| Fluid transport in a porous medium has important implications for understanding natural
geological processes. At a sufficiently large scale, a fluid-saturated porous medium can be
regarded as a two-phase continuum, with the fluid constituent flowing in the Darcian regime.
Nevertheless, a fluid mediated chemical reaction can in some cases change the permeability
of the rock locally: Mineral dissolution can cause increased permeability, whereas
mineral precipitation can reduce the permeability. This might trigger a complicated
hydro-chemo-mechanical coupling effect that causes channeling of fluids or clogging of the
system. If the fluid is injected or produced at a sufficiently high rate, the pressure might
increase enough to cause the onset and propagation of fractures. Fractures in return create
preferential flow paths that enhance permeability, localize fluid flow and chemical reaction,
prevent build-up of pore pressure and cause anisotropy of the hydro-mechanical
responses of the effective medium. This leads to a complex coupled process of
solid deformation, chemical reaction and fluid transport enhanced by the fracture
formation.
In this work, we develop a new coupled numerical model to study the complexities of
feedback among fluid pressure evolution, fracture formation and permeability changes due to
a chemical process in a 2D system. We combine a discrete element model (DEM) previously
used to study a volume expanding process[1, 2] with a new fluid transport model based on
poroelasticity[3] and a fluid-mediated chemical reaction that changes the permeability of the
medium. This provides new insights into the hydro-chemo-mechanical process of a
transforming porous medium.
References
[1] Ulven, O. I., Storheim, H., Austrheim, H., and Malthe-Sørenssen, A.
“Fracture Initiation During Volume Increasing Reactions in Rocks and
Applications for CO2 Sequestration”, Earth Planet. Sc. Lett. 389C, 2014a, pp.
132 – 142, doi:10.1016/j.epsl.2013.12.039.
[2] Ulven, O. I., Jamtveit, B., and Malthe-Sørenssen, A., “Reaction-driven
fracturing of porous rock”, J. Geophys. Res. Solid Earth 119, 2014b,
doi:10.1002/2014JB011102.
[3] Ulven, O. I., and Sun, W.C., “A locally mass-conserving dual-graph lattice
model for fluid-driven fracture”, in prep. |