Interaction of Water-Based Drilling Additives with Arab Heavy Crude Oil Emulsions: Impact on Rheology and Separation Behavior

Abstract

Crude oil is produced as an emulsion, where the naturally occurring interfacially active species present in the crude help to emulsify the formation water or injected water. The behavior of the emulsion is significantly impacted by the existing physicochemical factors such as external chemical species, temperature, pressure, and shear rate or mixing intensity. The drilling additives utilized during drilling operations can potentially impact the flow and separation behavior of water in a crude oil emulsion. Herein, we studied the impact of three water-based drilling fluid additives on emulsions’ rheological and separation behavior as a function of water cut, temperature, and additive concentration. The crude oil forms tight and stable emulsions concomitant with its high asphaltene content with brine and does not separate without a demulsifier, even at a temperature of 76.5 °C. The impact of the drilling additives on the emulsion separation behavior in the absence of a demulsifier was not prominent except for the pusher pill, which induces some separation above 37.8 °C with a resulting emulsion separation index of 15–35%, depending upon the temperature and concentration. We also observed a favorable or detrimental impact of the drilling fluid additives on the demulsifier’s separation action depending upon the water cut and temperature of the system. The drilling additives tested in this study impact the emulsion behavior, favorable or detrimental, depending upon the type and concentration of the additive used, temperature, and water cut of the system.