The Effects of Sample Storage Conditions on the Microbial Community Composition in Hydraulic Fracturing Produced Water

The petroleum industry has an increasing interest in understanding the microbial communities driving biofouling and biocorrosion in reservoirs, wells, and infrastructure. However, sampling of the relevant produced fluids from subsurface environments for microbiological analyses is often challenged by high liquid pressures, workplace regulations, operator liability concerns, and remote sampling locations. These challenges result in infrequent sampling opportunities and the need to store and preserve the collected samples for several days or weeks. Maintaining a representative microbial community structure from produced fluid samples throughout storage and handling is essential for accurate results of downstream microbial analyses. Currently, no sample handling or storage recommendations exist for microbiological analyses of produced fluid samples. We used 16S rRNA gene sequencing to monitor the changes in microbial communities in hypersaline produced water stored at room temperature or at 4 degrees C for up to 7 days. We also analyzed storage at -80 degrees C across a 3-week period. The results suggest ideal handling methods would include placing the collected sample on ice as soon as possible, but at least within 24 h, followed by shipping the samples on ice over 2-3 days, and finally, long-term storage in the -20 degrees C or -80 degrees C freezer.