Pressure Drop Reduction of Stable Water-in-Oil Emulsion Flow: Role of Water Fraction and Pipe Diameter

Abstract

Abstract Emulsified acids provide significant benefits in stimulating oil and gas wells by slowing the reaction rate with carbonates and reducing corrosion in the tubular goods. However, pumping emulsified acids can result in high friction losses and hence reducing stimulation effectiveness. Therefore, reducing friction pressure loss is an important factor in expanding the application of emulsified acids. This experimental work aims to investigate a possible friction reduction through the control of water fraction as well as pipe diameter. Surfactant-stabilized water-in-oil emulsions with different water fraction were created. Pressure drop measurements of the flow of all formed emulsions were conducted in a flow loop consisting of 1-in and 0.5-in horizontal pipe diameters at 77 oF emulsion temperature. Such results were explained in terms of emulsion viscosity as well as the average droplet size and distribution of the emulsion dispersed phase (water). The results showed that stable water-in-oil emulsions are strong function of the dispersed water fraction. As water fraction increased, emulsion pressure drop increased. This was attributed to the increase in the emulsion viscosity due to an increase in the water fraction. Therefore, water-in-oil emulsion frictional pressure drop can be reduced by reducing water fraction. In addition, decreasing pipe diameter from 1-in to 0.5-in resulted in up to 74% reduction in emulsion friction factor and such dependency was clearer as water fraction increased. Introduction Under certain conditions, the injection of water into a crude oil pipeline results in a significant reduction of pressure loss, thereby facilitating oil transportation. Therefore, cocurrent flow of oil and water in pipelines has attracted the interest of researchers (Russel et al. (1959), Charles et al. (1961), Hasson et al. (1970), Oglesby et al. (1979), Arirachakaran et al. (1989), Valle and Kvandal (1995), Beretta et al. (1997), Angeli and Hewitt (2000), Soleimani et al. (2000) and Al-Yaari et al. (2008, 2009 & 2012)). However, the majority of studies reported in the literature, is mainly focused on either oil-water flow patterns or separated flows. The pipeline flow behavior of water-in-oil and/or oil-in-water emulsions has received less attention compared with separated flows.