Understanding the mechanisms of fluid flow and fracturing in poorly consolidated porous media

The fundamental processes of fluid flow and fracturing within porous media play a crucial role in various applications within the fields of energy geomechanics and groundwater hydrology. Design parameters include the composition and properties of the fluid, the hydraulic and mechanical properties of the porous media, and the injection methods. These parameters are selected based on the specific objectives of each application, such as inducing fractures or uniformly replacing pore fluids through infiltration, the depth of the operation, and whether the application is conducted in soil or rock.

Many of these operations take place in weakly-cemented and poorly-consolidated sands, which constitute the host rock for a significant portion of active aquifers and oil and gas reservoirs. These materials exhibit higher porosity and permeability compared to stronger rocks, resulting in a different response under fluid injection conditions. Fluid experiments are conducted on artificially cemented porous media to reveal the underlying mechanisms. The synthetic rock specimens used in the experiments are generated via microbially induced carbonate precipitation (MICP), a method that leads to the formation of calcium carbonate around silica particles. The resulting bio-treated specimens have prescribed properties (i.e., permeability, porosity, strength). The experimental behavior is then analyzed, encompassing factors such as infiltration/fracturing response regimes and fracturing patterns. Critical concepts from advanced geomechanics and groundwater hydrology are utilized to interpret the findings, including the brittleness index (BI), the cavity expansion theory, and the sand erosion problem.