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

Digboi, located in the Tinsukia district of Assam, is the oldest oil field in India and remains operational today. Oil was first discovered in the region in 1889, and the first commercially viable well (Well No. 1) began production in October 1889 [t4, t5]. The Digboi refinery, commissioned in 1901, is also the oldest operating refinery in India [t4, t6]. While other major fields like Naharkatiya (1954), Ankleshwar (1958), and Bombay High (1976) were discovered much later, Digboi has maintained continuous production for over a century [c4, t3]. Although its current output has declined to approximately 240 barrels per day compared to its peak during World War II, it is historically significant as the birthplace of the Indian oil industry [t4, t6]. Today, the field is managed by Oil India Limited (OIL) [c1, t4].

Sources

1. [1] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 8: Energy Resources > 3. The Brahmaputra Valley > p. 13
2. [2] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 8: Energy Resources > Petroleum > p. 9