Can heating-induced creep result in shale barriers for P&A applications?

Abstract

It has been shown that some shale formations form barriers around a casing of a well due to shale creep that results in closure and sealing of the annulus around the casing. The existence of such shale barriers facilitates plug and abandonment (P&A) operations, which includes significant cost reductions. The question is whether barrier-forming shale creep or plastic deformation can be stimulated if no barrier has been formed over the lifetime of the well. Recent laboratory experiments with core plugs from different field-shale facies as well as numerical simulations suggest that controlled heating may help stimulate plastic deformation in shale that may result in shale barriers. The experimental results show that undrained heating under deviatoric stress may result in large plastic shear strains. Thermo-hydro-mechanically coupled finite-element simulations confirm that heating of a well may result in a sufficiently strong reduction of the borehole radius to close the gap between shale formation and casing.