(456a) The CO2-Solubility and Viscosity Enhancing Potential of CO2-Philes Functionalized With Aromatic Groups

Cummings, S., University of Bristol
Enick, R., University of Pittsburgh
Lee, J. J., University of Pittsburgh
Perry, R. J., Global Research, General Electric
Beckman, E. J., University of Pittsburgh

The low viscosity of CO2 at typical enhanced oil recovery (EOR) conditions is responsible for a poor mobility ratio that causes viscous fingering and poor sweep efficiency, leading to reduced efficiency and yield. To overcome this problem, there is a need to develop CO2-soluble additives that will increase the effective viscosity of CO2 without the use of a co-solvent. The only known polymeric direct thickener poly(fluoroacrylate-co-styrene) (polyFAST) has been shown to significantly increase the viscosity measured by falling cylinder viscometry and Berea sandstone core mobility experiments. The proposed mechanism of aggregation responsible for this viscosity enhancement is believed to be π-π stacking between aromatic rings. However, high molecular weight polymers like polyFAST require significant amounts of expensive fluorinated moieties in order to impart solubility. In addition to their cost, fluorinated compounds have undesirable environmental impacts.

Therefore, this work focuses on the development of less expensive and safer hydrocarbon-based CO2 thickeners.  Because our prior studies have demonstrated that unacceptably high pressures are required to dissolve non-fluorous polymers, this study entails the use of small, associating compounds to create a thermodynamic illusion of a polymer. Each CO2 thickening candidate consists of at least one non-fluorous CO2-philic segments and at least two slightly CO2-phobic functionalities that promote intermolecular aggregation (e.g. aromatic groups).  Solubilities of a range of newly synthesized molecules in CO2 and their associated viscosity enhancing abilities will be presented.  Preliminary results indicate that it is possible to design such novel CO2-thickening candidates that are up to 1wt% soluble in CO2 at pressures commensurate with EOR.