The $30 Billion Liability of Inactive Oil and Gas Wells in the US and Gulf States.
A survey of wells along the Gulf of Mexico coast indicates that there are 14,000 wells that aren't producing, are unlikely to be brought back into service, and are uncapped. The estimated cost of capping them all would run into the area of $30 billion dollars. In most cases, one of the major oil companies will be responsible for these costs. The risk of uncapped wells is that material doesn't necessarily stop coming out of them when the equipment the well was connected to is switched off and removed.