Iran has discovered about a dozen new oil fields with in-place reserves of 30 billion barrels, head of exploration at National Iranian Oil Company (NIOC) says.

Some 4.7 billion barrels of these reserves are recoverable, said Seyyed Saleh Hendi who also announced the discovery of 128 trillion cubic feet of gas.

New discoveries, which happened over the past four years, show that more gas finds are likely, while any new oil find is not believed to be sizable, the official told reporters in Tehran.

“We have to say goodbye to (finding) such big fields as Yadavaran and Azadegan and get used to discovering smaller fields,” Hendi added.

Iran's proven oil reserves of 157 billion barrels are the world’s third largest, while its gas reserves are the largest. Taken together, the country owns the biggest hydrocarbon reserves in the world.

Iran produces about four million barrels per day of crude oil, some 1.5 million bpd of which are used at home.

Many of the reserves and energy facilities are located in the country’s south which has been hit by a wave of sandstorms in recent years.

Sandstorms have blanketed a number of cities and towns in recent days, leading to power outages in the oil-rich Khuzestan province.

On Saturday, a senior official said power supply had been restored within hours of an outage in southwestern Iran that hit crude oil production by 700,000 barrels.

Bijan Alipour, managing director of the National South Oil Company, said part of the output cutback in the Karoun area was planned and aimed at storing about 300,000 barrels produced by the West Karoun fields.

"As power supply has been reestablished, processing plants have resumed production according to schedule and the reduced hours will be compensated as much as possible," Alipour said in a statement, published on the Ministry of Petroleum’s Shana news website.

The outages caused water treatment facilities to temporarily shut down, cutting supplies to many neighborhoods in major cities such as Ahvaz.