In the oil industry, it is important to increase the mobility of hydrocarbon fluids (oil and/or gas) and decrease the mobility of water. Doing so results in an increase in oil production and a decrease in unwanted water production. Polymers have been widely used to increase water viscosity, causing a decrease in water mobility. Surfactants have been used to change reservoir wettability and to clean the rock surface. The use of surfactants changes the formation wettability from oil wet to water wet. This results in an increase in oil production from various water wet sandstone and carbonate formations. Low water salinity has also been used to enhance oil recovery. The mobility of the oil should be more than the mobility of the water to ensure maximum extraction efficiency. As a result, viscosity measurements are very important in determining the impact of a viscous fluid in enhanced oil recovery (EOR). We measured the viscosity of mixed fluids used in the oil industry such as brines of varying concentration (Sodium Chloride and Calcium Chloride solutions) and various polymer solutions at different temperatures.

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We have examined the relationships between primary, secondary, and tertiary structures of polysaccharides exhibiting the rheological property of friction (drag) reduction in turbulent flows. We found an example of an exopolysaccharide from the yeast Cryptococcus laurentii that possessed high molecular weight but exhibited lower than expected drag reducing activity. Earlier correlations by Hoyt showing that beta 1 --> 3, beta 2 --> 4, and alpha 1 --> 3 linkages in polysaccharides favored drag reduction were expanded to include correlations to secondary structure. The effect of sidechains in a series of gellan gums was shown to be related to sidechain length and position. Disruption of secondary structure in drag reducing polysaccharides reduced drag reducing activity for some but not all exopolysaccharides. The polymer from C. laurentii was shown to be more stable than xanthan gum and other exopolysaccharides under the most vigorous of denaturing conditions. We also showed a direct relationship between extensional viscosity measurements and the drag reducing coefficient for four exopolysaccharides.

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