Mexico’s oil regulator announced on Nov. 28 a final list of 17 oil companies representing a dozen countries that have prequalified to bid on the country’s first-ever deepwater oil auctions, set for Dec. 5.

The highly anticipated tenders include an auction to pick a partner for Mexican national oil company Pemex to develop its promising Trion Field as well as 10 separate deepwater fields, including four clustered around Trion just south of Mexico’s maritime border with the U.S.

All the fields are in the country’s territorial waters in the Gulf of Mexico (GoM), in the Perdido Fold Belt and Salina Basin along the southern rim of the GoM.

The prequalified companies constitute 15 bidders, eight of which successfully sought to prequalify as individual operators while seven consortia did so as well.

The prequalified individual bidders are BHP Billiton, BP, CNOOC, ExxonMobil, Petronas, Pemex, Statoil and Total.

The seven consortia are Atlantic Rim and Royal Dutch Shell; Eni and Lukoil; Murphy, Ophir, Petronas unit PC Carigali and Sierra Offshore Exploration; PC Carigali and Sierra; Statoil, BP and Total; Total and ExxonMobil; and Chevron along with Pemex and Inpex Corp.

The later consortium marks the first time Pemex has sought to tie up with another oil company in the hopes of jointly developing an E&P project.

Juan Carlos Zepeda, president of the oil regulator known as the CNH, said it will not be known until Dec. 5 whether the prequalified firms will bid on Trion or the other deepwater blocks up for grabs.

“It’s a large number of bidders,” Zepeda said. “We have companies that are competing as individuals and as consortia, and some of them are even participating in more than one consortium.” He added that about half of Mexico’s prospective oil resources are located in the Gulf’s deep waters.

Zepeda emphasized that companies are barred from bidding more than once on the same project.

The auctions will mark the fourth phase of the so-called Round One tender, a major part of an energy reform launched in 2013 that ended the decades-long monopoly enjoyed by Pemex and aims to reverse a dozen years of declining crude output.