Residual air saturation changes during consecutive drainage-imbibition cycles in an air-water fine sandy medium
Residual air saturation changes during consecutive drainage-imbibition cycles in an air-water fine sandy medium
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DOI：
10.1016/j.jhydrol.2013.08.050
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发表时间：
2013-10
影响因子：
6.4
通讯作者：
Yan Li;G. Flores;Jun Xu;W. Yue;Yuxin Wang;Tiangang Luan;Qing-bao Gu
中科院分区：
文献类型：
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作者：
Yan Li;G. Flores;Jun Xu;W. Yue;Yuxin Wang;Tiangang Luan;Qing-bao Gu
为了阐明特殊（动态、非平衡）条件下残余空气饱和度的变化，对气水两相砂岩柱中的饱和度-毛管压力（S-p）关系进行了研究，包括由预定水位波动产生的连续排水-吸吸循环下的残余空气饱和度。使用 TDR（时域反射计）探头、T5 张力计和数据记录仪在线测量和记录水饱和度和毛细管压力。结果表明，在动态流动条件下，在一系列吸入循环过程中，随着初始空气饱和度的变化，残余空气饱和度突然从不稳定状态转变为稳定状态，并且只有当吸入过程的初始空气饱和度超过0.49时，才会出现稳定的非零残余空气饱和度，约100%。主吸液过程的价值加倍。一旦获得稳定的残余空气饱和度，所有随后的残余空气饱和度在接下来的吸入循环中保持稳定和恒定。在此阈值之前，如果有足够的吸入时间，残余空气饱和度逐渐下降。研究结果还表明，不稳定和稳定的残余空气饱和度主要是由于被困在孔隙内部的离散孔隙尺度空气球和位于互连孔隙中的孔隙网络尺度空气球分别造成的。
To clarify changes of residual air saturation under special (dynamic, nonequilibrium) conditions, the saturation–capillary pressure (S–p) relationship including the residual air saturation under consecutive drainage–imbibition cycles, generated by scheduled water level fluctuations, in an air–water two-phase sandy column was investigated. Water saturation and capillary pressure were measured online and recorded using TDR (Time Domain Reflectometry) probes, T5 tensiometers and a datalogger. The results show that under dynamic flow conditions the residual air saturation changed suddenly from an unstable to a stable state with changes in initial air saturation during the series of imbibition cycles, and stable nonzero residual air saturation only occurred when the initial air saturation of the imbibition process exceeded 0.49, ca. double the value of the main imbibition process. Once stable residual air saturation was obtained, all the subsequent residual air saturations remained stable and constant in the following imbibition cycles. Before this threshold point, the residual air saturation gradually fell given sufficient imbibition time. The results also indicate that the unstable and stable residual air saturations were mainly due to discrete pore-scale air globules trapped in the interiors of pores and pore-network scale globules located in interconnected pores, respectively.