title: Controls on Methane Occurrences in Shallow Aquifers Overlying the Haynesville Shale Gas Field, East Texas.
abstract: Understanding the source of dissolved methane in drinking-water aquifers is critical for assessing potential contributions from hydraulic fracturing in shale plays. Shallow groundwater in the Texas portion of the Haynesville Shale area (13,000 km2) was sampled (70 samples) for methane and other dissolved light alkanes. Most samples were derived from the fresh water bearing Wilcox formations and show little methane except in a localized cluster of 12 water wells (17% of total) in a approximately 30 × 30 km2area in Southern Panola County with dissolved methane concentrations less than 10 mg/L. This zone of elevated methane is spatially associated with the termination of an active fault system affecting the entire sedimentary section, including the Haynesville Shale at a depth more than 3.5 km, and with shallow lignite seams of Lower Wilcox age at a depth of 100 to 230 m. The lignite spatial extension overlaps with the cluster. Gas wetness and methane isotope compositions suggest a mixed microbial and thermogenic origin with contribution from lignite beds and from deep thermogenic reservoirs that produce condensate in most of the cluster area. The pathway for methane from the lignite and deeper reservoirs is then provided by the fault system.
authors.affiliation: Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, 10100 Burnet Road, Austin, TX.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Nicot
authors.affiliation: Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, 10100 Burnet Road, Austin, TX.|Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 2305 Speedway, Austin, TX.
authors.forename: Toti
authors.initials: T
authors.lastname: Larson
authors.affiliation: Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, 10100 Burnet Road, Austin, TX.
authors.forename: Roxana
authors.initials: R
authors.lastname: Darvari
authors.affiliation: Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, 10100 Burnet Road, Austin, TX.
authors.forename: Patrick
authors.initials: P
authors.lastname: Mickler
authors.affiliation: St. Edward's University, 3001 South Congress, Austin, TX.
authors.forename: Michael
authors.initials: M
authors.lastname: Slotten
authors.affiliation: St. Edward's University, 3001 South Congress, Austin, TX.
authors.forename: Jordan
authors.initials: J
authors.lastname: Aldridge
authors.affiliation: Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, 10100 Burnet Road, Austin, TX.
authors.forename: Kristine
authors.initials: K
authors.lastname: Uhlman
authors.affiliation: Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, 10100 Burnet Road, Austin, TX.
authors.forename: Ruth
authors.initials: R
authors.lastname: Costley
mesh_terms: D004784:Environmental Monitoring; D060587:Groundwater; D008697:Methane; D059206:Natural Gas; D061329:Oil and Gas Fields; D013781:Texas; D014874:Water Pollutants, Chemical
chemical_list: D059206:Natural Gas; D014874:Water Pollutants, Chemical; D008697:Methane