Laboratory Study Investigating Emulsion Formation in the Near-Wellbore Region of a High Water-Cut Oil Well

Abstract

Summary An experimental study was conducted to determine the morphology of oil/water mixtures produced into a high water-cut well. This information is important for determining the feasibility of downhole oil/water separation. Core-flow and microflow experiments were performed to simulate the two-phase flow process in the near-wellbore region of a high water-cut well. In the core-flow experiments the morphology of oil/water mixtures leaving different types of porous media was observed and the droplet-size distribution was determined for different fluid properties and flow parameters. In the microflow experiments the flow regimes and breakup mechanisms of the oil phase in the pore space were visualized and observed. The experimental results show that the oil/water mixture emerging from the porous medium depends strongly on its wettability. When the porous medium is oil-wet, the produced oil is mainly in the form of large drops that are formed at the porous end face. From water-wet porous media, small oil droplets are produced at high flow rates; their sizes are typically of the pore size's order and are formed inside the porous medium. A correlation between the droplet size and relevant fluid, and flow and porous-medium parameters has been developed, allowing for the assessment of circumstances in which downhole separation can be problematic. The experimental results have also shown that in water-wet porous media a transition from capillary-dominated to dispersed flow takes place in the capillary number range investigated (10-5<Nc<10-3).