Selection and Optimization of Demulsifier Based on Physio-Chemical Characteristics of Emulsion

Abstract

The presence of crude oil/water emulsions is a burden in the petroleum industry. It leads to several operational and economic issues related to crude production, transportation, and refining processes. The stability of the emulsified oil is affected by water content, presence of organic/inorganic materials, formation brine salinity, and temperature. In reservoir fluid studies, applying chemical demulsifiers on emulsion samples is common to break the emulsion and reduce the water content to an acceptable level (less than 1 wt. %) to generate representative fluid composition results. However, this process depends heavily on the crude and the water compositions and the type of demulsifier used. An incompatible choice of demulsifier could strengthen the emulsion's stability or alter the fluid composition. This introduces the need to understand specific physiochemical properties to identify the root causes of demulsifier ineffectiveness. In this study, two demulsifiers containing different functional groups (Type 1 and Type 2) were evaluated for their emulsion breakage ability. Nine oil samples from various fields were mixed with formation water in the first round and seawater in the second. The water-oil ratio of 80:20 was achieved using a blender for 1.5 minutes at 300 RPM. Saturates, Aromatics, Resins, and Asphaltene (SARA), viscosity, density, and sulfur content were determined for all oil samples. Furthermore, chemical analysis was conducted on all water samples to determine Total Dissolved Solids (TDS). After applying both demulsifiers at the same concentration (1% of total volume), separated water volumes were measured at 5, 10, 15, and 20 minutes and used to calculate the emulsion separation index (ESI). Results of this work showed that Type 1 demulsifier performed better than Type 2 in the formation water and seawater and while using different oils due to the resistance of the non-ionic surfactant to salinity, polarity, and water hardness. This study shows a methodology for effectively determining the optimum chemical demulsifier type to break emulsions by adequately understanding the chemistry of the oil, brine, resulting emulsions, and demulsifiers used.