POTENTIAL EFFECT OF BIOT'S COEFFICIENT ON ROCK FAILURE IN CO2 STORAGE SITE SMEAHEIA, NORTHERN NORTH SEA

A 3D field-scale numerical simulation can reveal the possible CO2 injection-induced rock mechanical failure risks. However, the grain compressibility, also known as Biot's coefficient for a poroelastic material, has little consideration, though it is complex and uncertain. Therefore, in this study, we investigated the possible effect of Biot's coefficient on the numerical simulation using the Smeaheia 3D field-scale geomechanical model. The Smeaheia area is a potential CO2 storage site located in the northern North Sea. Considering the relationship between porosity and Biot's coefficient, the 0.8 value is chosen for the simulation, later compared with coefficient 1. A seismic property-driven stress-strain-based one-way coupling is examined. Because the coefficient influences the effective stresses, the Mohr circles shifted right away from the potential Coulomb failure envelope. For instance, the top reservoir in the after injection scenario changes its tensile failure risk to a non-failure condition when using the coefficient value 0.8 instead of the commonly used value 1. The injection-induced vertical upliftment of the rock layer is also affected by the Biot's coefficient values. This sensitivity study reveals that the Biot's coefficient significantly influences the mechanical behaviour of the subsurface rocks; hence, it needs detailed investigation while assessing the injection-induced rock mechanical behaviour.