Enhanced Oil Recovery of Viscous Oil by Injection of Water-in-Oil Emulsion Made with Used Engine Oil

AbstractWater-in-Oil (W/O) emulsion has been proven to be an effective driving fluid for viscous oil (>100cp) recovery. However, finding an oil that is cheap and easily available to make the emulsion is a problem. In a recent patent, crude heavy oil was used to make W/O emulsions to recover the same oil in a sand pack flooding experiment, with almost 100% recovery achieved. This crude oil emulsion was stabilized by oleophilic nanoparticles without any surfactant required. However, its viscosity was unfavorably high: a 60% water content W/O emulsion is over 10 times more viscous than the original oil—far beyond the required level for mobility control, resulting in poor injectivity.This paper introduces a new idea of making W/O emulsion with a very common material— used engine oil. Over a billion gallons of engine oil are used in the US every year, and it has been a major contributor to pollution due to improper disposal. However this used engine oil could be a very good candidate to make W/O emulsions. First of all, the soot (organic carbons) from the breaking down of the engine oil provides perfect solid particles to stabilize the emulsion; secondly, its moderate viscosity permits an optimal viscosity to be achieved when making an emulsion. The detergent in the original engine oil and the acidity caused by oxidation of the oil may also help stabilize the W/O emulsions.In this research different types of used engine oil (mineral based, synthetic) were tested to make W/O emulsions simply by blending in brine. A series of stable emulsions were obtained with varied water contents from 40~70%. Viscosities of these emulsions were measured, ranging from 102~104 cp at low shear rates and ambient temperature. As a potential driving fluid, used engine oil emulsions can be targeted at various heavy oil reservoirs because of the wide viscosity range.