India's Oil and Natural Gas Corp. announced Saturday a big oil discovery in the D1 oilfield off the West Coast that will boost the state-run firm's declining oil production.

The discovery "will catapult D1 to become the third largest field in western offshore after prolific Mumbai High and Heera," ONGC said in a statement. Earlier, the D1 was known to have initial oil in-place of the order of 600 million barrels (82.20 million tonnes). After the discovery of the new pool, its total in-place reserves are expected to be in excess of 1 billion barrels, the statement said.

D1 is situated about 200 km West of Mumbai city in Deep Continental Shelf at a depth of 85 meter - 90 meter. The field comprises four blocks, D1-4, D1-12, D1-14 and D1-2/5.

The latest discovery is ONGC's biggest in recent years. The company has also made three other smaller discoveries in the past month, according to a Reuters report.

The find, reported to the Directorate of General Hydrocarbons, has unfolded an additional oil bearing zone of about 142 meters. On complete development of the field D1, the production is expected to go up to 60,000 barrels of oil per day. This additional development program will start yielding results from January 2014, ONGC said.

"This discovery indeed has come up with a lot of promise signifying a substantial increase in the production for the company," said Sudhir Vasudeva, chairman and managing director of ONGC. "Finally we have made it to a large discovery which was eluding us for long."

Meanwhile, the company reported a higher-than-expected 48 percent jump in its June quarter net profit at 60.8 billion rupees, up from 41 billion rupees a year earlier. The profits jumped owing to higher crude oil prices, despite the government cap on prices of certain petroleum products, and foreign exchange fluctuations.