Publication Date

8-13-2021

Date of Final Oral Examination (Defense)

July 2021

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Geophysics

Department

Geosciences

Major Advisor

Lee Liberty, M.S.

Advisor

Dylan Mikesell, Ph.D.

Advisor

Qifei Niu, Ph.D.

Abstract

Understanding the migration behavior of carbon dioxide (CO2) during long-term geological storage is crucial to the success of carbon capture and sequestration technology. I explore p-wave and s-wave seismic properties across the Little Grand Wash fault in east-central Utah, a natural CO2 seep and analogue for a long-failed sequestration site. Travertines dated to at least 113,000 k.y. and geochemical surveys confirm both modern and ancient CO2 leakage along the fault. Outgassing is currently focused in damage zones where the total fluid pressure may reduce the minimum horizontal effective stress. Regional stress changes may be responsible for decadal- to millennial-scale changes in CO2 pathways.

I identify subsurface geologic structure in the upper few hundred meters and relate surface CO2 outgassing zones to seismic reflection and first arrival tomography data. I tie my hammer seismic results to borehole logs, geology from outcrops, and geochemical data. I generate velocity tomograms that cross the fault zone and construct rock physics models. I identify high porosity and/or high fracture density zones from slow seismic velocity zones. These zones match mapped fault locations, are fully saturated, and are conduits for upward fluid/gas migration. Anomalously high seismic velocities at the fault are consistent with ancient CO2 flow pathways. Low CO2 flux regions show seismic velocities consistent with shallow unsaturated host rock. Studying the behavior of CO2 in this system can give insight of potential risks in future sequestration projects.

DOI

https://10.18122/td.1865.boisestate

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