Wastewater production footprint of conventional and unconventional oil and gas wells in North America

Hydrocarbon recovery from conventional and unconventional wells, such as those using hydraulic fracturing (HF), generates substantial volumes of highly saline wastewater, known as flowback and produced water (FPW). Traditional evaluations of FPW management have focused on volume and chemical additives in HF fluids, neglecting variations in FPW volumetric production and salinity. Here we introduce two parameters to better assess the environmental impact of FPW: total produced salts (TPS), which accounts for both volume and salinity, and produced salts intensity, the ratio of TPS to the energy content of recovered hydrocarbons. Analysing a database of over 620,000 HF and conventional wells in North America, we found that more than 355 billion tonnes of salts were produced from 2005 to 2019, with HF wells contributing over 85%. Projections indicate that more than 1.5 trillion tonnes of salts will be produced by wells drilled between 2019 and 2050, predominantly from HF wells. TPS and produced salts intensity are crucial for assessing environmental risks, treatment costs and resource extraction potential, providing valuable metrics for regulators and planners. Recovering hydrocarbons from oil and gas wells results in highly saline wastewater, also known as flowback and produced water. The introduction of two parameters to estimate the environmental impact of these by-products, relative to energy produced, provides an important tool for assessing the risks associated with the planning and use of wells.