New Delhi, Sept. 20: State-owned explorer ONGC Ltd has made a significant oil discovery near Mumbai High in the Arabian Sea. The oil well is estimated to hold in-place reserves of 20 million tonnes.

"Nine objects or zones were tested and all of them were found to be hydrocarbon bearing. The last object tested flowed 3,300 barrels of oil... there are deeper zones where oil and gas both are encountered," a company official said.

"It is a large discovery, going by Indian standards, and is in a different play than discoveries made in the neighbouring Mumbai High fields," he added.

The discovery in well WO-24-3 is estimated to hold an in-place reserve of about 20 million tonnes, the official said, adding that the company plans to drill appraisal wells to determine the size of the new find's recoverable reserves.

Mumbai High, the country's biggest oilfield, produces 205,000 barrels of oil per day (just over 10 million tonnes per annum) and the new find will add to the production in less than two years.

ONGC is carrying out further appraisal of the discovery and has intimated the Directorate General of Hydrocarbons, the upstream regulator.

The new find, which comes almost 50 years after ONGC began production in Mumbai High, will help the company to maintain the production levels from the basin for a longer time than currently estimated.

Mumbai High is ONGC's flagship oil producing asset.

Along with other small fields along the western offshore, it produces 16 million tonnes per annum of oil, which is 44 per cent of India's crude production of 36mt.

ONGC produced 25.5 million tonnes of oil in 2016-17, which will reach 28-29 million tonnes by 2019-20, the official said. He said the company was able to reverse the flagging output at its western offshore fields as it focused on areas where it was easier to find oil.

Meanwhile, Cairn Energy today said final hearing in the international arbitration it has initiated against a Rs 10,247-crore retrospective tax demand raised by India, has been pushed back by about six months to August 2018.

This included completing three sub-sea wells at the Mumbai High field and using innovative technology to produce more oil at B-193 satellite and D1 or NBP fields.