Optimization Of Shale-gas-water Management Systems Based On Multi-level Programming Approach

In recent years,energy shortage and environmental pollution have been intensified internationally.Shale gas,as one of alternative energy sources,has attracted wide attention across the world.Hydraulic fracturing has been increasingly used for gas production from shale gas reservoirs.A major concern associated with Hydraulic fracturing is high consumption of water resources.Huge water consumption could limit the popularization of shale gas development,particularly where water shortage continues to be a major obstacle.Because of the complexity of shale-gas water system,firstly,a new bi-level optimization model(MBU-MWL)based on goals at maximizing system benefit at the upper level and minimizing water demands at the lower level is built to solve a real-world case across Pennsylvania and West Virginia.Different water resources allocations are determined.Optimized water demands,gas production,pollutants discharge and satisfactory degrees under nine scenarios considering different boundaries of the couple objective function values intervals are assessed.Sensitivity analysis is investigated to examine the variations in a model’s outputs caused by small changes in the model’s input parameters.Secondly,a tri-level optimization model(MWU-MBM-MPL)based on water-benefit-environment nexus shale system is conducted in Pennsylvania.Two transportation models(truck,pipeline)and four sewage treatment methods(CWT facilities,WIT wells,onsite treatment,onsite storage)are considered in the constraints.Results show that surface water would be the largest contributor to gas production(with over 80.00%)but groundwater occupies for the least proportion(with less than 2.00%);MBU-MWL model could balance the tradeoff between the energy sector and the water authority;compared with traditional single objective model,the MWU-MBM-MPL model can provide better decision alternatives in balancing system benefit,water resources and pollutants discharge.