Hydrocarbon molecules are the main building blocks of crude oil and natural gas, and determining their thermochemical properties is important to understand carbon reservoirs and fluxes in the Earth.
Geologists and geochemists believe that nearly all of the hydrocarbons in commercially produced crude oil and natural gas are formed by the decomposition of the remains of living organisms buried under layers of sediments in the Earth's crust, a region that extends five to 10 miles below the Earth's surface.
But "abiogenic" hydrocarbons of purely chemical deep crustal or mantle origin could occur in some geologic settings, such as rifts or subduction zones, said Giulia Galli, professor of chemistry and of physics at UC Davis and senior author on the study.
"Our simulation study shows that methane molecules can combine to form larger hydrocarbon molecules when exposed to the very high temperatures and pressures of the Earth's upper mantle. We don't say that higher hydrocarbons actually occur under the realistic 'dirty' Earth mantle conditions, but the pressures and temperatures are right," she said.
Galli and her colleagues used the University of California's Mako computer cluster in Berkeley and computers at the Lawrence Livermore National Laboratory to simulate the behavior of carbon and hydrogen atoms at the enormous pressures and temperatures found 40 to 95 miles deep inside the Earth.
They used sophisticated techniques based on first principles (the basic properties of carbon and hydrogen atoms) and the computer software system Qbox, developed at UC Davis by Francois Gygi, a professor in the Department of Computer Science.
The researchers found that hydrocarbons with multiple carbon atoms can form from methane, (a molecule with only one carbon and four hydrogen atoms) at temperatures greater than 1,500 K (2,240 degrees F) and pressures 50,000 times those at the Earth's surface, conditions found about 70 miles below the surface.
"In the simulation, interactions with metal or carbon surfaces allowed the process to occur faster; they act as 'catalysts'," said Leonardo Spanu, assistant researcher at UC Davis and the first author of the paper.
The research does not address whether hydrocarbons formed that deep in the Earth could migrate closer to the surface and contribute to exploitable oil or gas deposits. However, the study is fundamentally important because it points to possible microscopic mechanisms of hydrocarbon formation under very high temperatures and pressures.
Galli and some of her collaborators at UC Davis are part of a larger project, the Deep Carbon Observatory, supported by the Alfred P. Sloan Foundation; Galli is co-chair of the observatory's Physics and Chemistry of Carbon directorate. The aim of the observatory is to study the Earth's carbon cycle, including the presence of hydrocarbons and the possibility of microbial life deep in the planet.
Galli's co-authors are Davide Donadio at the Max Planck Institute in Mainz, Germany; Detlef Hohl at Shell Global Solutions, Houston; and Eric Schwegler, Lawrence Livermore National Laboratory.
The research was supported by Shell.
Andy Fell | EurekAlert!
New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg
Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences