Stimulating shale creep as a strategy for long-term well integrity during decommissioning

This study explores the potential of shale as a barrier for well decommissioning, focusing on its creep behavior and mineral transformations under various chemical conditions. Advanced mineralogical analyses and multi-stage triaxial creep tests were conducted on dry samples and those saturated with synthetic brine and Na 2 SiO 3 solution. Geochemical modeling revealed that Na 2 SiO 3 promotes quartz dissolution and albite precipitation, altering the shale’s structure. In contrast, the synthetic brine scenario produced relatively minor mineral changes; the increased strain relative to the dry baseline is therefore interpreted as consistent with physico-chemical effects of saturation and clay–fluid interactions rather than substantial dissolution or precipitation. Empirical and analytical creep models were applied to predict long-term deformation, demonstrating their applicability for extrapolating time-dependent shale behaviour beyond laboratory test durations. This research highlights the role of chemical stimulation in enhancing creep deformation and improving shale’s effectiveness as a sealing barrier, contributing to long-term well integrity. • This multidisciplinary study integrates mineralogical assessment, geo-mechanical testing, and geochemical analyses to evaluate shale as a natural barrier during well decommissioning and abandonment. • Multi-stage triaxial creep tests show that dry shale sample is more brittle (higher stiffness) compared to sodium silicate or formation-analogue brine-treated samples, which exhibit more ductile and compliant behavior. • Geochemical modeling shows sodium silicate solution, employed as creep stimulation technique, softens the tested shale by quartz dissolution and mineral precipitation. • Sodium silicate exposure produced the greatest creep strain, consistent with quartz dissolution and secondary mineral formation predicted by geo-chemical modelling. • The capability of different creep models to predict shale deformation was assessed, and corresponding parameters were obtained from short-term tests to forecast long-term creep behavior reliably.