Reserves additions in 2012 reflect new developments with significant funding commitments as well as revisions and extensions of existing fields resulting from drilling, studies and analysis of reservoir performance. The annual reporting of proved reserves is the product of the corporation’s long-standing, rigorous process that ensures consistency and management accountability in all reserves bookings.During 2012, ExxonMobil added 4 billion oil-equivalent barrels to its resource base, driven primarily by resource additions in the United States and Canada, as well as Romania, Tanzania, Nigeria, Australia and Papua New Guinea. Additions include continued success in by-the-bit exploration discoveries, undeveloped resource additions and strategic acquisitions. ExxonMobil’s by-the-bit conventional exploration success in 2012 included discoveries in Romania, Tanzania, Nigeria, Australia and Papua New Guinea. In addition, discovery and delineation of North American unconventional assets contributed to the resource base. Overall, the corporation’s resource base totaled 87 billion oil-equivalent barrels at year-end 2012, 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. CAUTIONARY NOTE: Proved reserves in this release, for 2009 and later years are based on current SEC definitions, but for prior years the referenced proved reserve volumes are determined on bases that differ from SEC definitions in effect at the time. Specifically, for years prior to 2009 included in our 10-year average replacement ratio, reserves are determined using the SEC pricing basis but including oil sands and our pro-rata share of equity company reserves for all periods. Prior to 2009, oil sands and equity company reserves were not included in proved oil and gas reserves as defined by the SEC. For years prior to 2009 included in our 19 straight years of at least 100 percent replacement, reserves are determined using the price and cost assumptions we use in managing the business, not the historic prices used in SEC definitions. Reserves determined on ExxonMobil's pricing basis also include oil sands and equity company reserves for all periods.
The reserves replacement ratio is calculated for a specified period utilizing the applicable proved oil-equivalent reserves additions divided by oil-equivalent production.The terms “resources” and “resource base” include quantities of discovered oil and gas that are not yet classified as proved reserves but that are expected to be ultimately recovered in the future. The term “resource base” is not intended to correspond to SEC definitions such as “probable” or “possible” reserves. The term “project” as used in this release does not necessarily have the same meaning as under SEC Rule 13q-1 relating to government payment reporting. For example, a single project for purposes of the rule may encompass numerous properties, agreements, investments, developments, phases, work efforts, activities, and components, each of which we may also informally describe as a “project.” About ExxonMobil ExxonMobil, the largest publicly traded international oil and gas company, uses technology and innovation to help meet the world’s growing energy needs. ExxonMobil holds an industry-leading inventory of resources, is the largest refiner and marketer of petroleum products, and its chemical company is one of the largest in the world. Follow ExxonMobil on Twitter at www.twitter.com/exxonmobil.