Evidence for High Rates of Gas Transport in the Deep Subsurface
Abstract
Barometric pumping caused by atmospheric pressure fluctuations contributes to the motion of gases in the vadose zone. While the resulting gas transport is often negligible in unfractured porous rocks, rates of transport in fractured media can be significant. Deep atmospheric pumping has implications for nuclear gas detection, water balance, and contaminant transport. We present results from a tracer test conducted to characterize deep subsurface fractured basalt and investigate the effects of barometric pumping on gaseous contaminant mobility. The tracer test provides data to constrain permeability, porosity, and diffusivity in a numerical representation of the experiment. A numerical model is used to simulate gas flow and dispersive transport under fluctuating pressure conditions. Tracer test and simulation results suggest that barometric pumping induces 10 to 100 times more mixing in the basalt than predicted by gas diffusion alone. Within the basalt fractures, estimates of gas velocity reach maximums of nearly 1,000 m/day.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 01, 2019
- Source ID
- 10.1029/2019gl082394
Entities
People
- E. E. Snyder
- Hakim Boukhalfa
- Hannah Behar
- John P Ortiz
- L. J. Salazar
- Philip Stauffer
- Thomas Rahn
Organizations
- Defense Threat Reduction Agency
- Los Alamos National Laboratory
- New Mexico Institute of Mining and Technology
- United States Department of Energy