页岩气开发地下水污染风险评价指标体系构建

为分析页岩气开发对地下水环境风险的影响，采用文献计量学和频数统计法，进行页岩气开发地下水污染风险共性指标筛选，并通过分析页岩气开采环境的特征，进行页岩气开发地下水污染风险个性指标识别，构建了页岩气开发地下水污染风险评价指标体系.结果表明，页岩气开发的钻井、水力压裂和压裂返排以及返排后处理等阶段为发生污染地下水风险的主要环节，其中钻井阶段钻井液、水力压裂阶段压裂液、压裂返排阶段返排液和甲烷气体的泄漏是影响地下水环境的重要污染源；筛选出页岩气开发地下水污染风险共性指标14个，其中地下水埋深、含水层岩性、溶解性总固体和氨氮涉及行业项目多且频数占比较高，为核心评价指标；识别出页岩气开发地下水污染风险个性指标12个，分别为地质状况指标（断裂性质、褶皱发育状况）、开采过程污染物指标（返排液返排率、返排液回用率、钻井废水产生量、压裂废水产生量、钻井泥浆循环率、设备泄漏概率和废弃井分布），以及地下水特征污染物（苯系物、放射性物质和甲烷含量及其碳同位素形态等）.研究显示，通过频数统计和理论分析识别页岩气开发地下水污染源，可以快速有效地确定页岩气开发对地下水环境影响因素，并构建地下水污染风险评价指标体系，对页岩气开发地下水环境管理具有重要参考价值. 

Building up a Risk Assessment Index System of Groundwater Pollution in Shale Gas Development

In order to analyze the impact of shale gas development on groundwater environmental risks, using bibliometrics and frequency statistics approach to screen common groundwater pollution risk indicators, as well as analyzing the shale gas mining environment characteristics to identify featured groundwater pollution risk indicators, a shale gas development groundwater pollution risk assessment index system is built. The analysis results show that, during shale gas exploitation, drilling shaft, fracturing and flowing back of fracturing fluid are considered as the key link of groundwater pollution. In the above three stages, drilling fluid leakage, hydraulic fracturing fluid, fracturing outlet liquid and methane gas are the main pollution sources affecting groundwater environment. Fourteen common groundwater pollution risk indicators are screened out, in which groundwater depth, aquifer lithology, the total dissolved solid and ammonia-nitrogen are the core assessment indicators with extensive industry projects involvement and high frequency proportion. Twelve featured groundwater pollution risk indicators in shale gas development are identified, which are geological condition indicators (i.e., nature of faults, fold development status), mining process pollutants indicators (i.e., return flow rate and reuse rate of fracturing flowback fluids, drilling wastewater production, fracturing wastewater volume, drilling mud circulation rate, probability of equipment''s leakage and distribution of abandoned wells), and groundwater contaminants (i.e., benzene series, radioactive materials, methane content and their carbon isotopes) respectively. The research shows that identifying the pollution sources of shale gas exploitation on groundwater environment through frequency statistics and theoretical analysis can quickly and effectively determine the influence factors of shale gas development on groundwater environment and construct the index system of groundwater pollution risk assessment,which have important reference value for shale gas exploitation of groundwater environment management.