Mexican state oil company Petroleos Mexicanos said Tuesday that it signed three technology-sharing agreements with the U.K.'s BP PLC (BP), including one for deepwater exploration.

The five-year agreements, which are technical in nature and don't involve funding, also include a general collaboration accord and studying the potential of injecting air instead of nitrogen in fractured deposits to improve extraction.

The two companies have been working together through similar deals since 1996, Pemex said.

Pemex started drilling deepwater wells in 2004, and the company estimates that the bulk of its undiscovered oil and gas reserves lie in deep waters in the Gulf of Mexico.

However, current budget restrictions are expected to make it difficult for Pemex to finance deepwater projects, and the country's constitution bars private companies from forming associations with Pemex to explore for and extract oil.

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