| Title | Fractional Dynamics in Fault Structures |
|---|---|
| Authors | Anna SUZUKI, Toshiyuki HASHIDA, Kewen LI, Roland HORNE |
| Year | 2016 |
| Conference | Stanford Geothermal Workshop |
| Keywords | tracer test, column experiment, fault zone, non-Fickian diffusion, truncated distribution, tempered anomalous diffusion |
| Abstract | Fault zones clearly affect the flow paths of fluids at the scale of geothermal reservoirs. Fault-related fracture damage decreases to background levels with increasing distance from the fault core according to a power law. This study investigates mass transport in such a fault-related structure using nonlocal models. A column flow experiment has been conducted to create a permeability distribution that varies with distance from a main conduit. The tracer response curve describes a preasymptotic curve implying subdiffusive transport, which is slower than the normal Fickian diffusion. As long as permeability of the surrounding layers varies with distance from a main conduit, the tracer response can be modeled by the time fractional advection dispersion equation (time fADE). In contrast, if the surrounding area is a finite domain, an upper truncated behavior in tracer response (i.e., exponential decline at late time) is observed. The tempered anomalous diffusion (TAD) model captures the transition from sub-diffusive to Fickian transport, which is characterized by a smooth transition from power-law to an exponential decline in the late-time breakthrough curves. |