Geological Society of America

T70 Field Tracer Studies for Aquifer Characterization

Sunday, 22 September 2019
1:30 PM - 5:30 PM
Room 105BC, West Building

HIGH RATES OF TRACER GAS TRANSPORT IN A DEEP FRACTURED BASALT

Paper number: T70-2
Program: Technical Sessions
Time: 1:45 PM – 2:05 PM

Authors

Philip H. Stauffer Presenting Author
Los Alamos National Laboratory, Los Alamos, NM
Thom Rahn
Los Alamos National Laboratory, Los Alamos, NM
John P. Ortiz
Los Alamos National Laboratory, Los Alamos, NM
Hakim Boukhalfa
Los Alamos National Laboratory, Los Alamos, NM
Hannah Behar
University of Minnesota Duluth, Duluth, MN
Hannah Behar
Earth and Environmental Science, Los Alamos, NM
Emily E. Snyder
Los Alamos National Laboratory, Los Alamos, NM
Emily E. Snyder
New Mexico Institute of Mining and Technology, Soccorro, NM

Abstract

In the phenomenon known as barometric pumping, atmospheric pressure fluctuations contribute to the motion of gases in the vadose zone. While the resulting gas transport is often negligible in homogeneous media, rates of transport in fractured media can be significant. We present results from a tracer test that was conducted to characterize deep subsurface fractured basalt and investigate the effects of barometric pumping on gaseous contaminant mobility. The tracer testing provided data to constrain permeability, porosity, and diffusivity in a numerical representation of the experiment. The numerical model was then used to simulate gas flow and transport under fluctuating pressure conditions. Results from the tracer test and simulations suggest that barometric pumping induces 10x to 100x more mixing in the basalt than standard diffusive theory would predict. Further, within the basalt fractures, estimates of average linear velocity reach maximums of nearly 1000 m/day.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-339331

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