Interpreting fluid pressure anomalies in shallow intraplate argillaceous formations
Interpreting fluid pressure anomalies in shallow intraplate argillaceous formations
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DOI：
10.1002/2015gl064140
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发表时间：
2015-06
影响因子：
5.2
通讯作者：
C. Neuzil
中科院分区：
文献类型：
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作者：
C. Neuzil
调查显示，在板内环境中，浅层（深度< ~ 1 km）泥质地层中的孔隙流体势存在明显孤立的高点或低点的几个例子。具有压力异常的地层的区别在于：（1）与没有异常的地层相比，具有较小的水力传导率与地层厚度的比值;（2）具有较小的水力（或压力）扩散系数。这与由约10−17至10 − 16 s − 1的应变速率、过去104至106年的重大扰动事件或两者的某种组合引起的瞬态达西流一致。可能的原因包括侵蚀下冲、构造应变和冰川作用。在这种概念化中，异常提供了过去106年地层尺度流动特性、流动历史和局部地质作用力的限制，特别是指示了低渗透率区（10−19-10−22 m2），这可能有助于隔离核废料。
Investigations have revealed several instances of apparently isolated highs or lows in pore fluid potential in shallow (< ~ 1 km depth) argillaceous formations in intraplate settings. Formations with the pressure anomalies are distinguished by (1) smaller ratios of hydraulic conductivity to formation thickness and (2) smaller hydraulic (or pressure) diffusivities than those without anomalies. This is consistent with transient Darcian flow caused by strain at rates of ~ 10−17 to 10‐16 s‐1, by significant perturbing events in the past 104 to 106 annum or by some combination of the two. Plausible causes include erosional downwasting, tectonic strain, and glaciation. In this conceptualization the anomalies provide constraints on formation‐scale flow properties, flow history, and local geological forcing in the last 106 annum and in particular indicate zones of low permeability (10−19–10−22 m2) that could be useful for isolation of nuclear waste.