ARE MULTI-WELL PADS FOR UNCONVENTIONAL SHALE GAS DEVELOPMENT BETTER FOR THE ENVIRONMENT THAN SINGLE WELL PADS?

Growing interest in natural gas extraction in the southeastern US has led to much speculation and legislative changes to facilitate future developments of unconventional gas reservoirs in the region. However, owing to rapid growth and changes in hydraulic fracturing and horizontal drilling techniques elsewhere, there are still many unanswered questions about the impacts of unconventional gas development on the environment. One change that has occurred has been the transition from single-well to multi-well pads. Although initially buoyed by economic and practical factors (e.g., less surface disturbance, lower traffic, and less infrastructure during construction and gas extraction), the transition from single to multi-well pads may also have fewer adverse environmental impacts. Here, we test the hypothesis that natural gas wells located on multi-well pads are better for the environment than single well pads. Statistical tests conducted on well data, notices-of-violation, and wastewater records that were acquired from the State of Pennsylvania are used to assess the impact of multi-well pads on the environment. In the Marcellus shale, Pennsylvania has the largest unconventional shale gas reservoir in the world that has undergone rapid natural gas development since 2005. We thus use data from the Marcellus shale to draw conclusions about how the transition from single to multi-well pads has impacted notices-of-violations (used as a proxy for environmental impacts), and wastewater generation (total versus recycled wastewater). Results indicate that although there were more wastewater volumes per well generated on multi-well pads, there were less violations per well and more recycled wastewater volumes per well on multi-well pads than single well pads, suggesting that multi-well pads may be less harmful to the environment than single well pads. It is hoped that these results will equip policy makers with the tools necessary to address the challenges associated with unconventional shale gas development.