Role of limestone micro-porosity on dissolution patterns during reactive transport with carbonated water

In this work, we have investigated the effect of two different limestone textures (namely Lavouxand Euville limestone) on the reactive transport. These two rock-types have a similar chemical composition(pure calcite) but differ by their macro- and micro-structures. An extensive workflow of experiments hasbeen carried out to characterize the macro- and micro-porous systems of the cores, and to understand theinteraction between the different properties that are relevant for the reactive transport. It includes 5 µm pixelresolution 3D scans of the cores and miscible tracer injections conducted before and after the alteration.Core alteration has been conducted using carbonated water to be more representative of CO2 storageconditions. Experiments have been conducted at ambient temperature (25°C) and at 10 bar of pore pressure.Results have shown that Lavoux limestone has higher micro-porosity and better-connected grains thanEuville limestone. Mass transfer of the reactive fluid in the micro-porosity, where most of the reactivesurfaces are, is limited for Euville. Consequently, Lavoux limestone showed a more homogeneous andsustained dissolution front, while Euville developed early breakthrough and localized. The two cores initialflow properties have been altered to a completely different extent. The absolute permeability has beenmultiplied by more than 100 for Euville core, while it has been increased by less than 2 for Lavoux core.