Optimal design of water networks for shale gas hydraulic fracturing including economic and environmental criteria

This work proposes an optimization approach for designing efficient water networks for the shale gas production through the recycle and reuse of wastewater streams reducing the freshwater consumption and effluents considering economic and environmental goals. The economic objective function aims to minimize the total annual cost for the water network including the costs associated with storage, treatment and disposal (capital cost) as well as freshwater cost, treatment cost and transportation costs. The environmental objective is addressed to deal with the minimization of the environmental impact associated with the discharged concentration of total dissolved solids in the wastewater streams and the freshwater consumption through an environmental function that represents the benefit for removing pollutants using the eco-indicator 99 methodology. The methodology requires a given scheduling for the completion phases of the target wells to be properly implemented by the available hydraulic fracturing crews during a time horizon. The model formulation is configured to determine the optimal sizes for the equipment involved by the project, particularly the sizes for storage and treatment units are quantified by the optimization process. A case study is solved to evaluate the effectiveness of the proposed optimization approach. [GRAPHICS] .