Sechin said a refinery and port owned by the Indian firm were worth around $10 billion and $2.9 billion respectively.
India and Russia signed a deal on Saturday to pave the way for a group led by Rosneft to acquire Essar.
Officials from Russian lender VTB VTBR.MM, which is giving Essar $3.9 billion in credit for debt reconstruction, said Rosneft would pay around $3.5 billion for its stake in Essar, the same amount as European trader Trafigura and Russian fund UCP.
Reporting by Denis Pinchuk; Writing by Jack Stubbs; Editing by Andrew Heavens
Our Standards: The Thomson Reuters Trust Principles.