Abstract
As the traditional polymer stabilizer is eliminated to improve the injectability of foam in low-permeability reservoirs, the stability, plugging capacity, conformance control and oil recovery performance of the surfactant-alternating-gas (SAG) foam become significantly important for determining its adaptability to permeability and heterogeneity, which were focused and experimentally researched in this paper. Results show that the SAG bubbles are highly stable in micron-sized channels and porous media (than in the conventional unconstrained graduated cylinder), making it possible to use in enhanced oil recovery (EOR). Such bubbles formed in porous media could be passively adjusted to match their diameter with the size of the pore. This endows the SAG foam with underlying excellent injectability and deep migration capacity. Permeability adaptability results indicate a reduced plugging capacity, but, increased incremental oil recovery by the SAG foam with decreased permeability. This makes it a good candidate for EOR over a wide range of permeability, however, parallel core floods demonstrate that there is a limiting heterogeneity for SAG application, which is determined to be a permeability contrast of 12.0 (for a reservoir containing oil of 9.9 mPa s). Beyond this limit, the foam would become ineffective.
Published Version
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