Rules for Flight Paths and Time of Flight for Flows in PorousMedia with Heterogeneous Permeability and Porosity

Porous media like hydrocarbon reservoirs may be composed of a wide variety of rocks with different porosity and permeability. Ourstudy shows in algorithms and in synthetic numerical simulations that the flow pattern of any particular porous medium, assumingconstant fluid properties and standardized boundary and initial conditions, is not affected by any spatial porosity changes but willvary only according to spatial permeability changes. In contrast, the time of flight along the streamline will be affected by both thepermeability and porosity, albeit in opposite directions. A theoretical framework is presented with evidence from flow visualizations.A series of strategically chosen streamline simulations, including systematic spatial variations of porosity and permeability,visualizes the respective effects on the flight path and time of flight. Two practical rules are formulated.Rule 1states that anincrease in perme abilitydecreases the time of flight, whereas an increase in porosity increases the time of flight.Rule 2states that the permeability uniquely controls the flight pathof fluid flow in porous media; local porosity variations do not affect thestreamlinepath. The two rules are essential for understanding fluid transport mechanisms, and their rigorous validation therefore is merited.