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Impact of an historic underground gas well blowout on the current methane chemistry in a shallow groundwater system
Proceedings of the National Academy of Sciences of the United States of America ( IF 11.1 ) Pub Date : 2018-01-09 00:00:00 , DOI: 10.1073/pnas.1711472115
Gilian Schout 1, 2, 3 , Niels Hartog 2, 3 , S. Majid Hassanizadeh 2 , Jasper Griffioen 1, 4
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Blowouts present a small but genuine risk when drilling into the deep subsurface and can have an immediate and significant impact on the surrounding environment. Nevertheless, studies that document their long-term impact are scarce. In 1965, a catastrophic underground blowout occurred during the drilling of a gas well in The Netherlands, which led to the uncontrolled release of large amounts of natural gas from the reservoir to the surface. In this study, the remaining impact on methane chemistry in the overlying aquifers was investigated. Methane concentrations higher than 10 mg/L (n = 12) were all found to have δ13C-CH4 values larger than −30‰, typical of a thermogenic origin. Both δ13C-CH4 and δD-CH4 correspond to the isotopic composition of the gas reservoir. Based on analysis of local groundwater flow conditions, this methane is not a remnant but most likely the result of ongoing leakage from the reservoir as a result of the blowout. Progressive enrichment of both δ13C-CH4 and δD-CH4 is observed with increasing distance and decreasing methane concentrations. The calculated isotopic fractionation factors of εC = 3 and εD = 54 suggest anaerobic methane oxidation is partly responsible for the observed decrease in concentrations. Elevated dissolved iron and manganese concentrations at the fringe of the methane plume show that oxidation is primarily mediated by the reduction of iron and manganese oxides. Combined, the data reveal the long-term impact that underground gas well blowouts may have on groundwater chemistry, as well as the important role of anaerobic oxidation in controlling the fate of dissolved methane.

中文翻译:

历史性地下气井井喷对浅层地下水系统中当前甲烷化学的影响

当钻入深层地下时,井喷具有很小但真正的风险,并且可能对周围环境产生直接而重大的影响。然而,很少有文献证明其长期影响。1965年,在荷兰的一口气井钻探过程中,发生了灾难性的地下井喷,导致大量天然气从储层到地表的不受控制的释放。在这项研究中,研究了上覆含水层对甲烷化学的剩余影响。甲烷浓度高于10毫克/升(Ñ = 12)均发现有δ 13 C-CH 4个-30更大的值‰,典型产热来源的。既δ 13 C-CH 4和δD-CH图4对应于储气库的同位素组成。根据对当地地下水流动状况的分析,这种甲烷不是残留的,而是很可能是由于井喷而不断从储层泄漏的结果。既δ的逐渐富集13 C-CH 4和δD-CH 4与距离的增加和降低甲烷浓度观察到。的所计算的同位素分馏因子ε c ^ = 3和ε d= 54表示厌氧甲烷氧化在一定程度上是观察到的浓度降低的原因。甲烷羽流边缘溶解的铁和锰的浓度升高表明,氧化主要是由铁和锰的氧化物的还原介导的。综合起来,数据揭示了地下气井井喷可能对地下水化学产生的长期影响,以及厌氧氧化在控制溶解甲烷命运方面的重要作用。
更新日期:2018-01-10
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