Which one of the following oil fields of India is the oldest and still producing oil ?

Digboi oil fields of India is the oldest and still producing oil. Digboi has the distinction of being India's oldest continuously producing oilfield. Digboi refinery, now a division of Indian Oil Corporation, had a capacity of about 0.65 MMTPA as of 2003. The Digboi refinery is the world's oldest oil refinery still in operation.