点蚀形态。分析了点蚀密度与腐蚀程度之间的关系。讨论了环境因素，包括钙、氯、氧含量、钢微观结构和多相流，对水垢形成和腐蚀机制的影响。结果为石油生产管中水垢的形成和沉积物下腐蚀过程提供了重要的见解。