Abstract

Solvent-based method is an important method for recovering heavy oil. In the case of solvent flooding, its sweeping efficiency might be adversely affected by the sharp difference in mobility between solvent and heavy oil. It is of great importance to develop new techniques for decreasing the mobility of solvent phase. Solvent-alternating-surfactant injection, where foam creation can be expected, might be a feasible approach for achieving such purpose by increasing the apparent viscosity of solvent phase. The foam stability plays an important role in this process. In this study, the foam stability of C3H8/surfactant/heavy-oil system under reservoir condition has been examined experimentally by using the pressure/volume/temperature (PVT) system. The following factors are considered in the experiments: surfactant concentration, salinity, temperature, and the presence of pure C16H34 as pseudo-heavy oil. During the experiments, foam is generated by sparging C3H8 at a constant flow rate through the surfactant Triton X-100 solution and then stirring the mixture with a magnetic stirrer. The foam stability is subsequently evaluated in terms of its height change as a function of time. The critical micelle concentration (CMC) of surfactant Triton X-100 is confirmed firstly by conducting three runs of experiments at three different surfactant concentrations. Then the foam stability tests are performed by using such validated CMC at different salt concentrations and different temperatures. It is found that the increasing surfactant concentration contributes to an increase in foam stability, while foam stability is insensitive to surfactant concentration when the surfactant concentration is above the threshold CMC. An elevated temperature is detrimental to foam stability. At a higher temperature, the effective surfactant CMC also increases. Foam stability is negatively affected by increasing salinity; but such negative effect is found to be in small scale. As the C16H34 is added to the solution, significant decrease of foam stability occurs.

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