Impact of gas/liquid phase change of CO2 during injection for sequestration

Journal of the Mechanics and Physics of Solids
By: , and 

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Abstract

CO2 sequestration in deep saline formations is an effective and important process to control the rapid rise in CO2 emissions. The process of injecting CO2 requires reliable predictions of the stress in the formation and the fluid pressure distributions – particularly since monitoring of the CO2 migration is difficult – to mitigate leakage, prevent induced seismicity, and analyze wellbore stability. A key aspect of CO2 is the gas–liquid phase transition at the temperatures and pressures of relevance to leakage and sequestration, which has been recognized as being critical for accurate predictions but has been challenging to model without ad hoc empiricisms.
This paper presents a robust multiphase thermodynamics-based poromechanics model to capture the complex phase transition behavior of CO2 and predict the stress and pressure distribution under super- and sub- critical conditions during the injection process. A finite element implementation of the model is applied to analyze the behavior of a multiphase porous system with CO2 as it displaces the fluid brine phase. We find that if CO2 undergoes a phase transition in the geologic reservoir, the spatial variation of the density is significantly affected, and the migration mobility of CO2 decreases in the reservoir. A key feature of our approach is that we do not a priori assume the location of the CO2 gas/liquid interface – or even if it occurs at all – but rather, this is a prediction of the model, along with the spatial variation of the phase of CO2 and the change of the saturation profile due to the phase change.
Publication type Article
Publication Subtype Journal Article
Title Impact of gas/liquid phase change of CO2 during injection for sequestration
Series title Journal of the Mechanics and Physics of Solids
DOI 10.1016/j.jmps.2025.106232
Volume 203
Year Published 2025
Language English
Publisher Elsevier
Contributing office(s) Earthquake Science Center
Description 106232, 14 p.
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