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Abstract Many wells around the world suffer from compromised integrity in the form of leaking annular cement sheaths. Fixing leaking annular cement barriers is generally a labor intensive and costly proposition, particularly in offshore environments. If the leaking cement sheath is opposite a creeping shale or salt formation, there is a possibility of such a mobile formation "healing" the voids, cracks and annuli in the cement sheath and re-establishing annular barrier integrity. Such "healing" can be relatively easily achieved using heaters deployed in the wellbore without the need to create annular access. Large scale "shale-as-a-barrier (SAAB)" rock mechanics tests were carried out in the investigation reported here using a custom-built temperature-controlled triaxial frame to test shale core samples with an inner borehole. This borehole contained a simulated casing string and an annular cement sheath, which could be compromised either by using rubble-ized cement in the annulus or using repeated pressure cycles in the wellbore to attempt to create a micro-annulus at the casing-to-cement interface. The integrity of the annular barrier (or lack thereof) was probed throughout the test using pressure pulse decay experiments, and at the end of the test by breakthrough testing. The creep rate in the North Sea Lark shale was beneficially manipulated using elevated shale sample temperature. In the experiments with rubble-ized cement, it was found that thermally stimulated shale creep can plug the cracks, fractures and voids present within the cement material effectively to form a barrier. In the experiments with intact cement subjected to casing pressure cycles, evidence was obtained that thermally stimulated creep can support the annular cement barrier. The effect of elevated temperature, representing the effect of the deployment of a heater in an actual well setting, proved crucial to magnify and accelerate the creep phenomenon responsible for plugging the flow paths in the compromised cement. With many hundreds of thousands of wells around the work already leaking (or potentially leaking at some point in the future) and/or showing casing pressure at surface because of compromised annular cement barriers, it is important to find (cost-)effective long term remedial solutions. For wells intersection shale or salt formations that either creep at in-situ stress and temperature conditions, or can be induced to creep through thermal stimulation, the remediation using such creep to restore and improve the cement barrier is simple, practical (can be deployed with existing downhole heaters), cost-effective, and is expected to last for an indefinite timeframe. It thereby has the potential to revolutionize P&A operations on wells with compromised integrity.