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Disruptive technology meets the intractable challenge of fugitive-gas emissions

04th October 2017

Optical-gas imaging (OGI) makes gas clouds visible and operates as an infrared sensor capable of operating within the thermal spectrum

In 2016, regulatory authorities in North America started taking seriously the fact that methane is a very powerful greenhouse gas in its raw, or unburnt, form. They also took note that recent advances in thermal-imaging technology had lent credence to the assertion that fugitive emissions, or unintentional gas leaks, are happening on a much greater scale than ever before.

Combined with an unprecedented expansion in US onshore extraction and processing of natural gas, a basis for a perfect storm exists. An estimated USD2 billion of natural gas is lost each year to leaks.

The idea of natural gas as a clean fuel that can contribute to a reduction in urban pollution and greenhouse gas emissions is well-accepted both within the oil and gas industry and beyond.

Even the most prominent voices advocating for non-fossil-fuel renewable technology, including Greenpeace, publicly have accepted the important role natural gas plays in acting as a clean-fuel stepping-stone from energy based on coal or oil toward energy less reliant on fossil fuels. 

This strategy of expanded exploitation of natural gas is working, and globally so. For example, on April 21, 2017, the UK enjoyed its first 24-hour power-generation period completely free of coal since the year 1880. In the US, natural gas has surpassed coal as the nation’s leading power-generating fuel source, with its growth-rate surpassing any other energy source for power generation.

Reasons for uncertainty
Climate change commitments have been made by many western, economically-developed countries. Gas is a key weapon in the fight against CO2 emissions. In Asia, growing unease about air quality in post-industrial China has led to some impressive deals with natural gas supply countries such as Russia and Australia, but it is also this very supply chain that sometimes calls into question the greenhouse gas-reducing credentials of natural gas and its categorisation as a clean fuel

In the US, awareness of the raw-methane emissions environment in the natural gas production and supply-value chains has been growing. Emissions traces seen from space mirror the concentrations of activity around unconventional oil and gas production.

“Methane is a powerful greenhouse gas in its unburnt form,” Laith Amin, senior vice president, Digital Enterprise at Advisian, says. “In fact, raw methane is 86 times more potent as a greenhouse gas than CO2 when impact is considered over a 20-year period. Ultimately experts agree that if natural gas is to rival coal as a means of reducing greenhouse gas emissions, then emissions of raw methane in the supply chain must be held to less than one per cent of total production.”

In the US, raw-methane emissions estimates have been ranging from a lower-level estimate of two per cent of overall production to around 17 per cent. Alarmingly, the US Environmental Protection Agency (EPA) in recent years has increased its estimate of emissions in upstream gas operations by 134 per cent, bringing the overall total to 1.4 per cent of total production (which from time to time they flag as a possible  underestimation), or 40 per cent higher than the target that must be met for gas to provide comparative advantage over coal.

Methods of measurement
But why do these estimates vary so widely? “To answer this question, it is essential to also examine the method of measurement itself—and there are several different methods used,” Amin explains. “One method to estimate leak-emissions rates from equipment items having the potential to leak in any plant environment is simply to apply emissions factors and schedules provided by regulators. The emissions-per-equipment item then can be aggregated to a plant total to produce a volume for undesirable leaks, or fugitive emissions. 

This method takes no account of the actual leak rates, or if in fact the equipment is leaking at all. “The second, so-called incumbent, method is what is referred to as EPA Method 21. A measurement instrument, i.e., a flame ionisation detector, is held near the stream of a suspected leak and measures the concentration of the fugitive gas in the atmosphere (typically on a parts-per-million basis).

“It is difficult to underestimate the impact of Method 21-type emissions measurements on the oil and gas industry in recent decades. This method verifies that there is in fact a leak—vital information that can be passed on to repair programmes. In this way, significant greenhouse-gas reductions have been possible over the years, not to mention the valuable gas retained in the supply chain for end use.

“However, the historic success of Method 21 testing still does not explain the wide variances in estimates for fugitive greenhouse gas emissions, nor adequately explain why, if the method is as effective as supposed, a methane emissions footprint is visible from satellites to an extent that alerts regulators to a growing problem. These questions themselves illustrate our increasing sophistication, in terms of technology and otherwise, in informing ourselves as to the nature of fugitive gas emissions.”


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