This study describes the geothermal system in Mezőberény (Hungary) and on-site activities done within the DESTRESS project. The major challenge at the site was a poor injectivity, observed after a certain time of operation of the geothermal system. First, an evaluation of all available data of the site and the wells in the vicinity of the location has been conducted. After that, a well-logging and stimulation program was designed. The logging aimed to study a possible filling of the well with e.g. sands from the reservoir, corrosion or precipitation products, which would reduce the injectivity. A cleaning and circulation of fluids in the well was done to test the well integrity performance. The first operational phase was complemented by a thermal stimulation using cold water injection. In the second phase, we performed a chemical soft stimulation using a coiled tubing unit to inject the chemicals as close as possible to the target horizons. Lift tests before and after the injection of the chemicals and a final injection test were conducted to compare the results with the findings of the first operational phase. Results of this study are 1) Insights into chemical, physical, and biological processes as possible injection problems based on given and new data; 2) A summary of the estimation of well integrity based on the operational experiences, tests, and logging data; and 3) An evaluation of the hydraulic properties of the system based on all test data. General conclusions are given on further development of the site.