UPDATE 1-PetroChina buys Keppel stake in refiner SPC for $1 bln

* PetroChina to pay around S$1.47 bln for 45.51 pct SPC stake

* PetroChina needs to make offer for rest of firm

* Keppel, PetroChina to seek offshore oil opportunities

* First overseas acquisition of a public firm by PetroChina (adds details, quotes)

By Harry Suhartono

SINGAPORE, May 24 (Reuters) - Asia's largest oil and gas producer PetroChina (0857.HK: Quote, Profile, Research) is buying Keppel Corp's (KPLM.SI: Quote, Profile, Research) 45.5 percent stake in Singapore Petroleum Company (SPC) for S$1.47 billion ($1.02 billion) and plans to make a general offer to buy the rest of the firm.

SPC's main asset is a refinery in Singapore, Asia's oil trading and pricing hub, and so the acquisition may give PetroChina more leverage and flexibility in oil trading.

It is the first overseas acquisition of a public company by PetroChina, and the move for downstream fuel production adds to efforts by Chinese oil majors to buy upstream oil exploration assets around the world to secure energy supplies.

"SPC will become a new platform for the implementation of our international strategy and will provide a broader foundation and stable path for development," PetroChina said in a statement.