Original scientific paper

https://doi.org/10.4154/gc.2024.11

Hydrogeological parameterisation of the Daruvar thermal aquifer: integration of fracture network analysis and well testing

Ivan Kosović ; Croatian Geological Survey, Zagreb, Croatia
Bojan Matoš ; University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering, Zagreb, Croatia
Stefano Casiraghi ; Università degli Studi di Milano Bicocca, Dipartimento di Scienze dell'Ambiente e della Terra, Milan, Italy
Gabriele Benedetti ; Università degli Studi di Milano Bicocca, Dipartimento di Scienze dell'Ambiente e della Terra, Milan, Italy
Tihomir Frangen ; Croatian Geological Survey, Zagreb, Croatia
Kosta Urumović ; Croatian Geological Survey, Zagreb, Croatia
Ivica Pavičić ; University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering, Zagreb, Croatia
Andrea Bistacchi ; Università degli Studi di Milano Bicocca, Dipartimento di Scienze dell'Ambiente e della Terra, Milan, Italy
Silvia Mittempergher ; Università degli Studi di Milano Bicocca, Dipartimento di Scienze dell'Ambiente e della Terra, Milan, Italy
Marco Pola ; Croatian Geological Survey, Zagreb, Croatia
Staša Borović ; Croatian Geological Survey, Zagreb, Croatia

Abstract

Highly fractured Mesozoic carbonate rocks are the main reservoir of many geothermal resources in northern Croatia, being of environmental, cultural, and economic value for the local and regional communities. The Daruvar thermal springs (temperatures < 50°C) represent the outflow area of an intermediate scale, tectonically controlled, hydrothermal system hosted in Triassic carbonate rocks. Several investigations have been conducted in the Daruvar area detailing the architecture of regional and local fracture networks and quantifying the hydrogeological parameters of the thermal aquifer. In this work, an integrated approach based on structural and hydrogeological investigations was employed to model the network of fractures in the reservoir and quantify its impact on the hydraulic properties. Structural investigations were conducted in the Batinjska Rijeka quarry, considered as an outcrop analogue of the thermal aquifer, employing both a classical field approach and the virtual quantitative analysis of a 3D digital outcrop model. Structural analysis of the digital outcrop model allowed identification of two sub-vertical systems of discontinuities, dipping to the NW and the WSW respectively, in accordance with the data collected through direct field measurements. The main geometric features of the discontinuity network and their statistical distributions were employed to construct discrete fracture network models at both the outcrop scale (approximately 100 m) and the aquifer scale in Daruvar (approximately 700 m). Calibration of the input parameters allowed modelling of porosity and permeability values that reproduce the field values assessed through pumping tests, well tests, and well logging. This work highlights the importance of integrating geological and hydrogeological investigations to obtain a more reliable reconstruction and quantification of the processes driving the fluid flow in fractured aquifers and affecting the spatial distribution of their hydraulic properties.

Keywords

fracture network; carbonate aquifer; digital outcrop model; discrete fracture network modelling; northern Croatia

Hrčak ID:

318263

URI

https://hrcak.srce.hr/318263

Publication date:

21.6.2024.

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