Caprock compressibility and permeability and the consequences for pressure development in CO2 storage sites

The Nanoscale Basis of CO2 Trapping for Geologic Storage

“…Knowledge of the properties of shales and mudstones lags behind that of other sedimentary rocks despite their importance in a range of areas including basin modeling, ,,− radioactive waste management, ,, wellbore stability, − soil science, fault rupture, the behavior of subduction zones, , and the subsurface retention of hydrocarbons. , The relative scarcity of experimental data on these rocks derives in part from the significant challenges associated with their fine-grained nature. Sample alteration during core retrieval and storage (in particular, the formation of microcracks associated with unloading and drying) may not be entirely avoidable. ,,,− Porosity and pore structure are challenging to characterize, because most of the pore space is located in pores with widths between 2 and 10 nm, beyond the range of standard microscopy tools, and a significant fraction is located in pores narrower than 2 nm that are not probed by N 2 adsorption or mercury intrusion porosimetry (MIP). ,,,,,,,− Examination of the microstructure of shales and mudtones increasingly relies on nanoscience tools such as small angle neutron scattering (SANS). − Studies of mudstone and shale routinely report the clay content of the solid (mass fraction of particles <2 μm in diameter) but less frequently its clay mineralogy (mass fraction of clay minerals). ,,,, Experimental challenges associated with sample preservation, geomechanics, and the characterization of clay mineralogy are particularly crucial, because the porosity, permeability, and geomechanical properties of clayey media are highly sensitive to clay mineralogy, the stress history of the rock, and the solution with which the rock is in contact. ,,,,,,,− ,…”

“…Compilation of experimental data (blue) and model predictions (orange) on the core scale properties of shales and mudstones: (a) porosity ϕ as a function of maximum historical effective stress σ e,max ; (b) logarithm of the permeability k v as a function of porosity; (c) log k V as a function of phyllosilicate mass fraction X clay in the solid phase. Blue squares represent well-characterized shales and mudstones (Keuper claystone, Kirtland formation, Nordland shale, Draupne shale, Fjerritslev formation, Norwegian shelf Jurassic mudrocks, Chimney Rock and Gothic shale, ZeroGen shale, Tuscaloosa mudstone and marine shale, Boom clay, Toarcian–Domerian shale, Opalinus clay, Callovo–-Oxfordian clay, Couche Silteuse, Muderong shale, North German Basin claystones, Wilcox shale, Kimmeridge shale, Floyd shale, Chattanooga shale, Conasauga shale, Duvernay shale, Wakkanai mudstone). ,,,,− ,,,,− ,− ,− ,,,− Thick blue lines show a representative selection of normally consolidated clay-rich sediments either retrieved from a range of depths or compacted to a range of ϕ values using a standard oedometric test. ,,,,, Permeability values were measured by water advection at the core scale in the direction normal to the bedding or in an unspecified direction. In the case of hydrocarbon-bearing shales, very few hydraulic permeability data are available; helium permeability values were included if they had been obtained on samples pretreated to remove all other fluids .…”

Interaction between a fractured marl caprock and CO2-rich sulfate solution under supercritical CO2 conditions

“…The success of long-term CO 2 storage will ultimately depend on the caprock sealing capacity. Caprocks with low permeability (e.g., k = 10 −19 m 2 for Fjerritslev Formation of the Vedsted site in Denmark; Mbia et al, 2014) are suitable to prevent CO 2 leakages.…”

Acid Water–Rock–Cement Interaction and Multicomponent Reactive Transport Modeling

“…We addressed the quantitative interpretation of the effect of mineral dissolution and precipitation reactions on rock porosity and fracture permeability. Given that reservoir and cap (seal) rock permeability (k = 10 -19 -10 -18 m 2 ; Alcalde et al, 2013;Mbia et al, 2014) can be several orders of magnitude smaller than fracture permeability, fluids will flow preferentially through fractures or microcracks, where chemical alteration induced by the CO 2 -rich fluids can bring about changes in physical and chemical properties. Since carbonate rocks are common in reservoir and seal formations of potential CO 2 -storage sites worldwide (e.g.…”