ExxonMobil Corp. added 1 billion boe of proved oil and natural gas reserves in 2015, which replaced 67% of production and included a 219% replacement ratio for crude oil and other liquids, the supermajor said Friday. However, natural gas reserves fell, reflecting lower prices.

In the past decade, the Irving, TX-based producer has replaced 115% of the reserves it produced, including the impact of asset sales.

“ExxonMobil has a successful track record of proved reserves replacement over the long term, demonstrating the strength of our global strategy to identify, evaluate, capture and advance high-quality opportunities,” CEO Rex Tillerson said. “Our proved reserves represent a diverse portfolio that positions us to create shareholder value as we supply long-term energy demand growth. We will continue to apply our disciplined, paced investing approach as we develop our industry-leading resource base.”

Proved reserves totaled 24.8 billion boe at the end of 2015, with liquids representing 59%, versus 54% in 2014. The reserves life at current production rates is 16 years. Most of the additional reserves are from Canada and overseas, with liquid additions totaling 1.9 billion boe.

However, gas reserves at the end of 2015 were reduced by 834 million boe, primarily in the United States, to reflect the change in prices. The company, the largest U.S. gas producer, expects the reserves to be developed and booked in the future.

Reserves additions reflect new developments, as well as revisions and extensions of existing fields resulting from drilling, studies and analysis of reservoir performance, ExxonMobil noted. Consistent with U.S. Security and Exchange Commission requirements, ExxonMobil reports reserves based on the historic average market prices on the first day of each calendar month during the year.

During 2015, 1.4 billion boe was added to the resource base through drillbit exploration discoveries, undeveloped resource additions and strategic acquisitions. Included was an oil discovery offshore Guyana and additional discoveries in Iraq, Australia, Romania and Nigeria. “Strategic unconventional resource additions” also were were made in the Permian Basin in West Texas, Canada and Argentina. The Permian has become one of ExxonMobil’s top U.S. targets (see Daily GPI, Feb. 2).

Overall, the resource base totaled more than 91 billion boe at year’s end, 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.