Possibility to Use CO2 as EGS Fluid in Hungary

Abstract

It is well known that the thickness of the Earth’s crust in the Pannonian Basin is shallower than the continental average in Europe. The crust is sank and thinned due the subcrustal erosion, while the sank basin was filled by tertiary sediments. The thickness is about 23km only. The covering sedimentary layers have weak thermal conductivity, in average of 2W/mK. Therefore it can be found higher than 200oC temperature at the depth of 4000m. This fact could provide favorable natural conditions to create Enhanced Geothermal Systems. Another natural capability is that Hungary has natural gas reservoirs with high content of CO2 even more than 90%. The low critical pressure of the CO2 allows to use it as a heat carrying and working fluid in EGS systems. A super critical Rankine cycle can be implemented for electric power production. Flow and heat transfer in such a system are investigated supposing a Hele-Shaw flow in a single equivalent fracture and one-dimensional heat conduction in the surrounding rock. The thermal power of the system can be estimated.