Study On Environmental Impact Of Global Shale Gas Extraction

With the development of economy and society,the demand for energy of human is increasing.Traditional fossil energy has been in short supply.As a new type of clean energy,shale gas has considerable recovery and development prospects.However,due to the complex of shale formations,shale gas wells must be used by hydraulic fracturing and horizontal drilling technology to obtain economic output.The extraction process makes serious environmental problems.A large amount of hydraulic fracturing fluid is consumed during the extraction of shale gas,which brings water pressure to the local system.Diesel oil is consumed during drilling and mining activities,which results in a large amount of greenhouse gas emissions.Indirect environmental impact is caused by raw material inputs.Maybe it's different between the environmental impact of shale gas extraction due to different burial depths and different raw material production processes in different countries.Therefore,it is necessary to explore the differences in the environmental impacts of shale gas extraction in different countries.Starting from the life cycle of shale gas extraction,this study applied Monte Carlo simulation and scenario analysis to quantify the consumption of raw mateirals,direct and indirect environmental impacts of shale gas in various coutries around the world based on survey data and literature review data.And through scenario analysis,this study quantified the total cumulation amount of the consumption of raw material in various countries under different lengths of horizontal well and different cumulation volumes of extraction.Comprehensive consideration of development technology progress,power structure changes,raw material production process improvements and other scenarios to quantify the potential environment impact of shale gas extraction.The specific research results are as follows:(1)The average input of cement,steel and diesel oil for shale gas are 331,460 and 694 t well^-1.In various shale gas countries,the average cement(steel)input of 168-351(249-507)t for vertical wells is 3-7(4-9)times that of 42-57(50-65)t for horizontal wells.Compared with the diesel oil input for each vertical well(165-325 t),horizontal well requires more diesel input(373-494 t).(2)The average of water consumption,energy consumption and greenhouse gases emission of single well(10³ m³ shale gas)of global shale gas extraction is 30070 m³ well^-1(0.89 m³ 10^-3 m^-3 shale gas),46 TJ well^-1(1.34 GJ 10^-3 m^-3 shale gas)and 3667 t CO₂e well^-1(0.11 t CO₂e 10^-3 m^-3 shale gas).Among them,water consumption,energy consumption and greenhouse gases emission of horizontal well account for 76-90%,44-67%and 43-66%,respectively;direct water consumption,direct energy consumption and direct greenhouse gases emission account for 67-85%,55-74%and 49-72%,respectively.(3)When the cumulative amount of shale gas extraction is same,the longer the horizontal well is,the more accumulated consumption of raw materials will be saved.When the horizontal well length increases from 1800 m to 5000 m,the average reduction rate of global cement,steel pipe and diesel input increase from 18%to 60%,19%to 62%,and 7%to 24%,respectively.(4)Scenario analysis shows that increasing the proportion of EAF steelmaking canreduce the energy consumption and greenhouse gas emissions of shale gas extraction,but it will bring greater water pressure.Increasing the proportion of solar/wind/tide power generation can reduce the environmental impact of shale gas extraction,but the impact is not significant.To reduce the environmental impact of shale gas extraction,efforts should be made to improve the energy use effiency,the fracturing flowback rate and wastewater recycling.