Electrical conductivity model using bowel-shaped capillary bundles to describe mineral precipitation-dissolution processes of water-saturated porous media

Abstract:

Mineral precipitation and dissolution constitute processes of major interest for hydrogeophysical studies of carbonate rocks as they have strong impact on aquifer and reservoirs properties. Geoelectrical methods are sensitive both to transport phenomena occurring in porous media and chemical processes involving rock-water interaction. Electrical conductivity therefore represents a key physical property to monitor precipitation and dissolution processes in the porous medium. However, its quantitative use depends on the effectiveness of the petrophysical relationship that relates the electrical conductivity to hydrological and intrinsic properties of interest. Indeed, in most published models, only porosity and tortuosity define the complexity of the microstructure. This simplification leads to unrealistic high tortuosity values ignoring the bottleneck effect, a well-known pore shape feature that can be captured by the analysis of constrictivity. In this work, we develop a new physical model to estimate the electrical conductivity by upscaling a microstructural description of water-saturated porous media based on a fractal distribution of bowel-shaped pores. This model is successfully compared to published data from both unconsolidated and consolidated samples, and during precipitation and dissolution numerical experiments. For the latter, we show that constrictivity is the parameter most impacted by geochemical processes.