Iran's oil minister said Monday that an oil field whose discovery President Hassan Rouhani announced at the weekend adds only 22.2 billion barrels to the country's estimated crude reserves.
Out of the amount at the site, only a tenth -- 2.2 billion barrels --- can be extracted due to technological limitations, the minister, Bijan Namdar Zanganeh, told reporters in Tehran.
Rouhani on Sunday announced the discovery of a field containing 53 billion barrels of oil in the southwestern province of Khuzestan, saying it was a "small gift by the government to the people of Iran".
The oil minister said the discovery added 22.2 billion barrels to the country's oil reserves.
"Considering that there was already 31 billion barrels of oil (in the region), the in situ amount added is 22.2 billion barrels," he said.
Due to the area's "dense and stone material", the amount that can be extracted is only "2.2 billion barrels, considering the current technology we have," he added.
The discovery spans 2,400 square kilometres (926 square miles), according to a map Zanganeh showed journalists.
It could potentially be expanded towards to southwest and east through further exploration.
The oil layer is about 3.1 kilometres (nearly two miles) deep, with an average thickness of 80 metres (yards).
Iran is a founding member of the Organization of the Petroleum Exporting Countries (OPEC).
It sits on the world's fourth-biggest oil reserves, estimated by energy giant BP at 155.6 billion barrels of crude, and also has the second-largest gas reserves.
Yet the Islamic republic has struggled to sell its oil since US President Donald Trump withdrew from a landmark 2015 nuclear deal and reimposed unilateral sanctions on Iran.
The remaining parties to the accord -- Britain, China, France, Germany and Russia -- have worked to save it by finding ways to bypass US sanctions, but their efforts have so far borne little fruit.