RIO DE JANEIRO, May 9 (Reuters) - Brazil's state-run oil

firm Petrobras must do a series of studies on the

impact on Indigenous groups in the Amazon area of planned

offshore drilling nearby in order to analyze the project's

viability, according to a federal agency and documents from

government agencies.

The wide-ranging studies demanded by Brazil's environmental

agency Ibama are meant to ascertain the "social, cultural and

environmental" impacts on Indigenous peoples of drilling in the

Foz do Amazonas basin, part of the so-called Equatorial Margin.

The demand for new studies were part of set of documents

sent by Ibama to Petrobras on April 17, and seen by Reuters.

The requirement is a fresh hurdle in the firm's attempts to

drill an exploratory well about 175 kilometers (110 miles) off

Brazil's northernmost coast, amid increasingly stiff resistance

from local Indigenous leaders in Amapa state.

All studies and requirements requested by Ibama within the

scope of environmental licensing and in accordance with

governing legislation were met by the company, said Petrobras in

a statement, adding that it is open to incorporating new

requests that may be necessary.

The company has said that drilling in the region would

have "no direct impact" on Indigenous communities and argued

that the time to require a formal consultation with them had

passed.

Petrobras CEO Jean Paul Prates has said he expects to start

drilling there this year still.

However, the additional studies are likely to take at least

six months, according to a person close to Brazil's Indigenous

affairs agency Funai.

That may further delay the plans to explore the Foz do

Amazonas basin in the Atlantic Ocean, considered Brazil's most

promising frontier for oil exploration because it shares geology

with the coast of nearby Guyana, where Exxon is developing huge

fields.

A year ago Ibama denied Petrobras a license to drill in the

area, citing possible impacts on Indigenous groups and the

sensitive coastal biome. Days later, Petrobras appealed the

decision, and has been waiting since then for Ibama's response.

In October, Ibama asked Funai to weigh in on the matter

before it decides on the appeal. Funai proposed in December that

Ibama should require several more studies to assess impacts,

according to a government memo.

On April 17, Ibama sent the memo to Petrobras, notifying the

firm it must attend to it.

"Ibama's understanding is that Petrobras must meet these

demands," the agency said in a statement to Reuters, adding that

a final say on the appeal would be impossible without it.

Funai declined to give a timeline on how long the studies

would take, adding that it depends on the schedule set by

Petrobras and a consultancy hired for the studies, which will be

submitted to the Indigenous peoples.

Funai's memo in December outlined requirements for a

study to assess how the project would affect Indigenous

communities and their customs, local flora and fauna and

economic activity in the area, culminating in a "Viability

Analysis."

Funai said that if the project is deemed "viable," the

studies will be used to propose "measures to mitigate, control

and compensate for impacts, if necessary."

Ibama's decision to require the study proposed by Funai

is a win for the Council of Chieftains of the Indigenous People

of Oiapoque (CCPIO), an umbrella group representing the 8,000

Indigenous people in the area.

Since 2022, CCPIO has cited impacts from Petrobras

activities in the region on Indigenous communities, demanding a

13-month formal consultation regarding their views on the

project.

CCPIO coordinator Cacique Edmilson Oliveira considers the

regulatory decision a victory, he told Reuters by phone, adding

the studies will provide Indigenous communities with a greater

understanding about what's happening.

"I think it's important to have this data," said

Oliveira. "We will not run the risk of suffering any harm."

He said the oil company will have to take into account

the fact that coastal Indigenous lands could be threatened by

drilling even though the plan is to search for oil offshore.