Effect of water salinity on surfactant-stabilized water-oil emulsions flow characteristics

Turbulent frictional drag and high pressure drop in acid stimulation treatments limit the injection rate. Consequently, frictional pressure drop reduction is highly desirable. Flow loop experiments were conducted to study the effect of water salinity on the flow characteristics of surfactant stabilized emulsions with volumetric water to oil ratio of 70/30 (the preferable composition while emulsified acid use). The emulsion stability, type, droplet size, and shear dependent viscosity were correlated to pressure drop in a flow loop consisting of 2.54-cm and 1.27-cm diameter horizontal pipes test sections at 25 °C. At low aqueous phase salinity (≤5 kppm), oil-in-water (O/W) emulsions were formed, and their stability decreased with increasing salinity. Although the same mixing procedure was followed, increasing the aqueous phase salinity (≥20 kppm) resulted in water-in-oil (W/O) emulsions and their stability was enhanced with increasing salt concentration. In addition, the results showed a significant reduction in emulsion viscosity as well as pressure drop with decreasing water salinity, especially for W/O emulsions (salinity ≥20 kppm). For W/O emulsion in laminar flow conditions, the friction factor was reduced by up to 36.4% when pipe diameter was decreased from 2.54-cm ID to 1.27-cm ID as a result of a reduction in droplet size. Based on the available results, controlling the aqueous phase salinity as well as droplet size can be used as a friction loss reduction method for the emulsified acid flow.