Scaling Analysis Of Capillary Transition Zones

Unsaturated flow in aquifers commonly includes a transition zone reflecting the balances among viscous, gravity, and capillary forces. Saturation varies within this zone, affecting properties of interest, including effective permeability and acoustic velocities. Moreover, in systems with a rising or falling water table, the shape and length of the transition zone varies. In this study, capillary transition zone is studied through reservoir simulation and scaling analysis is used to investigate how the length of capillary transition zones changes during production. Two new dimensionless numbers - capillary time and capillary length are first introduced. Thirty models with different grain sizes have been run. The length of capillary transition zone is calculated through reservoir simulation and results are summarised using capillary time, capillary length, and gravity number. It is concluded that the capillary length are the same when capillary times and gravity numbers are the same in different models.