Mexico's state-owned oil company announced Friday it will offer a farm-out arrangement to private firms to join in the exploration of a deep-water field in the Gulf of Mexico. It would be the first time that Petroleos Mexicanos has formed an association with a private firm for deep-water drilling.

Pemex Director Jose Antonio Gonzalez called it "a watershed moment in Pemex's history."

The Trion field, located in the Perdido belt just 25 miles (40 kilometers) south of the U.S. maritime border, is estimated to hold the equivalent of 480 million barrels in proved, potential and possible oil and gas reserves.

The company, known as Pemex, said the offer will be put up for bid in coming days and a winner will be announced on Dec. 5.

Officials estimate it will take $11 billion in investments to develop the field in waters about 8,200 feet (2,500 meters) deep.

Farm-outs are agreements where service providers take an interest in field, usually part of the oil and gas production, rather than payment.

Gonzalez did not specify what compensation the farm-out scheme would involve.

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