Field-scale fault reactivation experiments by fluid injection highlight aseismic leakage in caprock analogs: Implications for CO2 sequestration

Yves Guglielmi , Christophe Nussbaum , Frédéric Cappa (1) , Louis de Barros (1) , Jonny Rutqvist , Jens Birkholzer

1 GEOAZUR 7329 - Géoazur

Observations on tens-of-meter scale experiments of fault activation by fluid injection conducted in shales allow exploring how aseismic and seismic events may jeopardize the integrity of a sealing caprock overlying a CO 2 sequestration reservoir. We contrast the behavior of shale faults with another set of experiments conducted in carbonates. Significant fluid leakage occurs along the initially low-permeability shale faults when rupture is activated. Most of the leakage pathway closes when fluid injection ceases and fluid pressure drops. Dilatant slip on the fault plane alone does not explain the observed leakage behavior, which is also caused by fault opening favored by the softness of the shale, and by the structure of the fault zone that prevents fluids from diffusing into the adjacent damage zone. Experiments show a large amount of aseismic deformation. Small-magnitude seismicity (M w <-2.5) is observed outside the pressurized leakage patch. Stress transferred from this aseismic deformation patch can build up to stress-criticality and favor seismicity. Thus, in terms of fault activation in caprocks, aseismic fault slip leading to increased permeability and a loss of seal integrity is of great concern.

Domaines: Géophysique [physics.geo-ph]; Géologie appliquée

Yves Guglielmi, Christophe Nussbaum, Frédéric Cappa, Louis de Barros, Jonny Rutqvist, et al.. Field-scale fault reactivation experiments by fluid injection highlight aseismic leakage in caprock analogs: Implications for CO2 sequestration. International Journal of Greenhouse Gas Control, 2021, 111, pp.103471. ⟨10.1016/j.ijggc.2021.103471⟩. ⟨hal-03354747⟩