Canadian integrated oil company Imperial Oil (IMO 0.21%) said Wednesday that it plans to acquire a 50% stake in Celtic Exploration, which is being acquired by ExxonMobil (XOM -0.46%).

Exxon owns a majority stake in Imperial and is awaiting regulatory and shareholder approval to complete the $2.6 billion buyout of 100% of Celtic. (The deal is valued around $3.1 billion when debt is included.) Imperial's deal for the 50% stake will be $1.56 billion and open up nearly 650,000 acres of natural gas-rich shale properties in western Canada.

Imperial CEO and Chairman Bruce March commented on the value of the deal by saying, "We continue to leverage our strong balance sheet and solid financial position to grow the company through strategic resource capture in key opportunity areas. This new venture represents a significant opportunity to leverage ExxonMobil's expertise in shale gas development and add value for Imperial shareholders."

The natural gas acres, located in the Montney shale and Duvernay shale fields, currently produce 72 million cubic feet of natural gas per day. Imperial's stake  will be confirmed as soon as Exxon's deal for Celtic is finalized.