Methane in Groundwater: Pathways

Abstract

Groundwater can contain measurable quantities of methane associated with in situ processes of methanogenesis and desorption from geologic materials, and also from external migration from deeper gas‐bearing units. It may also contain “fugitive gas” due to leakage from exploration and production of hydrocarbons or from the microbial breakdown of organic contaminants introduced to the aquifer. More recently, natural gas production via high volume hydraulic fracturing of tight formations has been implicated as a route for both methane and other fluids to enter groundwater resources. While distinguishing the source of the gas is often critical, secondary processes such as mixing and aerobic and anaerobic oxidation make these identifications difficult. Important to these determinations is an understanding of the hydrology, geology, and history of development in the watershed, coupled with detailed geochemical and isotopic analysis.