SOURCES OF FLUIDS IN SHALLOW GROUNDWATER NEAR NATURAL GAS EXTRACTION - WELD, ADAMS, AND BOULDER COUNTIES, COLORADO

Higher energy demand and a desire for energy independence has increased natural gas extraction across the U.S. Advances in directional drilling and hydraulic fracturing technologies have driven a substantial increase of oil and gas production, while also increasing environmental concerns. Though, there is little publically available water quality data addressing these concerns. The lack of data prevents a thorough understanding of the potential risk(s) associated with oil and gas production on shallow groundwater systems. This is especially true in rural and semi-arid/arid regions where groundwater may be heavily used for domestic and agricultural purposes and wells often go unregulated or untested. To address this knowledge gap, in part, a research study was conducted to understand basic water quality and the source(s) of salinity and fluids in shallow groundwater of the semi-arid Front Range of Colorado where there is extensive oil/gas production.

Forty-one domestic groundwater, one precipitation, and eight surface water samples were collected in Adams, Boulder, and Weld counties, Colorado (Summer 2013). The fort-one residential and municipal wells extract water from aquifers overlying the deep Niobrara formation, a target of the recent oil and gas exploration and production boom of northern Colorado. The depth of the groundwater wells sampled ranged from 20 to over 800 feet, likely producing from alluvial, the Laramie-Foxhills, and Arapahoe aquifers of the northern part of the Denver Basin. Major, minor, and trace elemental analyses, alkalinity, and stable isotopes (O and H) were performed on waters to understand the source(s) of salinity and fluids. The pH of groundwater and surface waters ranged from 6.79 to 8.81, consistent with most natural waters. Alkalinity was titrated within 24-hours of sampling and ranged between 2.39 and 14.48 meq/kg. The combined geochemical analyses will be used to constrain the origin and migration of fluids, possible mixing relationships, and basic water quality.