Evaluation of modified starches for improved oil recovery
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abstract
Hydrolyzed polyacrylamides (HPAM) products have been widely used as selective relative permeability modifiers in recovery processes. Limitations to these traditional products have prompted a search for cheaper, more stable, and environmentally friendly alternatives. This article describes rheological, chemical, and physical properties of selected modified starches and evaluates their effectiveness in oil recovery applications. Waxy corn and tapioca starches were used in concentrations ranging from 0.2 to 3% (m/v), prepared in 0 to 6% NaCl concentrations, heated to 95C and tested at various temperatures (25, 40, 60, 75, and 90C). An empirical rheological model to characterize the viscosity of the starches was developed, and results were used in a simulation model for performance testing. Injectivity studies were used to quantify polymer retention and adsorption. Simulations studies indicate that modified starch flooding showed an increase of 6 to 8% in cumulative oil production over a commercial polyacrylamide flooding. In addition, the results show superior performance and economic benefits in using modified starch rather than polyacrylamides in the simulated reservoir conditions. Benefits in increased fractional oil recovery and reduced water-oil ratio will lead to lower material costs, reduced water treatment and handling costs, and a better process efficiency.
