Wastewater Generation and Disposal from Natural Gas Wells in Pennsylvania

Abstract

The recent boom in natural gas production in Pennsylvania has generated huge volumes of wastewater. Key drivers have been a combination of high prices for natural gas, advances in horizontal drilling, and hydraulic fracturing; a technique used to explore ‘unconventional’ gas formations. Using data gathered by the Pennsylvania Department of Environmental Protection, the volumes of waste generated and waste disposal methods were examined. Comparing wastewater and gas production from unconventional natural gas exploration in the Marcellus shale (hereafter ‘Marcellus wells’), and conventional natural gas (hereafter ‘conventional wells’) found Marcellus wells were more efficient, producing approximately three times more natural gas per gallon of wastewater. Waste composition was similar between the two well types, but Marcellus wells produced an average of 1.355 million gallons (Mgal) of waste and 1,301 million cubic feet of natural gas (MMcf) over four years compared with an average of 0.120 Mgal of waste and 32.2 MMcf from conventional wells for the same timeframe. While the Marcellus wells are more efficient, the unconventional drilling has created a boom in natural gas production in the northeast, dramatically increasing wastewater generation. A timeline looking at regulatory changes over this period, and the resulting shifts in disposal options, showed a transition from historical disposal methods, relying heavily on dilution, to the current framework relying on reuse, injection wells and advances in dissolved solid treatments. With growth expected in to continue in Pennsylvania and to spread to the neighboring states of West Virginia and Ohio, waste generation will continue increasing in the northeastern region. Based on this assessment of waste generation, disposal options, and future growth, the northeast needs to focus on improving wastewater recycling and advanced wastewater treatment options that remove dissolved constituents prior to disposal. Given the ecological damage seen as shale gas expanded into the northeast and the regulatory restrictions that have been created, well operators in the northeast must develop a system of reuse and treatment for wastewater if shale gas is to continue expanding.