美国页岩气水力压裂开发对环境的影响

Environmental impacts of hydraulic fracturing in shale gas development in the United States

通过调研美国页岩气开发所面临的环境问题及研究进展,总结页岩气水力压裂开发对环境的影响,并探索对中国页岩气开发的参考意义。美国页岩气大规模商业性开发的环境风险主要包括水资源消耗与污染、引发地震及大气污染等。水资源消耗方面,通过评估能源生产耗水密度,可知与常规油气和其他能源生产方式相比,页岩气开发并非"高耗水"行业,其总用水量占地区总量比例较低,不会显著增加用水压力。水资源污染方面,由于水力压裂诱发连通储集层和地下水的裂缝而直接造成污染的可能性很低,且已知的浅层地下水污染案例可能与完井缺陷有关,提高井身完整性是防止污染的关键;页岩气规模开发阶段返排水总量大、污染物种类多、成分复杂,处理不当会造成污染,需要监测和评估其污染风险。现有证据表明页岩气开发不会引发破坏性地震。对页岩气井全生命周期的温室气体排放估计结论不一,在生产中应当采取更为有效的措施减少泄漏。页岩气开发环境影响方面的研究重点包括地表水和地下水污染监测方案与指标体系的建立、注入压裂液和储集层流体运移规律的分析、开发活动对高矿化度地层水及地下水层中天然甲烷运移的影响分析、页岩气开发返排水再利用和处理技术的应用。

Through comprehensive investigation of the environmental issues in shale gas development in the US, the environmental impacts of hydraulic fracturing in shale gas development are summarized to provide reference for the shale gas development and management in China. The environmental risks of large-scale commercial shale gas development in the United States include water consumption, water contamination, seismic inducement and air pollution. Compared to conventional oil and gas production and other energy producing industries, shale gas development is not exactly ＂high-water-consuming＂ in terms of water consuming intensity. Its water consumption, accounting for a small proportion of the total regional water consumption, will not add much more stress on water supply. In terms of water pollution, hydraulic fracturing is unlikely to cause fractures to directly connect reservoir to the shallow aquifer, the known contamination cases are most likely related to faulty well completion, therefore well integrity is the key to the prevention of contamination; the flow-back fluids in large scale shale gas development have the characteristics of large quantity, many kinds of pollutants and complex composition, thus improper treatment would lead to serious contamination, and continuous monitoring and assessment of the pollutants are necessary. Existing evidence shows that hydraulic fracturing is unlikely to trigger destructive earthquakes. Greenhouse gas emissions in the life cycle of shale gas wells were estimated differently, but no doubt more effective measures should be taken to minimize leakage. The research priorities include contamination monitoring program design, detection indicators, moving pattern of hydraulic fracturing fluid and formation fluid, the effects of shale gas development on high salinity formation water and methane migration, and treatment and re-use of flow-back fluid.