Relative Permeability Calculations from Two-Phase Flow Simulations Directly on Digital Images of Porous Rocks
Relative Permeability Calculations from Two-Phase Flow Simulations Directly on Digital Images of Porous Rocks
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DOI：
10.1007/s11242-011-9877-8
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发表时间：
2012-09
影响因子：
2.7
通讯作者：
T. Ramstad;N. Idowu;C. Nardi;P. Øren
中科院分区：
文献类型：
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作者：
T. Ramstad;N. Idowu;C. Nardi;P. Øren
我们对Bentheimer和Berea砂岩的x射线微层析成像孔隙空间图像进行了两相晶格玻尔兹曼（LB）模拟，得出了相对渗透率函数的系统研究结果。模拟模拟了测量相对渗透率的非稳态和稳态实验。对于稳态流动，我们重现了排水和渗吸相对渗透率曲线，这些曲线与现有的稳态实验数据非常吻合。通过使用Johnson、Bossler和Naumann方法，输入模拟的生产和压力剖面，通过显式计算得出非稳态驱替的相对渗透率。我们发现，与稳态数据相比，非润湿相排水相对渗透率被高估了。这是由于瞬态动力效应引起粘性不稳定。因此，计算出的水系非稳态相对渗透率与瞬态效应消失的稳态情况有本质区别。这些影响对入侵的非润湿流体的影响大于防御的润湿流体。非稳态渗吸相对渗透率与稳态渗吸相对渗透率相当。然而，活塞式前端的外观掩盖了大部分的位移，数据只能在有限的饱和度范围内确定。由非稳态驱替得出的相对渗透率表现出明显的速率效应，剩余饱和度在很大程度上取决于毛细管数。我们得出的结论是，LB方法可以提供一个通用的工具，从孔隙空间图像计算多相流特性，并探索施加的流动和流体条件对这些特性的影响。此外，该方法还可以适当地捕获动态效应，从而有机会检查稳态和非稳态设置之间的差异。
We present results from a systematic study of relative permeability functions derived from two-phase lattice Boltzmann (LB) simulations on X-ray microtomography pore space images of Bentheimer and Berea sandstone. The simulations mimic both unsteady- and steady-state experiments for measuring relative permeability. For steady-state flow, we reproduce drainage and imbibition relative permeability curves that are in good agreement with available experimental steady-state data. Relative permeabilities from unsteady-state displacements are derived by explicit calculations using the Johnson, Bossler and Naumann method with input from simulated production and pressure profiles. We find that the nonwetting phase relative permeability for drainage is over-predicted compared to the steady-state data. This is due to transient dynamic effects causing viscous instabilities. Thus, the calculated unsteady-state relative permeabilities for the drainage is fundamentally different from the steady-state situation where transient effects have vanished. These effects have a larger impact on the invading nonwetting fluid than the defending wetting fluid. Unsteady-state imbibition relative permeabilities are comparable to the steady-state ones. However, the appearance of a piston-like front disguises most of the displacement and data can only be determined for a restricted range of saturations. Relative permeabilities derived from unsteady-state displacements exhibit clear rate effects, and residual saturations depend strongly on the capillary number. We conclude that the LB method can provide a versatile tool to compute multiphase flow properties from pore space images and to explore the effects of imposed flow and fluid conditions on these properties. Also, dynamic effects are properly captured by the method, giving the opportunity to examine differences between steady and unsteady-state setups.