BP said in July it was planning to dump up to $30 billion in its overseas assets to help meet its financial obligations related to the Gulf of Mexico oil spill.
The company already offloaded much of its Egyptian, Canadian and U.S. assets to Apache Corp. for $7 billion and its Colombian portfolio to Talisman and Ecopetrol for $1.9 billion.
The BP interests in Vietnam include a 35 percent operating interest in the Lan Tay and Lan Do gas fields, while oil interests in Venezuela include a stake in the lucrative Orinoco belt.
The total probable reserves included in the deal add 290 million barrels of oil equivalent to TNK-BP's holdings.
"These are robust businesses which offer both existing production and potential opportunities for future growth," BP Chief Executive Officer Bob Dudley said in a statement. "We believe they will offer TNK-BP a solid foundation as it builds its business outside Russia."
BP keeps an economic interest in the Venezuelan and Vietnamese assets through its 50 percent partnership with TNK-BP.