FACTBOX: Possible changes to Brazil's petroleum law

(Reuters) - Brazil's government is considering changing some rules applying to the oil industry following huge reserve discoveries made by state oil company Petrobras (PETR4.SA)(PBR.N).

Here are some facts about Brazil's oil reserves and the possible changes to the law under consideration.

BRAZIL'S NEW OIL DISCOVERIES

* The Tupi field discovered by Petrobras in November has an estimated recoverable reserve of between 5 billion and 8 billion barrels, 85 percent of which is light crude, making it the world's second-biggest oil find in the past 20 years.

* Potential further subsalt oil reserves stretching for 500 miles along the coast from Espirito Santo to Santa Catarina state could push Brazil above Nigeria to become the world's 10th biggest oil producer, Petrobras says.

* Petrobras' partners in the subsalt discoveries include Galp (GALP.LS), ExxonMobil Corp (XOM.N), Amerada Hess (HES.N), BG Group (BG.L), Repsol (REP.MC) and Shell (RDSa.L). Currently, firms are given control over any oil they find in their concessions and pay royalties to the state government.

POSSIBLE CHANGES IN OIL RULES

* The government now wants to take more control of the fields to increase revenue for social welfare and education.

* The government is looking to create a state company to manage oil exploration and production contracts in the sub-salt cluster.

* It could shift to a production-sharing model, under which the government owns the oil but pays companies with part of it.

* It wants to renegotiate the distribution of oil revenue among states and municipalities.