Experimental Rock Characterisation of Upper Pannonian Sandstones from Szentes Geothermal Field, Hungary

Experimental Rock Characterisation of Upper Pannonian Sandstones from Szentes Geothermal Field, Hungary

The Upper Pannonian (UP) sandstone formation has been utilised for thermal water production in Hungary for several decades. Although sustainable utilisation requires the reinjection of cooled geothermal brine into the host rock, only a fraction of the used water is reinjected in the country. UP sand...

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Bibliographic Details
Published in:Energies (Basel) Vol. 15; no. 23; p. 9136
Main Authors: Koroncz, Péter, Vizhányó, Zsanett, Farkas, Márton Pál, Kuncz, Máté, Ács, Péter, Kocsis, Gábor, Mucsi, Péter, Fedorné Szász, Anita, Fedor, Ferenc, Kovács, János
Format: Journal Article
Language:English
Published: Basel MDPI AG 01-12-2022
Subjects:
Analysis
Aquifers
Critical flow
Environmental aspects
Experiments
Flow velocity
Grain size distribution
Hydraulics
Laboratories
Mechanical properties
Pannonian basin
Permeability
Porosity
R&D
Reinjection
Research & development
Rock mechanics
Rocks
Sandstone
SEM analysis
Simulation
Size distribution
Thermal water
thin-section analysis
Velocity
Water damage
XRD analysis
Hungary
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Summary:The Upper Pannonian (UP) sandstone formation has been utilised for thermal water production in Hungary for several decades. Although sustainable utilisation requires the reinjection of cooled geothermal brine into the host rock, only a fraction of the used water is reinjected in the country. UP sandstone formation is reported to exhibit low injectivity, making reinjection challenging, and its petrophysical properties are poorly known, which increases uncertainty in designing operational parameters. The goal of the study is to provide experimental data and to gain a better understanding of formation characteristics that control injectivity and productivity issues in Upper Pannonian sandstone layers. Petrographical characterisation and petrophysical laboratory experiments are conducted on cores retrieved from two wells drilled in the framework of an R&D project at the depth of between 1750 m and 2000 m. The experiments, such as grain density, porosity, permeability, and ultrasonic velocity, as well as thin section, grain size distribution, XRD, and SEM analyses, are used to determine Petrophysical Rock Types (PRT) that share distinct hydraulic (flow zone indicator, FZI) and petrophysical characteristics. These are used to identify well intervals with lower potential for injectivity issues. The results imply that fines migration due to formation erosion is one of the key processes that must be better understood and controlled in order to mitigate injectivity issues at the study area. Future investigation should include numerical and experimental characterisation of formation damage, including water–rock interaction tests, critical flow velocity measurements, and fines migration analysis under reservoir conditions.
ISSN:1996-1073
1996-1073
DOI:10.3390/en15239136