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Ground Water. 2014 Jan-Feb;52(1):9-19. doi: 10.1111/gwat.12095. Epub 2013 Jul 29.
Recent increases in the use of hydraulic fracturing (HF) to aid extraction of oil and gas from black shales have raised concerns regarding potential environmental effects associated with predictions of upward migration of HF fluid and brine. Some recent studies have suggested that such upward migration can be large and that timescales for migration can be as short as a few years. In this article, we discuss the physical constraints on upward fluid migration from black shales (e.g., the Marcellus, Bakken, and Eagle Ford) to shallow aquifers, taking into account the potential changes to the subsurface brought about by HF. Our review of the literature indicates that HF affects a very limited portion of the entire thickness of the overlying bedrock and therefore, is unable to create direct hydraulic communication between black shales and shallow aquifers via induced fractures. As a result, upward migration of HF fluid and brine is controlled by preexisting hydraulic gradients and bedrock permeability. We show that in cases where there is an upward gradient, permeability is low, upward flow rates are low, and mean travel times are long (often >10⁶ years). Consequently, the recently proposed rapid upward migration of brine and HF fluid, predicted to occur as a result of increased HF activity, does not appear to be physically plausible. Unrealistically high estimates of upward flow are the result of invalid assumptions about HF and the hydrogeology of sedimentary basins.
最近，水力压裂（HF）技术的使用增加，以帮助从黑色页岩中提取石油和天然气，这引起了人们对与 HF 流体和盐水向上迁移预测相关的潜在环境影响的关注。一些最近的研究表明，这种向上迁移可能很大，迁移的时间尺度可以短至几年。在本文中，我们讨论了从黑色页岩（如马塞勒斯、巴肯和鹰福特）向上迁移到浅层含水层的流体的物理限制，同时考虑了 HF 可能对地下带来的潜在变化。我们对文献的回顾表明，HF 仅影响上覆基岩整个厚度的非常有限的部分，因此，无法通过诱导裂缝在黑色页岩和浅层含水层之间建立直接的水力连通。因此，HF 流体和盐水的向上迁移受先前存在的水力梯度和基岩渗透率的控制。我们表明，在存在向上梯度的情况下，渗透率低，向上流速低，平均迁移时间长（通常 >10⁶ 年）。因此，最近提出的由于 HF 活动增加而预测的盐水和 HF 流体的快速向上迁移似乎在物理上是不合理的。向上流动的不切实际的高估计是对 HF 和沉积盆地水文地质的无效假设的结果。
