Wellbore stability charts for shale and carbonate formations during drilling operations with field applications

Wellbore instability issues represented by well collapsing resulted in a tremendous loss of time and money in the oil industry, where 90% are related to shale. Despite carbonate rocks experiencing fewer instability issues than shale or sandstone, most global hydrocarbon reservoirs are carbonate. Utilising a three-dimensional stability model adopting the Mogi-Coulomb failure criterion, stability charts predicting the collapse pressures during drilling in shale and carbonate formations have been generated. The introduced stability charts have been generated to cover the most common scenarios in Oman and similar locations. Six field case studies are conducted utilising the generated stability charts for geomechanical analysis. The fields applied mud densities at the associated drilling trajectories were consistent with the predicted results from the generated stability charts. These results support adopting the presented stability charts as a simplified geomechanical approach in oil fields.