Seminarium "Modeling of Complex Systems"

When acid is injected into soluble rocks such as limestone channels,termed "wormholes", are formed due to a reaction-infiltrationinstability arising from heterogeneity within the rock. The continuedgrowth of the wormhole is controlled by the coupling of flow andgeometry of both the wormhole and pre-existing pores in the rock.Previous studies have attempted to capture the evolution of flow andgeometry in models, starting with initial pore geometry fromtomographic scans of rocks and compare the model output to scans ofthe acidize rock. This study steps back from modeling and directlyobserves the evolution of wormhole formation. Rock cores are subjectedto acid injection in a cell, with parameters such as injection rateand acid concentration are controlled. To observe evolution this cellis placed in a tomograph and scans are performed while the rock isbeing acidized. The evolution of the flow field is also captured byinjecting a contrasting agent such as potassium iodide or heavy waterwhen scanned with X-Ray or neutron tomography, respectively. Initialresults show wormhole growth is controlled by focused flow at the tipof the wormhole and the character of wormhole geometry is stronglycontrolled by the pore space.