Flow of variable-density formation water in deep sloping aquifers: review of methods of representation with case studies
Flow of variable-density formation water in deep sloping aquifers: review of methods of representation with case studies
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DOI：
10.1016/0022-1694(94)02578-y
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发表时间：
1995
影响因子：
6.4
通讯作者：
S. Bachu
中科院分区：
文献类型：
--
作者：
S. Bachu
淡水水头的分布已经并将继续用于地下水流的表示和分析，包括深层倾斜含水层中可变性质地层水的流。由于压力、温度和盐度的变化，沉积盆地中地层水的流动受到压力和海拔（地形）差异产生的潜在力、密度差异产生的浮力以及温度和浓度梯度引起的渗透作用的驱动。由于流体和岩石特性的变化，不可能定义用于表示和分析流动的流动势。也不存在可以从中导出流动驱动力并且可以用于流动表示和分析的力势。即使忽略渗透效应，浮力仍然发挥作用，在某些情况下可能很重要。在水平或接近水平的含水层中，变密度水的侧向流动可以由淡水电位表面正确地表示，并且可以使用“环境”水头分布来分析垂直流动。然而，沉积盆地中地层水的流动主要是沿着承压倾斜含水层的层理流动。在这种情况下，由于无法计算和表示速度或推动力分布，淡水水头仍然是唯一可用于表示和分析流量的工具。通过忽略浮力，会引入流动强度和方向的误差，如果无量纲驱动力比超过估计为 0.5 左右的阈值，这些误差就会变得很大。通过阿尔伯塔省和亚诺斯沉积盆地的两个案例研究，说明了深层倾斜含水层中可变性质地层水流动的表征和分析方法的回顾。
Distributions of freshwater hydraulic heads have been, and continue to be, used in the representation and analysis of groundwater flow, including the flow of variable-properties formation water in deep sloping aquifers. Because of variations in pressure, temperature and salinity, the flow of formation waters in sedimentary basins is driven by potential forces resulting from pressure and elevation (topography) differences, by buoyancy resulting from density differences, and by osmosis caused by temperature and concentration gradients. Because of variations in both fluid and rock properties, it is not possible to define a flow potential to be used in representing and analysing the flow. Neither is there a force potential from which a flow-driving force can be derived, and which could be used in flow representation and analysis. Even if osmotic effects are neglected, buoyancy still plays a role which in certain cases may be important. In horizontal or near-horizontal aquifers, the lateral flow of variable-density water is correctly represented by freshwater potentiometric surfaces, and the vertical flow may be analysed using `environmental' hydraulic-head distributions. However, the flow of formation waters in sedimentary basins is mostly along bedding in confined sloping aquifers. In this case, short of calculating and representing either the velocity or the impelling force distribution, freshwater hydraulic heads remain the only tool available for representing and analysing the flow. By neglecting buoyancy, errors in flow strength and direction are introduced, which become significant if a dimensionless driving force ratio exceeds a threshold value estimated to be around 0.5. The review of representation and analysis methods for the flow of variable-properties formation water in deep sloping aquifers is illustrated with two case studies from the Alberta and Llanos sedimentary basins.