Gas well integrity and methane migration: evaluation of published evidence during shale-gas development in the USA

Abstract

More than 1 million wells may have been completed using hydraulic fracturing techniques in the USA alone; however, there have been few case studies exploring the impacts on water resources due to methane migration. This study evaluated the results of three investigations initiated by the US Environmental Protection Agency, that were subsequently described in published studies at Dimock in Pennsylvania, Parker-Hood County in Texas, and Pavillion in Wyoming, as well as another study completed at Sugar Run in northeast Pennsylvania. In addition, earlier investigations at Shaws Corner in Pennsylvania, Jackson County in West Virginia, Garfield County in Colorado, and Bainbridge in Ohio are summarized. The most common cause of incidents was the presence of uncemented sections of production casings in wells that allowed gas migration from intermediate depths to shallow freshwater aquifers. In three cases, an inadequate depth of the primary top of cement (TOC) also contributed to impacts. Sources of methane were best identified through analyses of isotopes on samples from production casings, annular spaces, and water wells. In Dimock, some isotope signatures changed with time, after the completion of remedial actions. In Parker-Hood County, where impacts were not related to gas well activity, noble gas analyses were also needed to determine the source of gas. At Pavillion, where maximum methane concentrations in water wells were <1 mg/L, no significant impacts were documented. For all the sites, most or all of the fugitive gas incidents may have been prevented by fully cementing production casings to the land surface.

Orphaned oil and gas well stimulus—Maximizing economic and environmental benefits

“…In addition to how well an abandoned well is plugged, leakage occurrence and rate depend on the integrity of the well (Gasda et al, 2004;King and King, 2013;King and Valencia, 2014;Davies et al, 2014;Lackey et al, 2017;Wisen et al, 2019;Ingraffea et al, 2020;Hammond et al, 2020;Abboud et al, 2020). Surface casing vent flows, surface casing pressures, and gas migration-all indicators of subsurface leakage-at active and unplugged abandoned wells-have been observed at 5.6% of wells in Pennsylvania (Ingraffea et al, 2020), 6.9% of wells in Colorado (Lackey et al, 2017), and 10.8% of wells in British Columbia (Wisen et al, 2019).…”

The role of supercritical carbon dioxide for recovery of shale gas and sequestration in gas shale reservoirs

“…85 Water contamination may occur especially in scenarios of shallow fracturing in the vicinity to aquifers and/or the regional groundwater levels, poorly cemented casing in the wellbores, and surface spills due to equipment failures or improper fluid-handling operations. 66,95,96 In addition to the leakage of fracturing fluids, flow-back fluids and wastewater may perturbate the groundwater equilibrium and the stability of geochemical and hydrodynamic processes in the subsurface. 88 The development of shale gas plays can also lead to air pollution.…”

Methane concentrations in streams reveal gas leak discharges in regions of oil, gas, and coal development

“…One example of a wetland that may be contaminated by natural gas from leaking shale gas wells is in Meshoppen Creek, as discussed by Wendt et al (2018). That site, located in Dimock where many problems with gas wells have been noted (Hammond et al, 2020), still retains a signal consistent with leakage from shale gas and is discussed briefly below. (Osborn et al, 2011;Wendt et al, 2018;Woda et al, 2018).…”

“…A common water quality impact related to shale gas development is contamination by fugitive migration of natural gas (e.g., Brantley et al, 2014;Cahill et al, 2017;Hammond et al, 2020;US EPA, 2016;Vengosh et al, 2014;Wen et al, 2017Wen et al, , 2016. Specifically, methane, CH4, like other forms of dissolved organic carbon (Blothe and Roden, 2009;Bruun et al, 2010), can reduce and mobilize metals that are deleterious to aqueous ecosystems when it enters aquifers (Woda et al, 2018).…”