Unlocking the mystery of the Four Corners Methane Hot Spot

Scientists zero in on the culprits behind a giant plume of greenhouse gases.

A silver van rolls slowly down a narrow road on the edge of the small town of Bayfield, Colorado, a farming-turned-bedroom community 20 miles east of Durango. With its darkly tinted windows and government plates, the van has an ominous appearance, not helped by the long, fishing-pole-like appendage, accessorized with wires and tubes, that extends from its top. Impatient drivers pull around the creeping vehicle, peering suspiciously as they pass. Just behind the local high school, the van stops abruptly, then reverses, then pulls forward again onto the shoulder before stopping.


The passenger-side door swings open and Gabrielle Petron, an atmospheric scientist with The National Oceanic and Atmospheric Administration and the Cooperative Institute for Research in Environmental Sciences at the University of Colorado, Boulder, hops out, gesturing to the following journalists to pull over and do the same. Petron wears jeans and hiking boots, a black jacket and sunglasses, all given flair by the saffron-orange scarf wrapped loosely around her neck and shoulders. Speaking with a slight French accent, she explains the van’s erratic behavior: Its sensors indicate the presence of above-background levels of methane, a potent greenhouse gas.

It’s not hard to find the probable source. Inside a chain-link-fenced enclosure next to the school’s tennis court, the pipes, valves and other equipment of a BP America natural gas well jut from the ground. Everything’s painted gold and purple, the school colors, with “Wolverine Pride” emblazoned on a metal box. Like many of the 40,000 or so oil and gas wells here in the San Juan Basin, this one extracts natural gas from the Fruitland coal formation. The natural gas, which is largely methane, is gathered here, processed and piped to market. Or at least most of it is: Some of that methane is apparently leaking from the wellhead and drifting into the atmosphere, contributing in its own small way to the notorious Four Corners Methane Hot Spot, a highly concentrated plume of greenhouse gas that hovers over the region. When scientists first noticed the hot spot in satellite imagery captured nearly a decade ago, it was so intense that they thought their equipment was malfunctioning. But more satellite imagery from 2009 confirmed the anomaly’s existence, and in 2014 a team of scientists published a paper on it that garnered widespread media attention. 

The obvious suspect behind the hot spot is the vast oil and natural gas industry infrastructure, which is woven like rebar into the landscape here, and burps and leaks methane and other hydrocarbons from valves, pipes, compressors and newly fractured wells. Other known contributors include an underground coal mine, from which methane is vented for safety, and a few landfills and two coal-burning power plants, which emit relatively small amounts of the gas.

But there’s a 155,000-ton gap between the emissions these facilities collectively report to the Environmental Protection Agency’s greenhouse gas inventory, and the amount of emissions the scientists estimate is needed to produce a plume as concentrated as the hot spot. Petron, along with a swarm of scientists under the aegis of the National Aeronautics and Space Administration and NOAA, descended on the region this spring, using planes, satellites and automobiles to try to account for all that unaccounted-for methane.  (See sidebar)

What they find could have wide-ranging implications. Natural gas emits about half the carbon per unit of energy generated as coal, and about a third less than oil, making it a good “bridge” fuel for transitioning from a coal-heavy energy system to one that’s carbon-free. Yet the main ingredient of natural gas — methane — has 30 times more global warming potential than carbon dioxide. If the scientists were to find that the natural gas industry is behind the extra emissions, it could further cloud the fuel’s current climate-friendly status. It might also indicate how hard the region’s oil and gas industry will be hit by regulations from the Obama administration as part of its strategy for reducing emissions from the industry by 45 percent.

The industry, however, blames the gap on another methane-spewing villain that lurks here in the San Juan Basin and in other coal- and natural gas-rich areas: geologic seeps, where methane leaks unbidden from the earth, as it has done for millennia. Environmentalists scoff at the theory, but researchers aren’t discounting it. “The seeps are definitely a piece of the puzzle,” says Devin Hencmann, with LT Environmental, the company that has monitored the seeps in the San Juan Basin for the last decade.

But just how big a piece? And where exactly does it fit into the hot spot puzzle?

