Pore-Scale Determination of Residual Gas Remobilization and Critical Saturation in Geological CO2 Storage: A Pore-Network Modeling Approach

Ramin Moghadasi*, Sajjad Foroughi, Farzad Basirat, Steven R. McDougall, Alexandru Tatomir, Branko Bijeljic, Martin J. Blunt, Auli Niemi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
25 Downloads (Pure)

Abstract

Remobilization of residually trapped CO2 can occur under pressure depletion, caused by any sort of leakage, brine extraction for pressure maintenance purposes, or simply by near wellbore pressure dissipation once CO2 injection has ceased. This phenomenon affects the long-term stability of CO2 residual trapping and should therefore be considered for an accurate assessment of CO2 storage security. In this study, pore-network modeling is performed to understand the relevant physics of remobilization. Gas remobilization occurs at a higher gas saturation than the residual saturation, the so-called critical saturation; the difference is called the mobilization saturation, a parameter that is a function of the network properties and the mechanisms involved. Regardless of the network type and properties, Ostwald ripening tends to slightly increase the mobilization saturation, thereby enhancing the security of residual trapping. Moreover, significant hysteresis and reduction in gas relative permeability is observed, implying slow reconnection of the trapped gas clusters. These observations are safety enhancing features, due to which the remobilization of residual CO2 is delayed. The results, consistent with our previous analysis of the field-scale Heletz experiments, have important implications for underground gas and CO2 storage. In the context of CO2 storage, they provide important insights into the fate of residual trapping in both the short and long term.

Original languageEnglish
Article numbere2022WR033686
JournalWater Resources Research
Volume59
Issue number6
Early online date20 Jun 2023
DOIs
Publication statusPublished - Jun 2023

Keywords

  • critical saturation
  • gas remobilization
  • geological CO storage
  • pore-network modeling
  • residual trapping

ASJC Scopus subject areas

  • Water Science and Technology

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