Reactive evolution of mineral surface area

Abstract:

Understanding the evolution of mineral surface area during mineral dissolution and precipitation reactions, such as those that occur during CO2 injection and sequestration in subsurface formation, is crucial to accurate assessment of mineral reaction rates. Reactive transport simulations are often used to simulate geochemical reactions. Simulations typically use a simplified approximations of mineral surface area based on spheres. The actual evolution of mineral surface area in porous media and applicability of this relationship, however, is not well understood. In this work, a reactive transport modeling tool, Crunchflow, is used to study the mineral surface area evolution for a sandstone sample from Bentheimer formation. The sample is reacted with CO2 saturated brine at 40º C and 100 bars pressure to match conditions pertinent for geologic CO2 sequestration. The initial and final mineral surface area of the sample is derived from SEM images and BET analysis using N2 gas adsorption. Simulations are carried out mimicking the field conditions considering the evolution of species concentrations in solution, surface area changes, porosity, and mineral weight percentages at different time intervals. Simulation results will be compared with the experimental data using image derived surface area and BET based surface area to determine which of the models match best.