The study of bubble size distribution in reservoir during foam flooding and optimization design of gas alternating foaming liquid injection

Foam flooding is one of the enhanced oil recovery (EOR) technologies that have great development potentials. The theoretical models of foam flooding at present include empirical models and mechanism models. The empirical models usually simplify the blocking effect of foam system in porous medium as a reduction coefficient of fluid mobility (mainly for gas phase). The mechanism models introduce the processes of foam propagation and decay, and its numerical simulation theory views these two processes as chemical reactions that involve reactants and products. However, these two kinds of foam models do not represent the micro-mechanical effects between the gas bubble and pore-throat in porous medium. In this work, a geometric model of pore-throat was established based on the core data of rate-controlled porosimetry. Then, the snap-off time of generating gas bubble in core sample was calculated with the data of foam flooding experiment. Finally, combined with numerical simulation, the distribution of bubble size in reservoir during foam flooding was calculated. Comparing different plans of gas alternating foaming liquid injection, it was found that when consuming the same amount of gas and foaming liquid, the increasing-ratio of gas alternating foaming liquid injection has a larger sweep range of foam and a more extended zone of effective-sized bubble than the constant-ratio injection does, which indicates that the increasing-ratio of gas alternating foaming liquid injection has a higher efficiency.