Chemical and oxidative biocides are designed to sanitize water by reducing aerobic and anaerobic bacterial populations in the fresh, brackish and reclaimed source waters. These biocides are used extensively in high-rate fracture stimulations to reduce formation damage, chemical degradation, biogenic H2S and microbial induced corrosion (MIC). Oxidative biocides work by removing electrons from the cell wall of aerobic and anaerobic bacteria. The same electron transfer mechanism can be detrimental to surface equipment. This study presents the impact of several oxidative biocides on the corrosion rate and pitting of different frac iron alloys and how those biocides effect the mechanical integrity of elastomer seals. It also presents different remediation methods to mitigate their oxidative effects. The oxidative biocides tested were Chlorine, Chlorine Dioxide and a Peracidic Acid blend. The corrosion rate of the iron alloys coupons was measured by weight loss analysis. This method can measure the rate of corrosion in pounds per square foot at time and was used to compare the impact of different residual oxidizers on the corrosion rate of the ground iron. Structural changes to the elastomers were detected visually. The results of the study showed that the corrosion rate varied depending on the alloy/residual oxidative biocide combination. Usually, Peracidic Acid blend or Chlorine had the highest corrosion rates across all alloys tested; depending on the oxidative biocide/alloy combination, the corrosion rate could vary by a factor of 2X over the nine-week timeframe. Elastomer testing over 6 weeks showed variability in the types of structural changes depending on the concentration and oxidative biocide tested. The lab and field testing included onsite monitoring of the corrosion rate, oxidation reduction potential (ORP), oxygen in solution and determination of the Langelier Saturation Index (LSI). The methodology has been effective in predicting iron failures related to the composition of the water and/or presence of oxidizers. Chemical solutions implemented to mitigate the surface iron failures included use of intermittent blends of water-soluble quaternary amines and surfactants. Since these remediation attempts have started, the replacement cost of frac iron has decreased from over 550K US$ per month, per frac spread to none, over a 3-month period.

The growing momentum to reduce emissions from fracturing equipment has been driven by many factors: increased focus from customers and ESG-minded investors, widespread availability of natural gas, and technological improvements to fracturing equipment. Hydraulic fracturing customers now have access to many competing equipment solutions to aid in reducing the emissions of hydraulic fracturing operations. The data presented in this study provides an objective review and comparison of emissions from diesel and natural gas-powered fracturing technologies. Technologies evaluated included Tier 2 and Tier 4 diesel and dual-fuel reciprocating engines, and electric fracturing equipment powered by natural gas-fueled genset. Reported measurements included regulated and nonregulated emissions constituents associated with hydraulic fracturing operations. Initial tests were conducted in accordance with 40 CFR parts 60 and 63, consistent with previous industry studies. To further align with OEM testing methodology and EPA guidance for testing nonstationary engines operating intermittently under dynamic loads, additional tests were performed in adherence to 40 CFR parts 1039 and 1065. Due to the wide diversity of platform designs and emissions-control strategies among various nonroad engine technologies used in hydraulic fracturing equipment, it is challenging to obtain consistent in-use emissions measurements. Additionally, because non-road engines, to this point, have not been required to comply with in-use testing rules at the level of those required for on-road operation, the study team expended considerable effort to design and implement measurement systems in compliance with current road emissions-testing standards. To better elucidate overall emissions-related performance of various technologies, the study implemented redundant measurements and included nonregulated emissions. Collected data was normalized using CO2e/HHP-hour (Carbon Dioxide Equivalence). Tier 2 engines produced more air quality emissions compared to their Tier 4 engine counterparts. Displacing diesel fuel with natural gas reduced total fuel burned and employing optimized blending strategies significantly improved control of hydrocarbon emissions and fuel economy. Properly optimized hybrid technologies control emissions without sacrificing operational performance. Dedicated natural gas engines enabled near-zero particulate emissions and tighter control of methane emissions. Balance between operational sustainability and environmental stewardship can be achieved through integration of diesel and natural gas-supplemented equipment. The field data presented in this study, for the first time, reveals and assesses the emissions generated from available hydraulic fracturing technologies. Prior to this study, such assessments were in part hypothesized or determined using theoretical methods. This unique data set will enable operators, service companies, and equipment manufacturers to make impactful decisions regarding planning, utilization and reporting of emissions during petroleum and natural gas extraction for years to come.

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