ExxonMobil Canada − the Canadian unit of ExxonMobil Corporation ( XOM - Analyst Report ) has finally completed the acquisition of Calgary-based oil and gas driller Celtic Exploration Ltd. in a deal valued at C$2.59 billion ($2.63 billion).

ExxonMobil’s proposal to purchase Celtic in Oct 2012 received consent from the Canadian government towards the end of Feb 2013. The deal was valued at C$3.1 billion after taking into consideration Celtic's convertible debentures, and bank debt and working capital obligations.

The acquisition is a move towards expanding ExxonMobil’s footprint in the unconventional energy plays in North America. The closure of the deal entails delisting of Celtic shares from the Toronto Stock Exchange.

Celtic’s output and proved reserves are heavily weighted towards natural gas. Despite the collapse in natural gas prices, ExxonMobil expects unconventional gas to play a dominant role in future supplies, owing to the rapid decline in conventional production.

With the XTO Energy Inc. acquisition, ExxonMobil gained access to significant unconventional resources with a major handle on North America's newest energy discoveries. The Celtic deal is the biggest opportunity since then and will help ExxonMobil to expand its presence in the world’s largest energy market.

The company’s efforts to build an unconventional resource portfolio both in North America and overseas are aimed at increasing production through increased exposure to large energy resources with a long reserve life and low field declines. Since the XTO acquisition, the company possesses more than 1.4 million unconventional acres in the U.S. and Canada.

In a separate deal, ExxonMobil’s subsidiary Imperial Oil Ltd. purchased a 50% working interest in Celtic following the completion of the transaction. The technical expertise and financial strength of Imperial, ExxonMobil and XTO will expedite the development of energy in the acquired unconventional, liquids rich acreage.

ExxonMobil holds a Zacks Rank #3, which is equivalent to a short-term Hold rating. However, there are other stocks in the oil and gas sector – Enerplus Corporation ( ERF - Snapshot Report ) , Range Resources Corporation ( RRC - Analyst Report ) and NGL Energy Partners LP ( NGL - Snapshot Report ) – which hold a Zacks Rank #1 (Strong Buy) and are expected to perform better.