The “Methane Mystery Mobile,” with its sensor arm extended above the van.
Jeremy Wade Shockley

A few hours before her stop at the school-grounds gas well in Bayfield, Petron and her research assistant, Eryka Thorley, who looks like she just stepped out of a Patagonia catalog in her skinny jeans, fleece jacket and white-rimmed shades, show a couple of journalists around what I’ve privately christened the Methane Mystery Mobile. On a cool, moist late April morning, it sits in the parking lot for a popular trailhead known as Carbon Junction. The Animas River — not yet polluted by the mining spill that will make national headlines later in August — runs by below, and just beyond it looms Carbon “Moving” Mountain, so nicknamed because, back in the 1930s, it grew violent for several months, shifting and sloughing and sliding for reasons unknown.

A computer monitor mounted on the van’s dash, between the driver and passenger seats, reveals current concentrations of carbon dioxide, methane and carbon monoxide in the air around the vehicle. In the back are more instruments, along with burly black plastic boxes containing glass cylinders for capturing air samples at specific sites. Petron initially studied mathematics in France, but eventually switched her focus to the atmosphere. “The beauty of the air and the abstractness of it reminded me of math,” she says. That very abstractness, unfortunately, makes it difficult for many of us to really grasp concepts such as climate change or greenhouse gases.

In pre-industrial times, the background level of methane on Earth was about 750 parts per billion. But beginning in about 1850, that level started shooting up, and now it’s approximately 1,800 parts per billion, or 1.8 parts per million. Here in the parking lot, the methane line jumps up and down with shifts in the wind, but remains higher than background levels, occasionally rising to 5 or more parts per million.

I look around me. The nearest natural gas or oil well is at least a mile away. There are no coal mines nearby, no feedlots, wetlands, rice paddies, landfills or any of the other common sources of methane emissions. But then again, there doesn’t need to be. The parking lot sits in a notch, formed by the Animas River, in the Hogback Monocline. If you think of the San Juan Basin as a lopsided bowl-shaped sandstone-, shale- and coal-filled layer cake, then the steep ridge of the monocline is the cake’s outer rim, where the layers are exposed. Petron leads us up a little canyon and points to the critical layer of the cake, an outcrop of the Fruitland coal formation. It’s the souvenir of a sultry swamp that lurked along the shores of a receding sea some 65 million years ago, and it’s brimming with methane, some of which is leaking out here. Despite its apparent enthusiasm to escape the earth, this methane was economically infeasible to extract until, in the 1980s, government-subsidized technology and tax credits combined to make it a moneymaker. That launched a boom that would make the San Juan Basin the nation’s number one coalbed methane producer.

Methane concentrations across the United States are low on the coasts (dark blues and purples) and higher in the country’s midsection (light blue, green and yellow), with the Four Corners hot spot, the red area highlighted with a circle, highest in concentration.
NASA/JPL-Caltech/University of Michigan

In 1993, at the tail end of the first major wave of drilling, a resident of the Pine River Ranch subdivision north of Bayfield complained to the Colorado oil and gas regulators that, after 10 years of providing clean water, his well had begun spewing methane. Similar phenomena had been reported in other parts of the basin, but those had been traced back to particular wells that had bad casing, which allowed methane to migrate from the gas well into the aquifer. This one was different. Investigators couldn’t find any leaky or badly cased gas wells nearby, but they noticed that the house and well were located along a low point in the Hogback Monocline, where the Pine River had eroded through it, right on top of the Fruitland outcrop. The methane, it appeared, was coming straight out of the coalbed.

Such natural seeps had been witnessed along the outcrop for a century or more, but it gradually became clear that they were getting more intense. Trees and bushes began dying off in places where they had long thrived, like Carbon Junction. Near Valencia Canyon Gap on the Southern Ute Indian Reservation, where the glowing embers of an underground coal fire had become visible, methane emanated with enough pressure to fling grains of sand several inches into the air, and hydrogen sulfide levels, at a hazardous 200 parts per million, forced the closure of a nearby road.

Things only got worse. Within a year after the changes were observed, “a half-mile long by 50- to 75-foot wide swath of previously healthy piñon and juniper trees, sagebrush and saltbrush stood dead as stark testimony to recent environmental changes,” lamented a comprehensive 1999 Bureau of Land Management report on the issue. Methane was seeping from some spots at 1 million parts per million, or 100 percent concentration. Back at the subdivision, methane invaded more wells and pooled in the crawlspaces of homes. Breathing methane poses no immediate threat to human health, but potential explosions were a serious concern. At the time, the methane’s effects on the climate remained in the background.

