Residual water formation during the CO2 storage process in deep saline aquifers and factors influencing it: A review

Yi Li, P. G. Ranjith, M.S.A. Perera, Qingchun Yu

Research output: Contribution to journalReview ArticleResearchpeer-review

28 Citations (Scopus)


Of the various potential CO2 sinks available deep underground, saline aquifers are dominant due to their huge storage capacity and broad worldwide distribution. CO2 injected into deep saline aquifers is stored in them through various trapping mechanisms, of which residual or capillary trapping can achieve greater CO2 storage capacity. However, the formation of residual water that mainly occurs during the CO2 drainage process has a negative influence on this CO2 residual trapping process, because it acts as a barrier to the CO2 flow through the aquifer's pore channels. This study is a comprehensive review to identify the influence of residual water saturation on CO2 sequestration and factors affecting it.

There are number of influencing factors on the residual water formation process, which are mainly related to the physical properties of the reservoir and the injected CO2 properties and process. These factors include, CO2-brine interfacial tension (IFT)-related factors, contact angles in brine-CO2-rock systems, aquifer rock mass heterogeneity and mineral composition, the permeability and porosity of the aquifer, two-phase equilibrium, and CO2 injection rate and duration. However, it should be noted that these factors mutually contribute to residual water formation in saline aquifers during CO2 sequestration and therefore, the overall influence decides the efficiency of the final residual water formation in the aquifer. This work is a state-of-the-art report on the effectiveness and evaluation of reservoirs for CO2 storage purposes.

Original languageEnglish
Pages (from-to)253-262
Number of pages10
JournalJournal of CO2 Utilization
Publication statusPublished - 1 Jul 2017


  • Deep saline aquifers
  • Influencing factors
  • Residual trapping
  • Residual water saturation
  • Underground CO storage

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