ExxonMobil Corp. said it added 4.5 billion boe of proved oil and natural gas reserves in 2018, replacing 313% of the year’s production, to a total of 24.3 billion boe at the end of the year.

Liquids represented 64% of the proved reserves, up from 57% in 2017, with some of the credit given to growth in the Permian Basin.

“We continue to add high-value, attractive assets to our portfolio that have positioned the company for long-term growth,” said CEO Darren W. Woods.

Reserves life at current production rates was estimated at 17 years. Over the past 10 years, the Irving, TX-based supermajor said it had added proved reserves totaling about 17 billion boe, replacing 108% of produced volumes, including the impact of asset sales.

Under U.S. Securities and Exchange Commission rules, reserves are reported based on the average of the applicable market price on the first day of each calendar month during the year. As a result of higher prices in 2018, about 3.6 billion boe, including volumes at the Kearl oilsands development in Canada, qualified as proved reserves additions at year’s end.

Proved additions from unconventional plays totaled around 1.2 billion boe, with significant additions from the Permian. ExxonMobil is the biggest leaseholder in the Permian, which it holds in parallel with pipeline and petrochemical infrastructure that extends from South Texas into Louisiana.

During the final three months of 2018, total oil, natural gas and other hydrocarbon output increased year/year hitting 4 million boe. From volumes produced in the Permian, global liquids production increased 4% to 2,348 b/d, while gas production fell to 9.97 Bcf/d from 10.44 Bcf/d.

Meanwhile, ExxonMobil recorded a downward revision for 2018 of 800 million boe related to its Netherlands assets, which resulted from an agreement with the Dutch government to curtail production at the Groningen gas field.

Reserves additions reflect new developments as well as revisions, including price impacts, and extensions of existing fields resulting from drilling, studies and analysis of reservoir performance.

ExxonMobil added 1.3 billion boe to its resource base in 2018 through organic exploration discoveries and strategic acquisitions, primarily in Guyana and Brazil. The resource base includes proved reserves and discovered resources that are expected to be ultimately recovered.

“Multiple new discoveries offshore Guyana, continued growth in the Permian Basin and a strategic acquisition in Brazil greatly enhanced our already strong portfolio of high-quality, low-cost-of-supply opportunities,” Woods said.