Enhanced gas recovery by CO2 injection : influence of monovalent and divalent brines and their concentrations on CO2 dispersion in porous media

Abba, MK

Abstract

This study aims to experimentally investigate the roles of different brine types and
concentrations on the longitudinal dispersion coefficient (KL) during enhanced gas recovery by
CO2 injection. Core flooding process was used to simulate the displacement of CH4 by
supercritical CO2 in a Buff Berea core sample at a pressure and temperature of 1400 psig and
50oC respectively, and a CO2 injection rate of 0.3 ml/min. Individual NaCl, KCl, CaCl2 and
MgCl2 solutions were prepared as test brines with ionic strengths (IS) of 1M, 2M, and 3M. The
results revealed that, at lower IS of 1M, MgCl2 and CaCl2 brines had the lowest KL while the
monovalent brines showed relatively higher KL. Divalent brines showed a higher degree of
salting out effects at higher concentrations resulting in higher KL. The salting and drying out
effects of divalent brines were responsible for higher CH4 recovery at 2M IS as CH4 comes out
of solution. A hyperbolic-type relationship exists between the two properties (KL and IS), where
KL decreases from 0 to 1M IS, and then increases sharply at IS >1M – this behaviour is most
pronounced in the divalent brines. Lowest contamination of the recovered CH4 was found to
be between formation water salinities of 5-15 wt.%, regardless of salt type, during EGR by
CO2 injection and sequestration. This study will not only present new knowledge on EGR
process but will also provide an avenue for establishing a screening criterion based on
formation water salinity for effective EGR process. This is a first experimental investigation
which establishes the relationship between salt types and concentration and the KL in porous
media.

Citation

Abba, M. (2020). Enhanced gas recovery by CO2 injection : influence of monovalent and divalent brines and their concentrations on CO2 dispersion in porous media. Journal of Natural Gas Science and Engineering, 84, 103643. https://doi.org/10.1016/j.jngse.2020.103643

• Journal Article Type: Article
• Acceptance Date: Sep 25, 2020
• Online Publication Date: Oct 9, 2020
• Publication Date: Dec 1, 2020
• Deposit Date: Sep 25, 2020
• Publicly Available Date: Oct 9, 2021
• Journal: Journal of Natural Gas Science and Engineering
• Print ISSN: 1875-5100
• Publisher: Elsevier
• Volume: 84
• Pages: 103643
• DOI: https://doi.org/10.1016/j.jngse.2020.103643
• Publisher URL: https://doi.org/10.1016/j.jngse.2020.103643
• Related Public URLs: https://www.journals.elsevier.com/journal-of-natural-gas-science-and-engineering