https://en.wikipedia.org/wiki/Relief_well
/? Zonal isolation Wikipedia: https://www.google.com/search?q=zonal+isolation+Wikipedia :
> Well cementing, Completion, Squeeze job, Cement bond log, Casing (should prevent fluid from contaminating e.g. aquifer zones)
Orphan wells: https://en.wikipedia.org/wiki/Orphan_wells :
> they estimate there are 29 million abandoned wells internationally
Orphaned wells in the United States: https://en.wikipedia.org/wiki/Orphaned_wells_in_the_United_S... :
> According to the Government Accountability Office, the 2.1 million unplugged abandoned wells in the United States could cost as much as $300 billion
https://en.wikipedia.org/wiki/Relief_well