The company will use its own funds to finance the new acquisitions, TNK-BP said in a statement.
"The acquisitions in Venezuela and Vietnam mark a milestone in TNK-BP's strategic expansion in the global energy market," said Mikhail Fridman, TNK-BP's executive chairman and one of its four Russia-connected shareholders.
Taken together, the Vietnamese and Venezuelan assets gave BP net reserves of 270m barrels of oil equivalent (boe), and its share in production from the Venezuelan assets is 25,000 boe per day, BP said in a separate press statement.
Last year TNK-BP produced 1.89m boe per day.
In Venezuela, the company will buy 40 percent of Petroperija and 26.6 per cent of Bouqeronin oil field projects, majority owned by Venezuela's state-owned PDVSA oil company.
It will also acquire a 16.7 percent stake in of the Petromanagas upgrader project, which processes tar-like Orinoco heavy crude into lighter synthetic oil that can be processed by traditional refineries.
The project holds gross reserves of 1.2 billion barrels barrels of oil equivalent.
In Vietnam, TNK-BP will acquire BP's 35 per cent stake in an offshore gas condensate project; a 32.7 percent stake in the Nam Con Son gas pipeline and a 33.3 percent stake in the Phy My 3 power plant.
All three of these assets form an integrated gas and power project with a production capacity of 30,000 barrels of oil equivalent per day, on a working interest basis.