Sustained casing pressure and fluid loss due to casing leaks are...

Sustained casing pressure and fluid loss due to casing leaks are ongoing and expensive problems in older oil and gas fields. To more safely and economically repair casing leaks in two mature fields in Wyoming, CamWest, Inc. utilized Seal-Tite's pressure-activated sealant technology in five wells. Mechanical integrity, confirmed by subsequent tests, was restored in four of the five wells, saving about $135,000 compared to conventional approaches. The sealant operations were performed without risky well interventions.

There seems to be plenty of products on the internet for this sort of repair for older wells