Chevron, the No. 2 U.S. oil company said on Wednesday that oil from a new seabed seep at its Brazilian offshore field is chemically different to crude from a November spill, and that the two leaks are unrelated.

Chevron, its drilling contractor Transocean and several of the two companies' employees are expected to face criminal charges on Wednesday for alleged environmental crimes related to the November spill, which spilled at least 2,400 barrels.

Oil from a seep found this month 3 km (1.9 miles) from Chevron's November seafloor leak -- which also triggered an $11 billion civil lawsuit -- is much heavier and has different chemical properties from crude in the earlier spill, Chevron told Reuters.

There is no evidence that the two sets of seeps are related, Chevron spokesman Kurt Glaubitz said in an email to Reuters.

Oil samples collected from the second seep and analyzed by the IPEX lab in Brazil and reviewed by Chevron indicate that the oil is not from the Frade production reservoir.

Chevron said oil from the recent seep contained no drilling mud, suggesting it is not a residual spill or a new complication of the November spill. Only around 1 barrel of heavier crude has been found flowing out of the new seep.

As a precaution, Chevron has shut output at the 61,500-barrels-per day Frade field in Brazil, and will complete a new geological study of the Frade prospect with its partners there, including Brazil's state-controlled Petrobras. Chevron has spent more than $2 billion developing the field.

The November spill came after a pressure kick forced Chevron to shut in a new production well at Frade, which resulted in oil, gas and mud breaching its well beneath the seabed and eventually flowing out into the Atlantic Ocean. The spilled oil did not reach shore.

Brazilian President Dilma Rousseff, a former energy minister and former chairwoman of state-led oil company Petrobras, a 30 percent partner in the Frade field, warned oil companies on Wednesday that they must strictly follow security procedures.

On this question there can be no exceptions to being within safety limits and knowing them, to never test them and never go beyond them, she said at the swearing in ceremony for the new head of Brazil's oil regulator, the ANP, in Rio de Janeiro.

The discovery of a new seep in the Frade field this month has led to allegations by a Brazilian federal prosecutor that Chevron's drilling has led to dangerous faults in the undersea oil reservoir at Frade, which could be irreparably damaged and may eventually leak much more oil.

That statement is not consistent with the facts, Glaubitz said.

The intensity of the legal moves against Chevron has raised concern that they may slow the development of Brazil's vast new oil reserves, said Adriano Pires, a former ANP director and head of the Brazil Infrastructure Institute, a Rio de Janeiro energy think tank.

This could make it harder for Brazil to realize its goal of surpassing the United States to become the No. 3 world oil producer after Russia and Saudi Arabia, he said.

At least one company does not agree. BP wants to make new oil acquisitions in Brazil and is not being deterred by the legal fallout from the Chevron spill, said Guillermo Quintero, head of BP's Brazilian operations.

Last year BP bought the Brazilian oil exploration and production assets of U.S. based Devon.

(Editing by Dale Hudson)

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