The Colorado Oil and Gas Conservation Commission formed an investigative team, and in 1995, it concluded that the most likely explanation for the sudden increase in methane seep at the subdivision — and by extension the cause for the apparent exacerbation at the other “natural” seeps — was the vast “dewatering” of the coal seam. Unlike “conventional” reservoirs of oil and gas found in sandstone or shales, coalbed methane is adsorbed, or bonded, to tiny pores in the coal by water pressure. In order to “liberate” the methane, drillers must first pump out the water from the coal seam. By 1999, just a decade or so after the boom had begun, coalbed methane wells on the Colorado side of the San Juan Basin alone had produced over 10 billion gallons of water, freeing the methane to migrate up the coal seam and escape from the outcrop.

Amoco — now BP, the biggest operator in the region — pushed back, bringing in its own consultants, who dusted off every historic account of flaming streams and wells and presented them as proof that the problem had always been there. The stories were entertaining and sometimes dramatic: A group of kids on a camping trip watch as an ember from their fire sets the Pine River aflame; ranchers light methane seeps to serve as natural Christmas lights; a man who likes his drink finds himself locked out by his wife, so he ignites the water well vent in order to stay warm. The consultants even brought up Carbon “Moving” Mountain, and suggested that its perturbations were the result of subterranean methane seep explosions.

They posited other possible causes for the exacerbated leakage: Perhaps drought or an increase in domestic wells was drying up the coalbed and liberating the methane, or maybe an uptick in precipitation was causing more water to leak through the outcrops into the coal seam, thus displacing methane and pushing it to the surface. They introduced enough uncertainty to obfuscate the official findings.

But even when Amoco’s consultants acknowledged that the industry, as a whole, might be to blame for the increased leakage, there was no way to pin a particular seep’s behavior on any particular well or company. And since no baseline data existed, there was really no way to know, for sure, that the leakage had increased, dying vegetation notwithstanding. The uncertainty was enough to help Amoco dodge litigation; when the homeowners sued the company, they lost. The company did purchase four contaminated homes and bulldoze them, and it has continued to help fund a multi-agency effort to map, model, monitor and mitigate the seeps. (When I asked BP representatives what they’re doing to mitigate leaks in their systems, they told me no one was available to speak to me.) As time went by, and no more homes were contaminated and the price of natural gas crashed, the issue faded from the public consciousness.

Until now.

  • Eric Kort, an atmospheric scientist from the University of Michigan and one of the authors of last year’s methane hot spot paper, explains how aerial efforts work with the ground campaign to map emissions in the San Juan Basin and elsewhere.

    Jeremy Wade Shockley
  • Gabrielle Petron, a scientist with CIRES at the University of Colorado, stands near a facility that uses methane seeping from the ground to generate enough electricity to power six homes.

    Jeremy Wade Shockley
  • Gabrielle Petron’s research assistant Eryka Thorley checks readings in the “Methane Mystery Mobile.”

    Jeremy Wade Shockley
  • LT Environmental workers monitor methane emissions from geologic seeps in the Fruitland coal outcrop.

    Jeremy Wade Shockley

Eric Kort, an atmospheric scientist with the University of Michigan, is the lead author of last year’s hot-spot study, and on an April morning he is preparing to lead a forum on methane in Farmington, New Mexico. Kort, who is tall and lanky with a light beard, his hair pulled back into a little bun, is clearly amazed at the turnout. Some 200 people have crowded into a college lecture room to hear scientists talk for four hours about hyperspectral imaging, isotopes and teragrams.

There’s a palpable tension in the room, hinting at what’s at stake in this fossil fuel-heavy region. Shirley “Sug” McNall, a local who has been butting heads for years with the oil and gas industry over its impacts on air quality, is here, listening anxiously, as are members of regional environmental groups, such as the San Juan Citizens Alliance and Western Environmental Law Center. Officials from the two huge coal power plants west of town, which together with the accompanying coal mines employ hundreds of people, look on somberly. Most anxious, though, are the natural gas industry leaders present, recognizable in part by their uniform: jeans, button-up shirt, fleece vest with company logo.

