Characterization of flowback and produced water from shale oil and gas wells fractured with different levels of recycled water

Hydraulic fracturing requires large volumes of water, and it is therefore crucial to establish sustainable water sources. We analyzed the flowback and water produced from three wells using different fresh-to-recycled water ratios for hydraulic fracturing: freshwater only, 20% recycled water, and one-seventh (∼15%) recycled water. Water samples were collected over a 36-day period (flowback started on day 0). There were no significant differences between the total organic carbon (TOC) levels of the wells, but the total dissolved solid (TDS) concentrations increased for all wells over time, and there were significant differences among the wells. The TDS level of the well fractured with 20% recycled water was significantly higher than that of the other wells. Liquid chromatography quadruple time-of-flight mass spectrometry revealed ethoxylated functional groups in all three wells. Agilent qualitative analysis software B.06.00 was used to perform a qualitative analysis based on the exact mass of organic compounds within 1 ppm mass accuracy. The results of this study provide new insights into the quality of flowback and produced water from wells fractured using different fresh-to-recycled water ratios and can be used as a reference for improving the reusability of treated water and reducing wastewater discharge.