ABSTRACT

Bacterial contamination from drilling and fracturing can lead to serious problems in unconventional oil and gas shale plays. Large water volumes for these processes are transported from aquifers, municipal waters, rivers, lakes, ponds or oilfield flowback water to the well site and stored in frac tanks or earthen impoundments. Typically, these waters are contaminated with bacteria. Furthermore, fracturing fluids contain gelling agents or polyacrylamide-based friction reducers which are readily available bacterial food sources. If these fluids are insufficiently treated, establishment of sulfate-reduction bacteria (SRB) and general heterotrophic bacteria (GHB) including acid-producing bacteria (APB) can lead to operational issues including: 1) biogenic sulfide production and formation souring, 2) plugging from iron sulfide scale production, 3) microbially influenced corrosion (MIC), and 4) premature degradation of fracturing fluids. As operators continue to search for solutions to control bacteria induced issues in unconventional shale plays, an ideal biocide with the following characteristics would be required: (1) safe (2) broad spectrum (against SRB, GHB including APB etc.) with fast kill times at low concentration (3) neutralization of hydrogen sulfide and other corrosion causing chemicals (4) removal of iron and other scale forming ingredients (5) compatible with drilling fluids (6) cost effective and readily available (7) scalable for future production model (multi-pad) (8) economy of scale: could be generated onsite with mobile unit. Super-oxidized water (hypochlorous acid solution) based biocide delivered with advanced high volume onsite generation technology is the perfect solution that meets all these criteria.

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