DOHA The world's biggest gas field is shared between Iran, which calls its share South Pars, and Qatar, owner of the North Field (also known as the North Dome).
Qatar has brought in international firms and used the field to become the world's largest exporter of liquefied natural gas (LNG), whereas Iran's development of South Pars has been hampered by protracted delays, in part because of international sanctions.
Iran and Qatar are respectively holders of the world's second and third largest natural gas reserves, behind Russia.
Their South Pars/North Field gas field holds an estimated 50.97 trillion cubic meters of in-situ gas and some 50 billion barrels of condensates, according to the International Energy Agency.
It covers an area of 9,700 square kilometers, of which 3,700 square kilometers (South Pars) is in Iranian territorial waters and 6,000 square kilometers (North Field) is in Qatari territorial waters.
The following brings together facts on Qatar's North Field.
LNG production in Qatar is divided between two companies, Qatargas and Rasgas. State oil company Qatar Petroleum (QP) owns a majority stake in both, with international oil companies holding smaller stakes in individual production trains.
RasGas is 70 percent-owned by QP and 30 percent-owned by ExxonMobil (XOM.N), while Qatargas is owned by a consortium including QP, Total (TOTF.PA), ExxonMobil, Mitsui (8031.T), Marubeni (8002.T), ConocoPhillips (COP.N) and Royal Dutch Shell (RDSa.L).
Qatar Gas Transport Company (known as "Nakilat", meaning "carriers" in Arabic) provides ships to transport Qatar's LNG. LNG, natural gas cooled to liquid form for export by tanker, is produced in large facilities known as trains.
Qatar expects to reach a goal of having the capacity to liquefy 77 million tonnes of natural gas annually by the end of the year, concluding a massive expansion plan that has made it the world's top LNG exporter only 14 years after shipping its first cargo.
In 2005 Qatar declared a moratorium on development of the North Field, to give the country time to study the impact of such a rapid increase in output on the reservoir.
The moratorium, expected to last until 2014, applies only to the Qatari side and not the Iranian side. Qatar's priority is to ensure the reservoir's longevity, it energy minister said in January.