Methane Sources and Migration Mechanisms in Shallow Groundwaters in Parker and Hood Counties, Texas-A Heavy Noble Gas Analysis.
This study places constraints on the source and transport mechanisms of methane found in groundwater within the Barnett Shale footprint in Texas using dissolved noble gases, with particular emphasis on84Kr and132Xe. Dissolved methane concentrations are positively correlated with crustal4He,21Ne, and40Ar and suggest that noble gases and methane originate from common sedimentary strata, likely the Strawn Group. In contrast to most samples, four water wells with the highest dissolved methane concentrations unequivocally show strong depletion of all atmospheric noble gases (20Ne,36Ar,84Kr,132Xe) with respect to air-saturated water (ASW). This is consistent with predicted noble gas concentrations in a water phase in contact with a gas phase with initial ASW composition at 18 °C-25 °C and it suggests an in situ, highly localized gas source. All of these four water wells tap into the Strawn Group and it is likely that small gas accumulations known to be present in the shallow subsurface were reached. Additionally, lack of correlation of84Kr/36Ar and132Xe/36Ar fractionation levels along with4He/20Ne with distance to the nearest gas production wells does not support the notion that methane present in these groundwaters migrated from nearby production wells either conventional or using hydraulic fracturing techniques.
University of Michigan , Department of Earth and Environmental Sciences, Ann Arbor, Michigan 48109-1005, United States.
Tao
T
Wen
University of Michigan , Department of Earth and Environmental Sciences, Ann Arbor, Michigan 48109-1005, United States.
M Clara
MC
Castro
University of Texas at Austin , Bureau of Economic Geology, Austin, Texas 78713-8924, United States.
Jean-Philippe
JP
Nicot
University of Michigan , Department of Earth and Environmental Sciences, Ann Arbor, Michigan 48109-1005, United States.
Chris M
CM
Hall
University of Texas at Austin , Bureau of Economic Geology, Austin, Texas 78713-8924, United States.
Toti
T
Larson
University of Texas at Austin , Bureau of Economic Geology, Austin, Texas 78713-8924, United States.
Patrick
P
Mickler
University of Texas at Austin , Bureau of Economic Geology, Austin, Texas 78713-8924, United States.
Roxana
R
Darvari
D060587:Groundwater; D008697:Methane; D061329:Oil and Gas Fields; D013781:Texas; D060986:Water Wells
D008697:Methane