Marcellus natural gas production expanded in 2012

PITTSBURGH (AP)-- This year was one of new records and new questions for the boom in Marcellus Shale natural gas drilling.

Previous doubts about the size of the vast resource were mostly put to rest, as data showed the Marcellus became the most productive natural gas field in the nation, even though well drilling slowed substantially.

Municipalities filed a lawsuit challenging a new state rule that limits local ability to regulate drilling. The state Supreme Court heard the case in October but didn't indicate when it will rule.

In March, Shell Oil Co. said a site about 30 miles north of Pittsburgh was its first choice to build a huge new petrochemical plant, which would turn natural gas liquids into consumer products, such as plastics and antifreeze.