Oil and Natural Gas Corporation will shut for a fortnight from March 1 a key facility at its largest gas field off Mumbai to hook up new units, leading to fall in gas output by 38 per cent.

ONGC [Get Quote], which had last month closed a production complex at the Bassein field, will shut the second complex BPA to enable additional gas wells in the South Bassein and Vasai East field to be hooked up to the production system.

Company officials said the gas output during the shutdown would fall from 17.72 million standard cubic meters per day from current 28.78 mmscmd.

The shutdown of BPB process complex in January led to fall in gas production from 25.5 mmscmd to 15.5 mmscmd. Officials said the company has invested Rs 2,937 crore (Rs 29.37 billion) in additional development of the South Bassein field and another Rs 1,688 crore (Rs 16.88 billion) in the Vasai East field to avoid the expected decline in production this year onward.

Under these two major development projects, two offshore platforms -- BCPA-2 and BCPB-2 -- are being installed near the existing process complexes of BPA and BPB at South Bassein field. With implementation of this project, additional 20.53 billion cubic meter gas and 1.974 million tons additional condensate would accrue.