Indirect and direct thickening of hydrocarbon liquids as novel hydraulic fracturing and enhanced oil recovery fluids

Mobility control is essential for successful improved or enhanced oil recovery process and can be achieved by injecting a fluid with ideal rheological properties. In water sensitive reservoirs where the use of conventional water-based fluids are impractical, oil-based fluids are a promising alternative. Natural gas liquid (NGL) has become an increasing attractive base fluid for mobility control applications. However, the challenges related to the poor mobility of the fluid resulting from its low density and viscosity must be overcome. Directly or indirectly thickening are promising techniques that modify the rheological properties of NGL to improve fluid mobility. A three-task plan was developed to investigate the direct rheological modification of NGL and characterize these properties in bulk and porous media. The solubility of the chemical additives was investigated in different solvents to represent NGL, including n-hexane and n-pentane. Next, the bulk rheology experiments were conducted to determine the impact of additive concentration, effect of temperature, hysteresis, and NGL composition to properly characterize the rheological properties of the thickened fluid. The third task considered the characterization of thickened fluid in porous media and determine if there was a correlation between bulk and apparent viscosity. An additive was identified that was successful in thickening both n-hexane and n-pentane significantly at additive concentrations as low as 0.25 wt.% at shear rates ranging from 1 s⁻¹ to 2500 s⁻¹⁻. The experiments in porous media combined with bulk viscosity measurements indicated that the sand-pack possibly acted as a natural method of mixing that aided in the viscosity enhancement of the fluid and the formations of macrostructures. Indirect thickening involves foaming the oil-based fluid. The experimental design to test the foaming surfactants involved a two-part additive screening. The additives were investigated in a single hydrocarbon fluid to determine their foaming potential. The additives were then tested in a multiple hydrocarbon system to determine if the addition of a secondary component may promote foamability or stability. Foaming additives were identified that stabilized foam in 100% diesel during the initial screening. Select additives were also successful in promoting foamability and stability in a n-pentane and crude oil mixturePetroleum and Geosystems Engineerin