The efficiency of carbon dioxide flooding is hindered by mobility problems resulting from the unfavorable mobility ratio, λCO2/λoil. Several approaches were tested in the past to improve CO2 flooding efficiency (16). One approach attempted direct thickening of CO2 by dissolving a commercially available polymer in the CO2. In this paper a novel idea to increase the CO2 viscosity is presented. The increasing of CO2 viscosity is attempted by insitu polymerization of monomers miscible with CO2. The polymerization is done while the monomer (solute) is in the CO2 supercritical phase (solvent). CO? viscosity changes are evaluated by direct measurement using a high pressure Ruska rolling ball viscometer.

Several runs have been made and polymerization has been successfully achieved – in the presence of CO2 supercritical phase – as evidenced by NMR and infrared spectrophotometry. Both gas and liquid phase monomers, measured at standard conditions, were tried and both were polymerized. Polymerization initiators that were used consist of commercially available peroxides with a weak O-O bond. Polymerization was carried out at approximately 160°F and 1800 psi. The values of temperature and pressure are typical for oil reservoirs in which CO2 is applied as a miscible fluid. Further evaluation of viscosity changes are done by flowing the mixture of CO2 and polymer in a high pressure sandpack.

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