Identify the place that is not an oil field:

Based on the provided geographical data, Naharkatiya is a significant oil field in Assam, located approximately 35 km southwest of Digboi, with production starting in 1954 [3]. Ankleshwar is the most important oil field in Gujarat, situated in the Bharuch district, and is known for its high-quality gasoline and kerosene [4]. Kalol is also a major oil-producing region in Gujarat, specifically within the Ahmedabad-Kalol region [3]. In contrast, Ledo is primarily known as a coal-mining center in the Tinsukia district of Assam, rather than a major oil field. While the context mentions various oil fields in the Brahmaputra valley and Gujarat, such as Digboi, Moran, and Mehsana, it does not list Ledo as an oil-producing site [4]. Therefore, Ledo is the correct answer as it is not an oil field.

Sources

1. [1] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 8: Energy Resources > 3. The Brahmaputra Valley > p. 13
2. [3] INDIA PEOPLE AND ECONOMY, TEXTBOOK IN GEOGRAPHY FOR CLASS XII (NCERT 2025 ed.) > Chapter 5: Mineral and Energy Resources > Iron Ore > p. 59
3. [2] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 8: Energy Resources > 2. The Gujarat Coast > p. 12
4. [4] NCERT. (2022). Contemporary India II: Textbook in Geography for Class X (Revised ed.). NCERT. > Chapter 5: Print Culture and the Modern World > Petroleum > p. 115