Typically, conventional reservoir simulators underestimate the recovery factor of heavy oil reservoirs under solution gas drive. We hypothesize that natural surfactants in oil (e.g. asphaltenes) cause this phenomenon in two ways: 1) by hindering the mass transfer rate of gas molecules through the gas-oil interface and 2) by enhancing the solubility of gas in the heavy oil. We investigate effect of surfactants on mass transfer rate of gas through gas-water interface and on the solubility of gas in oil. In bulk experiments, we observe that the addition of sodium dodecyl sulfate (SDS) does not influence the gas transfer rate while in the presence of a porous medium the growth of gas bubbles becomes increasingly difficult with increasing SDS concentration, which indicates that the interaction of the grain with fluids is an essential element in bubble growth in porous media. The effect a non-ionic surfactant on the solubility of methane in n-dodecane is also examined. The bubble point pressures of the gas+oil+surfactant system are determined experimentally.It is found that the bubble point pressures of the system decrease with increasing surfactant concentration, i.e., the surfactant enhances the solubility of methane in the oil.


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