Coinjecting of steam with surfactant to recover heavy crude oil is studied. Performance production of this process is achieved through analysis of the formed emulsions which provides mechanistic understanding of crude oil and surfactant interaction in the presence of steam.
Surfactants are used to reduce the interfacial tension between water and oil. While the nonpolar tail of a surfactant stays in the oil phase, its polar side remains in the water phase. Surfactant literature is in general built on light oil reservoirs, which form mostly by nonpolar hydrocarbons. However, for high-viscosity crude, the situation can be different due to its high-polarity components. Asphaltenes and resins are known as the polar components of crude oil, while saturates and aromatics are the nonpolar. Therefore, steam and surfactant-steam flood experiments were conducted on a heavy crude oil sample with low API gravity, high viscosity, and high polar fraction content. Firstly, the crude oil sample was blended with anionic surfactant solution via magnetic stir and formed emulsion phases were characterized. To determine steam’s effects, emulsions were exposed to steam and evaluated by optical microscopy, Fourier Transform Infrared Spectroscopy, dielectric constant, and zeta potential measurements. Secondly, core flood experiments were carried on to evaluate the surfactant-steam process. Lastly, produced oil samples from two flooding tests were analyzed under optical microscopy and the impact of polarity and ionic bond interaction were investigated on produced oil, produced water, and produced polar asphaltene samples.
Dielectric constant measurements is introduced as an indirect method to determine polarity and enhance emulsion characterization for heavy crude oils. It was observed that the high amounts of asphaltenes and resins in crude oil favor emulsion formation in steam process due to polar fractions of crude oil which are known as emulsifiers. However, zeta potential measurements showed that in surfactant-steam process emulsion formation is promoted due to electrical attraction of anionic head of surfactant with inorganic surface morphology of asphaltenes.
Our results provide important information on how the surfactant-steam process can be successful in heavy oil reservoirs that consist different amounts of polar components with high inorganic content. Developing the right emulsion characterization tools such as electrical properties will assist in choosing the best surfactant candidates for different heavy crude oils with high polar components, facilitating the surfactant-steam flooding processes.