MARCELLUS SHALE PRODUCED FLUID GENERATION AND INJECTION WELL DISPOSAL CAPACITY

As the United States seeks to use cleaner sources of domestic energy there has been increase in the exploration and extraction of hydrocarbons, especially natural gas, from unconventional resources such as the Marcellus shale. This increase in production has been facilitated by advents in horizontal drilling and hydraulic fracturing technologies. Shale gas is very promising as an abundant energy source, though environmental challenges exist with its development, including potential adverse impacts to water quality. Once a Marcellus shale well has been hydraulically fractured, approximately 10% of the volume of injected fluids (flowback fluids) may flow out of the well initially with continued generation of fluids (produced fluids) throughout the well’s productive life. Produced fluid TDS concentrations often exceed 200,000 mg/L, with elevated levels of strontium (Sr), bromide (Br), sodium (Na), calcium (Ca), barium (Ba), and chloride (Cl). The most recent data suggests an estimated 90% of the produced fluids were being recycled for hydraulic fracturing operations, however approximately 10% of the fluids are disposed of through use of Class II-D underground injection control (UIC) wells. One way to estimate the future volumes of produced fluids is to consider existing volumes of gas produced and associated volume of wastewater disposal. This analysis suggests that by 2040 approximately 4 to 8 times the current volumes of produced fluids could be generated compared to current rates, which signals that significantly more disposal capacity may be necessary than is currently available. Additional treatment capacity could emerge via innovative technologies or additional disposal well capacity or a combination of both.