Rice and 3 co-authors reported early 2017 that Methane leakage from hydrocarbon wells plays an important role in the groundwater-quality impacts of hydrocarbon development and presents a more likely hazard than hydraulic fracturing or formation fluids. Methane released from contaminated water wells has been linked with combustion risks and degraded water quality.
Potentially, methane can serve as a precursor to other fluids associated with hydrocarbon extraction, such as volatile organics. In this review, the authors surveyed studies relating to contamination of drinking-water aquifers by methane gas from leaking hydrocarbon wells. Challenges associated with linking methane in groundwater to hydrocarbon extraction are identified, highlighting the need for groundwater-quality and well-integrity databases. Science-based policy recommendations are made, including deeper surface casings and greater cement coverage for wells with deviated wellbores, remediation of faulty abandoned wells, and increased gas-migration monitoring.
The authors offered four hypotheses to quantify risks to groundwater quality from methane leakage:
- First, differentiation between thermogenic methane occurring in groundwater due to natural migration and thermogenic methane present due to hydrocarbon development can be used to alleviate the need for baseline measurements of methane in groundwater.
- Second, methane newly discovered in freshwater aquifers is unlikely to have originated from leaks beginning decades ago.
- Third, pertaining to the zone separating methane leakage from groundwater, relative permeability will have a larger impact on plume diameter than heterogeneity in intrinsic permeability.
- Fourth, thermogenic methane in groundwater will serve as a precursor to benzene, toluene, ethybenzene, and xylene (BTEX) under conditions where methane and BTEX coexist in a hydrocarbon reservoir and leakage is transported primarily in the aqueous phase.
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