Professor Dept. of Civil Engineering, University of North Dakota
Produced water in the unconventional U.S. Bakken oilfield has become a significant concern since oil and gas production growth has been substantial, and operating costs are increasing. Reusing this considerable amount of produced water has become necessary since the treated water can be used for potable supplies, irrigation, deep well injection, maintenance, and fracking, which improves profits and mitigates groundwater pollution. The total dissolved solids (TDS) in the ND Bakken formation are greater than 300g/l, which is much higher than the concentration of salt in seawater, therefore, it is reasonable to propose an alternative approach for produced water disposal by the recovery of value-added elements of produced water. The produced water is known to be rich in several minerals and valuable elements like potassium and magnesium and a trace amount of precious elements including lithium. Though, the high ratio of Mg2+ to Li+ in the produced water is one of the main challenges to extract lithium. In a prior study on produced water, a softening process using caustic soda, lime, and soda ash was employed, successfully removing 99.5% of hardness ions (Ca and Mg) under alkaline conditions. This study aims to provide valuable insights into recovering lithium ions from the precipitate of produced water by comparing the effects of various precipitating reagents. The recovery of these elements (Mg and Li) from produced water may create additional financial benefits to oil-producing areas. More importantly, this sustainable disposal of produced water may encourage the recycling and reuse practice, ultimately reducing the use of freshwater for hydraulic fracturing.
