Visualization of CO2 foam generation, propagation and sweep in a complex 2D heterogeneous fracture network

Abstract In this work, a visual two-dimensional (2D) heterogeneous fracture network model was designed to investigate CO2 foam generation, propagation and sweep with two different injection strategies (co-injection, COI; and surfactant solution alternating gas, SAG). In addition, gravitational effect was explored by this fracture model. In the case of the optimum foam quality (fg = 0.67), the results indicated the COI could form stable foam morphologies and differential pressures (ΔP), while the foam morphologies and ΔP showed a dynamic trend during each cycle of SAG. The ΔP of larger slug injection can establish 6–12 times than smaller slug injection in the fractured system. Because of CO2 breakthrough, the total sweep efficiency of continuous gas injection (CGI, 42%) and SAG (66%) were lower than COI (81%). Gravitational effect is insignificant during COI, whereas gravity has a considerable effect on SAG in terms of ΔP and sweep efficiency. As a result of gravitational effect, the entire ΔP curve decreased and required more fracture volume (FV) injected to achieve the final sweep efficiency during SAG. The results of this study provide preliminary observations that can provide new insights into mobility control by using CO2 foam in fractured tight reservoirs.