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A: Separation of samples on the basis of the relationship between the ratio of Cl -to Cl -+alkalinity and conductivity. Cl-and HCO3-type waters are distinguished; B: Grouping of the HCO3 -type samples based on HBO2 and Br -concentrations Clusters are high and low boron content. (modified from Varsányi & Ó.Kovács (2009), red: production well sample, blue: injection well sample)
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Fluid injection into overpressured regimes is only possible with an injection pressure higher than the aquifer pressure. The elevated aquifer pressure eventually prevents fluid inflow through reinjection. Elevated pressure (much higher than hydrostatic) in an aquifer under exploitation, however, can also evolve naturally due to overpressure dissipa...
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Citations
... We analysed the hydraulic conditions of the aquifer on a regional (~10 km) scale through characterizing the pressure regime. A more extensive study in this framework was done by Markó et al. (2021b). ...
... Consequently, unlike several regions of the Pannonian Basin (investigated and presented by e.g., Tóth & Almási, (2001) (2016)) unfavourable hydraulic conditions with elevated pressure or ascending flow could not be observed in our study area. The reason for that is most likely the thick and continuous underlying regional aquitard (Algyő Formation and Szolnok Formation to some extent) that blocks the local overpressure dissipation from beneath (Markó et al., 2021b). Therefore, a drawback in injection caused by hydraulics is not expected at the study site, the slightly subhydrostatic regime provides beneficial conditions for reinjection from a hydraulic perspective. ...
This study proposes a concept and presents a workflow to examine potential reasons for low injectivity of sandstone aquifers. Injection related problems are a major challenge for the sustainable utilization of geothermal waters. In order to completely understand and avoid the geothermal reinjection problems, potential problem sources acting on different scales should be taken into consideration. Thus, in the workflow, possible problem sources are considered on regional, reservoir and local scale and categorized into 1) effect of regional hydraulics (potential presence of overpressure and upward flow) 2) inadequate reservoir performance (limited extent, low permeability and performance) and 3) local clogging processes (particle migration, mineral precipitation, microbial activity). Hydraulic conditions are characterized by defining the pressure regime and the direction of vertical driving forces. The reservoir properties are given by determining the grain size and the size of the reservoir layers, as well as the permeability and the transmissivity of the reservoir and the capacity of the injector. Physical, chemical, and biological clogging processes are investigated by specifying the rock properties and determining particle content of the fluid; by analysing the type, probability and amount of the scaling and estimating the potential for corrosion; and by evaluating the possibility of biofilm formation. The concept and the workflow were first tested on a geothermal site (Mezőberény, SE Hungary, installed in 2012) that had to stop operation because of unsuccessful reinjection. The low injectivity of the well is a consequence of several separate problems and their interaction: Reservoir properties are insufficient due to low permeability and transmissivity of the reservoir and the limited vertical and horizontal extension of the sandstone bodies. Precipitation of car-bonates, iron and manganese minerals is predicted in hydrogeochemical models and observed in solid phase analysis. Microbial material is produced from the particularly high organic content of the produced thermal water. Injection problems due to hydraulic effects are not expected since the regional pressure regime is slightly subhydrostatic. In summary, reservoir properties determine a low injectivity, which is further decreased to a critical level by the clogging processes. The proposed generalized concept guides a detailed reservoir and geothermal system analysis which is essential for a sustainable geothermal operation.
The so-called, Green Transition EU strategy motivates
oil companies to turn towards a circular economy and
the production of green energy. The existing dataset
gained through hydrocarbon exploration and the
infrastructure of abandoned or barren hydrocarbon
wells provides huge potential for geothermal
reutilization. The geothermal potential of the Zala
region (SW Hungary) is assessed to be good, however,
there are only a few sites with ongoing reinjection,
which is urgently needed for the sustainability of the
systems.
However, Neogene (so-called Pannonian) siliciclastic
reservoirs in Hungary are the source of various
injection-related issues. By predicting the problems,
their mitigation becomes possible At the same time the
evaluation contributes to a geothermal potential
estimation as well. In this research, various scales of
problem sources are considered ranging from regional
hydraulics, reservoir scale properties and local clogging
processes based on methodological results of previous
studies (e.g., Markó et al., 2021a) to assess the
reinjection potential of abandoned hydrocarbon wells
in the region. As a first step, we evaluated the regional
hydraulic conditions including pressure analysis as well
as the reservoir extension on a regional scale.
Hydraulic analysis revealed quasi-hydrostatic
conditions in the Pannonian siliciclastic deposits,
dominated by the topography driven driving forces. In
the deeper regions, few overpressured data points can
be found in the Triassic rocks. Significant upward flow
was not detected. Accordingly, unlike certain
overpressured regions of the Pannonian basin, the
hydrostatic conditions are favourable for low-pressure
injection in the Zala region.
The reservoir conditions are tended to be favourable in
the southern and western part of the study area: in these
regions the porous reservoir formation is settled deeper
and has significant thickness (400-600 m) which
foresees sufficient vertical and horizontal extension of
the deltaic sandstone bodies.
This review paper briefly summarizes the research results of the majority (∼70%) women team of the Hydrogeology Research Group of Eötvös Loránd University, Hungary, led by Judit Mádl-Szőnyi. The group had originally focused on basin-scale groundwater flow systems and the related processes and phenomena but extended its research activity to other geofluids in answer to global challenges such as the water crisis, climate change, and energy transition. However, the core concept of these studies remained the basin-scale system approach of groundwater flow, as these flow systems interact with the rock framework and all other geofluids resulting in a systematic distribution of the related environmental and geological processes and phenomena. The presented methodological developments and mostly general results have been and can be utilized in the future in any sedimentary basins. These cover the following fields of hydrogeology and geofluid research: carbonate and karst hydrogeology, asymmetric basin and flow pattern, geothermal and petroleum hydrogeology, radioactivity of groundwater, groundwater and surface water interaction, groundwater-dependent ecosystems, effects of climate change on groundwater flow systems, managed aquifer recharge.
