Critical Thresholds for Deep CO2 Foam Generation: Effects of Injected Quality, Surfactant Concentration and Permeability

B. Wei, M. Yang, J. Tang, Y. Wang, J. Lu, W. R. Rossen

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Long-distance propagation of foam is one key to deep gas mobility control for enhanced oil recovery and CO2 sequestration. It depends on two processes: convection of bubbles and foam generation at the displacement front. Prior studies with N2 foam show the existence of a critical threshold for foam generation in terms of a minimum pressure gradient or minimum total interstitial velocity, beyond which strong-foam generation is triggered. The same mechanism controls foam propagation. There are few data for or for CO2 foam. We extend previous studies to quantify and for CO2 foam generation, and relate and with factors including injected quality (gas volume fraction in the fluids injected) - fg, surfactant concentration - Cs, and permeability - K. In each experiment, steady pressure gradient, ∇p, is measured at fixed injection rate and quality, with total interstitial velocity, vt, increasing-then-decreasing in a series of steps. The trigger for strong-foam generation features an abrupt jump in ∇p upon an increase in vt. In most cases, the data for ∇p as a function of vt identify three regimes: coarse foam with low ∇p, an abrupt jump in ∇p, and strong foam with high ∇p. The abrupt jump in ∇p upon foam generation demonstrates the existence of and for CO2 foam. We further show how and scale with fg, Cs and K. Conditions that stabilize lamellae reduce the values of the thresholds: both and increase with fg and decrease with increasing Cs or K. Specifically, scales with fg as (fg)2 and scales as (fg)4, and both and scale with Cs as (Cs)−0.4. The effect of K on the thresholds for foam generation is greater than the effects of fg and Cs. Our data in artificial consolidated cores show that scales with K as K−2 for CO2 foam, in comparison to K−1 for N2 foam in unconsolidated sand/bead packs. More data are needed to verify the confidence of these correlations. It is encouraging that in the cores with K = 270 mD or greater is less than 0.17 bar/m (~ 0.75 psi/ft), 2 to 3 orders of magnitude less than for N2 foam. Such low can be easily attainable throughout a formation. This suggests that: limited ∇p deep in formations is much less of a restriction for long-distance propagation of CO2 foam than for N2 foam. Foam propagation could still be challenging in low-K reservoirs (~ 10 bar/m for K = 27 mD). Nevertheless, formation heterogeneity and alternating slug injection of gas and liquid help foam generation and may well reduce the values of. More research is needed to predict long-distance propagation of foam under those conditions.

Original languageEnglish
Title of host publicationSociety of Petroleum Engineers - SPE Improved Oil Recovery Conference, IOR 2024
PublisherSociety of Petroleum Engineers (SPE)
ISBN (Electronic)9781959025245
Publication statusPublished - 2024
Event2024 SPE Improved Oil Recovery Conference, IOR 2024 - Tulsa, United States
Duration: Apr 22 2024Apr 25 2024

Publication series

NameProceedings - SPE Symposium on Improved Oil Recovery


Conference2024 SPE Improved Oil Recovery Conference, IOR 2024
Country/TerritoryUnited States

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Geotechnical Engineering and Engineering Geology


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