May 23 (Reuters) - An Exxon Mobil-led oil consortium

will need to decide by October whether it will go ahead and

develop a large natural gas find off the coast of Guyana, the

country's vice president said on Thursday.

The government has been pressing for a bonanza from mostly

untapped gas reserves found by the Exxon-led group. The

consortium, which includes Hess Corp ( HES ) and CNOOC Ltd

, is required under its production agreement to return

to the government by October about 20% of its massive Stabroek

block if that area remains undeveloped.

Exxon has said it hopes to complete an appraisal of the gas

findings by early next year and is considering how to best

commercialize the natural gas. The October deadline for

relinquishing untapped areas calls for it to make a decision

sooner.

That 20% of the undeveloped Stabroek area might include the

group's Haimara discovery, where it mostly found natural gas,

Guyana Vice President Bharrat Jagdeo said on Thursday during a

media briefing in Georgetown.

"We have had some discussions with Exxon and told them that

if they are not going to work on it, they have to relinquish.

They did some studies and said they might be able to move

forward with the project," Jagdeo said.

An Exxon spokesperson said it is in discussions with Guyana

over what areas will be relinquished. The consortium's

exploration agreement runs through 2027, the spokesperson added.

Haimara, the group's 12th finding of oil and gas in the

country, was announced in 2019. Exxon has said the Haimara-1

well found approximately 207 feet (63 meters) of a high-quality,

gas-condensate bearing sandstone reservoir.

There could be up to 16 trillion cubic feet of associated

gas in Exxon's areas, Jagdeo said, citing Exxon accounts.

Guyana is moving ahead to select a company that could

develop the gas project, which it estimates will require between

$10 billion and $15 billion in investment.

"We tested the market. We went out for expressions of

interest and had some really good, strong firms with good

credentials saying, 'We believe there is a viable project and we

want to work on it,'" he added, without identifying the firms.

The cabinet must approve the company selected and once

approved, that firm would be cleared to initiate talks with

Exxon over a project to monetize the gas reserves.