The need to enhance oil recovery after long term water flooding has propelled much studies owing to the fact that water production problems become eminent and oil recovery declines. In such situations, it has been seen that huge quantities of oil still remains un-swept in the low permeability areas. As of such, many oil recovery enhancement techniques have already been proposed. One of them is foam: a dispersion that is formed by trapping gas in a liquid and stabilizing by surfactants but with an inevitable drawback of being an unstable thermodynamic system. Therefore, gels and polymers have to be added in order to achieve better stability. Unfortunately, in high-temperature and high-salinity reservoirs, the elevated temperatures and high divalent cations concentration limit the use of polymers and gels. To this effect, there is need to develop high-performance surfactants that can form relatively stable foam in harsh environs.
Recently, a team of researchers led by Professor Caili Dai from China University of Petroleum (East China) and associate professor Qing You from China University of Geosciences (Beijing) developed a novel low interfacial tension nitrogen foam that has good formability and potential to reduce interfacial tension to a low level in high-temperature and high-salinity reservoirs. In order to achieve this and understand the foam displacement mechanisms, the researchers purposed to utilize the flat-panel sand model to simulate reservoirs on a larger scale. Their work is currently published in the research journal, Energy & Fuels.
The research method employed entailed the fabrication of the novel low interfacial tension (LIFT) nitrogen foam by using an amphoteric surfactant and sodium formate. Next, the researchers systematically studied the influence of surfactant concentration, organic bases concentration and the aging effect on the performances of the LIFT foam system through the modified Ross-Miles experiment. Finally, the researchers cross-examined the foam displacement capability in flat-panel sand model and etched-glass micromodels so as to analyze the foam displacement mechanisms for enhanced oil recovery.
From the experimental work undertaken, the authors observed that the LIFT foam had the capability to block high permeability channels and divert the following injection fluid to adjacent low permeability areas efficiently, from the case of the flat-panel sand model experiment. It was also seen that upon injection of the LIFT foam, a uniform pressure increase in the entire model was recorded. Finally, the etched-glass micromodel empirical setup revealed that the LIFT foam could block the high-permeability channels and improve sweep efficiency.
The study has presented the optimization of a novel LIFT foam system with excellent foaming ability, and has potential to reduce the interfacial tension to a low level in high-temperature and high-salinity reservoirs. It has been seen that when utilized in porous media, the foam can enhance oil recovery through the Jamin effect, squeezing effect, and dragging effect. Altogether, a comparison between the LIFT foam system and the common foam has shown that the former can emulsify oil and strip oil film from model surfaces with more ease and thus enhance oil recovery more easily.
Jiaping Tao, Caili Dai, Wanli Kang, Guang Zhao, Yifei Liu,Jichao Fang, Mingwei Gao, Qing You. Experimental Study on Low Interfacial Tension Foam for Enhanced Oil Recovery in High-Temperature and High-Salinity Reservoirs. Energy Fuels 2017, volume 31, pages 13416−13426Go To Energy Fuels