FILE PHOTO: The logo of commodities trader Glencore is pictured in front of the company's headquarters in Baar, Switzerland, July 18, 2017. REUTERS/Arnd Wiegmann//File Photo

By Trixie Yap, Yantoultra Ngui and Chen Aizhu

SINGAPORE (Reuters) - Global commodities traders Vitol and Glencore are expected to make formal bids for Chevron's 50% stake in Singapore's second-largest refinery, five people familiar with the matter said.

The value of the entire refinery is estimated at roughly $1 billion, said one of the people who has direct knowledge of the sale. The Switzerland-based firms were shortlisted this month and Chevron is seeking to receive final binding bids during October, the person added.

Vitol and Glencore, which have other refining assets in the Asia-Pacific, are keen to acquire more and boost trade volumes in the region, the sources said. Singapore is Asia's biggest oil trading hub and the world's largest bunkering port where refined products are blended, sold or re-exported.

The refinery on Jurong Island is one of three major refineries in the city-state and has a crude processing capacity of about 290,000 barrels per day. The other 50% is owned by Chinese state oil giant PetroChina through its Singapore Petroleum unit.

PetroChina has first right of refusal to purchase Chevron's share. It did not immediately respond to a Reuters request for comment on whether it planned to bid for the asset.

Reuters was not able to learn if other firms were also planning to make formal bids.

The sources were not authorised to speak to media and declined to be identified.

Chevron, Vitol and Glencore declined to comment. Morgan Stanley, appointed to handle the sale of Chevron's holding in the Singapore Refining Company as well as other Asian assets, also declined to comment.

The U.S. oil and gas major is in the midst of cutting up to $3 billion in costs by the end of 2026. Terminal and fuel storage facilities in Australia and the Philippines, as well as retail stations in Malaysia, are also available for sale, two of the sources said, adding that all these assets could be purchased as a bundle or separately.

Vitol owns a 32,000 barrel-per-day refinery in Tanjung Bin, Malaysia, and has a 50% stake in the ATB Oil terminal at Tanjung Pelapas, next to Singapore's Jurong Island. It also owns Viva Energy, which operates the 120,000-bpd Geelong refinery in Australia.

Glencore, through a joint venture with Indonesia's Chandra Asri, owns part of Singapore's Aster Chemicals and Energy, which was acquired from Shell in a deal completed in April.

Aster currently operates a 237,000-bpd refinery and chemical complex on Pulau Bukom and Jurong Island.

(Reporting by Trixie Yap, Yantoultra Ngui and Chen Aizhu; Editing by Florence Tan, Tony Munroe and Edwina Gibbs)