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Steve Slivicki Thesis Defense

May 5 @ 12:00 pm - 1:00 pm MDT

Steve Slivicki

ACTIVE SOURCE SEISMIC CHARACTERIZATION OF A LEAKY CO2 RESERVOIR: LITTLE GRAND WASH FAULT, UTAH.

A carbon capture and sequestration (CCS) approach requires economical methods to monitor reservoir CO¬2 flowpaths through time. I explore the use of an inexpensive surface seismic approach to monitor the time-varying response of a leaky CO2 reservoir. My site is located in east central Utah, where the Little Grand Wash fault provides a natural analogue for a failed sequestration site. This fault and related anticlinal trap provides a conduit to collect and deliver CO¬2 from shallow reservoirs to the atmosphere. Soil flux measurements and outgassing at the Crystal Geyser provide the surface expression of CO¬2 along and near the fault, and borehole and past geophysical data provide a structural and stratigraphic framework for the site.

Through historic and new temperature data, I identify and characterize eruption cycles at the Crystal Geyser. I show that the frequency and duration of eruptions is changing through time, and I observe an overall increase in eruptions as a fraction of total observed time. With a new seismic monitoring approach, I show that a surface-based accelerated weight drop source into a fixed geometry geophone spread is repeatable and appropriate for time-lapse studies to monitor travel time and amplitude reservoir changes. I show repeated surface and body wave measurements with a 30-hour time-lapse dataset. I model seismic velocity changes with changing CO¬2 saturation within the main Navajo Sandstone reservoir. My models show that during initial saturations, seismically resolvable reservoir changes are possible to monitor. However, I show that a critically saturated reservoir, like that along the Little Grand Wash fault, shows travel time or amplitude changes that are below the resolving capabilities of most surface-based seismic systems. While my surface based seismic approach is not appropriate for monitoring CO2 changes at my field site, this same approach could be used to monitor CO2 changes during initial CCS injection.

Advisor: Lee Liberty

Co-Advisors: Dylan Mikesell, Jeffrey Johnson