Reforms give Pemex the right to most proven oil reserves, but private firms can compete for the bulk of the possible reserves, the Mexican government said.

Mexican lawmakers last week put the final touches on legislation that opens Mexico up to private investors after more than 70 years under a monopoly controlled by state-run Petroleos Mexicanos, or Pemex.

Under a new measure, Pemex has the rights to more than 80 percent of the proven and probable oil reserves in Mexico, while private companies can compete for nearly 80 percent of the possible reserves.

Pemex Director Emilio Lozoya said his company would now work to establish joint ventures for new exploration activity to tap into unrealized reserves.

The reform "strengthens and enhances the ability of operation and investment" in the Mexican oil sector, he said in a statement Wednesday.

The legislation is a victory for Mexican President Enrique Peña Nieto, who came to power in 2012 with promises of sweeping economic reform. The oil sector accounted for 13 percent of the country's export earnings last year and the government said reforms should draw in nearly $50 billion in new investments over the next three years.

Mexico set a goal of producing 3.5 million barrels of oil per day by 2025, which would be a 40 percent increase from 2013 levels.

The country, a top 10 oil producer, had an estimated 10 billion barrels of proven oil reserves as of 2013.