Big oil companies like Exxon have struggled in recent years to gain access to new supplies as countries with vast reserves like Venezuela have handed those over to state-run firms.

Investors like to see companies replace at least 100 percent of their output, since anything below that figure indicates the asset base is shrinking.

Exxon said last year’s reserve additions were the highest since the merger of Exxon and Mobil in 1999. Still Exxon shares fell 2 percent in morning trading, a drop an analyst linked to overall market weakness.

“My screen is just a sea of red today, a lot of energy companies are down quite a bit,” Mike Breard, energy analyst at Hodges Capital Management in Dallas said. “As long as a company as big as Exxon is replacing its production, it’s growing.

Exxon, the world’s largest publicly traded company, said it increased its proved reserves by 3.5 billion oil equivalent barrels, or 209 percent of its production, bringing its reserve base to 24.8 billion oil equivalent barrels.

Reserve additions from acquisitions and subsequent revisions totaled 3 billion oil-equivalent barrels. Additions also came from the Sakhalin-1 Arkutun Dagi project in Russia and other countries including Canada, the United States, Nigeria, Norway and Abu Dhabi, the Irving, Texas, company said.

Liquid additions totaled 905 million oil-equivalent barrels for a 102 percent replacement ratio and gas additions totaled 2.6 billion oil-equivalent barrels for a 328 percent replacement ratio.

Exxon purchased US natural gas company XTO last year, in a deal aimed at increasing Exxon’s shale gas business in the US and around the world. In its long-term outlook, Exxon sees natural gas demand growing, fueled primarily by power demand in developing countries.

The proved reserves base is split between 47 percent liquids and 53 percent gas, and includes oil sands extracted by mining and equity company reserves.