FACTBOX-Iraq's oil sector opens its doors

June 25 (Reuters) - For the first time since the fall of Saddam Hussein, foreign oil companies will get a chance to work on Iraq's oil reserves when Baghdad auctions off contracts to develop six of its most prized oilfields on June 29-30.

Two undeveloped gas fields are also on offer.

Criticism from within the Iraqi state-run oil industry, pressure on the oil minister, and the terms of the contracts themselves make the deals risky and troublesome, but global oil firms say the potential is tantalising.

Here are some facts about Iraq's oil industry:

HOW MUCH OIL AND GAS IS THERE?

Iraq is listed as having the world's third largest crude reserves at 115 billion barrels.

That estimate, however, is based on seismic data from nearly three decades ago and some experts believe there could be another 45 billion to 100 billion barrels of recoverable oil.

That could take Iraq's reserves close to top oil exporter Saudi Arabia's estimated 267 billion barrels.

Proven natural gas reserves are 112 trillion cubic feet. Around 60 percent of gas output is burned off because Iraq cannot make use of it. Baghdad has signed a deal with Royal Dutch Shell (RDSa.L) to stop that in the south.

PRODUCTION REALITY AND ASPIRATIONS

Iraq produces 2.3 million to 2.4 million barrels per day of crude, mainly from the southern fields. That is below the 2.5 million barrels per day produced before the invasion.

Iraq has an ambitious plan to boost output over 6 million bpd in five years. The first contracts are expected to add 1.5 million bpd. A second round of tenders later this year for 11 undeveloped fields could add another 2.5 million bpd.

A LITTLE HISTORY