Coal seam gas leaks a climate debacle
The fire that started in August 2012, near Dalby on Queensland’s Western Downs, never grew very big. Once the authorities got on to it, the blaze was easily extinguished.
It was blamed on some local kids messing about in the bush. It would not have amounted to any more than a minor act of delinquency except for one thing: what they ignited wasn’t grass or twigs, but a hole in the ground.
The forgotten hole hidden among the trees about 25 kilometres out of town was about the size of a plate and, unknown to anyone, was leaking colourless, tasteless, odourless, highly flammable methane, a greenhouse gas many times more potent than carbon dioxide.
But here’s the thing: the hole, an exploration bore, was sunk 32 years earlier. Presumably, it had been leaking methane all that time.
Another thing: there are possibly hundreds of other such holes, dug over many decades, Swiss-cheesing the coal basins of Queensland. No one knows exactly how many there are. Nobody knows how many of them leak gas, or how much.
Likewise, no one knows exactly how much methane – otherwise called coal seam gas or, when reticulated into our homes, natural gas – is produced as fugitive emissions by coalmining.
Nor do we know with any great certainty how much methane leaks from the still-operational coal seam gas extraction wells that have proliferated across southern Queensland and northern New South Wales.
And we have very little clue at all as to how much of it leaks out of the spaghetti of gas mains under our cities.
This poses an interesting question. How can government promise specific reductions in this country’s contribution to global warming if we don’t know how big that contribution is in the first place?
Yet we affect to know. The government produces regular updates on Australia’s “Greenhouse Accounts”, containing quite specific numbers on the amounts of various greenhouse gases produced here – expressed, because different gases have different greenhouse impacts, in terms of carbon dioxide “equivalent” tonnes. These accounts cover everything from cement manufacturing to the “enteric fermentation” of livestock – that is, their burps and farts.
Indeed, enteric fermentation is a big contributor. Agriculture accounts for about 17 per cent of Australia’s emissions, mostly in the form of methane. And about two-thirds of that comes out of farm animals.
Without meaning any disrespect to the people who compile these statistics, there is clearly a bit of educated guesswork involved in some areas. While it is possible to be fairly precise in measuring the greenhouse contribution of an industrial operation such as cement making, which is done according to an established formula, it’s harder to assess the gastric processes of cows, which vary according to diet. Or to put a firm figure on the amount of carbon dioxide released by the burning of savannah vegetation in the dry season.
And nothing is harder to quantify than the so-called fugitive emissions that result from the production, processing, transport, storage, transmission and distribution of fossil fuels. The government figures assert they amount to about only 8 per cent of Australia’s total emissions. However, as the name implies, they are elusive. As one academic expert told The Saturday Paper, there is “massive uncertainty” about the real quantity of fugitive emissions.
CSG bore leaks
Which brings us back to those holes in Queensland.
The Surat Basin, a 300,000-square-kilometre area mostly in central southern Queensland and extending into northern NSW, is today the centre of Australia’s burgeoning coal seam gas industry. Some 5000 new holes in the ground account for more than 90 per cent of Australia’s “unconventional” gas production, exported to the world.
But between the late 1960s and late 1980s, many more holes were drilled. Like we said, no one seems to know for sure but credible academics estimate hundreds of thousands of holes were drilled to understand the geology of the area and its coal deposits.
“The practice of the time was to just walk away from them in most cases,” says Professor Damian Barrett, who leads the CSIRO’s research team in unconventional gas, and is also director of the Gas Industry Social and Environmental Research Alliance (GISERA).
“It was done largely under the auspices of the Queensland government. And there is a potential for them to leak methane.”
Not all will, of course. In some cases, Barrett says, wells will have collapsed, sealing themselves off. In other cases, the drilling process never released methane. Still, the lore of the Western Downs is replete with stories about old wells catching alight during bushfires, about “gassy” water wells contaminated by methane flowing through the rock strata from old exploration bores, and about sinkholes formed by old bores collapsing.
Partly as a result of incidents such as the one in Dalby, scientists from the CSIRO and elsewhere have over recent times begun the painstaking process of locating these “legacy” holes.
It’s not easy. They may be hidden in scrub, with perhaps just a metre or so of old PVC conduit showing. In other cases, there is just a hole in the ground. Elsewhere, the hole is entirely hidden, having been covered by a thin layer of dirt, but still seeping gas.
Fortunately, scientists have sensitive detection equipment. Installed on vehicles it can detect unusual concentrations of the gas as they drive along. Through this process, says Barrett, “we think the [locations of the] majority of them are now known”.
Some believe otherwise. But in any case, much is still to be done to rectify the problem, as Barrett and others acknowledged in a report by GISERA in May this year.
They investigated a relatively small number of abandoned bore holes and found many to be leaking, “in some cases a lot – more than 100 litres per minute”.
And they have been doing so for decades. Given the vast number of old holes out there, the potential greenhouse contribution is very large.
On the basis of the small sample examined, the GISERA scientists recommended a “detailed investigation” to determine the full scope of the problem.
