Celtic Exploration Ltd. has received a friendly takeover offer valued at $3.1 billion from Canadian affiliates of U.S. energy giant Exxon Mobil Corp. (NYSE:XOM)

The Calgary-based company is mainly focused on natural gas areas in British Columbia and Alberta.

The total price of the ExxonMobil offer includes debt and spending obligations that the buyers would assume.

Celtic's shareholders are being offered $24.50 cash per share and a half-share of a new company, code-named Spinco — well above recent market prices.

Celtic's stock closed Tuesday at $18.12 on the Toronto Stock Exchange before the announcement.

The shares surged 46 per cent to $26.43 after markets opened Wednesday.

The difference between the new market price for Celtic shares and the ExxonMobil offer price may be at least partly attributable to the anticipated value of the Spinco shares.

The value of Spinco's assets are estimated at $2.32 per share, adding about $1.66 to the value of the cash ExxonMobil would pay for Celtic shares.