From our Dept. of Energy:
"Iran is OPEC's second largest oil producer and holds 10% of the world's proven oil reserves. It also has the world's second largest natural gas reserves (after Russia).
According to the Oil and Gas Journal (1/1/04), Iran holds 125.8 billion barrels of proven oil reserves, roughly 10% of the world's total, up from 90 billion barrels in 2003 (note: in July 2004, Iran's oil minister stated that the country's proven oil reserves had increased again, to 132 billion barrels, following new discoveries in the Kushk and Hosseineih fields in Khuzestan province). The vast majority of Iran's crude oil reserves are located in giant onshore fields in the southwestern Khuzestan region near the Iraqi border and the Persian Gulf. Iran has 32 producing oil fields, of which 25 are onshore and 7 offshore.
In October 1999, Iran announced that it had made its biggest oil discovery in 30 years, a giant onshore field called Azadegan located in the southwestern province of Khuzestan, a few miles east of the border with Iraq. Reportedly, the Azadegan field contains proven crude oil reserves of 26 billion barrels.
Since 1995, NIOC has made several other sizable oil discoveries, including the 3-5-billion-barrel Darkhovin onshore oilfield, located near Abadan and containing low sulfur, 39° API crude oil.
In February 2001, NIOC announced the discovery of a very large offshore oil field, named Dasht-e Abadan, in shallow waters near the port city of Abadan. According to a top NIOC official, Dasht-e Abadan could contain reserves "comparable" in size to Azadegan. "
http://www.eia.doe.gov/emeu/cabs/iran.html