The problem with methane
To even begin to understand the complexity of the matter, one needs to know a little about methane, the second most abundant greenhouse gas after carbon dioxide. Carefully handled, it can be a much cleaner energy source than coal – producing about 50 per cent fewer greenhouse emissions.
But unburned methane is a very potent greenhouse gas.
“Over a 20-year period methane has a global warming potential 72 times greater than carbon dioxide,” says associate professor Bryce Kelly, a specialist in fugitive emissions at the University of New South Wales.
And the unfortunate fact is that atmospheric concentrations of methane have risen dramatically since pre-industrial times. While carbon dioxide levels have gone up about 40 per cent, methane has gone up 250 per cent. It is the second biggest contributor to climate change, reckoned to be responsible for about 20 per cent of global warming.
The bottom line, says Kelly, is that “if natural gas is not managed well, it becomes a major contributor to global warming”.
Even small leaks – a few per cent of a coal seam gas well’s production – can negate the advantage of gas over coal.
The good news is that Australian coal seam gas (CSG) extraction appears to have been relatively well managed. CSIRO testing of a representative sample of CSG wells in Queensland and NSW showed little leakage.
But the picture is more complex than simply measuring what happens at the well heads.
In order to extract the gas, CSG miners have to depressurise saturated coal seams deep underground. That means pumping out vast quantities of water. Once fully operational, the CSG mines of the Surat basin will pump out 315 megalitres of water a day, the equivalent of 700 Olympic swimming pools.
Professor Barrett explains the process: “The methane is held in solution, under pressure. It’s a bit like the way carbon dioxide is held in a soda bottle. It stays in solution so long as the pressure is maintained, but once you release the pressure, the gas comes out.”
The worry is that this process of depressurisation will not only allow the methane to travel up the currently operating gas wells, but also to travel elsewhere, like up those thousands of old exploration holes.
Dalby-based well-driller Ian Hansen, who has more than 35-years experience putting down bores in the basin, is one of those concerned.
“As CSG extraction changes the pressure differentials in the aquifers, holes that have never leaked will all of a sudden be blowing gas.”
And maybe not just the old holes, but elsewhere.
It is a geological fact that some methane leaks through various other sources, says Barrett.
“There are natural seeps and cracks; we see some bubbling in the Condamine River, for example.”
But is that a natural phenomenon?
Drew Hutton, of the Lock the Gate Alliance, says not.
“There are places where you can set the Condamine alight. I’m an old Chinchilla boy. I swam in that section of the river as a kid. It never happened then.”
And the problem is not confined to the backblocks of Queensland.
A group of UNSW scientists, led by Kelly, have recently done what they call “preliminary surveys” to map fugitive emissions from Sydney’s gas distribution system.
They found “points along the main gas distribution system with methane concentrations as high as 6000 ppb [parts per billion], and whole city blocks where the methane concentration is above 2500 ppb”.
That equates to quantities about two to three times the usual atmospheric levels.
And while the gas concentrations were way below the “lower explosive limit” for gas leaks, they indicated major emissions of potent greenhouse gas.
Likewise, Kelly has measured big plumes of methane all along the coalmining areas of the Hunter Valley.
More work will be needed “to quantify the total greenhouse gas footprint of natural gas,” says Kelly. “Until better hard data is provided, claims about reducing our greenhouse gas footprint by using natural gas as a major energy source cannot be defended.”
Effect on emissions targets
The point here is that although the government claims fugitive emissions amount to just 8 per cent of our national contribution to climate change, we really don’t have a clue.
This point is pertinent to the COP21 global climate change conference concluding in Paris, to which the Australian government has been party.
Richard Denniss, of the progressive think tank The Australia Institute, has been present as part of the delegation from Kiribati, one of the island nations likely to disappear because of sea-level rise resulting from global warming.
At the urging of those island nations, Australia agreed to set a reduced target for global warming from 2 degrees Celsius to 1.5.
But it has refused to sign up to measures that would reduce subsidies to fossil fuel producers. It has insisted on the maintenance of special measures that allow Australia to increase industrial emissions by offsetting them against notional savings from not cutting down trees.
In short, says Denniss, the Australian negotiating position, while not as bluntly obstructive as in years past, has been a “masterclass in accounting procedures”.
“Australia just committed to a more ambitious target – 1.5 degrees – in exchange for an accounting rule allowing us to do less about it.
“They’ve made emissions an abstract concept amenable to definition.”
And the story of fugitive emissions is but one indicator of that.
“Australia’s commitment to climate change involves doubling our coal exports,” Denniss says. “How exactly will that help?”
It doesn’t help, of course, but the thing about Australia’s fossil fuel exports – gas and coal – is that they are counted against the targets of the countries that we export them to.
It’s just like that leaky bore hole near Dalby that the kids set fire to. The fact that no one measured it for 30 years made no difference at all to the reality that it was leaking greenhouse gas.
“The chemistry of climate change,” says Denniss, “is impervious to accounting tricks.”
This article was first published in the print edition of The Saturday Paper on Dec 12, 2015 as "Forgotten boreholes a climate debacle ". Subscribe here.