Reserves additions reflect new developments as well as revisions and extensions of existing fields resulting from drilling, studies and analysis of reservoir performance.Consistent with SEC requirements, ExxonMobil reports reserves based on the average of the applicable market price prevailing on the first day of each calendar month during the year. As a result of higher prices in 2017 relative to 2016, about 900 million oil-equivalent barrels in North America qualified as proved reserves under SEC guidelines due primarily to the extension of the projected economic end-of-field-life. 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. Resource Base ExxonMobil added 9.8 billion oil-equivalent barrels to its resource base in 2017 through by-the-bit exploration discoveries and strategic acquisitions. This was the largest addition to the resource base since the acquisition of XTO Energy in 2010. The resource base includes proved reserves, plus other discovered resources that are expected to be ultimately recovered. Through its acquisition of various entities from the Bass family of Fort Worth, Texas in 2017, ExxonMobil added significant resource in the Permian Basin, with upside potential in multiple additional prospective horizons. The company continues to maximize capital efficiency in its tight oil developments by taking advantage of contiguous acreage to drill long laterals with optimized completion designs. Key resource additions were also made in deepwater Brazil pre-salt with the acquisition of interest in the two billion gross oil-equivalent-barrel Carcara field, onshore Papua New Guinea with the acquisition of InterOil Corporation, and Mozambique with the purchase of an interest in Area 4. Three new discoveries offshore Guyana in 2017 also contributed to the by-the-bit resource additions. Additional exploration drilling in Guyana is planned in 2018 on the 11.5 million gross acres currently held offshore.
ExxonMobil's resource base totaled approximately 97 billion oil-equivalent barrels at year-end 2017, taking into account field revisions, production and asset sales.About ExxonMobil ExxonMobil, the largest publicly traded international energy company, uses technology and innovation to help meet the world's growing energy needs. ExxonMobil holds an industry-leading inventory of resources, is one of the largest refiners and marketers of petroleum products, and its chemical company is one of the largest in the world. For more information, visit www.exxonmobil.com or follow us on Twitter www.twitter.com/exxonmobil. CAUTIONARY NOTE: Proved reserve figures in this release are based on current SEC definitions. 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 "in-place" refers to those quantities of oil and gas estimated to be contained in known accumulations and includes recoverable and unrecoverable amounts.