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DIMAPUR — The Directorate of Geology and Mining (DGM) has come out with a report of its findings and suggestion on the recent incident of natural gas leakage at Pongma ward in Tizit town, Mon district.
The department in its report stated that the incident of gas leakage (biogas) occurred while drilling the ground for borewell water. The drilling work started on September 12 but the emission of gas occurred on September 16.
[bsa_pro_ad_space id=1]“The emission of gas occurred when the borehole was dug to about 140ft. The workers in order to check whether the gas was flammable lit the gas. The aquifer was struck at about 80ft to 98ft after which between 98ft to 140ft was clay,” it stated.
The gas was combustible in nature and was burning for nearly three hours. The workers through the directive of superintendent of police, Mon, as per the advice of the Geology and Mining department, put off the fire by filling the borehole with sand on the same day, the report stated.
On September 18, the department deputed a team comprising of Toshiakum, drilling engineer and Chingao Konyak, asst. geologist, to assess the extent of gas leakage.
As per the report, the location where the gas leakage occurred is in private plot having latitude N26°56'42.8" and longitude E90°03'52. 4."
The location, with an altitude of 62m, falls in the Singphan Oil Block (ONGC) and Schuppen belt, which are made up of imbricate thrusts with Naga Thrust in the west and Disang Thrust in the east.
As per the field observation on September 18, the gas leakage continued with hissing sound and the gas detector instrument (portable voice multi gas detector) showed the following readings: H2S - OPPM, CO - OPPM, O2 - 20.3 % and LEL- >50%.
Mitigation and suggestion:
Since the gas emission showed >50% LEL (lower explosive limit), which is highly explosive and the release of methane gas is on the higher side, the residents were advised to keep distance from the leakage point. The residents were also cautioned not to dig any borehole within the perimeter of at least 50 sq. feet. The borewell was directed to be filled with sand to contain the emission
“DGM with the help of residence will continue to monitor the gas emission for a week or two. Based on further observation the hole may be permanently sealed,” it stated
Foothill areas of Nagaland are geologically termed as ‘Belt of Schuppen’ and cover an area of approximately 3000 sq. km, from Mon district in the north to Peren district in the south.
“These areas are the bearing zones of oil, gas and coal. The reports of hydrocarbon gas leakage in this Schuppen belt have been reported a number of times in the past. This gas leakage indicates presence of oil, gas and coal,” the report stated.