Abstract
Petroleum has still maintained its position among energy sources, and there is a considerable demand for its higher production. A viable process that could improve oil production is acid stimulation. In this process though, acid-induced emulsion and sludge formation may profoundly compromise its performance. This study concentrates on experimental evaluation of these drawbacks considering the influence of several chemical additives that are usually used in acid stimulation including corrosion inhibitor, corrosion inhibitor intensifier, suspending, and iron control agents. In addition, the effect of operating conditions such as the volumetric ratio of acid and crude oil, mixing shear, ferric ions concentration, and various acid systems were studied during emulsion phase separation and sludge formation. Acid systems including HCl 15 and 28 wt% solutions, spent HCl, hybrid (a mixture of HCl and acetic acid), and emulsified acids (HCl in diesel) were also investigated. The results confirmed that although the additives are necessary for their main functionalities, nonetheless, they postponed the emulsion phase separation for at least 30 min. They also showed only meagre impact on the amount of formed sludge (<1 %), and a meaningful relationship could not be established between their presence and sludge formation. The acid phase volumetric ratio had an inverse impact on emulsion stability in such a way that 10 times more emulsion break happened by increasing the volumetric ratio from 0.25 to 0.75. Unlike previous studies, ferric ions formed less stable emulsions due to the presence of corrosion inhibitor and iron control agents. However, they were not able to control sludge formation. In addition, hybrid and emulsified acids showed high acid-crude oil emulsion stability for all samples along with higher amounts of sludge. Finally, spent acid showed less affinity to form sludge and emulsion.
Published Version
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