Dr. Jean Elkhoury: Dissolving fractures (11-11-2016)


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Dr. Jean Elkhoury (Schlumberger-Doll Research)

Dissolving fractures

Vendredi 11 novembre 2016 à 15h30 / Friday, November 11, 2016, 3:30 pm

Redpath Museum Auditorium, Université McGill

Abstract / Résumé :

A better understanding of fluid flow evolution in fractures subject to reactive flow is crucial in many applications. These include: oil and gas exploitation, underground waste fluid disposal, enhanced geothermal energy production, greenhouse gases sequestration, and induced seismicity among others. Mineral dissolution causes geometrical alteration in fractures that affects their mechanical strength and the evolution of the flow field through the fractures aperture. It is difficult to determine the influence of dissolution on fracture porosity and permeability given the competition between fracture opening due to dissolution and fracture closure caused by mechanical stresses and deformations. In this talk, I will present results from laboratory scale experiments that explore the small-scale physics of dissolution and deformation of fractures. We use optical profilometry and x-ray CT scans to characterize fracture porosity alteration and monitor effluent chemistry as well as pressure evolution to gain insight into the coupled processes at play. To first order, the evolution of the dissolution process, in both reservoir and cap rocks, depends on the dimensionless Damköhler number, Da (ratio of advection to reaction time scales). We observe a strong effect of the mechanical stresses when Da is large. Our 2D reactive-transport model produces results in qualitative agreements with the experiments. The results emphasize the importance of the coupled response of hydro-chemo-mechanical disequilibrium and the length-scales on the evolution of fracture permeability