Playbooks Supplements

Water Management Techbook 2017

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40 | May 2017 | WATER MANAGEMENT: CASE STUDIES A dvanced stimulation techniques, such as hydraulic fracturing of horizontal wells, have made the exploitation of low perme- ability oil and gas formations possible in recent years. Water, sand and various chemical additives are injected into the ground to fracture open a formation and unlock the oil and gas. While the various chemical additives typically make up less than 1% of the injected fluid (water and sand make up about 99%), they play an important role in the fracturing process. Some of the additives like acid, friction reducers (FR) and corrosion inhibitors only play a role during the fracturing process. Oth- ers, like biocides, play a role both during and after the fracturing process to protect the integrity of the fracturing fluid and to prevent souring of the well, respectively. Although biocides play a critical role in the overall effectiveness of a fracturing job, the tradi- tional selection process is usually limited to labo- ratory tests to evaluate their biocidal activity and effect on the performance of the fracturing f luid, which doesn't tell the whole story. Biocides that are typically selected using this traditional process include dibromonitrilopropionamide (DBNPA), glutaraldehyde and glutaraldehyde/quaternary ammonium blends. Enhanced selection process The enhanced selection process takes biocide eval- uation a step farther by considering additional fac- tors that affect biocide stability and performance in the presence of a wide range of fracturing additives, environmental conditions and secondary proper- ties of the biocide. The enhanced biocide selection process includes an evaluation of: • Compatibility with a full range of fracturing fluid additives; • Ability of biocide to withstand a wide range of environmental conditions (pH, tempera- ture and time); • Synergy with other fracturing fluid biocides; and • Other nonbiocidal properties (corrosion inhibition, clay control and emulsion control). A different picture appears when the enhanced selection process is used to evaluate biocides for frac- turing applications as performance limitations of the commonly used fluid biocides appear (Table 1). The result is that biocides such as DBNPA, glutaraldehyde and glutaraldehyde/quaternary ammonium blends no longer appear to be the best choice. A biocide offering compatibility in fracturing applications when using the enhanced selection process is Bellacide 300 from BWA Water Additives. This nonoxidizing biocide not only has the fast kill and compatibility with FR that are essential features for a fracturing fluid biocide but also has excellent compatibility with oxidizing biocides, such as bleach and chlorine dioxide (ClO 2 ), that the other commonly used fracturing fluid biocides lack. This is important since the popularity of bleach and ClO 2 as fracturing fluid biocides is increasing as operators look for cost savings. While oxidizing biocides are fast-acting bacte- ricides at low concentrations, their high reactivity means they are not very persistent in the fracturing Multiple factors should be considered when selecting a biocide for use in fracturing fluids. Optimizing Biocide Selection for Stimulation Applications By Jeffrey F. Kramer BWA Water Additives

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