Step 1: Map the story of Indian oil chronologically.
Production began in Assam (Digboi) in the colonial era, the oldest oil field in Asia still working today. Discovery then spread to Gujarat's onshore fields, and the big turning point came with the offshore discovery of Bombay High in the Arabian Sea.
Step 2: Explain why Bombay High matters most.
Bombay High alone has supplied a large share of India's total crude output since its discovery, making the western offshore shelf the backbone of the country's petroleum sector, alongside newer offshore finds in the Krishna-Godavari basin.
Step 3: Connect production to processing and the demand gap.
Crude from these fields moves through pipelines to refineries such as Jamnagar, Koyali, Mathura and Haldia, but because India's economy consumes far more petroleum than it produces domestically, a large volume of crude oil still has to be imported every year.
Final Answer:
Tracing petroleum development from Assam's early wells through Bombay High to modern refineries shows a growing but still import-dependent petroleum sector in India.$\boxed{\text{Historic growth, still import-dependent}}$