The Pathway‐Flow Relative Permeability of CO2: Measurement by Lowered Pressure Drops
The Pathway‐Flow Relative Permeability of CO2: Measurement by Lowered Pressure Drops
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DOI：
10.1002/2017wr020580
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发表时间：
2017-10
影响因子：
5.4
通讯作者：
Yi Zhang;O. Nishizawa;Hyuck-Jin Park;T. Kiyama;X. Lei;Z. Xue
中科院分区：
文献类型：
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作者：
Yi Zhang;O. Nishizawa;Hyuck-Jin Park;T. Kiyama;X. Lei;Z. Xue
介绍了一种测量低渗透岩石中超临界CO2相对渗透率的简单方法。该方法建立在假设二氧化碳渗流通道在较低压降下是稳定的基础上。最初，在相对较高的压力降下形成连续的二氧化碳流动路径。然后，在监测相关流量的同时，执行降低压降的几个后续步骤。当压降低于阈值时，假设所创建的流道足够稳定，并且在连续流动期间不会有明显变化，平均饱和度和流量达到准稳定状态。然后根据达西定律的推广形式，从几个降压降下的压降和流量之间的关系计算出二氧化碳的相对渗透率。我们使用数值模拟和使用X射线CT成像的实验测试来演示该方法。结果表明，流道在较低压降下的稳定性假设是正确的。发现降压降与相应的CO2流量之间存在线性关系。此外，测量结果表明，在低渗透岩石中，如果二氧化碳饱和度高于建立渗流通道所需的阈值，则二氧化碳的相对渗透率仍然可以很高。该方法对于测量低渗透岩石中非润湿流体的孔道流动相对渗透率具有重要意义。
We introduce a simple method to measure the relative permeability of supercritical CO2 in low‐permeability rocks. The method is built on the assumption of the stability of formed CO2 percolation pathway under lowered pressure drops. Initially, a continuous CO2 flow pathway is created under a relatively high‐pressure drop. Then, several subsequent steps of lowered pressure drops are performed while monitoring the associated flow rates. When the pressure drop is lower than a threshold value, the created flow pathway is assumed to be adequately stable and does not vary significantly during successive flows, with the average saturation and flow rate achieving a quasi steady state. The relative permeability of CO2 is then calculated from the relationship between the pressure drop and flow rate at several lowered pressure drops according to the extended form of Darcy's law. We demonstrate this method using both numerical modeling and an experimental test using X‐ray CT imaging. The results indicate the validity of the assumption for the stability of flow pathway under lowered pressure drops. A linear relationship between the lowered pressure drops and the corresponding CO2 flow rate is found. Furthermore, the measurement results suggest that the relative permeability of CO2 can still be high in low‐permeability rocks if the CO2 saturation is higher than the threshold value required to build a flow pathway. The proposed method is important for measuring the pathway‐flow relative permeability of nonwetting fluids in low‐permeability rocks.