For them, the hot spot is like a big bull’s-eye, centered right over their heads, drawing unwanted attention to them and their industry. The San Juan Basin is one of the nation’s most prolific natural gas fields, and the economy was built on the industry’s shoulders. As goes national sentiment toward the fuel, so goes the financial fate of Farmington restaurants and Wal-Marts, schools and government. And for now, at least, it appears as if these scientists hold that fate in their hands.

Click to view larger.

Click to view larger.

Beginning a decade or so ago, environmentalists and politicians of all stripes began hailing natural gas as the most potent weapon to dethrone King Coal and reduce carbon emissions. From 2007 to 2010, in fact, the Sierra Club’s Beyond Coal campaign was largely funded by $26 million in donations from natural gas giant Chesapeake Energy. Not only does natural gas burn more cleanly than coal, emitting half the carbon and a fraction of the sulfur dioxide, particulates, mercury and other pollutants; it’s also more versatile. Like coal, gas can be used to produce steam to turn turbines that produce round-the-clock baseload power. But gas can also be used to power combustion turbines — similar to jet engines — that can be ramped up to produce juice in a matter of minutes to provide backup for variable solar and wind energy.

As the so-called shale revolution yielded a natural gas glut and decreased prices, the fuel became affordable enough to compete with coal. After chipping away at coal’s supremacy for several years, this April, for the first time, natural gas generated more electricity in the U.S. than coal. That same month, carbon dioxide emissions from the electric power sector reached a 27-year low, after steadily declining for the last several years. It was a big win for the climate. Or was it?

In 2011, Cornell University’s Robert Howarth dropped a bomb on the natural gas party when he published a study suggesting not only that natural gas wasn’t as clean as hyped, but that it may ultimately have a larger greenhouse gas footprint than coal, thanks to methane leakage. Though the study’s conclusions and methods remain in dispute, it woke people up to the fact that, in addition to the on-the-ground environmental impacts of drilling, the fuel has a tender Achilles’ heel when it comes to saving the climate. Methane has 86 times more global warming potential than carbon dioxide over a 20-year span, and up to 30 times over a century. That means that for every 100 tons of carbon dioxide kept out of the atmosphere, it only takes three or four tons of methane leaking from a pipeline or other infrastructure to offset the gain. Howarth concluded that in order for natural gas to retain its greenhouse gas superiority over coal, leakage rates had to stay below 2.8 percent.

EPA greenhouse gas inventory data show that the national leakage rate is about 1.5 percent, which sounds pretty good. Unfortunately, several independent studies have found that actual emissions are often far higher than what gets reported to the agency. Petron and her colleagues, for example, found that oil and gas production in the Denver-Julesburg Basin in Colorado emitted three times more methane than the EPA inventory showed. And in 2014, Kort, Petron and others published a paper in Science documenting that, nationwide, measured emissions were 1.5 times higher than those in the inventory. Now they’re trying to see if the same is true here in the Four Corners. To achieve concentrations like those found in this hot spot, says Kort, emissions would need to total about 590,000 metric tons per year. That’s upwards of 150,000 metric tons more than the amount all the emitters in the region report to the EPA’s greenhouse gas inventory.

Kort had speculated that the increase could result from fugitive emissions that the companies don’t know about, like the apparent slow leak in the wellhead that showed up on Petron’s monitor, or perhaps from known emissions from facilities that fall below the inventory’s reporting threshold. Pipelines frequently rupture, releasing huge quantities of gas: A High Country News analysis of data from the Pipeline and Hazardous Materials Safety Administration revealed that ruptured pipes have leaked enough methane since 2010 to heat 170,000 homes for a year. Perhaps hundreds of abandoned gas and oil wells, leaking but unaccounted for, are to blame. If this is true, it could put the coalbed methane field’s leakage rate as high as 8 percent.

Industry flacks balk at such hypotheses, though. “The San Juan Basin is well-known as a large area of natural seepage — when methane emissions are naturally occurring and not the result of energy development,” writes Katie Brown for Energy In Depth, a PR outlet for the Independent Petroleum Association of America. Such claims, however, are “little more than a bogus, rhetorical diversion to avoid responsibility and to undermine ongoing rule-making efforts,” says Erik Schlenker-Goodrich, executive director of the Western Environmental Law Center.

