Produced water (PW) is salty water trapped in the reservoir rock and brought up along with oil or gas during production. It subsists under high pressures and temperatures, and usually contains hydrocarbons and metals. Therefore, it must be treated before being discharged to surface water. Different techniques are being used to treat PW through phase separations, system control and design, and chemical treatments. In this paper, we discuss our experimental results on treating PW through electrocoagulation (EC).
“Produced water” is the oil and gas industry term for any water that comes out of the oil or gas reservoir as part of the production process. Oil reservoirs often contain large volumes of water, while gas reservoirs typically have smaller quantities. Sources of produced water include:
The physical and chemical properties of produced water are not consistent. Variation depends on factors such as reservoir geology, hydrocarbon composition, geographical location, and water injection history.
Produced water contains contaminants that require removal before proper disposal or reuse. Some of the impurities or substances likely to be found in produced water include: oil, naturally occurring radioactive materials (NORM), waxes, greases, sand, scales, dissolved salts, CO2 (carbon dioxide) and H2S (hydrogen sulfide) gases, hydrocarbons, production chemicals, and various metals.
The treatment of produced water will differ according to the intended disposal method or reuse purpose. Filtration, cyclonic separation, flotation, and evaporation are among the commonly used treatment techniques.
Post-treatment, there are a number of options available for disposal or reuse, each of which will have different water treatment criteria associated with it:
Due to increasing environmental awareness and regulations, disposal to surface waters and evaporation ponds is becoming less prevalent. Produced water is considered an industrial waste, subject to standards defined and issued by the U.S. Environmental Protection Agency.
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