Application of foam flooding for residual oil production in granitoid cores from the “X” oil field in Kazakhstan

Foam has been recognized as a diverting agent that enhances sweep efficiency. Foam flooding is also speculated to improve microscopic displacement efficiency in the reservoir core by the same mechanism. Incremental recovery of remaining oil in "X" oilfield core following sequential waterflooding and immiscible gas flooding is investigated using foam with both N₂ and CO₂.

Limited laboratory tests on "X" oilfield core indicated excellent enhanced oil recovery (EOR) potential by foam processes, with and without the inclusion of nanoparticles. The recovery process sequence was repeated with Berea and Indiana limestone for comparison. The baseline analyses for gas flooding across all lithologies indicated that immiscible CO₂ flooding is more efficient than N₂ flooding, presumably due to increased interaction mechanisms for CO₂ with both water and oil. Without the incorporation of nanoparticles, N₂ foam flooding was superior to CO₂ foam, as seen from the average enhanced recovery of 8.15 % of Original Oil in Place (OOIP) for the "X" core samples using N₂ foam compared to 2.45 % with CO₂ foam. The superior performance of N₂ foam was consistent also with Berea and Indiana limestone tests. Additionally, the introduction of nanoparticles to the foam system further improved recovery, with an average increase of 5.05 % in the recovery factor. However, the greater apparent viscosity of the N₂ foam with nanoparticles (around 9 cP) is undesirable, since it might impair injectivity and interwell mobility despite significant recovery efficiency improvement. Overall, the study results show that foam flooding is a promising option for sweep efficiency improvement in "X" oilfield core.