Success of SAG Foam Processes in Heterogeneous Reservoirs

In principle, miscible gas injection can displace nearly all<br>of the oil from the portions of a reservoir swept by gas.<br>However, reservoir heterogeneity, low gas density and high<br>gas mobility reduce sweep efficiency and drastically decrease<br>recovery. Fortunately, the use of foam can reduce gas mobility<br>and the effect of heterogeneity and therefore increase sweep<br>efficiency. Based on the work of Shan and Rossen, an optimal<br>design strategy is proposed here for surfactant-alternating-gas<br>(SAG) foam processes and tested in a homogeneous reservoir<br>and in two layered rectangular reservoirs. Fractional-flow<br>theory, Stone’s and Jenkins’ model for gravity segregation,<br>and an idealized model developed by Shan and Rossen are<br>used design the process and interpret the results.