While oil is a finite resource — at least in the short term of thousands, rather than hundreds of millions of years — some of the largest natural gas reserves in the world are biogenic, which means they’re being created by microbes today and could potentially be a renewable resource.
Jennifer McIntosh, a groundwater geochemist in The University of Arizona's Hydrology and Water Resources Department, is studying the factors that influence how microbes create these gas fields and how fluids migrate in the subsurface.
She also is exploring how conditions miles underground could be modified to create more gas resources and how they might be used to sequester carbon dioxide from the atmosphere.
Her work is of vital interest to the oil and gas industry in the areas of exploration and exploitation of microbially generated gas fields.
The biogenic gas deposits are found in sedimentary basins worldwide, including in the mid-continent United States and Canada — specifically the Michigan, Illinois, and Appalachian basins. These biogenic gas deposits are also found in basins in the West, such as the San Juan Basin in northern New Mexico and the Powder River Basin in Wyoming and Montana.
SUMMER FIELD WORK
McIntosh has ongoing, funded projects in all three mid-continent basins, and she and her students will spend this summer sampling oil, gas and groundwater wells in the Michigan, Illinois and Appalachian basins. Her team (which includes Ph.D. student Stephen Osborn and undergraduate Justin Clark) also will be sampling in Southwestern Ontario, studying the sustainability and recharge history of the area's major aquifer system.
McIntosh's research focuses on understanding how groundwater flow affects microbes that generate methane within organic-rich shales and coal beds that are found up to 4 kilometers underground.
The sedimentary basins she is studying were inland seas during the Paleozoic Age (540 to 250 million years ago). These seas eventually filled with sedimentary rocks — sandstones, shales and carbonates — and sank beneath the Earth's surface.
These basins also contain highly saline brine, with a salinity ranging from about 100,000 mg/liter to 400,000 mg/liter, making it about 10 times saltier than seawater, which registers about 35,000 mg/liter.
Devonian Age (415 to 360 million years ago) black shales within these basins contain high concentrations of organic carbon, which is a food source for microbes called methanogens, McIntosh explained. Methanogens consume the shale, producing methane as a byproduct along the less-salty, shallow margins of the basins where they live. Fresh water has diluted the brine along these margins, creating a methanogen-friendly environment, whereas undiluted brine is toxic to the microbes.
ICE SHEET DROVE WATER DEEP UNDERGROUND
Fresh water was driven into these basin margins during Pleistocene glaciation when pressure from the Laurentide ice sheet drove dilute waters deep underground. This occurred multiple times over a period of approximately two million years, and as recently as 18,000 years ago, when the ice sheet was melting and large amounts of fresh water suddenly became available.
In addition to providing a friendly environment for methanogens, these Pleistocene-age meltwaters are an important groundwater resource for large metropolitan areas, such as Chicago because of the large volumes of high-quality water available in these basins.Today, the basins are isolated from shallower groundwater aquifers.
pressure) processes. The gases created by these different processes have different isotopic signatures."
It’s important to determine how the gas was created because this helps geologists determine where they should explore for gas in a specific region, McIntosh said.
The research also is important for determining the source and timing of freshwater recharge and how that recharge affects the water quality and sustainability of the underground water resources being pumped by Midwestern cities.
WHERE DID THE METHANOGENS COME FROM?
One of the questions McIntosh is studying is whether methanogens were deposited with the sediment during the Devonian and were sitting dormant in a saline environment before the ice sheet melted or if they were surface microbes that migrated with the water from the ice sheet and evolved to exploit their new environment."If the microbes came with the groundwater, you would want to explore for new deposits in areas that have active groundwater recharge,"
McIntosh said. "If they were dormant within shale, you could possibly dilute the brine to encourage growth by adding fresh water to wells. So this work has a lot of consequences for gas exploration and production."
Regardless of their origin, methanogens have been producing methane in the mid-continent United States and Canada for about the past 18,000 years, unlike other thermogenic gas reserves that were created over geologic time scales measuring millions of years.
IT'S A HUGE RESOURCEBiogenically produced natural gas is a huge resource, McIntosh noted.
"There are large, unexplored areas, such as the western Canada sedimentary basin and the Hudson Bay," she said. "So it's important in those areas to determine the source of water recharge — if it's modern recharge or if the water was recharged beneath this continental ice sheet," she said. "Again, this has to do with where you explore for natural gas, the rates of microbial activity in the subsurface, and groundwater resources."
McIntosh's research also is important to radioactive waste storage and carbon dioxide absorption.
"Understanding how groundwater flows in these saline aquifers and sedimentary basins affects the security of the carbon dioxide in these aquifers," she said. "Once you get it into these saline aquifers, you want to know how much fluid flow you're going to have over a geologic time scale. When you're interested in things like radioactive waste or carbon dioxide in deep aquifers, you need to take things like the next ice age into account."
CARBON DIOXIDE STORAGE
McIntosh noted that carbon dioxide is much more strongly absorbed in organic matter than methane. So flushing carbon dioxide through a coal bed or a black shale, will cause the carbon dioxide to be absorbed onto the coal or shale, while displacing the methane."So you actually sweep the methane out of the reservoir," she said.
"I'm interested not only in how CO2 will displace methane in these coals and shales, but if it could potentially generate more methane," she said. Methane is produced in black shales and coal beds through CO2 reduction. So it's possible that bacteria could consume the carbon dioxide and produce more methane.
"These are anaerobic bacteria," she said. "They can exist in the subsurface and reproduce forever as long as they have sources of energy and the environmental conditions — pore space, temperature, salinity, sulfate concentration — are favorable."
McIntosh conducts her research in collaboration with microbiologists Klaus Nüsslein and Steven Petsch, of the University of Massachusetts Amherst; hydrologist Mark Person, at Indiana University; geologist Peter Warwick, at the USGS; hydrogeochemist Stephen Grasby, at the Geological Survey of Canada; hydrogeochemist Anna Martini, at Amherst College; and noble gas geochemist Chris Ballentine, of the School of Earth and Atmospheric and Environmental Sciences at the University of Manchester.
Her research is funded through the Geological Survey of Canada, the USGS, NSF, the American Chemical Society and the New York State Energy Research Development Authority.CONTACT INFORMATION:
In times of climate change: What a lake’s colour can tell about its condition
21.09.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?
21.09.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy