The buzz accompanying Canada’s Duvernay shale cranked up from a dull roar to something like the earsplitting decibel level of a jackhammer on Oct. 17.

That day, ExxonMobil Canada made $3.1 billion worth of noise by snatching up Calgary-based Celtic Exploration Ltd. (TSX: CLT).

The deal, which is subject to governmental approval, would give ExxonMobil Canada, a subsidiary of Exxon Mobil Corp. (NYSE:XOM), dominion over 545,000 net acres of the liquids-rich Montney shale.

It also includes 104,000 net acres of Alberta’s Duvernay, a play where recent well results have drawn ...