Technology-dependent emissions of gas extraction in the US

The KIT measurement instrument on board of a minivan directly measures atmospheric emissions on site with a high temporal resolution. -  Photo: F. Geiger/KIT
The KIT measurement instrument on board of a minivan directly measures atmospheric emissions on site with a high temporal resolution. – Photo: F. Geiger/KIT

Not all boreholes are the same. Scientists of the Karlsruhe Institute of Technology (KIT) used mobile measurement equipment to analyze gaseous compounds emitted by the extraction of oil and natural gas in the USA. For the first time, organic pollutants emitted during a fracking process were measured at a high temporal resolution. The highest values measured exceeded typical mean values in urban air by a factor of one thousand, as was reported in ACP journal. (DOI 10.5194/acp-14-10977-2014)

Emission of trace gases by oil and gas fields was studied by the KIT researchers in the USA (Utah and Colorado) together with US institutes. Background concentrations and the waste gas plumes of single extraction plants and fracking facilities were analyzed. The air quality measurements of several weeks duration took place under the “Uintah Basin Winter Ozone Study” coordinated by the National Oceanic and Atmospheric Administration (NOAA).

The KIT measurements focused on health-damaging aromatic hydrocarbons in air, such as carcinogenic benzene. Maximum concentrations were determined in the waste gas plumes of boreholes. Some extraction plants emitted up to about a hundred times more benzene than others. The highest values of some milligrams of benzene per cubic meter air were measured downstream of an open fracking facility, where returning drilling fluid is stored in open tanks and basins. Much better results were reached by oil and gas extraction plants and plants with closed production processes. In Germany, benzene concentration at the workplace is subject to strict limits: The Federal Emission Control Ordinance gives an annual benzene limit of five micrograms per cubic meter for the protection of human health, which is smaller than the values now measured at the open fracking facility in the US by a factor of about one thousand. The researchers published the results measured in the journal Atmospheric Chemistry and Physics ACP.

“Characteristic emissions of trace gases are encountered everywhere. These are symptomatic of gas and gas extraction. But the values measured for different technologies differ considerably,” Felix Geiger of the Institute of Meteorology and Climate Research (IMK) of KIT explains. He is one of the first authors of the study. By means of closed collection tanks and so-called vapor capture systems, for instance, the gases released during operation can be collected and reduced significantly.

“The gas fields in the sparsely populated areas of North America are a good showcase for estimating the range of impacts of different extraction and fracking technologies,” explains Professor Johannes Orphal, Head of IMK. “In the densely populated Germany, framework conditions are much stricter and much more attention is paid to reducing and monitoring emissions.”

Fracking is increasingly discussed as a technology to extract fossil resources from unconventional deposits. Hydraulic breaking of suitable shale stone layers opens up the fossil fuels stored there and makes them accessible for economically efficient use. For this purpose, boreholes are drilled into these rock formations. Then, they are subjected to high pressure using large amounts of water and auxiliary materials, such as sand, cement, and chemicals. The oil or gas can flow to the surface through the opened microstructures in the rock. Typically, the return flow of the aqueous fracking liquid with the dissolved oil and gas constituents to the surface lasts several days until the production phase proper of purer oil or natural gas. This return flow is collected and then reused until it finally has to be disposed of. Air pollution mainly depends on the treatment of this return flow at the extraction plant. In this respect, currently practiced fracking technologies differ considerably. For the first time now, the resulting local atmospheric emissions were studied at a high temporary resolution. Based on the results, emissions can be assigned directly to the different plant sections of an extraction plant. For measurement, the newly developed, compact, and highly sensitive instrument, a so-called proton transfer reaction mass spectrometer (PTR-MS), of KIT was installed on board of a minivan and driven closer to the different extraction points, the distances being a few tens of meters. In this way, the waste gas plumes of individual extraction sources and fracking processes were studied in detail.

Warneke, C., Geiger, F., Edwards, P. M., Dube, W., Pétron, G., Kofler, J., Zahn, A., Brown, S. S., Graus, M., Gilman, J. B., Lerner, B. M., Peischl, J., Ryerson, T. B., de Gouw, J. A., and Roberts, J. M.: Volatile organic compound emissions from the oil and natural gas industry in the Uintah Basin, Utah: oil and gas well pad emissions compared to ambient air composition, Atmos. Chem. Phys., 14, 10977-10988, doi:10.5194/acp-14-10977-2014, 2014.

