Gas-related explosions can have adverse effects on human health – GTE environment study

Apr 26, 2022 News

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By Davina Bagot

Kaieteur News – Gas releases from the planned Gas-to-Energy (GTE) project at Wales, West Bank Demerara can result in explosions which can pose grave risk to human and environmental health, according to the Environmental Impact Assessment (EIA) for the project, which was conducted by the Environmental Resources Management (ERM).
In the EIA document, prepared for Esso Exploration and Production Guyana Limited (EEPGL), ExxonMobil’s subsidiary which will be developing the project, it was explained that a loss of integrity of the offshore pipeline, resulting in a natural gas release can be caused due to corrosion, objects striking the pipeline, and a buildup of stress in the pipe wall, causing buckling.
The EIA goes on to say that if an unplanned release of gas from damaged subsea pipelines occurs, the released gas will generate a gas plume that rises from the seafloor to the sea surface.
Therefore, “Fire or explosion accidents can occur when the released gas disperses into the atmosphere and encounters ignition sources, which could have an adverse impact on human life and environment in the immediate vicinity of the fire.” ERM added that the consequences of a release would likely be less severe offshore as it “is extremely unlikely that there will be an ignition source to cause a fire, and the gas will passively disperse without affecting any resources” rather than an onshore occurrence.
However, a release close to the Floating Production Sharing and Offloading (FPSO) vessel could result in a fire onboard the FPSO. EEPGL said that to reduce the likelihood of a gas release, the offshore pipeline design and installation will vary depending on the pipeline depth.
“At a minimum, the pipeline will be laid in a trench, with sections closer to the nearshore area buried, which will reduce the likelihood of an external impact causing a release. The offshore pipeline will be constructed using international good practices, which will reduce the likelihood of stresses building up in the pipeline walls and thereby reduce the likelihood of buckling,” the EIA notes.
Added to that, the oil company said that a gas leak would be quickly detected and isolated using emergency shutdown valves.
While onshore pipeline integrity failures are rare, if a loss were to occur, the most likely causes would be due to a third party striking the line, or corrosion of the pipe.
A strike to the buried line can occur as a result of a third party excavating in close proximity to the pipeline without knowing the exact location of the pipeline and would present a source of ignition for the released gas, which could result in the immediate ignition of the gas, the EIA notes. But if, “the release is not ignited immediately, a flammable gas cloud would be formed and this could ignite, causing either a flash fire or explosion. An explosion would only be likely to occur if the gas is released into a congested space. A congested space can be defined as any space within which there is an obstruction to the free movement of a gas through the space. The most likely places where obstructions would be present near the onshore pipeline would be densely forested areas or thick undergrowth.
The strength of the explosion would be correlated to the proportion of the gas cloud within the congested area. The higher the proportion of the gas cloud that is within a congested area, the stronger the resultant explosion would be. Consequently, open areas—such as that characterised by the onshore pipeline corridor—are unlikely to be conducive to an explosion in the case of a natural gas release from the onshore pipeline,” according to the EIA.
The Gas-to-Energy project is being pursued by EEPGL, on behalf of itself and its co-venturers – Hess Guyana Exploration Limited and CNOOC Petroleum Guyana Limited. It proposes to bring the associated natural gas, produced from the Liza field in the Stabroek Block, to shore for use.
The Government of Guyana is pursuing a separate project to construct a power plant that would use a portion of this associated natural gas as a fuel source. Accordingly, EEPGL, at the request of the Government, is proposing the Project to provide fuel for the Power Plant.
The project will involve capturing associated gas produced from crude oil production operations on the Liza Phase 1 (Destiny) and Liza Phase 2 (Unity) Floating, Production, Storage, and Offloading (FPSO) vessels, transporting approximately 50 million standard cubic feet per day.
Construction will begin after the company receives all necessary authorisations, with a target date of August 2022 for start of NGL Plant site preparation, and will take approximately three years. The combined offshore and onshore pipeline system is targeted to be ready to deliver rich gas by end of 2024, and the NGL Plant is targeted to be operational by mid-2025. The project has a planned life cycle of at least 25 years.
The aspect of the project for which the oil company is responsible, that is to say, the installation of the offshore and onshore pipelines, is set to cost a whopping US$1.3B.

 

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