Sustainable Produced Water Treatment in Oilfields Using a Low-Cost Multistage System

Abstract

Produced water is a byproduct of oil and gas development, and because of its contaminant content and volume, is a significant environmental and logistical problem. This wastewater stream can include suspended solids, dissolved salts, residual hydrocarbons and the leftover treatment chemicals, depending on the reservoir characteristics and production practices. It can be particularly challenging to manage produced water at remote or resource constrained oilfield facilities where it is difficult to install traditional treatment facilities, which can be costly, energy intensive, and require significant maintenance. It introduces a reusable multistage treatment system, modular, field-ready and low-cost, that is capable of converting produced water into a reusable resource to reduce the freshwater requirement and environmental impact. The planned system has three successive stages. The first step of mechanical filtration is the removal of larger suspended particles like sand and silt. The filtered stream is then passed into the evaporation unit which uses solar energy in the form of the ambient sun to reduce the water volume and control salinity. Lastly, the water goes through a natural adsorption bed that absorbs any remaining hydrocarbons, contaminants, and odor-causing compounds using biochar and bentonite. Performance of the system is evaluated by turbidity, total dissolved solids (TDS) and oil concentration before and after the treatment process. Results indicate that this setup can significantly reduce the quality of produced water produced while maintaining a relatively simple operating signature. The study estimates a production water recycling capacity of approximately 5,000 bbl and removal of up to 3.5 tons of contaminants per scenario. The multi-stage approach resulted in about a 70% improvement in water clarity and an estimated 35% reduction in operating costs when compared to a conventional benchmark process. The treated water can be used for certain non-potable uses, including use in drilling fluids, dust control on lease roads, and reinjection, depending upon water-quality criteria that are specific for each use. Overall the system is a practical and sustainable treatment pathway for small-to-medium size and remote oilfields where conventional treatment infrastructure is not readily available.