(Adds details on joint venture stakes, key dates and backgroundon Trion field)
By David Alire Garcia and Ana Isabel Martinez
MEXICO CITY, July 27 (Reuters) - Mexico's oil regulator onWednesday said state-owned oil company Pemex must take a minimum45 percent stake in its first-ever proposed joint venture withwould-be private partners to develop oil reserves in the Gulf ofMexico's deep waters.
Global oil majors are widely expected to bid in the Decemberauction to help develop the Trion light oil field in the PerdidoFold Belt just south of Mexico's maritime border with the UnitedStates.
Companies such as Royal Dutch Shell and Exxon Mobil operate lucrative developments in nearby U.S. waterswhile Mexico has yet to achieve commercial production on itsside of oil-rich Perdido due to a lack of technical expertise totap such fields.
The call for bids to partner with cash-strapped Pemex onTrion follows the constitutional energy reform enacted in 2013which promised to reverse a decade-long slump in crudeproduction by luring new players to explore for and produce oil.
The regulator said the Trion joint venture will be bid outin the form of a license contract, which is similar to aconcession, and will include two operators, one of which musthave between a 30 to 45 percent stake in the project.
Interested bidders have until Sept. 15 to pre-qualify forthe auction by meeting both financial and technical minimumrequirements, while the final version of the contract and bidterms will be published on Sept. 30.
The license contract to partner with Pemex on the projectwill be awarded on Dec. 5. Mexico will also auction 10 separatedeep water fields, including four that surround Trion, inDecember.
Under the terms of the energy reform, Pemex can partner withcompanies in exploration and production projects, but ratherthan being allowed to pick its partners, they will instead beselected by an auction run by the oil regulator, known as theNational Hydrocarbons Commission.
The partnership will allow Pemex to share the investmentneeded to successfully develop the field, the company's firstmajor deep water oil project.
The Trion field holds some 480 million barrels and willrequire about $11 billion worth of investment.
The field covers about 483 square miles (1,250 square km)and is located under more than 8,202 feet (2,500 meters) ofwater. (Additonal reporting by Adriana Barrera; Editing by BernardOrr)
