On the Optimization of Water-Energy Nexus in Shale Gas Production Under Price Uncertainties

This study presents a robust framework for water-energy nexus optimization in shale gas production and distribution network under uncertainty. Sustainable design of the network is achieved through treatment of wastewater using thermal membrane distillation (TMD), whereby a detailed design model is incorporated within the network superstructure in order to account for the energy requirement of the treatment unit. The proposed model also takes into account the scheduling problem associated with production of shale gas, optimal shale gas production and distribution networks. There are various uncertainties associated with the network. Among different uncertain variables, uncertainties associated with price and demand are most crucial as they can impact the optimal configuration significantly. Incorporation of uncertainty in the model seeks to meet the demand of natural gas consumers while accounting for the uncertainties associated with the price of natural gas, natural gas liquids and electricity. In this work, uncertainties are modelled via randomly generated scenarios using beta distribution of the price, based on historical data. Three different scenarios are generated from past data. The stochastic model is applied to a case study through the maximization of total profit and comparison is made with the results from deterministic approach. Results from the three different scenarios show 14.47%, 10.98%, and 12.26% increase in the profit, respectively, compared to deterministic approach. Savings in the freshwater requirement for fracturing and in energy associated with water management amounted to 23.2% and 42.7%, respectively.