Coupled Hydro-Mechanical-Chemical response of rock to high pressure CO2 injection
Conference Paper
Overview
Additional Document Info
View All
Overview
abstract
The injection of CO2 into a subsurface brine-saturated rock leads to a creation of acidic fluid that can influence the hydraulic and mechanical properties of involved formations. This may lead to the risk of degrading a storage capacity or causing a transport disturbance. We experimentally investigate the chemical effect of injected high-pressure CO2 on the hydro-mechanical behavior of water-saturated Berea sandstone and Indiana and Apulian limestones as representatives of reservoir rock, as well as Opalinus Clay as a potential caprock. CO2 injection appears to have little effect on poroelastic properties of the sandstone and shale, while the corresponding solid and bulk moduli of calcite-rich materials decrease significantly after a few weeks of treatment. This discrepancy is explained by the dissolution of calcite, which leads to an observable increase in micron range size pores in the limestones. The permeability and bulk viscosity (tendency to time-dependent deformation) increase in all tested rock after the CO2 treatment.. A coupled hydro-mechanical-chemical (HMC) model based on the poroviscoelastic framework is suggested where the chemical effect is considered through the dissolution of calcite. The proposed HMC model predicts the increase in rock's porosity with the duration of CO2 treatment, while the chemical potential coefficient appears to be a function of calcite content, porosity, and specific surface. The model can be used to assess the changes in the mechanical response of water-saturated rock caused by injection of high-pressure CO2, along with the corresponding changes in permeability and storage capacity.
