NMR Studies of the Effect of CO2 on Oilfield Emulsion Stability

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• 作者：Nicholas N. A. Ling ; Agnes Haber ; Thomas J. Hughes ; Brendan F. Graham ; Eric F. May ; Einar O. Fridjonsson ; Michael L. Johns
• 刊名：Energy & Fuels
• 出版年：2016
• 出版时间：July 21, 2016
• 年：2016
• 卷：30
• 期：7
• 页码：5555-5562
• 全文大小：471K
• 年卷期：0
• ISSN：1520-5029

文摘

Formation of water-in-crude oil emulsions is a pervasive problem for crude oil production and transportation. Here we investigate the effectiveness of a comparatively low pressure CO₂ treatment in terms of breaking these water-in-crude oil emulsions. To this end, we used unique benchtop nuclear magnetic resonance (NMR) technology to measure the droplet size distribution (DSD) of the emulsions. Treatment with 50 bar CO₂ for 2 h resulted in significant emulsion destabilization; this was replicated when CO₂ was replaced by N₂O, which has a solubility in both the aqueous and oil phases similar to that of CO₂. Low solubility gases, N₂ and CH₄, by contrast had no effect on emulsion stability. Treatment with CO₂ was also found to have no effect on a model water-in-paraffin oil emulsion stabilized by a synthetic surfactant (Span 80). Collectively, this supported the hypothesis that emulsion destabilization results from CO₂ precipitation of asphaltenes as opposed to emulsion droplet film disruption during depressurization, which are the two competing theories reported in the literature to explain the observed supercritical CO₂ destabilization of emulsions. Treatment of a water-in-crude oil emulsion featuring partial removal of asphaltenes from the oil phase was consistent with this hypothesis, as the effect of the CO₂ treatment on emulsion destabilization was significantly more pronounced.