"Since 2005, we had to stop gas exploration works in Tichna as the area falls under the Tichna (Trishna) Bison National Park and Wildlife Sanctuary. We are yet to get the necessary clearances from the Forest, Environment and Climate Change Ministry and National Board for Wildlife," ONGC Executive Director S.C. Soni told IANS.

The "Maharatna" Oil and Natural Gas Corporation has, since 1962, established around 41 billion cubic metre (BCM) of recoverable gas reserves in Tripura's eleven gas fields, including the Tichna field in southern Tripura adjoining Bangladesh.

"We expect within the next 5-6 months we would get the necessary clearances from the appropriate authorities. The Prime Minister's consent is likely to be required in this regard," Soni added.

Another senior ONGC official, who is looking after the Tichna field exploration activities, said that the company has been losing crores of rupees in revenue as the area had been idle for so many years.

According to the official, exploration activities in the Tichna area started in 1962 and exploratory drilling started in 1987 before the commercial discovery of gas in 2000.

"The Tripura State Board for Wildlife had given its clearance long back. In October 2007, the Environment and Forests Ministry had asked the ONGC to obtain permission from the National Board for Wildlife before obtaining environment clearance," the official told IANS, preferring anonymity as he is not authorised to speak to the media.

He said that the ONGC has also filed an online application along with necessary documents.

The Tichna Bison National Park and Wild Life Sanctuary, 111 km south of Agartala, is famous for the gaur or Indian bison and other animals, including leopards and barking deer and the endangered spectacle monkey. It is situated over a 194.71 sq km area .

Soni said: "Gas production from the Tichna field is envisaged to start from December 2021... This very much depends upon the timely clearances."

Soni said ONGC had drilled 223 wells in Tripura till April, of which 116 were found to be gas bearing. This corresponds to a record 2:1 success ratio against the world success ratio of 5:1.

The company had earlier commissioned its first commercial gas-based power project in India, located in southern Tripura and run by ONGC Tripura Power Co (OTPC), formed by ONGC, the Tripura government and Infrastructure Leasing and Financial Services Ltd (IL&FS).

The 726 MW capacity combined cycle project (using both water and natural gas), situated at Palatana, 60 km from Agartala, has been supplying electricity to the northeastern states and 100 MW to Bangladesh.

"We are also supplying gas to several power plants in Tripura owned by NEEPCO (North Eastern Electric Power Corporation) and the Tripura government. The combined installed electricity generation capacity of these power projects, including the Palatana plant, is 1,016 MW," Soni said.

"Besides, the ONGC has been supplying piped natural gas (for cooking) and compressed natural gas (for running vehicles) to the Tripura Natural Gas Company.

Soni said that the company plans to produce and supply 5.1 MMSCMD (million metric standard cubic metres per day) by mid-2018 to various consumers in Tripura for another 20 years through drilling of 153 new wells and creation of new surface infrastructural facilities, including the laying of 282 km of pipelines of gas grid network and 600 km of well-flow lines.

The ONGC has also planned a Rs 5,000 crore (more than $775 million) fertiliser plant in northern Tripura in association with the state government and Chambal Fertilisers and Chemicals Ltd., a Rajasthan-based company.