Bi-objective optimization of water management in shale gas exploration with uncertainty: A case study from Sichuan, China

Abstract

Shale gas exploration relies heavily on freshwater inputs while generating large amounts of wastewater. With the quick development of shale gas, water management during exploration has increasingly become a hotspot from both environmental and economic perspectives. This study investigated all the key water-consuming phases in exploration and optimized the freshwater use and flowback water control using a bi-objective programming model with the consideration of uncertainties in each phase, aiming at the optimal trade-offs between economic and environmental objectives. The model conducted a case study of shale gas projects in Sichuan, China. The results show that (a) Tolerance of the uncertainty in water demand for hydraulic fracturing can effectively reduce both economic and environment cost, thereby reducing total system cost. (b) System costs depends on risk preferences of decision-makers. (c) Direct reuse is the best strategy to treat wastewater at the early phase of hydraulic fracturing; while more constraints other than onsite treatment costs should be considered when treating produced water during the production phase. (d) There exists an “economics of scale” in the water management during shale gas exploration.