Mechanical weakening of a mudrock seal by reaction with CO2-charged fluids

This work addresses the topic of leakage with low-permeability cap rocks, particularly relevant in the context of Carbon-Capture and Storage (CCS). Here we studied a natural CO2 analogue near Green River, Utah, USA; The observed chemo-mechanical changes are on the millimeter scale, which required small-scale petro- physical, mineralogical, and micro-mechanical analyses. This study demonstrates that mechanical weakening of cap rocks might occur, but only over time scales of ∼100,000 yr and over small distances. Considering the thickness of cap rocks above CO2 storage reservoirs, we do not anticipate a considerable threat of losing containment integrity over time scales of hundreds to thousands of years as a result of these small-scale fluid-rock interactions.