All told, the Mexican-state led company has requested to keep 83% of its probable reserves and 31% of prospective reserves in the process known as Round Zero, Mexico's Energy Secretariat (Sener) said on Monday as it begins a 180-day review of the requests.

But Pemex also plans to release "important areas for individual participation in future rounds" in areas including the tough-to-crack Chicontepec field and unconventionals, Sener said following Pemex's Friday filing of its wish list.

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