Vietnam has emerged in recent decades as a major petroleum producer in Southeast Asia. In recent years, the country has increased exploration activities, encouraged foreign investments as well as introduced market reforms to support the petroleum industry. Vietnam's proven oil reserves are estimated at 4.4 billion barrels, while proven natural gas reserves were at 21.8 Tcf, with most of these resources located offshore. PetroVietnam is the operator and regulator of the local petroleum industry. Oil and gas production is undertaken by its upstream unit, PetroVietnam Exploration and Production, or through its joint venture with other companies.