# Assessing salt precipitation and weak acid interaction in subsurface CO2 injection: Potential 50% strength decline in near-wellbore reservoir sandstones

**Authors:** Mohammad Nooraiepour, Krzysztof Polanski, Mohammad Masoudi, Szymon Kuczynski, Hannelore Derluyn, Liebert Parreiras Nogueira, Bahman Bohloli, Stanislaw Nagy, Helge Hellevang  
**arXiv:** [2401.14852](https://arxiv.org/abs/2401.14852)  
**Date:** 2024-01-26  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2401.14852v2/

## Key points

- Predictive modeling is crucial for understanding physico-chemical processes and potential challenges for scale-up in CO2 storage sites.
- Dramatic injectivity decline can occur due to salt precipitation pore clogging in high-salinity reservoirs, even over a short period.
- The study investigates the adverse impact of CO2-induced salt crystallization on the geomechanical properties of near-wellbore reservoir sandstones.
- Laboratory experiments involved geochemical CO2-brine-rock interactions at elevated pressures and temperatures using two sets of porous sandstone with different petrophysical qualities.
- Salt-affected specimens exhibited up to a 50% reduction in Young's and shear moduli, along with twice the increase in Poisson's ratio compared to their intact condition.

## Summary

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Predictive modeling is crucial for understanding physico-chemical processes and potential challenges for scale-up in CO2 storage sites. One significant issue that can arise is dramatic injectivity decline due to salt precipitation pore clogging in high-salinity reservoirs, even over a short period. This study specifically focuses on investigating the adverse impact of CO2-induced salt crystallization in porous media on the geomechanical properties of near-wellbore reservoir sandstones. The research begins with a comprehensive review of CO2 chemo-mechanical interactions with sandstones, recognizing that the impact of salt precipitation cannot be isolated from the precursor effects of interaction with CO2 and carbonic acid. Laboratory experiments were conducted involving geochemical CO2-brine-rock interactions at elevated pressures and temperatures using two sets of porous sandstone with different petrophysical qualities. Two paths were followed in the experimentation process: first, treatment with CO2-acidified brine at 10 MPa fluid pressure and 60°C for 7 days; second, a continuation subset involving supercritical injection until complete dry-out and salt precipitation. Subsequently, core samples underwent testing in a triaxial apparatus at varying stresses and temperatures to evaluate their elastic moduli. The results revealed that salt-affected specimens exhibited up to a 50 percent reduction in Young's and shear moduli, along with twice the increase in Poisson's ratio compared to their intact condition. Notably, the deterioration was more pronounced in tighter rocks with higher initial stiffness. This study provides valuable insights into the potential 50% strength decline observed in near-wellbore reservoir sandstones due to salt precipitation and weak acid interaction during subsurface CO2 injection.