Evaluation of Mechanical Strength of a Barents Sea Shale by Applying the Most Common Failure Criteria

SUMMARY One of the important factors in formation of a petroleum reservoir and also a successful CO2 storage operation is an efficient seal that prevents migration of accumulated hydrocarbon or injected CO2 to the surrounding environments. In siliciclastic environment, shales and mudrocks are most common seals that prevent migration of hydrocarbon and CO2 from reservoirs. This study investigates the most common failure criteria (Mohr-Coulomb Criterion, Drucker-Prager Criterion, Mogi Empirical Criterion and Hoek and Brown Criterion) by using a triaxial data set. The maximum effective principal stress (σ1), one of the most important mechanical properties of caprocks that has crucial importance in rock strength calculations, has been predicted with the mentioned failure criteria. The applied data are obtained from a range of triaxial tests that were performed on a Barents Sea Shale cored from the Hekkingen Formation in two depth intervals. Among the applied failure criteria, Mogi failure criterion had the best performance in predicting the σ1 of the tested shales, while the traditional MohrCoulomb criterion showed good prediction compared to complicated calculations suggested by other criteria. Also the observed considerable discrepancies between the obtained mechanical parameters for horizontal and vertical samples at same depth reveals the anisotropy in the Hekkingen Formation.