Micro- and macroscale consequences of interactions between CO₂ and shale rocks

In carbon storage activities, and in shale oil and gas extraction (SOGE) with carbon
dioxide (CO₂) stimulation fluid, CO₂ comes into contact with shale rock and its pore fluid. As a
reactive fluid, the injected CO₂ displays a large potential to modify the shale’s chemical, physical,
and mechanical properties, which need to be well studied and documented. The state of the art on
shale–CO₂ interactions published in several review articles does not exhaust all aspects of these
interactions, such as changes in the mechanical, petrophysical, or petrochemical properties of shales.
This review paper presents a characterization of shale rocks and reviews their possible interaction
mechanisms with different phases of CO₂. The effects of these interactions on petrophysical,
chemical and mechanical properties are highlighted. In addition, a novel experimental approach is
presented, developed and used by our team to investigate mechanical properties by exposing shale
to different saturation fluids under controlled temperatures and pressures, without modifying the
test exposure conditions prior to mechanical and acoustic measurements. This paper also underlines
the major knowledge gaps that need to be filled in order to improve the safety and efficiency of
SOGE and CO₂ storage