With “key” additions from new project start-ups in North America and overseas, ExxonMobil Corp. added 2 billion boe to its internal proved reserves numbers in 2009, which is the highest in 10 years, the oil major said Tuesday.

ExxonMobil said it replaced 133% of its production, and excluding the impact of asset sales, reserves additions replaced 134% of output. ExxonMobil based its proved reserves additions using its internal long-term pricing basis, which differs from that of the Securities and Exchange Commission (SEC), which now requires producers to use 12-month average prices to calculate year-end reserves.

“The long-term nature of the industry, and the large size of the discrete projects that provide a significant portion of the corporation’s reserves additions, make it appropriate to consider a time horizon longer than a single year,” ExxonMobil said. “The 10-year average reserves replacement ratio on the corporation’s basis is 112%, with liquids replacement at 99% and gas at 131%.

“The reserves additions made during this period comprise a diverse range of resource types and have broad geographical representation. ExxonMobil’s reserves life at current production rates is 15.7 years.”

At the end of 2009 ExxonMobil’s proved reserves base, using its long-term pricing calculations, had increased to 23.3 billion boe, split nearly evenly between liquids (51%) and natural gas (49%). Using the SEC’s 12-month average pricing basis, proved reserves replacement in 2009 was 1.5 billion boe, and ExxonMobil replaced 100% of its production, including the effect of asset sales, oilsands extracted by mining and equity company reserves.

Last year’s reserve additions were driven by the start-up of several significant projects, which increased the portion of proved reserves already developed to 67%, ExxonMobil said. Reserve additions from the Papua New Guinea liquefied natural gas (LNG) project and the Gorgon Jansz LNG project in Australia together totaled almost 1 billion boe, said ExxonMobil. Other reserve additions followed start-ups in other countries, including the United States, Canada, Angola and Norway.

ExxonMobil also said it added 3.9 billion boe to its resource base in 2009, “with key additions from Canada, the United States, West Africa, Australia and the United Kingdom.” ExxonMobil uses the terms “resources” and “resource base” to include quantities of discovered oil and gas that are not yet classified as proved reserves but are expected to be ultimately recovered in the future. The terms are not intended to correspond to SEC definitions such as “probable” and “possible,” the company said.

The resource base additions “are a result of continued by-the-bit exploration success, undeveloped resource additions and revisions to our existing resources from ongoing studies,” said the oil major. “Overall, the corporation’s resource base grew by 2.4 billion boe to 74.8 billion boe, taking into account production and asset sales. The resource base includes proved reserves, plus other discovered resources that are expected to be ultimately recovered.”

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