Temporal analysis of flowback and produced water composition from shale oil and gas operations: Impact of frac fluid characteristics

摘要

Flowback/produced water reuse cannot be optimized without a thorough understanding of the quality of the water that needs to be treated for reuse, including the temporal variability. Samples for flowback/produced water were collected over a 200-day period (day 0 refers to when flowback began) from two wells. One of the frac fluids had an initial pH greater than 10 and used a guar-based gel and the second fluid contained a non-guar polysaccharide based polymer with an initial pH of less than 6. Total dissolved solids (TDS) and total organic carbon (TOC) were used as macro-indicators and key ions (barium, calcium, chloride, magnesium, sodium, strontium, boron and iron) were compared to TDS with the different frac fluids and there were significant positive correlations observed between the key ions and TDS with relatively high values of the coefficient of determinant (over 0.85). The concentrations of calcium, chloride, sodium and strontium are statistically equivalent between the two fluids. A mass balance approach was applied to evaluate the quantity of mass of injected additives that was recovered over the 200-day period. Recoveries of zirconium, potassium and aluminum ranged from 3% to 33% after 200 days, and notable differences were observed between frac fluids. (C) 2016 Elsevier B.V. All rights reserved.