UPDATE 1-Talisman to invest $1.1 bln in Vietnam oil fields

(Adds Petrovietnam's reserves forecast, quote)

HANOI, April 24 (Reuters) - Canada's Talisman Energy (TLM.TO) plans to invest $1.1 billlion to develop commercial production of two offshore oilfields in Vietnam, state media reported on Friday.

The newspaper Dau Tu (Investment) quoted Michael Horn, Talisman's representative in Vietnam, as saying the company would make the investment in Hai Su Trang (White Sealion) and Hai Su Den (Black Sealion) fields.

State oil firm Petrovietnam said in a statement on Friday it estimated Hai Su Den and Hai Su Trang held 171.2 million barrels and 59.6 million barrels of crude oil reserves respectively.

"The production from the two fields would help Petrovietnam maintain crude oil output in 2011 as well as ensure national energy security," Petrovietnam said.

The two fields, part of a larger joint exploration project between Talisman and Petrovietnam in Vietnam's offshore block 15-2/01, would be put into commercial production by September 2011, Petrovietnam said earlier this week.

Combined production from the two fields is estimated at 35,000 barrels per day, Petrovietnam said.

Petrovietnam, which has a 40 percent stake in the joint venture, also said it had discovered a smaller field nearby called Hai Su Bac (Silver Sealion), with tests showing flow of around 600 barrels of crude oil per day.

The company said it was conducting tests to assess the commercial viability of the find. (Reporting by Nguyen Nhat Lam; Editing by Alan Raybould)