A unique approach to monitoring groundwater supplies near Ohio fracking sites

This image shows a drilling rig in Carroll County, Ohio. -  Amy Townsend-Small
This image shows a drilling rig in Carroll County, Ohio. – Amy Townsend-Small

A University of Cincinnati research project is taking a groundbreaking approach to monitoring groundwater resources near fracking sites in Ohio. Claire Botner, a UC graduate student in geology, will outline the project at The Geological Society of America’s Annual Meeting & Exposition. The meeting takes place Oct. 19-22, in Vancouver.

Botner’s research is part of UC Groundwater Research of Ohio (GRO), a collaborative research project out of UC to examine the effects of fracking (hydraulic fracturing) on groundwater in the Utica Shale region of eastern Ohio. First launched in Carroll County in 2012, the GRO team of researchers is examining methane levels and origins of methane in private wells and springs before, during and after the onset of fracking. The team travels to the region to take water samples four times a year.

Amy Townsend-Small, the lead researcher for GRO and a UC assistant professor of geology, says the UC study is unique in comparison with studies on water wells in other shale-rich areas of the U.S. where fracking is taking place – such as the Marcellus Shale region of Pennsylvania.

Townsend-Small says water samples finding natural gas-derived methane in wells near Pennsylvania fracking sites were taken only after fracking had occurred, so methane levels in those wells were not documented prior to or during fracking in Pennsylvania.

Hydraulic fracturing, or fracking, involves using millions of gallons of water mixed with sand and chemicals to break up organic-rich shale to release natural gas resources.

Proponents say the practice promises a future in lower energy prices, an increase in domestic jobs and less dependence on foreign oil from unstable overseas governments.

Opponents raise concerns about increasing methane gas levels (a powerful greenhouse gas) and other contamination involving the spillover of fracking wastewater in the groundwater of shale-rich regions.

“The only way people with private groundwater will know whether or not their water is affected by fracking is through regular monitoring,” says Townsend-Small.

The Ohio samples are being analyzed by UC researchers for concentrations of methane as well as other hydrocarbons and salt, which is pulled up in the fracking water mixture from the shales. The shales are ancient ocean sediments.

Botner’s study involves testing on 22 private wells in Carroll County between November 2012 and last May. The first fracking permits were issued in the region in 2011. So far, results indicate that any methane readings in groundwater wells came from organic matter. In less than a handful of cases, the natural methane levels were relatively high, above 10 milligrams per liter. However, most of the wells carried low levels of methane.

The UC sampling has now been expanded into Columbiana, Harrison, Stark and Belmont counties in Ohio. Researchers then review data on private drinking water wells with the homeowners. “We’re working on interacting with these communities and educating them about fracking as well as gathering scientific data, which is lacking on a very sensitive issue,” says Botner. “It can also be reassuring to receive data on their water supplies from an objective, university resource.”

The team also is seeking additional funding to begin monitoring groundwater wells near wastewater injection wells, where fracking brine is deposited after the wells are drilled.


Funding for Botner’s research to be presented at the GSA meeting is supported by a grant from the Missouri-based Deer Creek Foundation.

Botner is among UC graduate students and faculty who are presenting more than two dozen research papers, PowerPoint presentations or poster exhibitions at the GSA meeting. The meeting draws geoscientists from around the world representing more than 40 different disciplines.

UC’s nationally ranked Department of Geology conducts field research around the world in areas spanning paleontology, Quaternary geology, geomorphology, sedimentology, stratigraphy, tectonics, environmental geology and biogeochemistry.

The Geological Society of America, founded in 1888, is a scientific society with more than 26,500 members from academia, government and industry in more than 100 countries. Through its meetings, publications and programs, GSA enhances the professional growth of its members and promotes the geosciences in the service of humankind.

Contaminated water in 2 states linked to faulty shale gas wells

Faulty well integrity, not hydraulic fracturing deep underground, is the primary cause of drinking water contamination from shale gas extraction in parts of Pennsylvania and Texas, according to a new study by researchers from five universities.

