The NIOC is exclusively responsible for the exploration, extraction, transportation and exportation of crude oil, as well as sales of natural gas and liquefied natural gas (LNG).
Having provided the domestic refineries and manufacturing plants with crude oil required for the petroleum products, the NIOC exports its surplus production according to commercial considerations in the framework of the quotas determined by the Organization of Petroleum Exporting Countries (OPEC) and at the prices prevalent in the international markets. The NIOC also signs some long term contracts on "buy-back" basis with foreign companies in order to exploit national oil fields and export its products. The NIOC exports natural gas and liquefied natural gas via the "National Iranian Gas Export Company" which is one of its subsidiaries.
NIOC's oil and gas reserves in early 2005 was as follows;
*Recoverable liquid hydrocarbon reserves in early 2005, 136.99 Goilbbl 10% of world's total.
*Recoverable gas reserves in early 2005 , 28.17 m3 (15% of world's total).
Current NIOC production capacities include over 4 Moilbbl of crude oil and in excess of 500 million cubic meters of natural gas per day. In 2008, the average extraction cost of oil was less than $5 per barrel. This does not include processing (refining) and distribution costs.
Iran’s cumulative oil production has reached to 61 Goilbbl by the end of 2007, most of these volume produced after 1951, under the supervision of NIOC.
Iran's overall export crude oil was valued at $51 billion in 2007.