HANOI, May 7 (Reuters) - Affiliates of Vietnam's state oil firm PetroVietnam have made two new oil findings with combined initial reserves of 100.5 million barrels of crude oil, its exploration and production arm PVEP said on Tuesday.

The discoveries are essential for the oil industry of Vietnam, which has been struggling to raise its crude oil output due to shrinking proven reserves, amid rising fuel demand.

Drilling at the R79 well in the Rong Field in the Block 09-1 off southeast Vietnam found initial reserves of 16.5 million barrels of crude oil, PVEP said in a statement.

The field is operated by Vietsovpetro, a Vietnam-Russia joint venture.

The other finding was at BA-1X well at Bock PM3 CAA off southern Vietnam, with initial reserves of 84 million barrels, said PVEP, which holds a 30% stake in the block. Production at BA-1X started on May 5 at 2,100 barrels per day.

Vietnam's crude oil output in the first four months of this year fell 3.6% from a year earlier to 2.78 million metric tons, according to government data. (Reporting by Khanh Vu; Editing by Martin Petty)