The scientists from Duke, Ohio State, Stanford, Dartmouth and the University of Rochester
published their peer-reviewed study Sept. 15 in the Proceedings of the National Academy of Sciences. Using noble gas and hydrocarbon tracers, they analyzed the gas content of more than 130 drinking water wells in the two states.

“We found eight clusters of wells — seven in Pennsylvania and one in Texas — with contamination, including increased levels of natural gas from the Marcellus shale in Pennsylvania and from shallower, intermediate layers in both states,” said Thomas H. Darrah, assistant professor of earth science at Ohio State, who led the study while he was a research scientist at Duke.

“Our data clearly show that the contamination in these clusters stems from well-integrity problems such as poor casing and cementing,” Darrah said.

“These results appear to rule out the possibility that methane has migrated up into drinking water aquifers because of horizontal drilling or hydraulic fracturing, as some people feared,” said Avner Vengosh, professor of geochemistry and water quality at Duke.

In four of the affected clusters, the team’s noble gas analysis shows that methane from drill sites escaped into drinking water wells from shallower depths through faulty or insufficient rings of cement surrounding a gas well’s shaft. In three clusters, the tests suggest the methane leaked through faulty well casings. In one cluster, it was linked to an underground well failure.

“People’s water has been harmed by drilling,” said Robert B. Jackson, professor of environmental and earth sciences at Stanford and Duke. “In Texas, we even saw two homes go from clean to contaminated after our sampling began.”

“The good news is that most of the issues we have identified can potentially be avoided by future improvements in well integrity,” Darrah stressed.

Using both noble gas and hydrocarbon tracers — a novel combination that enabled the researchers to identify and distinguish between the signatures of naturally occurring methane and stray gas contamination from shale gas drill sites — the team analyzed gas content in 113 drinking-water wells and one natural methane seep overlying the Marcellus shale in Pennsylvania, and in 20 wells overlying the Barnett shale in Texas. Sampling was conducted in 2012 and 2013. Sampling sites included wells where contamination had been debated previously; wells known to have naturally high level of methane and salts, which tend to co-occur in areas overlying shale gas deposits; and wells located both within and beyond a one-kilometer distance from drill sites.

Noble gases such as helium, neon or argon are useful for tracing fugitive methane because although they mix with natural gas and can be transported with it, they are inert and are not altered by microbial activity or oxidation. By measuring changes in ratios in these tag-along noble gases, researchers can determine the source of fugitive methane and the mechanism by which it was transported into drinking water aquifers — whether it migrated there as a free gas or was dissolved in water.

“This is the first study to provide a comprehensive analysis of noble gases and their isotopes in groundwater near shale gas wells,” said Darrah, who is continuing the analysis in his lab at Ohio State. “Using these tracers, combined with the isotopic and chemical fingerprints of hydrocarbons in the water and its salt content, we can pinpoint the sources and pathways of methane contamination, and determine if it is natural or not.”

Drilling for hydrocarbons can impact aquatic life

This large drilling sump exhibits ponding both on the surface and perimeter. -  Joshua Thienpont
This large drilling sump exhibits ponding both on the surface and perimeter. – Joshua Thienpont

The degradation of drilling sumps associated with hydrocarbon extraction can negatively affect aquatic ecosystems, according to new research published November 6th in the open-access journal PLOS ONE by Joshua Thienpont and colleagues at Queen’s University and other institutions.

Hydrocarbons are a primary source of energy as combustible fuel. Although hydrocarbon exploration and extraction are profitable enterprises, hydrocarbons contribute to the formation of greenhouse gases and are therefore a major stressor to the environment.

During the process of exploring for hydrocarbons, drilling sumps are used to permanently store the waste associated with drilling. In the Mackenzie Delta region of Canada’s western Arctic, more than 150 drilling sumps were constructed for this purpose. Although the areas surrounding the sumps were believed to be frozen by the surrounding permafrost, recent findings suggest that these areas may actually be thawing. In this study, the authors examine the environmental effects of this type of drilling sump containment loss in the Mackenzie Delta.

