Mexico's state oil company Pemex retained rights to 83 percent of the country's proven and probable oil reserves Wednesday, as the government began implementing landmark energy reforms.
The allocation, which is equivalent to an estimated 20.6 billion barrels, is the first step in overhauling the country's energy industry, ending Pemex's 76-year monopoly and opening the sector to foreign companies.
Under the reforms, which President Enrique Pena Nieto signed into law Monday, Pemex had to apply to the government to retain the rights to the oil fields it wanted to keep -- a so-called "Round Zero" before the first round of bidding from other firms.
Energy Minister Pedro Joaquin Coldwell said Pemex was keeping "83 percent of 2P reserves (proven and probable), which amounts to 100 percent of its request, and 21 percent of possible reserves, which amounts to 67 percent of its request."
The allocation represents a total surface area of around 90,000 square kilometers (22 million acres) and an estimated 20.6 billion barrels of crude oil equivalent, he said at a public event in the capital.
That is enough for 15 years of production at the company's current output of 2.5 million barrels a day, he said.
The decision makes Pemex the world's fifth-largest oil company by proven reserves, excluding those belonging to OPEC member states, said energy undersecretary Lourdes Melgar.
The reforms, the centerpiece of Pena Nieto's efforts to kick-start Latin America's second-biggest economy, aim to modernize Mexico's exploration and drilling technology and reverse Pemex's falling production.
Coldwell said the government hopes to attract around $50 billion in investment between 2015 and 2018, both from firms partnering with Pemex and the allocation of the remaining oil rights.