基于生命周期评价的页岩气开采返排-产出水处理技术选择

为探究页岩气开采废水(即返排-产出水)处理技术对环境生态的影响,针对页岩气开采废水的处理后内部回用以及达标排放两种管理模式,结合生命周期评价的理念,运用Simapro分析工具,创建LCA模型,对典型处理技术进行清单分析,评估处理技术中的资源、能源消耗和环境负荷,量化分析其对人群健康、生态环境质量和资源方面的影响,建立一种页岩气开采返排-产出水处理技术选择的评价方法.同时,以国内某页岩气田产出水处理工程为例,评估所选用处理技术的潜在环境影响.结果表明,内部回用模式下选用的混凝-絮凝处理技术对环境生态影响最小;达标排放模式下针对有机物去除,选用铁电极的电絮凝技术或曝气生物滤池对环境生态的影响较小.对于较低含盐量的开采废水的脱盐,选用的脱盐技术正渗透对环境的影响比反渗透小,但反渗透的脱盐效果更好.对于较高含盐量开采废水的脱盐,选用的多效蒸发-机械蒸汽再压缩技术对环境生态的影响较小.

LCA - assisted selection of shale gas extraction flowback - produced water treatment technologies

Due to the rapid development of China’s shale gas industry in recent years, it is necessary to evaluate impacts of shale gas extraction wastewater treatments on the environment and ecology. According to the two management modes of internal reuse and discharge after the treatment of wastewater from shale gas extraction (i.e. flowback-produced water (FPW) and the idea of life cycle assessment (LCA)), the Simapro tool was used to conduct inventory analysis of typical treatment technologies. Then a case study of a produced water treatment project in a shale gas field in China was designed to evaluate the potential environmental impacts of the selected treatment technology. The results show that the coagulation-flocculation treatment technology used in the internal reuse mode had the least impact on the environment and ecology. For the removal of organic matter in the emission standard mode, the electrocoagulation with iron electrode or biological aerated filter had less impact on the environment and ecology. For desalination of extraction wastewater with low salt content, the ecological environment impact of forward osmosis is lower than that of reverse osmosis, but the desalination effect of reverse osmosis is better. For desalinating salted extraction wastewater, the selected multi-effect evaporation and mechanical vapor recompression technology demonstrated less impact on the environment and ecology.