Because drilling fluids are saline, they tested whether leakage to surface waters was occurring by measuring changes in conductivity, as saline is more conductive than pure water. They also hypothesized that if saline-rich wastes from drilling sumps were impacting lakes, there should be changes in the types of life forms present. Zooplankton, for example, are a key component of aquatic ecosystems and various species survive differently in saline versus fresh water.

Through an analysis of lake sediments, they found changes in the community composition of zooplankton due to sump degradation. These results suggest that climate change and permafrost thaw can have deleterious consequences to aquatic life through the degradation and leaking of drilling sumps.

Thienpont elaborates, “The leaching of wastes from drilling sumps represents a newly identified example of one of the cumulative impacts of recent climate change impacting the sensitive freshwater ecosystems of the Arctic.”

Probing methane’s secrets: From diamonds to Neptune

New research from Carnegie on methane under pressure will help scientists understand the chemistry of planetary interiors, including Neptune and and Uranus, as well as hydrocarbon energy resources and diamond formation here on Earth. -  Courtesy of Alexander Goncharov, Carnegie Institution for Science.
New research from Carnegie on methane under pressure will help scientists understand the chemistry of planetary interiors, including Neptune and and Uranus, as well as hydrocarbon energy resources and diamond formation here on Earth. – Courtesy of Alexander Goncharov, Carnegie Institution for Science.

Hydrocarbons from the Earth make up the oil and gas that heat our homes and fuel our cars. The study of the various phases of molecules formed from carbon and hydrogen under high pressures and temperatures, like those found in the Earth’s interior, helps scientists understand the chemical processes occurring deep within planets, including Earth.

New research from a team led by Carnegie’s Alexander Goncharov hones in on the hydrocarbon methane (CH4), which is one of the most abundant molecules in the universe. Despite its ubiquity, methane’s behavior under the conditions found in planetary interiors is poorly understood due to contradictory information from various modeling studies. The work is published by Nature Communications.

Lead author Sergey Lobanov explains: “Our knowledge of physics and chemistry of volatiles inside planets is based mainly on observations of the fluxes at their surfaces. High-pressure, high-temperature experiments, which simulate conditions deep inside planets and provide detailed information about the physical state, chemical reactivity, and properties of the planetary materials, remain a big challenge for us.”

For example, methane’s melting behavior is known only below 70,000 times normal atmospheric pressure (7 GPa). The ability to observe it under much more extreme conditions is fundamental information for planetary models.

Moreover, its reactivity under extreme conditions also needs to be understood. Previous studies indicated little information about methane’s chemical reactivity under pressure and temperature conditions similar to those found in the deep Earth. This led to the assumption that methane is the main hydrocarbon phase of carbon, oxygen, and hydrogen-containing fluid in some parts of the Earth’s mantle. But the team’s work shows that it is necessary to question this assumption.

Using high-pressure experimental techniques, the team–including Carnegie’s Lobanov, Xiao-Jia Chen, Chang-Sheng Zha, and Ho-Kwang “Dave” Mao–was able to examine methane’s phases and reactivity under a range of temperatures and pressures mimicking environments found beneath Earth’s surface.

At pressures reaching 790,000 times normal atmospheric pressure (80 GPa), methane’s melting temperature is still below 1,900 degrees Fahrenheit. This suggests that methane is not a solid under any conditions met deep within most planets. What’s more, its melting point is even lower than melting temperatures of water (H2O) and ammonia (NH3), other very important components in the interiors of giant planets.

As the temperature increases above about 1,700 degrees Fahrenheit, methane becomes more chemically reactive. First, it partly disassociates into elemental carbon and hydrogen. Then, with further temperature increases, light hydrocarbon molecules start to form. Pressure also affects the composition of the carbon-hydrogen system, with heavy hydrocarbons becoming apparent at pressures above 250,000 times atmospheric pressure (25 GPa), indicating that under deep mantle conditions the environment is likely methane poor.

These findings have implications both for Earth’s deep chemistry and for the geochemistry of icy gas giant planets such as Uranus and Neptune. The team argues that this reactivity may play a role in the formation of ultradeep diamonds deep within the mantle. They assert that their findings should be taken into account in future models of the interiors of Neptune and Uranus, which are believed to have mantles consisting of a mixture of methane, water, and ammonia components.

