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Seismic Response of Natural CO2 Gas Migration Through the Little Grand Wash Fault, Utah Slivicki and Liberty

Session: Critical Zone, Environmental and Cryospheric Seismology [Poster]

Type: Poster

Date: 4/22/2021

Presentation Time: 03:45 PM Pacific

Description: 

We explore the seismic response to CO2 charged eruptions and to gas migration within shallow reservoirs along the Little Grand Wash fault in east-central Utah. We deployed 200 5 Hz 3-C Nodal geophones for 30 days in late 2020 to track seismic tremors throughout the eruption/recharge cycle. Additionally, we conducted a 30-hour active source time-lapse surface seismic survey across the fault to capture reservoir and water elevation changes. We installed a pressure and temperature sensor in the Crystal Geyser that captured 30 days of CO2 changed eruption signals that were sourced from a range of reservoir depths. Geyser eruptions of 1-3 m in height ranged from minutes to hours, with deeper eruptions expelling higher water temperatures. We captured 13 eruptions at the geyser that were likely sourced from the 200-300m deep Navajo sandstone. These eruptions lasted between one and 23 hours with a near-constant 16.9 dC water temperature recorded at the well. Preliminary seismic analysis reveals reservoir-derived seismic signals on stations spaced as far as 1300 m apart. These signals appear as 1-30 Hz tremor that each last between 5 to 20 minutes. Ongoing analysis of the complete dataset will unravel the relationship of geyser eruptions to gas migration at reservoirs that range from 100 to 400 m depth. Our active source experiment consisted of 120 5-m spaced 10 Hz vertical geophones. This array extended across the fault where elevated CO2 values are observed in previous studies and where surface outgassing bubbles are visible. We observe changing surface and body wave signals over the scale of minutes to hours that relate to changing hydrostatic pressures and to gas migration at reservoir depths.

Presenting Author: Stephen J. Slivicki

Student Presenter: Yes

Authors