Development of slender transport pathways in unsaturated fractured rock: Simulation with modified invasion percolation

Abstract

[1] Slender transport pathways have been found in laboratory and field experiments within unsaturated fractured rock. Here we consider the simulation of such structures with a Modified form of Invasion Percolation (MIP). Results show that slender pathways form in fracture networks for a wide range of expected conditions, can be maintained when subsequent matrix imbibition is imposed, and may arise even in the context of primarily matrix flow due to the action of fractures as barriers to inter-matrix block transport.

Criteria for and statistics of electron diffusion regions associated with subsolar magnetic field reconnection

“…Thus model concepts of magnetopause structure and dynamics must be revised in view of new experimental and theoretical results. It is also noted that an event on the Cluster satellites similar to those discussed herein has been studied by Andre et al [2004].…”

Self organized spatio‐temporal structure within the fractured Vadose Zone: The influence of dynamic overloading at fracture intersections

“…When the capillary barrier fails, only one of the fractures is likely to be invaded, as the invasion pressure for each will be different. Such low flow behavior generates slender plumes as has been found experimentally [ Glass et al , 2003a, 2003b] and simulated using modified invasion percolation models, even without considering fracture intersections as capillary barriers [ Glass et al , 2004]. However, the pressure at the intersection can be pushed above the invasion pressure of the barrier if a large volume of water is passed from above and causes the pool height to rise above the minimal height required for breach.…”

On the Importance of Gravity in DNAPL Invasion of Saturated Horizontal Fractures

“…P c is calculated as follows: where σ is the DNAPL‐water interfacial tension, θ is the contact angle (measured through the wetting fluid), b is the aperture, and α is a fitting parameter that accounts for the variable aperture geometry. Equation represents a simplification of the Young‐Laplace equation, where α = 2 if the local aperture geometry is two parallel plates (Glass and Yarrington ; Ji et al ; Glass et al ) and α = 4 if the local interface geometry is a tubular pore (Kueper and McWhorter ; Glass and Yarrington ). It is expected that the value of α in a variable aperture fracture is between 2 and 4, as it is neither a parallel plate nor tubular pore (Kueper and McWhorter ).…”

“…The IP algorithm considers the interface between the invading fluid and defending fluid, in this case the non-wetting and wetting fluids, respectively, computes the pressure required to invade each adjacent element, and the invading fluid "invades" the element with the lowest invasion pressure. The algorithm then repeats this computation and invasion step for each new interface location (Glass and Yarrington 1996;Ji et al 2003;Glass et al 2004;Petchsingto and Karpyn 2010). In this work, the invasion pressure is computed as a sum of the capillary pressure, P c , and the gravitational pressure, P g (Ioannidis et al 1996;Meakin et al 2000;Glass and Yarrington 2003).…”

“…In other IP models, typically only one element is invaded with each step (Glass and Yarrington 1996;Ji et al 2003;Glass et al 2004;Petchsingto and Karpyn 2010). In this study, the number of elements invaded within a single step is denoted as N .…”