The fire started from a part of the Group Gathering Stations (GGS) number 3 of ONGC's Assam Asset at Geleki in Sibsagar around midnight.
The fire rapidly spread through the entire GGS burning thousands of tonnes of oil.
It took many hours for the ONGC's fire department to douse the flame.
Bodies of two workers were found from the spot, though their names have not been disclosed so far.
The exact quantum of loss or the reason for the fire are yet to be ascertained.
Senior officials have rushed to the spot.