sentences:  ONGC has discovered 6 of the 7 commercially producing Indian Basins, in the last 50 years, adding over 7.15 billion tonnes of In-place Oil & Gas volume of hydrocarbons in Indian basins.Against a global decline of production from matured fields, ONGC has maintained production from its brownfields like Mumbai High, with the help of aggressive investments in various IOR (Improved Oil Recovery) and EOR (Enhanced Oil Recovery) schemes.ONGC has many matured fields with a current recovery factor of 25–33%.