Terahertz time-domain spectroscopy for oil and gas detection

This image shows R0% (vitrinite reflectance) dependence of α (absorption coefficients) of kerogen of different maturities at selected frequencies. -  ©Science China Press
This image shows R0% (vitrinite reflectance) dependence of α (absorption coefficients) of kerogen of different maturities at selected frequencies. – ©Science China Press

A greater understanding of the evolutionary stage of kerogen for hydrocarbon generation would play a role in easing the world’s current energy problem. Professor ZHAO Kun and his group from the Key Laboratory of Oil and Gas Terahertz Spectrum and Photoelectric Detection (CPCIF, China University of Petroleum, Beijing) set out to tackle this problem. After five years of innovative research, they have developed terahertz time-domain spectroscopy (THz-TDS) as an effective method to detect the generation of oil and gas from kerogen. Their work, entitled “Applying terahertz time-domain spectroscopy to probe the evolution of kerogen in close pyrolysis systems”, was published in Science China Physics, Mechanics & Astronomy, 2013, Vol. 56(8).

The evolution stages of kerogen and hydrocarbon generation are critical aspects of oil-gas exploration and source rock evaluation. In sedimentary rock, about 95% of the organic matter is kerogen, the key intermediate in the formation of oil and gas. The specific kerogen type and maturity level will determine the characteristics of the hydrocarbons that will be generated. Previous research has led to two primary observations: (i) kerogen serves as a significant energy source as recoverable shale oil and coal where reserves far exceed the remaining petroleum reserves; and (ii) kerogen possesses a significant sorption capacity for organic compounds. Kerogen is primarily composed of alicyclics, aromatics, and other functional groups. Therefore, the ability to generate oil and gas from kerogen is determined primarily by its specific composition and structure. However, each generation technique has advantages and disadvantages within the specific parameters of the kerogen. Thus, there is a need for new methods to characterize the numerous stages and mechanisms of hydrocarbon generation from kerogen.

Vitrinite reflectance (R0%), defined as the proportion of normal incident light reflected by a polished planar surface of vitrinite (found in kerogen), is commonly used to characterize the maturity stage of kerogen. Those stages are defined as: the immature (IM) stage, where it generally cannot produce oil and gas (R0%<0.5); the early mature (EM) stage, or heavy oil zone (0.5<R0%<0.7); the middle mature (MM) stage, which is a primary zone of crude oil generation, also referred to as the oil window (0.7<R0%<1.2); the late mature (LM) stage, or zone of light oil and natural gas (1.2<R0%2.0).

To meet the challenges of applying optical characterization in oil and gas exploration, we applied THz-TDS as a nondestructive, contact-free tool for identifying the transformational paths and hydrocarbon generation ability of kerogen. Specifically, the absorption coefficients at different temperatures and pressures indicated the maturity regime of the kerogen, which were in good agreement with the results of programmed pyrolysis experiments.

By comparing the kerogen THz curves under different R0% and the maturity stages of the hydrocarbons, we can conclude that a relationship exists between the kerogen THz optical constants and the maturity stage. The THz optical constant curves at a given frequency can be divided into several sections denoted by the IM, EM, MM, LM, and OM stages. The kerogens cannot generate any significant amount of oil or gas when in the IM stage (R0%<0.5). Therefore, the functional groups and characteristics do not alter, which results in little observed change of the THz optical constants. In the primary oil generation zone (0.7<R0%<1.2), methyl, methylene, aromatic hydrocarbon, oxygen, and nitrogen functional groups separate from the kerogen, and oil and gas begin to be generated. The residual kerogen forms macromolecules with aromatic components. From the changes in the molecular structures and features relative to those of the initial kerogen, the values of the first peak of the THz absorption coefficient curve (see Figure) and the real parts of the relative dielectric permittivity curves characterize the oil-generating stage of kerogen. At a more mature stage (R0%<1.2), alkyls in aromatic groups separate from the kerogen and begin to generate hydrocarbons in the primary gas zone (see Figure).

