ENVIRONMENTAL IMPACT OF DEEP WELL DISPOSAL OF LIQUID WASTES FROM HYDRAULIC FRACTURING

Horizontal drilling and hydraulic fracturing (i.e., fracking) have revolutionized hydrocarbon extraction from gas shale and tight geologic formations. As much as five million gallons of water is used to frack a single horizontal well with significant water returning to the surface as flowback and produced water. This returned water has poor quality. While recycling and reuse of waste water are actively pursued as preferred alternatives, deep-well injection remains the most common means to dispose of flowback and produced water. Unsurprisingly, handling, transport, and disposal of waste fluids pose the greatest environmental threat from fracking. The technology used to dispose of fluid by deep-well injection has been around for several decades and has not been updated to reflect either the significant increase in the volume of liquid waste or in response to improvements in disposal technology. Threats to the environment, in general, and to groundwater, in particular, have been evaluated to provide a basis to evaluate the risks posed by disposal of liquid wastes from hydraulic fracturing. The biggest risks to groundwater occur when liquid wastes are injected into a horizon that is pressurized and near an existing borehole or well whose integrity is comprised due to age, improper abandonment and plugging, or questionable because of incomplete or missing documentation. Threats to surface water occur when surface facilities do not provide for adequate secondary recovery, comprehensive monitoring, or sufficient isolation from sensitive environmental features.