Operational tests at the Mezőberény geothermal site successfully completed
As previously reported, a European team of scientists is analysing key drivers and searching for solutions to improve the geothermal heating plant's performance in Mezőberény, Hungary. The onsite operations have just been successfully completed and the obtained results are being evaluated in detail at the German Research Centre in Potsdam and the Technical University in Delft, the Netherlands.
The heating plant in Mezőberény comprises a production well and an injection well whereby formation water is circulated among the wells and the natural underground reservoir cyclically, closing the reinjection loop of the doublet system. Despite the local effort of conducting the heating plant effective functioning, several handicaps have been observed along the operational process of reinjecting formation water into the natural underground reservoir. Aware of the observed operational constraints, the scientists, in collaboration with Hungarian companies, performed well integrity and injection tests on-site to analyse and evaluate the actual well conditions and propose further technological applications that could lead to carry on the heating plant.
A workover rig was located on site in late January 2021 to perform well logging measurements and well integrity tests. The operations campaign started measuring the well's inner sizes to validate its free passageway for upcoming downhole tools. Once the well gauges sizes were verified, then it was cleaned and circulated with bottom hole assemblies and environmentally friendly fluids. After conditioning the well logging downhole measurements, hydraulic test was performed to collect information of well integrity and injection parameters through the well screen sections.
The results from well logging data show that the wellbore is accessible to the bottom true vertical depth, near 2 km, which is an essential downhole feature for further operations. The logging data delivered up to date also displays no signs of aggressive corrosion damage in the downhole piping system called casing. The temperature and neutron logging data suggest that the filters or screens in the deeper well section located at the reservoir's face can work as pathways or channels for fluids injection. Complementary to well logging measurements, a set of hydraulic tests were conducted to verify the saleability of the casing-cement interface. The positive results point to the premise that no damaged interface prevails in the well. After testing the well conditions hydraulically and evaluating the equipment's reliability, a cold brine injection test was performed to evaluate the reservoir admission and temperature cooling reaction over time. The well logging and hydraulic testing operations were successful in terms of confirming the well integrity, unplugged screens pathways and formation admission parameters. The premier evaluation of the combined injection tests corroborates low formation injectivity values which adduce that upcoming stimulations procedures will be advisable to improve the reservoir injectivity performance.
The downhole measurements have generated large amounts of data and new information which are now being analysed. The analysis and results will be decisive contributions for supplementary stimulation action plans.