Bangalore/New Delhi: Oil and Natural Gas Corp. Ltd (ONGC) will not be immediately able to securely plug a leaking deepwater well off the Andhra Pradesh coast because cyclone Nilam is expected to make landfall by Wednesday.

The G-1#9 well in the Bay of Bengal, which had been temporarily capped, has been leaking natural gas for the past two months.

“Due to cyclonic weather on the east coast, the capping operations have been kept on temporary halt. As soon as the weather improves, the capping of the well would be taken up," ONGC said in a statement.

“The well is not entirely uncontrolled, it is under partial control. However, our work may get affected due to this east coast storm. We will be able to cap the well shortly," chairman and managing director Sudhir Vasudeva said. “Gas is bubbling underwater and there is no chance of it coming to the surface. It is not coming to the environment. There is no pollution. There is also no possibility of an oil leak."

“The observed leakage is only of gas which is insignificant and is localized within a very limited area. It has not caused any environmental damage. ONGC vessels have noticed normal fauna (bird and fish) activity around the area. Normally, gas is non-polluting to the marine environment," ONGC added.

India’s biggest oil and gas explorer is battling concerns over its production capabilities and diminishing yields at ageing oil fields. Most of its domestic fields are more than 30 years old. While local reserves increased to 1,287 million tonnes of oil equivalent (mtoe) in 2011-12 from 1,243 mtoe in 2010-11, production declined to 52.4 million tonnes (mt) from 52.6 mt in that period.

The India Meteorological Department said on Tuesday that cyclone Nilam will cross northern Tamil Nadu and adjoining southern Andhra Pradesh coast between Cuddalore and Nellore near Chennai by 31 October evening. The agency warned of rough seas off northern Tamil Nadu, Puducherry and southern Andhra Pradesh in the next 48 hours.

The state-run explorer has three ways to stem the leak—a surface blowout preventer (BOP), a sub-surface BOP, or drilling a relief well.

“The debris accumulated around the X-Mas Tree (welllead production equipment) has already been cleared by the ROV (remotely operated vehicles), in preparation for capping activities...The custom-made capping stack has been prepared and transported to offshore...As an alternative measure, a relief well has been planned to side-track the well G-1#9 and the equipment for the relief well has been kept in readiness," ONGC said.

“We will do whatever is required," Vasudeva said.

ONGC is entrusted with ensuring India’s energy security and has a total of 125 rigs working on various drilling operations across the country. It plans to spend about 15,000 crore to drill 480 wells in 2012-13. ONGC drilled 415 wells in 2011-12 at an investment of about 13,000 crore.

“The flow should have been arrested earlier," a person aware of the development said, requesting anonymity.

The company is targeting production of more than 130 mtoe in 2030, of which half will come from assets owned by overseas arm ONGC Videsh Ltd.

The explorer plans to spend 2.65 trillion in the five years to March 2017.