Determining the „geothermal reinjection potential” into sedimentary formations using datasets of hydrocarbon exploration

The so-called Green Transition EU strategy encourages oil businesses to move towards a circular economy and create green energy. The data already collected in the past during hydrocarbon exploration offer enormous possibilities for geothermal reutilization. Revealing this led to the joint project with MOL Plc. to evaluate the geothermal potential for Zala county, Hungary. Although the preliminary geothermal potential of the Zala region (SW Hungary) is assessed to be good, sustainable thermal water use is critical due to the need for reinjection, with only one operating doublet. The study focuses on the geothermal assessment of the siliciclastic Neogene formations.

Due to the need for reinjection wells for sustainable thermal water production, the evaluation has to handle the potential injectivity for the same siliciclastic reservoir. However, several injection-related problems are associated with the Neogene (so-called Pannonian) siliciclastic reservoirs in Hungary. Predicting the issues makes it possible to mitigate them, and it contributes to a “reinjection potential” assessment which can be part of the geothermal potential estimation.

Based on methodological contribution from previous studies (e.g., Markó et al., 2021), this research considers a variety of problem scales, including regional hydraulics, reservoir scale properties, and local clogging processes. As a next step, in the recent study, we investigate the extension of the reservoir sandstone bodies of the deltaic aquifer. This is done by interpreting 3D seismic volumes by amplitude extraction to detect sand-prone volumes combined with well-logs to delineate the reservoir. The analysis helps to predict where to drill the next reinjection well as well as to evaluate the potential of the existing hydrocarbon wells.

The first author was supported, and the research was financed through the KDP-2021 Cooperative Doctoral Programme of the Ministry of Innovation and Technology (Hungary) from the source of the National Research, Development and Innovation Fund, grant number: KDP_2021_ELTE_C1789026. The study was funded by the National Multidisciplinary Laboratory for Climate Change, RRF-2.3.1-21- 2022-00014 project.