Determining Effective Antimicrobial Treatments for Long-Term Protection of Hydrocarbon Reservoirs

Abstract

Abstract Conventional antimicrobial treatments for hydraulic fracturing fluids, flow-back water, and produced water include chemistries such as glutaraldehyde, tetrakis-(hydroxymethyl)-phosphonium sulfate (THPS), and quaternary ammonium compounds (quats). While the rapid microbial kill efficacy of these biocides in top-side water sources are effectively demonstrated by traditional microbial enumeration methodologies, such as “bug-bottles”, the long-term potential for protection of the oil and gas reservoirs from microbial-induced damage has received limited attention. A stringent two-stage laboratory method has been developed to assess rapid and long-term biocide efficacy, ranging from the mild, top-side conditions of water sources in drilling and fracturing operations to the harsh conditions of downhole environments. Specifically, water sources used in stimulation and fracturing operations were treated with various concentrations of biocide combinations and incubated at elevated temperatures during the course of the laboratory experimental procedure. At predetermined time points during the two-month test, the heat-aged samples were challenged with oil and gas field microbial contaminants (acid-producing and sulfate-reducing bacteria) to evaluate extended biocide performance in water chemistries and temperatures that mimicked downhole environments. This paper discusses a summary of effective biocide treatments for the holistic protection of hydraulic fracturing operations from microbial contamination.