We report a novel type of viscosity modifier relying on the supramolecular assemblies that have pH-adjustable viscosities and robust tolerance against high temperatures and salinities, and are resistant to shear-induced degradation. This technology is developed collaboratively by Texas A&M University, Incendium Technologies, and VaalbaraSoft.
When reservoir oil is displaced by plain waterflooding, the injected water fingers through the reservoirs because of the high mobility ratio (Rachford Jr. 1964). Water fingers leave most of the oil behind, which leads to inefficient oil recovery. Hence, the viscosity modifiers are often added in the displacing fluid, (i.e., water) to better match the viscosity of reservoir oil and enable a uniform advance of the waterfront to effectively sweep the reservoir oil.
Currently, for oil recovery applications, most commonly used viscosity modifiers are water-soluble polymers such as hydrolyzed polyacrylamide, polyvinyl alcohol, and poly(vinylpyrrolidone) (Taylor and Nasr-El-Din 1998). Likewise, water-soluble biopolymers, in particular polysaccharides such as xanthan and guar, are also used in some fields (Alquraishi and Alsewailem 2012).
Current Technology Limitations
While the above-mentioned viscosity modifiers can satisfy part of the oil recovery needs, these polymers still experience some challenges that hinder their effectiveness. For example, when the viscosity of reservoir oil is high, so should the displacing fluid be to match the mobility ratio. The current heuristics suggest that polymer flooding should be applied in reservoirs with oil viscosities between 10 and 150 cP (Taber et al. 1997).
The key factor limiting the recommended range is that for oil viscosities greater than 150 cP, the injected-water-viscosity values required for a favorable mobility ratio correspond to prohibitively low values of polymer injectivity. In addition, pumping high-viscosity displacing fluids tends to lead to clogging in oil wells, which results in a major economic well operating loss.
One potential solution is to use dis-placement fluids with an adjustable viscosity, with the fluid having a low viscosity at the injection site and a high viscosity upon reaching the oil phase. Furthermore, having an adjustable-viscosity displacement fluid can help to reduce pumping-related operational costs because pumping efficacy generally decreases as fluid viscosity increases. The above-mentioned polymers do not offer viscosities that can be controlled in such a fashion.