Mechanisms of synergistic enhancement of steam flooding by CO2 and chemical agents in heavy oil reservoirs

Key words:  steam flooding  heavy oil  carbon dioxide  chemical agent  deep heat transfer

Abstract:

In order to solve the problem that steam injection alone is difficult for heat transport into the deep layers of heavy oil reservoir, a steam injection technique assisted by adding carbon dioxide (CO₂) and chemical agents was proposed and investigated in this study. This technique can not only reduce the ineffective heat dissipation of steam, but also can expand the heat transport distance of steam. At the same time, CO₂ can be effectively captured and sequestered in the heavy oil reservoir, which is beneficial for greenhouse gas emission reduction. The results show that CO₂ and chemical agents can adsorb on the surface of steam condensing medium to form a heat insulation film, which can hinder the heat exchange between steam and heat transfer medium, slow down the heat release process, increase the heat transport distance of the steam, and thus mobilize the heavy oil from the deep formation. The experimental results show that the steam heat loss can be reduced by 5.48% with oil recovery rate increased by 14.5% under the synergistic effect of CO₂ and chemical agents. The results can provide theoretical guidance for the optimization of the gas and chemical-assisted steam flooding technique.