Physical-chemical evaluation of hydraulic fracturing chemicals in the context of produced water treatment

Abstract

Produced water is a significant waste stream that can be treated and reused; however, the removal of production chemicals-such as those added in hydraulic fracturing-must be addressed. One motivation for treating and reusing produced water is that current disposal methods-typically consisting of deep well injection and percolation in infiltration pits-are being limited. Furthermore, oil and gas production often occurs in arid regions where there is demand for new water sources. In this paper, hydraulic fracturing chemical additive data from California are used as a case study where physical-chemical and biodegradation data are summarized and used to screen for appropriate produced water treatment technologies. The data indicate that hydraulic fracturing chemicals are largely treatable; however, data are missing for 24 of the 193 chemical additives identified. More than one-third of organic chemicals have data indicating biodegradability, suggesting biological treatment would be effective. Adsorption-based methods and partitioning of chemicals into oil for subsequent separation is expected to be effective for approximately one-third of chemicals. Volatilization-based treatment methods (e.g. air stripping) will only be effective for approximately 10% of chemicals. Reverse osmosis is a good catch-all with over 70% of organic chemicals expected to be removed efficiently. Other technologies such as electrocoagulation and advanced oxidation are promising but lack demonstration. Chemicals of most concern due to prevalence, toxicity, and lack of data include propargyl alcohol, 2-mercaptoethyl alcohol, tetrakis hydroxymethyl-phosphonium sulfate, thioglycolic acid, 2-bromo-3-nitrilopropionamide, formaldehyde polymers, polymers of acrylic acid, quaternary ammonium compounds, and surfactants (e.g. ethoxylated alcohols). Future studies should examine the fate of hydraulic fracturing chemicals in produced water treatment trains to demonstrate removal and clarify interactions between upstream and downstream processes.

Comparison of chemical-use between hydraulic fracturing, acidizing, and routine oil and gas development

“…Chemical disclosure is widely recognized as a fundamental prerequisite for the open and transparent analysis of the hazards and risks associated with chemicals [2,4,10,27,45,46]. Previous studies have shown that many oil and gas field chemicals are not expected to have negative environmental or health impacts, but that some compounds, including surfactants, biocides, and corrosion inhibitors may be harmful to the environment, and that in many cases there is insufficient information to confidentially evaluate the potential environmental impact of chemicals that are used in significant amounts on oil and gas fields [19–24,47,48]. …”

“…Compounds reported by CASRN mostly had corresponding mass-usage information, important for risk analysis, but 97 did not have toxicity profiles in the public databases used in this study (Table 2; S3 Table). Altogether, 70% of the chemical additives reported in the SCAQMD could not be fully evaluated using data-based hazard analysis approaches [20,21,47], suggesting that current reporting requirements may need to be strengthened, if the regulatory objective includes generating data needed for risk assessments.…”

Flowback verses first-flush: new information on the geochemistry of produced water from mandatory reporting

“…3, 34 The reason for this change in clay-control strategy is not known and may be inconsequential from a risk management perspective, but in the absence of publicly available information on the toxicity, biodegradability, or other environmentally critical properties of clay control agents, it may be premature to dismiss risk from these materials altogether. 3-5, 43 Twenty of the newly identied chemicals were chlorinated, brominated, or iodated aromatic hydrocarbons (Table S-1 †). Halogenated aromatic compounds can be environmentally persistent and toxic, so there is specic interest in the use of these types of compounds in the context of produced water reuse and risk assessment.…”

A Market-Based Economic Instrument to Better Use Water in Agriculture

“…Sustainability is an appealing label attached to all sectoral economies despite the wide range of uncertainties, loopholes, and hidden side-effects that may occur in any real production system. Circular economy (CE) is probably the most provocative pathway to rethinking, redesigning [1], reducing, reusing [2], recycling [3], and recovering resources used by different sectors of the economy [4]. Reframed in this context, farming is all about managing the growth processes of plants and animals sustainably, and one mandatory input in these processes is water.…”