Event Title

Hydrogeochemical Characterization of Leaking Carbon Dioxide-Charged Fault Zones in East-Central Utah

Location

Space Dynamics Laboratory

Event Website

http://water.usu.edu/

Start Date

3-26-2004 1:15 PM

End Date

3-26-2004 1:30 PM

Description

The possibility of global climate change has spurred research to aid in the disposal of greenhouse gases. One method of mitigating atmospheric emissions is the injection of CO2 deep into the ground. Deep saline aquifers may provide a viable storage option. However, the storage capacity and integrity of deep aquifers is still poorly understood. We study natural CO2-rich subsurface systems to advance the knowledge of the impacts of CO2 on the subsurface from structural, chemical, and migrational standpoints. We examined two fault zones in east-central Utah that leak CO2-rich fluids to the surface as evidenced by groundwater-leaking abandoned oil wells, springs, and geysers, and numerous tufa/travertine deposits located along the traces of the faults. Chemical and isotopic characterization of the leaking groundwaters and CO2 gases define sources and paths of water and gas flow. The six groundwater-leaking wells, springs, and geysers in the fault zones have pH values ranging from 6.07 to 6.50 and have low water temperatures of 12.9 to 17.7°C. They lie in the sodium-chloride chemical facies and have high dissolved HCO3- concentrations of 58.4 to 72.4 meq/L. Total dissolved solid concentrations range from 13,848 to 21,228 mg/L. Solute chemistries indicate that simple halite and carbonate dissolution alone are not occurring. Hydrogen and oxygen isotopic data point to a meteoric origin of the groundwaters and shallow circulation depths. Water temperatures, the geothermal gradient in the area, and the mean annual temperature at the location of recharge were used to estimate circulation depths, which coincide with the Wingate Sandstone for some of the water emanations. Values of δ13C of dissolved carbon in water for three locations are 0.0, 0.7, and 1.2‰. The gases have high CO2 concentrations (95.66 to 99.41 vol. %) and have δ13C values of ~ -6.60‰. The helium isotope R/Ra values for two locations are 0.302 and 0.310, which may reflect a mixture of crustal gas and a small amount of entrained air. Carbon and helium isotopic data point to an inorganic origin of the CO2 that is most likely clay-carbonate reactions that occurred during the burial of the Colorado Plateau, or metamorphic reactions at the locations of igneous intrusions. These data support an interpretation of the flow system in which a free CO2 gas phase forms from clay-carbonate or metamorphic reactions. This free CO2 migrated and entered many aquifers in the basin. The faults cut a north-plunging anticline and there is no top seal formation. Thus, the CO2-rich groundwaters may flow from the north until they reach the faults that impede lateral flow. The faults do not stop vertical leakage, and CO2-rich groundwater from as deep as the Wingate Sandstone leaks to the surface.

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Mar 26th, 1:15 PM Mar 26th, 1:30 PM

Hydrogeochemical Characterization of Leaking Carbon Dioxide-Charged Fault Zones in East-Central Utah

Space Dynamics Laboratory

The possibility of global climate change has spurred research to aid in the disposal of greenhouse gases. One method of mitigating atmospheric emissions is the injection of CO2 deep into the ground. Deep saline aquifers may provide a viable storage option. However, the storage capacity and integrity of deep aquifers is still poorly understood. We study natural CO2-rich subsurface systems to advance the knowledge of the impacts of CO2 on the subsurface from structural, chemical, and migrational standpoints. We examined two fault zones in east-central Utah that leak CO2-rich fluids to the surface as evidenced by groundwater-leaking abandoned oil wells, springs, and geysers, and numerous tufa/travertine deposits located along the traces of the faults. Chemical and isotopic characterization of the leaking groundwaters and CO2 gases define sources and paths of water and gas flow. The six groundwater-leaking wells, springs, and geysers in the fault zones have pH values ranging from 6.07 to 6.50 and have low water temperatures of 12.9 to 17.7°C. They lie in the sodium-chloride chemical facies and have high dissolved HCO3- concentrations of 58.4 to 72.4 meq/L. Total dissolved solid concentrations range from 13,848 to 21,228 mg/L. Solute chemistries indicate that simple halite and carbonate dissolution alone are not occurring. Hydrogen and oxygen isotopic data point to a meteoric origin of the groundwaters and shallow circulation depths. Water temperatures, the geothermal gradient in the area, and the mean annual temperature at the location of recharge were used to estimate circulation depths, which coincide with the Wingate Sandstone for some of the water emanations. Values of δ13C of dissolved carbon in water for three locations are 0.0, 0.7, and 1.2‰. The gases have high CO2 concentrations (95.66 to 99.41 vol. %) and have δ13C values of ~ -6.60‰. The helium isotope R/Ra values for two locations are 0.302 and 0.310, which may reflect a mixture of crustal gas and a small amount of entrained air. Carbon and helium isotopic data point to an inorganic origin of the CO2 that is most likely clay-carbonate reactions that occurred during the burial of the Colorado Plateau, or metamorphic reactions at the locations of igneous intrusions. These data support an interpretation of the flow system in which a free CO2 gas phase forms from clay-carbonate or metamorphic reactions. This free CO2 migrated and entered many aquifers in the basin. The faults cut a north-plunging anticline and there is no top seal formation. Thus, the CO2-rich groundwaters may flow from the north until they reach the faults that impede lateral flow. The faults do not stop vertical leakage, and CO2-rich groundwater from as deep as the Wingate Sandstone leaks to the surface.

https://digitalcommons.usu.edu/runoff/2004/AllAbstracts/19