ExxonMobil Corp. last year added 3.5 boe to its proved reserves, replacing 209% of production. It was the company's 17th consecutive year of reserve replacement exceeding 100% of production.

Excluding asset sales, reserves additions replaced 211% of production, the Irving, TX-based supermajor said Tuesday.

The company added 14.6 billion boe to its resource base in 2010, representing the largest annual growth and largest total resource base since the Exxon and Mobil merger (see Daily GPI, Dec. 2, 1998), driven by resource additions from the United States, Canada, Iraq, Australia, West Africa and Europe, the company said.

The resource base associated with the company' XTO Energy Inc. acquisition (see Daily GPI, Dec. 15, 2009) is 60 Tcfe. Overall, the company's resource base grew by 9.7 billion boe to 84.5 billion boe, taking into account field revisions, production and asset sales. The resource base includes proved reserves, plus other discovered resources that are expected to be ultimately recovered.

Last year's reserve additions were the most since the merger of Exxon and Mobil and reflect acquisitions and new developments, as well as revisions and extensions of existing fields resulting from drilling, studies and analysis of reservoir performance.

Reserves additions from acquisitions and subsequent revisions totaled 3 billion boe. Additions also came from the Sakhalin-1 Arkutun Dagi project in Russia and other countries including Canada, the United States, Nigeria, Norway and Abu Dhabi. Liquid additions totaled 905 million boe for a 102% replacement ratio and gas additions totaled 2.6 billion boe for a 328% replacement ratio.

At year-end ExxonMobil's proved reserves base had increased to 24.8 billion boe, including 2.8 billion boe from XTO. The proved reserves base is split between 47% liquids and 53% gas and includes oilsands extracted by mining and equity company reserves.

The 2010 proved developed reserves addition of 3.3 billion boe was also the highest since the Exxon and Mobil merger, driven by the startup of several projects, the results of ongoing work programs and the acquisition of XTO.

The 10-year average reserves replacement ratio is 121%, with liquids replacement at 95% and gas at 158%. ExxonMobil's reserves life at current production rates is 15 years, the company said.

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