This study was a collaborative effect involving many university and company researchers. It was supported by a grant from the National Key Scientific Instruments and Equipment Development, a 973 grant from the Department of Science and Technology of China, and a grant from the Beijing National Science Foundation. Being nondestructive and contactless, this method has shown great promise to improve kerogen analysis. The technique needs to be applied in more instances that involve reservoir rocks and further research will determine whether it can be established as a key tool in petroleum exploration and impact the oil and gas industry.

Sequestration and fuel reserves

A technique for trapping the greenhouse gas carbon dioxide deep underground could at the same be used to release the last fraction of natural gas liquids from ailing reservoirs, thus offsetting some of the environmental impact of burning fossil fuels. So says a paper to be published in the peer-reviewed International Journal of Oil, Gas and Coal Technology.

While so-called “fracking” as a method for extracting previously untapped fossil fuel reserves has been in the headlines recently, there are alternatives to obtaining the remaining quantities of hydrocarbons from gas/condensate reservoirs, according to Kashy Aminian of West Virginia University in Morgantown, USA, and colleagues there and at Kuwait University in Safat.

Earlier experiments suggests that using carbon dioxide instead of nitrogen or methane to blast out the hydrocarbon stock from depleted reservoirs might be highly effective and have the added benefit of trapping, or sequestering the carbon dioxide underground. Aminian and colleagues have calculated the economic benefits associated with the enhanced liquid recovery and demonstrated that the approach is technically and financially viable.

The team explains that the mixing of carbon dioxide with the condensate reservoir fluid results in a reduction of the saturation pressure, the liquid drop-out, and the compressibility factor, boosting recovery of useful hydrocarbon and allowing the carbon dioxide to be trapped within. The team found that the process works well regardless of the characteristics of the reservoir or even the rate at which the carbon dioxide is injected into the reservoir, the amount that is recovered remains just as high. Moreover, because of the compressibility of the carbon dioxide it is possible to squeeze out 1.5 to 2 times the volume of reservoir gas for the amount of carbon dioxide pumped in, there is also then the possibility of pumping in an additional 15% once as much reservoir liquid as can be retrieved has been extracted.

Lost City pumps life-essential chemicals at rates unseen at typical black smokers

The carbonate structures at the Lost City Field include these spires stretching 90 feet tall. The white, sinuous spine is freshly deposited carbonate material. Added digitally to this image are the remotely operated vehicles Hercules and Argus that were used to explore the hydrothermal vent field during an expedition in 2005 funded by the National Oceanic and Atmospheric Administration. - Credit:  Kelley, U of Washington, IFE, URI-IAO, NOAA
The carbonate structures at the Lost City Field include these spires stretching 90 feet tall. The white, sinuous spine is freshly deposited carbonate material. Added digitally to this image are the remotely operated vehicles Hercules and Argus that were used to explore the hydrothermal vent field during an expedition in 2005 funded by the National Oceanic and Atmospheric Administration. – Credit: Kelley, U of Washington, IFE, URI-IAO, NOAA

Hydrocarbons — molecules critical to life — are being generated by the simple interaction of seawater with the rocks under the Lost City hydrothermal vent field in the mid-Atlantic Ocean.

Being able to produce building blocks of life makes Lost City-like vents even stronger contenders as places where life might have originated on Earth, according to Giora Proskurowski and Deborah Kelley, two authors of a paper in the Feb. 1 Science. Researchers have ruled out carbon from the biosphere as a component of the hydrocarbons in Lost City vent fluids.

Hydrocarbons, molecules with various combinations of hydrogen and carbon atoms, are key to cellular life. For instance, cell walls can be built from simple hydrocarbon chains and amino acids are short hydrocarbon chains hooked up with nitrogen, oxygen or sulfur atoms.

“The generation of hydrocarbons was the very first step, otherwise Earth would have remained lifeless,” says lead author Proskurowski, who conducted the research while earning his doctorate from the University of Washington and during post-doctoral work at Woods Hole Oceanographic Institution.

Some researchers believe the first building blocks of life made their way from outer space while others hypothesize that the right ingredients were generated by geological process on Earth, perhaps at hydrothermal vent systems where seawater seeps into the seabed and picks up heat and minerals until the water is so hot it vents back into the ocean.

