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Changes in seal capacity of fractured claystone caprocks induced by dissolved and gaseous CO 2 seepage
Author(s) -
Andreani M.,
Gouze P.,
Luquot L.,
Jouanna P.
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl034467
Subject(s) - caprock , geology , brine , dissolution , permeability (electromagnetism) , quartz , porosity , calcite , petroleum engineering , geotechnical engineering , petrology , mineralogy , chemistry , paleontology , biochemistry , organic chemistry , membrane
Claystone caprocks are often the ultimate seal for CO 2 underground storage when residual CO 2 gas reaches the reservoir top due to buoyancy. Permeability changes of a fractured claystone due to seepage of CO 2 ‐enriched brine and water vapor‐saturated CO 2 gas are investigated. Results show that brine flow induces a large porosity increase (up to 50%) in the vicinity of the fracture due to dissolution of calcite and quartz, while permeability remains unchanged. Conversely, cyclic flows of CO 2 ‐brine and CO 2 ‐gas increase the fracture aperture abruptly after each gas flow period, producing a progressive decrease of the caprock seal capacity. Aperture increase is controlled by decohesion of the clay framework within a micrometer‐scale‐thick layer induced by CO 2 ‐gas acidification. Results show that hydraulic aperture increases linearly with duration of the preceding CO 2 ‐brine flow period, emphasizing the kinetic control of the quartz grains dissolution during the brine flow periods.