Adds more details on deal and context in paragraphs 3-4

SAO PAULO, Dec 28 (Reuters) - Engie Brasil EGIE3.SA said on Thursday it has reached a deal to sell a 15% stake in natural gas pipeline firm TAG to Canadian investment fund Caisse de Depot et Placement du Quebec (CDPQ) for 3.1 billion reais ($641 million).

After the deal's conclusion, CDPQ will raise its stake in TAG to 50%, while Engie Brasil will own 17.5% and its French parent company will hold the rest, giving it an indirect 50% stake.

In 2019, Engie and CDPQ jointly acquired a 90% stake in TAG from state-run oil firm Petrobras PETR4.SA for about $8.6 billion, purchasing the remainder the following year.

TAG owns and operates a large part of Brazil's natural gas pipelines with some 4,500 kilometers (2,800 miles) over 10 states in Brazil.

($1 = 4.8501 reais)

(Reporting by Peter Frontini;
Editing by Chris Reese and David Alire Garcia)

((Peter.Siqueira@thomsonreuters.com; +55 11 56447727;))