The state-run firm said a lack of funds had kept it from boosting its exploration activities.
“The rise in recoverable reserves has slowed to an alarming rate, affecting the sustainability of the development of Vietnam’s oil and gas industry,” the company said in a statement on its website.
Vietnam’s crude oil output in 2018 was expected to fall 14.7 percent to 11.3 million metric tonnes, or 227,130 barrels per day, the government said in March.