Demonstration of a successful soft chemical stimulation in a geothermal sandstone reservoir in Mezőberény (Hungary)

Geothermal energy projects often lack sufficient permeability for a sustainable operation. If natural permeability is low, it can be enhanced by stimulation treatments. These can be of thermal, hydraulic or chemical nature. The challenge is to stimulate the reservoir successfully and at the same time to do it in an environmentally safe way. This is called soft stimulation and was extensively tested in the context of the EU-Horizon2020 DESTRESS project at several geothermal sites worldwide. This paper describes the successful thermal and chemical stimulation of a geothermal doublet in Mezőberény (Hungary), targeting a sandstone reservoir at 2000 m depth. A geothermal system was constructed in 2011–2012 aimed at exploiting the geothermal potential in the Békés Basin for a district heating system. The system with one production well and one reinjection well faced a severe injectivity drop during a 3-week operational period at the end of 2012, so that the operation had to be stopped. Historical data analysis, well logging, sampling and eventually a tailored stimulation program was designed in a ‘soft’ manner, according to standards developed in the DESTRESS project. The stimulation successfully increased the injectivity by 4 – 10 times, so that the system is ready to go into operation again.