Flowback Water Management in the Marcellus Shale Play: Treatment Options and New Water Supply

Gas exploitation from the Marcellus shale relies on a sustainable management of the water, from water consumption to wastewater treatment. The aim of this study is to propose a holistic and sustainable approach to flowback management in Pennsylvania. The key of the project is to evaluate treatment option for subsequent reuse of flowback water for hydraulic fracturing in an effort to decrease the water footprint of natural gas extraction in the Marcellus shale. Alternative water sources, such as acid mine drainage (AMD), may also be considered as part of the overall management strategy. This project expands on this idea by selecting AMD sites suitable for frac water makeup based on the parameters such as water flow rate, sulfate and iron content, pH, alkalinity and acidity. An Arc-GIS database is being developed to pair drilling sites and AMD sources and enable cost estimation for AMD transport to the well sites.

AMD is often located in the vicinity of the drilling sites and can be used as a water supply to complete the fraction lost during the fracturing process. In addition, mixing the high sulfate content AMD with flowback water induces the precipitation of barium and part of the strontium, which could be responsible for scale formation in the shale that reduces the well permeability. Treatability studies are in progress to determine the compatibility between the flowback water and the AMD. Understanding the chemistry of water blending is fundamental to selecting appropriate AMD. In particular, barium and strontium in the flowback water precipitate with the sulfate ions in the AMD. Finally, to meet fracturing fluid quality criteria additional treatment steps are being evaluated in this study.