Original scientific paper

https://doi.org/10.4154/GC.2015.02

Modeling microfracture geometry to the asses the function of a karst system (Vízfő spring catchment area, Western Mecsek Mountains, Hungary)

Marton Bauer ; Department of Mineralogy, Geochemistry and Petrology, University of Szeged
Tivadar Tóth M. ; Department of Mineralogy, Geochemistry and Petrology, University of Szeged

Abstract

One of the current objectives of karst research is to understand the spatial dynamics of karstic processes that increase ordecrease pore volume. Although we can construct 3D numerical models, it is a complex, multi-step process. These modellingapproaches combine a dissolution algorithm, a flow and/or transport model and an algorithm to reconstruct thespatial geometry of fracture networks. The paper focuses on the last task, and does not consider the first two problems. We applied the RepSim code, a DFN (discrete fracture network) type fracture geometry modelling software that usesfractal behavior of fracture patterns, for simulations. This method simulates fracture systems at a reservoir scale. The input parameters (length distribution, aperture, orientation and fractal dimension of the fracture midpoints) weredetermined using field measurements and evaluation of digitized images. The primary images were of outcrops fromthe surface and from two caves. The examined area is the karstic block of the Mecsek Mountains in SW Hungary, which is one of the most exploredkarstic regions in that country. There are seven small and one relatively large (Vízfő) catchment areas in the mountains. The large catchment was used as the study area, which lithologically consists of sandstones and limestones,both intensely fractured by subsequent tectonic events. The spatial distribution of cave entrances and dolinas is unevenacross the study area. This phenomenon has not yet been investigated. Here, a relationship is inferred between the original (prekarstic) microfracture network geometry and the spatial distributionof the aforementioned karst forms. The results show that the region can be divided into two zones that fracturedin distinctly different ways. Their fracture network communication features, porosity and permeability differ.Additionally, sub-regions could develop inside the catchment area where dissolution-cementation processes couldhave been differently effective, determining the spatial distribution of the dissolution governed karstic forms (e.g.caves, dolinas).

Keywords

fracture geometry; 3D modelling; Vízfő spring; Western Mecsek Mts.; Hungary

Hrčak ID:

141048

URI

https://hrcak.srce.hr/141048

Publication date:

27.2.2015.

Visits: 1.586 *