Monitoring concentration and isotopic composition of methane in groundwater in the Utica Shale hydraulic fracturing region of Ohio

Abstract

Degradation of groundwater quality is a primary public concern in rural hydraulic fracturing areas. Previous studies have shown that natural gas methane (CH) is present in groundwater near shale gas wells in the Marcellus Shale of Pennsylvania, but did not have pre-drilling baseline measurements. Here, we present the results of a free public water testing program in the Utica Shale of Ohio, where we measured CH concentration, CH stable isotopic composition, and pH and conductivity along temporal and spatial gradients of hydraulic fracturing activity. Dissolved CH ranged from 0.2 μg/L to 25 mg/L, and stable isotopic measurements indicated a predominantly biogenic carbonate reduction CH source. Radiocarbon dating of CH in combination with stable isotopic analysis of CH in three samples indicated that fossil C substrates are the source of CH in groundwater, with one C date indicative of modern biogenic carbonate reduction. We found no relationship between CH concentration or source in groundwater and proximity to active gas well sites. No significant changes in CH concentration, CH isotopic composition, pH, or conductivity in water wells were observed during the study period. These data indicate that high levels of biogenic CH can be present in groundwater wells independent of hydraulic fracturing activity and affirm the need for isotopic or other fingerprinting techniques for CH source identification. Continued monitoring of private drinking water wells is critical to ensure that groundwater quality is not altered as hydraulic fracturing activity continues in the region. Graphical abstract A shale gas well in rural Appalachian Ohio. Photo credit: Claire Botner.

Modeling of methane migration from gas wellbores into shallow groundwater at basin scale

“…For example, instances of methane occurrence in groundwater reported in some of observational studies (Molofsky et al 2013;Li and Carlson 2014;Siegel et al 2015;McMahon et al 2017) were not spatially correlated with locations of oil and gas wells, which could further confirm the migration of methane to different distances and directions from the gas well. Our simulations corroborate the results of previous studies that methane observation in groundwater is not concentrically aligned around the leakage source (Jackson et al 2013;Steelman et al 2017;Cahill et al 2017;Rice et al 2018a;Moortgat et al 2018;Botner et al 2018). • The low-permeability layer, i.e., claystone, is assumed to be horizontal.…”

“…Some observational is being analyzed. The top panels show the geometry of the claystone layers at shallow depths, in black color studies (Molofsky et al 2013;Li and Carlson 2014;Siegel et al 2015;McMahon et al 2017;Nicot et al 2017;Botner et al 2018) found no correlation between thermogenic methane in water samples from groundwater wells and just the distance to hydrocarbon wells corroborating our findings.…”

“…10b, c), methane is observed at a distance of more than 2 km from the gas well. Our simulations indicate that the complex shape of the methane plume in the subsurface, the arrival time to groundwater (in case of occurrence), and distances from a leaky gas well vary significantly based on hydrogeological characteristics of formations intercalated between aquifer and gas reservoir (Osborn et al 2011;Jackson et al 2013;Darrah et al 2014;Steelman et al 2017;Cahill et al 2017;Botner et al 2018).…”

Gas Seepage-Induced Features in the Hypoxic/Anoxic, Shallow, Marine Environment of Amfilochia Bay, Amvrakikos Gulf (Western Greece)

“…Nevertheless, the degassing is clearly determined by a geologic structure: a fault-controlled pockmark. Radiocarbon dating of CH 4 could clarify if the gas is modern or fossil, e.g., [52].…”

Assessing potential impacts of shale gas development on shallow aquifers through upward fluid migration: A multi-disciplinary approach applied to the Utica Shale in eastern Canada

“…Until now, few studies have documented such variations (e.g. : Coleman and McElreath, 2012;Gorody, 2012;Humez et al, 2015;Sherwood et al, 2016;Smith et al, 2016;Currell et al, 2017, Botner et al, 2018 and they have relied on only a few wells and/or on a few sampling events.…”