The Lost City hydrothermal vents, discovered by Kelley and others during a National Science Foundation expedition in 2000, are formed in a very different way than the black smoker vents scientists have known about since the 1970s. Black smokers are so named because it can appear as if smoke is billowing from them. In fact the smoke is actually dark iron- and sulfur-rich minerals precipitating when scalding vent waters — as hot as 760 F –meet the icy cold depths. The spires and mounds that form are darkly mottled mixes of sulfide minerals.

In contrast, structures at the Lost City hydrothermal vent field are nearly pure carbonate, the same material as limestone in caves, and they range in color from white to cream to gray. The structures drape the cliffs at Lost City and range from the size of tiny toadstools to the 18-story column, named Poseidon, that dwarfs most known black smoker vents by at least 100 feet. The field was named Lost City in part because it is on top of a submerged mountain named Atlantis and was discovered by chance during an expedition on board the research vessel Atlantis.

Water venting at Lost City is generally 200 F. The fluids do not get as hot as the black smokers because the water is not heated by magma but rather by heat released during serpentinization, a chemical reaction between seawater and mantle rock.

That’s also the reason for all the hydrocarbons.

Lost City is located about 2,300 miles east of Florida on the Mid-Atlantic Ridge, one of the world's largest undersea mountain ranges. - Credit: University of Washington
Lost City is located about 2,300 miles east of Florida on the Mid-Atlantic Ridge, one of the world’s largest undersea mountain ranges. – Credit: University of Washington

Naturally occurring carbon dioxide is locked in mantle rock. At Lost City, the reaction between the rock and seawater produces 10 to 100 times more hydrogen and the hydrocarbon methane than a typical black smoker system found along mid-ocean ridges, the Science co-authors found.

The Lost City system forms hydrocarbons in higher concentrations and with more complexity than do typical black smoker systems on mid-ocean ridges, says Kelley, a University of Washington professor of oceanography who was the principal investigator for a 2005 National Oceanic and Atmospheric Administration’s expedition that gathered the samples analyzed for the Science paper.

The hydrocarbons being produced at Lost City are not formed from atmospheric carbon dioxide dissolved in seawater because none of the carbon carries the radioisotopic signature that would be present if they had been exposed to sunlight, Proskurowski says.

Analysis of rock from Lost City shows that the hydrocarbons are not coming from the living biosphere. Rock in contact with seawater has a very consistent ratio of carbon dioxide to helium. But the rock at Lost City had a strikingly different ratio. It turns out that the depleted amount of carbon dioxide in the rocks roughly equals the amount of hydrocarbons being produced in the fluids, he says.

“The detection of these organic building blocks from a non-biological source is possible evidence in our quest to understand the origin of life on this planet and other solar bodies,” Proskurowski says.

Lost City is exceptional, Kelley says, because chemical reactions in the seafloor produce acetate, formate, hydrogen and alkaline fluids. All these substances may have been key to the emergence of life, according to work published recently by Michael Russell and A.J. Hall of Glasgow and William Martin of Germany. In addition, acetate and formate found in Lost City fluids may have been an important energy source for the ancestors of methanogens, microorganisms that live off the methane at places like Lost City. It’s perhaps one more bit of evidence about where life may have originated, Kelley says.

Other co-authors of the paper, “Abiogenic Hydrocarbon Production at Lost City Hydrothermal Field,” are Marvin Lilley and Erick Olson from the University of Washington, Jeffrey Seewald and Sean Sylva from Woods Hole Oceanograhic Institution, Gretchen Früh-Green from the Swiss Federal Institute of Technology and John Lupton with NOAA’s Pacific Marine Environmental Laboratory.

The Lost City hydrothermal vent field is about 2,300 miles east of Florida, on the Mid-Atlantic Ridge, at a depth of 2,600 feet. Microorganisms there thrive in alkaline vent fluids, some nearly as caustic as liquid drain cleaner. This contrasts to the previously studied black-smoker vents where organisms have adjusted to acidic water. Lost City microbes live off methane and hydrogen instead of the carbon dioxide that is the key energy source for life at black-smoker vents.

Although nobody has found another field like Lost City, Kelley says she’s sure others exist because there are so many other places where mantle rock has been thrust up through the seafloor, exposing it to seawater and serpentinization. It is likely that even more mantle rock was present in the oceans of early Earth, Kelley says.