CHEMICAL ADDITIVE CONSIDERATIONS FOR THE REUSE OF PRODUCED WATER

It is well known that the process of hydraulic fracturing uses large numbers and quantities of chemical compounds, some of which are used in high volumes and are acutely and chronically toxic. However, absent from most scientific and regulatory conversations is the fact that chemical use in hydraulic fracturing is only one instance throughout the entire oil and gas (O&G) development process when chemical additives, sometimes in high masses, are used. Increasingly produced water from O&G development is being considered and deployed for “beneficial reuse” in such applications as irrigation of agriculture, recharge of aquifers, or to increase flow in streams and other aquatic environments. However, routine operations of O&G development (e.g., drilling, routine maintenance, well completions) and enhanced oil recovery (e.g., steam injection and water flooding) also use chemical additives that are not considered in regulations governing the reuse of produced water. The only jurisdiction in the United States that mandates the disclosure of chemical use in O&G wells during both hydraulic fracturing as well as other routine operations (acidizing, wellbore maintenance, drilling, etc.) is the South Coast Air Quality Management District (SCAQMD) in California. Mandatory chemical additive disclosure from routine O&G operations is also recently required for O&G operators under a regulatory order in the San Joaquin Valley of California that send their produced water to water districts to irrigate food crops. In this study, we analyze the chemical types, toxicity, environmental persistence of chemical constituents, the mass and frequency of the chemicals injected, among other factors in both of these emerging datasets to determine the potential risks of “beneficial reuse” of these produced waters. Preliminary results from the SCAQMD indicate that out of 548 chemical additives are used down-hole for routine activities, of which more than 70% do not have a unique CASRN and/or lack information on their toxicity, making it difficult to assess their risk to human health and the environment. Of the compounds identified by unique CASRN, approximately 50% were also used in hydraulic fracturing in California according to the Independent Scientific Study of Well Stimulation in California, commissioned by California Senate Bill 4.