USING CO2-SOLUBLE SURFACTANTS TO IMPROVE MOBILITY CONTROL DURING CO2 ENHANCED OIL RECOVERY VIA THE IN-SITU FORMATION OF CO2- IN-BRINE FOAMS

摘要

CO2 flooding of oil formations is a commercial success, producing 280000 barrels of oil each day from domestic oilfields. This technology could become even more successful if the tendency for the extremely low viscosity CO2 to finger through the porous media (rather than uniformly sweeping through the reservoir) could be suppressed. The addition of small amounts of CO2-soluble, water-soluble, liquid, non-ionic surfactants to the supercritical CO2 allows CO2-in-brine foams or emulsions to be formed within the rock as the CO2-surfactant solution mixes with the brine in the pores. The resultant foam has far less mobility (i.e. a higher apparent viscosity) and higher sweep efficiency than pure CO2, thereby enabling more oil to be recovered with less CO2. In this work, we identify many inexpensive CO2 soluble surfactants, assess their ability to stabilize foams, measure the mobility of the foam flowing through porous media, and visualize the formation and movement of the foams using CT imaging of the high pressure displacement in porous media. The Huntsman branched, nonylphenol ethoxylate with ～12 EO units, Surfonic N 120, was particularly promising with respect to lab results and also appears to be a viable pilot-test candidate because it is very inexpensive, it is required in dilute concentration, and it exhibits a low pour point that inhibits freezing of the surfactant during the winter.