Injection Triggered Occlusion of Flow Pathways in a Sedimentary Aquifer in Hungary

Abstract

Reasons for injectivity decline were investigated at a geothermal site located in SE Hungary. Due to low injectivities, production rates have to be reduced and the site faces negative commercial implications. In addition to historical operation data, fluid and rock samples were investigated in the laboratory. Analysis and experiments focus on physical, chemical and biological processes and their interaction. Results show different processes being responsible for injection-triggered occlusion of flow pathways. Fines migration is caused by washouts in loosely cemented rocks, from where fine sand or clay particles are transported and injected into lower aquifer layers. Precipitation of minerals is caused by cooling or oxygen exposure. Biological activity is seen at production and injection site. In order to fully understand the processes taking place in the injection well, borehole measurements will be run in summer 2019. After evaluating the results, a specially tailored stimulation concept will be applied in the injection well. A combined chemical-mechanical treatment takes place at different depth. Borehole measurements and hydraulic tests will be done again after the stimulation to show the effect of the stimulation. A multiple monitoring and sampling program came along with activities onsite. Activities are taking place in the frame of the DESTRESS project. The DESTRESS project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 691728.