TIME TO SETTLE THE FRACKING DEBATE: BUT HOW?

Studies that specifically identify shale‐gas drilling as a source of fugitive methane in water wells remain scarce and are often countered by numerous field surveys suggesting that methane in groundwater is natural. However, it is becoming clear that stray gas contamination from a small percentage of leaking gas-wells is often superimposed on this background flux of natural gases in hydrocarbon‐rich basins.

Given the hydrogeological complexity of these settings, the industry‐standard approach of using “predrill” surveys to establish methane concentrations prior to drilling is a blunt instrument in light of a lack of genuine “baseline” data in predrilling studies. Further, most pre-drill studies have relied on methane concentrations alone and thus are limited in their ability to identify gas sources and hence require robust multi‐tracer geochemical evaluations designed to distinguish sources of natural gas. Future studies must integrate bottom‐up (driven by geochemical data) and top‐down (modeling‐driven) approaches to better understand fundamentals of gas transport in the subsurface.

Here we will review the lessons learned from various studies in the US (Pennsylvania, New York, West Virginia, Arkansas, Texas, and Ohio), Canada, Australia, and South Africa. My presentation will include a summary of the geochemical, hydrological, and statistical approaches used to evaluate the occurrence and frequency of stray gas contamination related to shale-gas development. From these datasets, we propose an integrated data, modeling, and statistical approach to interrogate the occurrence, prevalence, and implications of gas contamination in shallow aquifers.