Downhole Transformation of the Hydraulic Fracturing Fluid Biocide Glutaraldehyde: Implications for Flowback and Produced Water Quality.
Hydraulic fracturing fluid (HFF) additives are used to enhance oil and gas extraction from unconventional shale formations. Several kilometers downhole, these organic chemicals are exposed to temperatures up to 200 °C, pressures above 10 MPa, high salinities, and a pH range from 5-8. Despite this, very little is known about the fate of HFF additives under these extreme conditions. Here, stainless steel reactors are used to simulate the downhole chemistry of the commonly used HFF biocide glutaraldehyde (GA). The results show that GA rapidly (t1/2< 1 h) autopolymerizes, forming water-soluble dimers and trimers, and eventually precipitates out at high temperatures (∼140 °C) and/or alkaline pH. Interestingly, salinity was found to significantly inhibit GA transformation. Pressure and shale did not affect GA transformation and/or removal from the bulk fluid. On the basis of experimental pseudo-second-order rate constants, a kinetic model for GA downhole half-life predictions for any combination of these conditions within the limits tested was developed. These findings illustrate that the biocidal GA monomer has limited time to control microbial activity in hot and/or alkaline shales, and may return along with its aqueous transformation products to the surface via flowback and produced water in cooler, more acidic, and saline shales.
Department of Chemistry, Colorado State University , 1872 Campus Delivery, Fort Collins, Colorado 80523, United States.
Genevieve A
GA
Kahrilas
Department of Civil and Environmental Engineering, Colorado State University , 1320 Campus Delivery, Fort Collins, Colorado 80523, United States.
Jens
J
Blotevogel
Biotechnology Solutions, LLC , 15232 Black Falls Lane, Sugar Land, Texas 77498, United States.
Edward R
ER
Corrin
Department of Chemistry, Colorado State University , 1872 Campus Delivery, Fort Collins, Colorado 80523, United States.|Department of Civil and Environmental Engineering, Colorado State University , 1320 Campus Delivery, Fort Collins, Colorado 80523, United States.|Department of Soil and Crop Sciences, Colorado State University , 1170 Campus Delivery, Fort Collins, Colorado 80523, United States.
Thomas
T
Borch
D004202:Disinfectants; D005976:Glutaral; D000067071:Hydraulic Fracking; D062065:Wastewater; D060753:Water Quality
D004202:Disinfectants; D005976:Glutaral; D062065:Wastewater