4/24/2013 - Fracture Dissolution and Deformation Under Reservoir Conditions


12:00 PM - 1:00 PM
Geology 1707

Presented By:
Jean E. Elkhoury - HSSEAS


Geometrical alteration in fractures, caused by mineral dissolution, changes the contact area between fracture surfaces and affects their mechanical strength. 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 closer caused by mechanical stresses and deformations. Here, I will present results from detailed laboratory scale experiments on fractured rock samples and simulations that explore the small-scale physics of dissolution and deformation of fractures under reservoir conditions. To first order, the evolution of the dissolution process, in both reservoir and cap rocks, depends on the dimensionless Damkohler number Da (ratio of advection to reaction time scales). In the regime of small Da (large flow velocities), the influence of the mechanical stresses is stronger on the cap rock. Comparison of the simulated dissolved aperture fields with measured aperture fields after flow-through shows strong qualitative agreement. We use our reactive-transport model to explore the role of reaction and flow rates on dissolution and the resulting alteration of porosity and permeability beyond our experimental conditions. Our results emphasize the importance of fracture length-scales and the coupled response of hydro-chemo-mechanical disequilibrium in fractured reservoirs under reservoir flow and stress conditions critical in the up-scaling to field scale.

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