Assessment On Regional Aqueous Environmental Security During Shale Gas Development

Advances in horizontal drilling and hydraulic fracturing technologies have accelerated the rapid expansion of the shale gas industry.However,the process of shale gas exploitation,exerts potential influences on the regional water environment.In order to assess the regional aqueous environmental security during shale gas development,this study first select reliability-resilience-vulnerability(RRV)metrics and as its pollutant characteristic index,where Calcium(Ca2+),Magnesium(Mg2+),Chloride(Cl)and pH are introduced.In the case study of water environment system in Pennsylvania,Monte-Carlo simulation and geostatistics are aggregated together and the statistical analysis,structural analysis and Kriging interpolation of indicator observations are performed by means of GS+ and ArcGIS software.Risks and spatial variation rules of regional water environment system are assessed and spatial characteristics and correlations of observations and RRV results are simultaneously characterized.On the basis,this study identifies spatiotemporal variations of pollution risks for dissolved methane in shallow groundwater to study the migration process of dissolved methane in shallow groundwater.In this study,the study area and observation data were meshed and time-segmented firstly,and then RRV results corresponding to each grid in each period are calculated and Copula functions are applied to construct the joint probability distribution of resilience and vulnerability.On the basis,Gas Migration Index(GMI)is structured and the spatiotemporal variation characteristics of GMI are studied and the utility of GMI is verified.In study case located in the southwestern area of Bradford County,Pennsylvania,RRV results reveal the synergistic mechanism among RRV and GMI results show that methane pollution risks gradually spread from central part to northern region.Utility verification results show GMI can better characterize the spatiotemporal variation characteristics of methane pollution risks than single metric.This study may provide feasible guidance and suggestions on pollution control measures and management policies to protect water environment quality.