By Denise Brehm
Civil & Environmental Engineering

A $1.5 million grant from the Department of Energy to a young professor in the Department of Civil and Environmental Engineering, Ruben Juanes, could lead to a better understanding of methane, a potential source of enormous amounts of energy.

The discovery in the 1970s of accumulations of methane under the ocean floor has fueled hopes of tapping into this energy resource, which some researchers estimate has the potential to provide twice the energy of all other fossil fuels combined. But mining this resource won’t be as simple as obtaining oil or gas from underground basins, because much of the methane is in the form of hydrate clathrates—crystalline ice-like compounds composed of methane molecules caged in a lattice of water molecules.

These hydrates occur naturally at low temperatures and high pressures, like those typical of most of the ocean floor. They are thermodynamically stable at depths greater than 500 meters, and within a region of tens to hundreds of meters thick below the ocean floor, known as the Hydrate Stability Zone (HSZ). Below that zone, the temperature is high enough that hydrates are no longer stable and methane exists only as a gas.

Juanes’ research will provide information essential to the possible mining of this resource and, more importantly, provide clues to the role that ocean-sediment methane plays in the global carbon cycle.

Until now, most research interest in methane has been directed toward the detection of methane hydrates (mostly by means of seismic surveys) and the development of conceptual geologic models. However, significant gaps in knowledge remain, particularly in terms of quantitative and predictive modeling. Juanes will mathematically describe how methane migrates below and through the HSZ, where the existence of methane in the form of a gas is an anomaly.

“We invariably find that methane gas and hydrate co-exist in the hydrate stability zone, where hydrates are thermodynamically stable,” said Juanes. “Clearly, the system as a whole is out of thermodynamic equilibrium, and we want to understand why this happens, and what the implications are for estimating natural fluxes of carbon into the ocean and the amount of methane hydrate accumulated worldwide.”

This methane research carries importance beyond the potential provision of energy. It could also help illuminate a causal link between past geologic change and climate change.  For instance, it has been postulated that if the temperature at the bottom of the ocean floor rises significantly during a period of global warming, it could be possible for a large amount of the methane hydrates to dissociate (escape from the ice lattice), causing the sudden release of vast amounts of methane into the ocean and, subsequently, the atmosphere.

Juanes collaborates on this DOE-funded project with Steve Bryant of the University of Texas at Austin.