Flaring from natural gas wells lights up the night sky in the San Juan Basin of northern New Mexico.
Jeremy Wade Shockley

Methane bubbles up through the streambed in Archuleta County, Colorado.
Jeremy Wade Shockley

At the forum, Kort, Petron and other scientists assure the audience that they have no ax to grind, and that they will look at all potential sources, including geologic seeps. This, along with Kort’s Zen-like demeanor, seems to ease the earlier tension. The scientists’ analysis of what Kort calls a “fire hose of data” won’t be published until next year, but ongoing research hints at what they might find. Monitored seeps along the Colorado side of the coal outcrop have leaked more than 45,000 metric tons of methane per year, which has the same warming potential as the carbon dioxide emitted from more than 200,000 cars annually. And still more methane is leaking from other parts of the outcrop that aren’t monitored, in New Mexico, or on the Southern Ute Reservation, where data about the seeps has not been made public. The seeps are a significant source. But by its own count, ConocoPhillips’ San Juan Basin operations collectively released six times that amount –– 277,000 tons –– in 2013, making it the largest such emitter in the nation.

Also lingering is the question of how much, if any, of the seeps’ emissions can or should be attributed to the coalbed methane industry. A report published in 2000 as part of the multi-agency project to map, model and monitor the coal outcrop again established a link between drilling and the seeps, but some mystery remains. “How much is natural and how much is exacerbated,” Petron says, “it’s not something we understand yet.” And we probably won’t understand it anytime soon. While Hencmann and his colleagues continue to collect reams of data, the stats mostly fall into an analytic void. The researchers have found, for example, that the total emissions from the seeps in their monitoring zone has increased each year since 2007, yet no one is currently trying to determine why. It could be drought, it could be changes in the gas field, or it could be something else entirely. Hencmann hopes the attention on the hot spot will revive flagging efforts to decipher the seeps.

Without understanding the connection between the anthropogenic and the natural seeps, there’s no real mechanism for encouraging or requiring companies to mitigate those seeps. Unless we know how much the industry is responsible for, we can’t truly calculate the leakage rate of the region’s natural gas systems and therefore can’t ever really know how big its greenhouse gas footprint is.

A new round of research could have global implications. Similar basins, with similar geologies and seeps, exist all over the world, says Taku Ide, a petroleum engineer who studied methane-fueled fires in the coal outcrop on Southern Ute land. The Intergovernmental Panel on Climate Change estimates that, worldwide, geologic seeps could be emitting as much as 40 to 60 million metric tons of methane per year, putting them on par with landfills or coal mines. “The San Juan Basin is the most advanced in terms of work that’s been done to serve as a model, to drive the conversation across the U.S.,” says Ide. “It could be a model child.” If, that is, the national conversation sparked by the hot spot kicks new studies into gear.


Coal from the nearby San Juan Mine is piled up at the San Juan Generating Station in northwestern New Mexico. The power plant emits huge amounts of carbon dioxide, but relatively little methane. The mine, however, is one of the biggest single methane emitters in the region.
Jeremy Wade Shockley

Just south of Farmington, white sandstone cliffs rise from the swatch of green along the San Juan River. From atop these cliffs, you can look out over a landscape that is beautiful and battered, sacred and sacrificed. You can see the nation’s energy past, and perhaps its future, from here.

To the west, two massive coal-burning power plants stand in the high desert. Each kicks out more than 11 million tons of carbon dioxide each year, along with a soup of particulates, sulfur dioxide and mercury. When the wind rises, as it does frequently, a fine gray dust lifts up into the air from the multimillion-ton piles of coal-combustion waste piled near the Four Corners plant, its sooty gray stacks juxtaposed against the beige backside of the Hogback monocline.

Environmentalists and Navajo activists have struggled for years to shut down the plants, protesting and filing lawsuits, and recently their efforts have had some success. Four Corners recently shut down three of its five generators to comply with regional haze rules, and San Juan Generating Station plans to shut down two of four units and replace one with a natural gas-fired “peaker” plant –– if opponents don’t succeed in retiring the plant altogether.

The victories have come in part with the help of an unexpected ally, also visible from this cliff-top vantage point: The coalbed methane and conventional natural gas fields that pockmark thousands of square miles here. Much of this gas is piped to California, where utilities buy it at a relatively cheap price to run power plants, thereby helping to wean themselves from the two coal plants here. President Obama’s Clean Power Plan, released this summer, will likely tilt the nation’s energy balance further away from coal and toward natural gas, at least until more renewables take hold. That could do more to clean up this area’s coal-sullied air and landscape.

But it would also increase demand on, and activity in, the natural gas fields. More wells would be drilled and more pipelines built, providing more avenues for methane to escape, adding to the hot spot and further diminishing natural gas’ green cred in the battle to curb climate change. Unless, that is, the gas companies can get a handle on all those leaks.

This summer, the EPA announced an overhauled program designed to get companies to voluntarily clean up their act, and industry officials have promised to comply, since it’s in their best interest to keep their cash crop from slipping away. A spokesperson with ConocoPhillips says that the company has already reduced overall emissions by 48 percent on its own, mostly by using “off-the-shelf” solutions. But just 10 of New Mexico’s 475 natural gas producers participate in the EPA’s current EnergySTAR program, and with natural gas prices so low, there’s little incentive to invest much into leak prevention. That’s why activists are pressing for strong regulations that will push the entire industry to tighten up.

Methane gas escapes from a natural gas storage tank near Aztec, New Mexico, in this thermal camera image captured by Andrew Thorpe of NASA’s Jet Propulsion Laboratory.
Shaun Stanley

In August, the EPA released its new rules requiring operators to plug leaks of methane, ozone-forming volatile organic compounds and other toxics on new and modified facilities. They’ll also require drillers to capture the methane that burps out of any newly fractured oil or gas well. Since the rules don’t apply to existing infrastructure, they will do little to reduce the methane cloud already hovering over the San Juan Basin. But the BLM will hand down its own rules in coming months, and they are expected to apply to these existing facilities. The majority of the wells in the San Juan Basin are under BLM jurisdiction, so the new rules should have an effect on the hot spot. Indeed, Interior Secretary Sally Jewell invoked the Four Corners hot spot when announcing the need for such rules in March. The BLM regulations may resemble Colorado’s, implemented last year, which require companies to install leak-detection and prevention equipment and take other measures to reduce emissions. Chris Colclasure of the Colorado Air Pollution Control Division says it’s too soon to quantify the effects of the rules, but he believes they work and are not too onerous for the companies. In fact, several energy firms have endorsed the regulations, saying they’re good for business.

While some oil and gas lobbyists have portrayed the new rules as an attack on the industry, the Environmental Defense Fund’s Mark Brownstein says that compliance won’t require that much from operators, many of whom say they’re already doing what the regulations require. Whereas the administration’s limits on carbon dioxide emissions make it virtually impossible to build a new coal-fired power plant, and are thus aimed at phasing out coal in the long run, the methane rules seem intended to sharpen up the natural gas industry’s green credentials, making it more appealing in the future.

The scientists working to decipher the methane mystery remain mum when it comes to specific regulations, but they have discussed what they think needs to be done. “If natural gas is to be a ‘bridge’ to a more sustainable energy future,” wrote Kort, Petron and several other researchers in a paper published by Science last fall, “it is a bridge that must be traversed carefully: Diligence will be required to ensure that leakage rates are low enough to achieve sustainability goals.”

Back at the gas well behind the high school, Petron lets me flip the little switch that snatches an air sample from the breeze for later analysis. It will tell Petron and Thorley precisely what isotopes of methane are here, and, just as importantly, what other compounds may be seeping out of the well. Methane’s not going to hurt anyone in the short term unless it builds up enough to explode, but benzene, another pollutant emitted by oil and gas wells, has both short- and long-term health effects and is a known carcinogen –– certainly not something you want your high-schoolers inhaling every day.

As we pull back onto the road and head toward another sample site, Petron reminds me of one simple, enduring fact of life here in oil and gas country: “Your air is being impacted,” she says bluntly. “You live on the edge of the gas field.”