Since the morning of May 27, natural gas has been continuously flowing out of a gas well in Assam following a blowout — or a sudden, uncontrolled release of gas/oil. With authorities unable to control it, experts from a Singapore firm reached Assam today. Meanwhile, people from surrounding villages have been evacuated, while a variety of fish and an endangered Gangetic dolphin have died.
Where is the oil rig?
The Baghjan 5 well is a purely gas-producing well in Tinsukia district, and is at an aerial distance of 900 metres from the Dibru-Saikhowa National Park. It was drilled by Oil India Limited (OIL) in 2006. It produces around 80,000 standard cubic metres per day (SCMD) of gas from a depth of 3,870 metres. As per officials, the current discharge is at 90,000 SCMD at a pressure of 4,200 PSI, far higher than the normal producing pressure of around 2,700 PSI. “It’s a very good reservoir, one of the most prolific gas reservoirs owned by OIL,” said Tridiv Hazarika, spokesperson of OIL.
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Why do blowouts happen?
Sometimes, the pressure balance in a well may be disturbed leading to ‘kicks’ or changes in pressure. If these are not controlled in time, the ‘kicks’ can turn into a sudden blowout. “The force with which a pressure cooker releases steam is understandable. Imagine a situation where one million pressure cookers do the same in an uncontrolled manner,” said geologist Siddhartha Kumar Lahiri of Dibrugarh University. He cited many possible reasons behind blowouts, “from simple lack of attention, poor workmanship, bad maintenance, old age, sabotage to morpho-tectonic factors”.
A device called a blowout preventer is usually installed in wells.
The gas well at Baghjan was being serviced, and a new sand was being tested at another depth in the same well. “We were also repairing the existing well-head (the exposed top portion),” said Hazarika.
“To repair the well-head, you need to temporarily ‘kill the well’ or shut down the producing zone,” said Hazarika. “The blowout preventer was also removed, since we were in the process of repairing the well-head. But suddenly, gas started to ooze out of the exposed well. Before anyone could do anything, it broke through our cement barrier,” he said. “How and why it happened, how the gas came out of the ‘killed zone’ is what we are inquiring into.”
In the recent past, two comparable blowouts have happened in Assam: at an OIL-owned oil well in Dikhom (Dibrugarh) in 2005 and an ONGC-owned oil well in Rudrasagar in the 1970s. The latter took three months to contain.
Why is it so difficult to control?
According to a Guwahati-based expert, “the control of a blowout depends on two things: the size of the reservoir and the pressure at which the gas/oil is flowing out. This reservoir was particularly difficult to control since it was a gas well and ran the risk of catching fire at any point”.
While many blowouts automatically collapse on their own, it can take up to months. To control a blowout, the first step is to pump in water, so that the gas does not catch fire. “Sheer magnitude of the event invites specialists to douse the fire,” Professor Lahiri said.
What is being done?
A crisis management team from OIL and ONGC intend to create a water umbrella to protect workers while they hook up the blowout preventer. “With very limited space and non-availability of open space above the well head, placement of the BOP is a huge challenge and entails a huge risk. It is planned to place the BOP on the well head through a hydraulically driven mechanical transporter,” OIL said in a release on Sunday. Drilling mud will have to be pumped in immediately after capping the well by the BOP.
About the water umbrella, Hazarika said: “For that we have had to build a temporary reservoir, channel cables or temporary pipelines from the Dangori river nearby”.
OIL has reached out to Singapore-based firm Alert Disaster Control, whose experts arrived in the state on Sunday. OIL said that they will carry out the first inspection of Baghjan gas well on Monday.
How serious is the impact to the neighbourhood?
As many as 1,610 families with 2,500-3,000 people have been evacuated to relief camps. There are reports of deaths of a river dolphin, and a variety of fish. While the administration has kept an ambulance with paramedical staff on standby, locals have complained of symptoms such as burning of eyes, headache etc.
As per Assam Pollution Control Board chairman, Y Suryanarayana, the gas — which is a mix of propane, methane, propylene and other gases — is flowing with the wind, towards the northeast. “That is a radius up to 5 km and condensate is mostly falling on bamboo, tea gardens, banana trees and betel nut trees,” he said.
While the well is outside the Eco Sensitive Zone of the park, Tinsukia’s divisional forest officers (wildlife), Rajendra Singh Bharti said the boundary does not matter since the gas is moving through the air. “Condensate is falling into Dibru-Saikhowa National Park too,” he said.
Also close is the Maguri-Motapung wetland —an Important Bird Area notified by the Bombay Natural History Society. “The park is famous for its birds, butterflies, wild cats, and feral horses,” said Bharti. “The impact is visible in the sense that you can see traces of condensate on the water bodies, the numbers of birds have decreased,” said Bharti, “Not because they have been killed but because they have flown away.”
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