Water resource impacts during unconventional shale gas development: The Pennsylvania experience
Water resource impacts during unconventional shale gas development: The Pennsylvania experience
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DOI：
10.1016/j.coal.2013.12.017
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发表时间：
2014-06-01
影响因子：
5.6
通讯作者：
Simon, Cesar
中科院分区：
文献类型：
--
作者：
Brantley, Susan L.;Yoxtheimer, Dave;Simon, Cesar
水平钻井和水力压裂技术的改进，使所谓的“非常规”天然气资源得以开发，从而彻底改变了能源格局。美国东北部的Marcellus油田记录了这项技术的发展速度：宾夕法尼亚州（PA）的非常规Marcellus威尔斯油井数量从2005年的8口增加到今天的7234口。巴勒斯坦权力机构的公开数据库显示，地表水和地下水受到污染的证据很少。这可以证明，影响巴勒斯坦权力机构沃茨的事件相对较少，污染物被迅速稀释。然而，以下因素阻碍了得出明确的结论：i）缺乏关于事件发生地点和时间的信息; ii）由于责任或保密协议，倾向于不发布与特定事件相关的水质数据; iii）感兴趣的分析物的样本和传感器数据稀少; iv）存在预先存在的水损害，这使得难以确定页岩气活动的潜在影响;虽然可用于评估PA污染事件的监测数据有限，但该州管理着一个在线违规数据库。总的来说，五分之一的天然气威尔斯钻井至少收到了一份来自巴勒斯坦权力机构监管机构的非行政违规通知。截至2013年3月，3.4%的气井威尔斯因油井建设问题获得了NOV，024%的气井威尔斯收到了与甲烷迁移到地下水有关的NOV。在2008年至2012年期间，该州收到的1000起类似投诉中有161起描述了涉及石油或天然气活动的污染：天然气占56%，盐水盐成分占14%。6%的属性受到沉积物、浊度和/或钻屑的影响。大多数的地下水污染的甲烷和/或盐成分的网站是在以前的冰川北方PA断裂流有时允许长距离的流体输送。没有记录到水力压裂或返排流体地下运输到供水系统的情况。如果与Marcellus相关的回流/生产沃茨确实进入地表水或地下沃茨，最有可能检测到的污染物是Na、Ca和Cl，但这些元素在天然沃茨中已经很常见。最具Marcellus特异性的“指纹”元素是Sr，Ba和Br。例如，在西南PA流中测量的可变Br浓度归因于2011年之前通过市政或工业废水处理厂允许将非常规页岩气威尔斯井的废水释放到PA流中。目前已停止排放，但少数工厂的盐水仍允许排放处理后的传统油/气盐水。总体而言，监管机构确定的涉及石油/天然气活动的饮用水供应问题在2010年达到顶峰，而泄漏率在2012年有所增加。尽管报告了许多轻微的违规行为和临时问题，但从巴勒斯坦权力机构的情况来看，页岩气的快速启动可能导致了与所钻威尔斯井相比相对较少的重大环境事件;然而，由于缺乏透明和可获得的数据，影响仍然难以评估。(C)2014爱思唯尔有限公司版权所有。
Improvements in horizontal drilling and hydrofracturing have revolutionized the energy landscape by allowing the development of so-called "unconventional" gas resources. The Marcellus play in the northeastern U.S.A. documents how fast this technology developed: the number of unconventional Marcellus wells in Pennsylvania (PA) increased from 8 in 2005 to similar to 7234 today. Publicly available databases in PA show only rare evidence of contamination of surface and groundwaters. This could document that incidents that impact PA waters have been relatively rare and that contaminants were quickly diluted. However, firm conclusions are hampered by i) the lack of information about location and timing of incidents; ii) the tendency to not release water quality data related to specific incidents due to liability or confidentiality agreements; iii) the sparseness of sample and sensor data for the analytes of interest; iv) the presence of pre-existing water impairments that make it difficult to determine potential impacts from shale-gas activity; and v) the fact that sensors can malfunction or drift.Although the monitoring data available to assess contamination events in PA are limited, the state manages an online database of violations. Overall, one fifth of gas wells drilled were given at least one non-administrative notice of violation (NOV) from the PA regulator. Through March 2013,3.4% of gas wells were issued NOVs for well construction issues and 024% of gas wells received NOVs related to methane migration into groundwater. Between 2008 and 2012, 161 of the similar to 1000 complaints received by the state described contamination that implicated oil or gas activity: natural gas was reported for 56% and brine salt components for 14% of the properties. Six percent of the properties were impacted by sediments, turbidity, and/or drill cuttings. Most of the sites of groundwater contamination with methane and/or salt components were in previously glaciated northern PA where fracture flow sometimes allows long distance fluid transport. No cases of subsurface transport of fracking or flowback fluids into water supplies were documented. If Marcellus-related flowback/production waters did enter surface or groundwaters, the most likely contaminants to be detected would be Na, Ca, and Cl, but those elements are already common in natural waters. The most Marcellus-specific "fingerprint" elements are Sr, Ba, and Br. For example, variable Br concentrations measured in southwestern PA streams were attributed to permitted release of wastewaters from unconventional shale gas wells into PA streams through municipal or industrial wastewater treatment plants before 2011. Discharge has now been discontinued except for brines from a few plants still permitted to discharge conventional oil/gas brines after treatment. Overall, drinking water supply problems determined by the regulator to implicate oil/gas activities peaked in frequency in 2010 while spill rates increased through 2012. Although many minor violations and temporary problems have been reported, the picture that emerges from PA is that the fast shale-gas start may have led to relatively few environmental incidents of significant impact compared to wells drilled; however, the impacts remain difficult to assess due to the lack of transparent and accessible data. (C) 2014 Elsevier B.V. All rights reserved.