Topic: Overview of the risks to water resources from hydraulic fracturing: An example from shale gas development in China
Speaker: Prof. Avner Vengosh
Date: Mar. 4, 2019
Time: 19:00
Venue: Auditorium, GTIIT
Abstract:
The rise of unconventional shale gas and tight sand oil extraction through horizontal drilling and high- volume hydraulic fracturing has significantly increased oil and gas exploration in the U.S., Canada, and China, and will soon be launched on a global scale. Shale gas is likely to play a major role in China's transition away from coal. In addition to technological and infrastructural constraints, the main challenges to China's sustainable shale gas development are sufficient shale gas production, water availability, and adequate wastewater management.
Research in the U.S. has identified several key environmental issues associated with unconventional energy development, including migration of natural gas from leaking wells, high water footprint of hydraulic fracturing and water availability, and contamination of surface water and shallow groundwater from accidental spills, leaks, and disposal of inadequately treated oil and gas wastewater, resulted in elevated levels of halides, ammonium, barium, and radium nuclides among other contaminants in downstream waterways, with high potential to trigger the formation of disinfection byproducts in downstream chlorinated drinking water.
New data show intensification of the water footprint of hydraulic fracturing in the U.S.; from 2011 to 2016 the water-use per well increased up to 770%, while flowback and produced water volumes generated within the first year of production increased up to 550%. Data of shale gas production and its water footprint from the Weiyuan gas field, one of the major gas fields in the Sichuan Basin show that the amount of water used for hydraulic fracturing (34,000 m3 per well) and the volume of flowback and produced (FP) water in the first 12 months (19,800 m3 per well) in the Sichuan Basin are also similar to the current water footprints of hydraulic fracturing in U.S. basins. The FP water from shale gas wells derives from blending of injected hydraulic fracturing water and entrapped saline (Cl ~ 50,000 mg/L) formation water.
Variations in the FP water geochemistry over time indicate that the mixing between the two sources varies with time, with a contribution of 75% (first six months) to 20% (>year) of the injected hydraulic fracturing water in the blend that compose the FP water. While most public attention has been focused on the risks of anthropogenic chemicals used in hydraulic fracturing, naturally occurring contaminants derived from the formation waters that are co-extracted with shale gas and oil pose high risks to the aquatic life and human health in cases where flowback and produced waters from shale gas and tight oil exploration are released to the environment. The management and safe disposal and reuse of wastewater generated from unconventional energy development is therefore essential in protecting the environment and water resources upon future development of shale gas in China.
主题：水资源面对水力压裂风险的概述：以页岩天然气在中国的发展为例
嘉宾：Avner Vengosh教授
日期：2019年3月4日
时间：19:00
地点：广东以色列理工学院科报厅
摘要：
水平钻井和大体积水力压裂技术的运用使非常规页岩气和致密砂油的开采能力和效率得到了较大提升，极大推动了美国、加拿大和中国的油气勘探，该项技术呈全球范围推广之势。页岩气很可能在中国的煤炭转型中发挥重要作用。除了技术和基础设施的限制外，中国可持续页岩气开发的主要挑战在于页岩气生产、水资源可利用量和废水的有效管理。
美国的研究已经确定了与非常规能源开发相关的几个关键的环境问题，包括泄漏井中天然气的迁移，水力压裂和可利用量的高水足迹，以及地表水和浅层地下水受意外溢出、泄漏和未充分处理油气及可利用水污染致下游水中的卤化物、铵、钡和镭核素水平升高，极可能引发下游饮用水氯化消毒副产物的形成。
最新数据显示美国在水力压裂的水足迹日益增强。从2011年至2016年，每口油井用水量增加到770％，而在生产的第一年内产生的返排和采油废水量则增加到550％。作为四川盆地主要气田之一的威远气田的页岩气产量及其水足迹数据显示，水力压裂用水量（每口井34,000立方米）和前12个月的返排和采油废水量（FP）（每口井19,800立方米）也与目前美国盆地水力压裂的水足迹相近。页岩气井的返排和采油废水量来自注入的作为水力压裂的水和捕获的地层盐水（Cl~50,000 mg / L）的混合。随着时间的推移，返排和采油废水量在地球化学上的变化表明两种来源之间的混合会随时间改变，在混合中用于水力压裂的用水占比为75％（前六个月）至20％（一年后）。虽然大多数公众的注意力都集中在水力压裂中使用人为化学品的危害上，但与页岩气和石油共同提取的地层水自然产生的污染物相比，在页岩气和致密油勘探过程中返排和采油向环境排放的废水，对水生生物和人类健康构成的威胁很大。因此，非常规能源开发产生的废水管理、安全处理和再利用对于中国页岩气未来发展和环境与水资源的保护极其重要。
