 |
| Titel |
Dissolution and precipitation of fractures in soluble rock |
| VerfasserIn |
Georg Kaufmann, Franci Gabrovšek, Douchko Romanov |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250125984
|
| Publikation (Nr.) |
 EGU/EGU2016-5651.pdf |
|
|
|
|
|
| Zusammenfassung |
| Soluble rocks such as limestone, anhydrite, and gypsum are characterised by their large
secondary permeability, which results from the interaction of water circulating through the
rock and dissolving the soluble fracture walls. This highly selective dissolution process
enlarges the fractures to voids and eventually cavities, which then carry the majority of flow
through an aquifer along preferential flow pathes.
We employ a numerical model describing the evolution of secondary porosity in a soluble
rock to discuss the evolution of single fractures in different rock types. Our main focus is
three-fold: The distinction of shallow versus deep flow pathes and their evolution on the one
hand; the effect of precipitation of the dissolved material in the fracture, and finally the
complication of fracture enlargement in fractures composed of several different soluble
materials.
We observe a similar evolution of void space for fractures composed of limestone and
gypsum, but on different time scales. For anhydrite, owing to its difference in the kinetical
rate law describing the removal of soluble rock, when compared to limestone and anhydrite,
the evolution is even faster.
Precipitation of the dissolved rock due to changes in the hydrochemical conditions can
clog fractures fairly fast, thus changing the pattern of preferential pathways in the soluble
aquifer, especially with depth.
Finally, limestone fractures coated with gypsum, as frequently observed in caves, will
result in a substantial acceleration of fracture enlargement with time, thus giving these
fractures a hydraulical advantage over pure limestone fractures in their competition for
capturing flow. |
|
|
|
|
|
|