Petrochemical giants Chevron and Spain’s Repsol have quit exploration at two offshore blocks in Mexican waters after early work suggested there are not enough resources to make it worthwhile to continue.

The two oil companies had won the rights to explore the blocks at a tender during the tenure of Mexico’s previous administration. They are only the latest in a list of foreign oil companies that won exploration rights in the recent past and are now returning them.

The list includes BP, Shell, and TotalEnergies with some companies returning more than one block to the state. Chevron has told the Mexican energy regulator that its work at the deepwater block offshore the state of Tabasco had yielded no promising results, while Repsol never conducted any meaningful exploration work at the shallow-water block it had won, according to the industry regulator Mexican hydrocarbons commission.

The Peña Nieto government had major ambitions about Mexico’s oil industry, leaning hard on foreign supermajors to spearhead a surge in production. However, the number of actual discoveries has been smaller than hoped for.

There is some glimmer of hope in that one oil company, Australia’s Woodside Energy is moving ahead with the ‘Trion field’ was discovered in 2012 and recently got the final go-ahead from its majority shareholders, Australia’s Woodside Energy. Woodside owns 60 per cent of the Trion field, with the remaining 40 per cent held by Mexico’s state-run oil firm, Petroleos Mexicanos (Pemex).

Pemex brought Woodside onto the project five years after discovery because it lacked the resources to develop Trion on its own. Woodside expects a 16 per cent return on the project with a short payback of four years, assuming $70 oil.

The reserves that the project will tap have been estimated at 479 million barrels of oil equivalent in oil and gas. Of these, Woodside’s share is seen at 287 million barrels of oil equivalent. According to Pemex estimates, the gross recoverable reserves of Trion are the equivalent of 485 million barrels of oil.