A new paper in the journal *Nature Geoscience* details how the team incorporated capillary pressure, a force acting within the narrow channels and pores of marine sediment, into a computer model to simulate methane hydrate growth and migration over time. Their results could improve assessments of methane hydrate resources, as well as estimates of the amount of methane released into Earth’s atmosphere and oceans under different climate conditions.
“Capillary-driven hydrate formation involves a positive feedback loop between the growth of gas bubbles in marine sediment and the formation of methane hydrate around them,” said lead author Zhenzhen Sun, a former Rice postdoctoral researcher who is now on faculty at Sun Yat-sen University in China. “Gas bubbles can accumulate and grow to centimeters or larger sizes when the rate of methane gas supply is larger than the rate of methane consumption by microbial decomposition.”
As gas pressure builds inside these bubbles, the researchers explained, it overcomes the capillary forces in the sediment and creates pathways for bubble expansion. When gas leaks into these pathways, hydrate forms on pore walls and mineral surfaces, creating hydrate-rich shells that further strengthen and grow the hydrate structures.
“What makes it interesting and different is that the gas bubbles are always at the center of the hydrate deposits, and the hydrate deposits protect the bubbles from the seawater, which would otherwise dissolve them,” said co-author Lucile Brunet, a postdoctoral research associate in Rice’s Department of Civil and Environmental Engineering and the lead author of a related paper in *Geochemistry, Geophysics, Geosystems*.
Co-author Andrea Fildani, an associate professor of civil and environmental engineering and of Earth, environmental and planetary sciences at Rice, said capillary-driven hydrate formation could be an important mechanism for the formation of gas hydrate deposits in marine sediments.
“Our model suggests that capillary-driven hydrate formation could explain both localized large deposits that were detected by seismic methods at depths of hundreds of meters below the seafloor as well as the more widespread hydrate deposits that are found within marine sediments just beneath the seafloor,” he said.
Fildani said that the model could be used to assess the stability of hydrate deposits under changing climate conditions. “Since gas hydrates can act like cages that trap methane within their crystal structure, preventing its release into the atmosphere, our findings have implications for understanding how much methane might be released as the climate warms,” he said.
Fildani and Brunet are members of the Rice Center for Energy Studies.
