Treatment and management of produced water from hydraulic fracturing using electro-coagulation technology
Hydraulic fracturing is a process adopted by the oil and gas industry to extract natural gas out of shale rock formations from depth ranging from 2,440 to 3,048 meters below the surface. Produced water is the largest by product of hydraulic fracturing. The composition of produced water can be toxic due to the presence of oil, grease, suspended and dissolved solids, heavy metals, chemicals that are part of fracturing fluid mixture which is injected to enhance gas production. The composition may vary significantly based on the geological formation. Safe disposal or treatment of produced water has been a challenge to the oil and gas industry both from an economic and environmental perspective. Over the last several years, many companies in the water treatment industry have developed technologies to treat produced water for safe disposal or for reuse in drilling new wells. The objective of this research is to characterize produced water samples collected from the Eagle Ford shale play region in Texas, and to assess the efficiency of treatment processes using the reactor developed by Elequa LLC, San Antonio, Texas which works on the principle of electro-coagulation. The reactor performance is then assessed based on the removal efficiency of various constituents. This method of treatment has been around since early 21 st century but has not been implemented to its full potential. A review of various other technologies developed and implemented for treatment of produced water is included in this report. The electro-coagulation reactor is tested for its efficiency in reducing the turbidity, total dissolved solids, total suspended solids and inorganic chemicals (i.e., cations) of major concern present in water produced from hydraulic fracturing. Based on test results, it is observed that there were significant levels of total suspended solids, total dissolved solids and inorganic cations present in produced water and that treatment with the electro-coagulation reactor decreased the values. There was a 75% to 97% reduction in these levels after the treatment. There were no additional pre-treatment methods used. Based on the research outcomes recommendations for modifying Elequa's Electro-coagulation reactor/technology to improve performance and an assessment of the efficiency of cathodes and anodes are provided.