| Abstract |
In the Pannonian Basin, the Earth?s crust is much shallower than the European average depth. This is largely a result of subcrustal erosion. The Pannonian basin, which over time sank and was filled with tertiary sediments, has an average thickness of only about 23km. The sedimentary layers which cover it have weak thermal conductivity, on the average only 2W/mK or so. It is therefore possible to encounter temperatures exceeding 200oC temperature at a depth of 4000m. This fact is the basis for optimism regarding the prospect of using Enhanced Geothermal Systems to exploit Hungary?s favorable natural conditions. Earlier this year (2014) the European Commission announced that a geothermal power plant near Ferencszállás, in south-eastern Hungary, would use geothermal energy from hot dry rock located in a compressional stress field. This Enhanced Geothermal System requires that four 4km.-deep production wells and two re-injection wells be drilled, and also pre-supposes the hydraulic fracturing of the reservoir beneath those compressional stress fields. Hungary?s natural gas reservoirs often have a high CO2, sometimes exceeding 90%. The low critical pressure of CO2 allows us to use it as a heat-bearing and working fluid in EGS systems. Using this CO2, we can also implement a super-critical Rankine cycle so as to produce electric power. The analysis of flow and heat transfer in such a system pre-supposed a Hele-Shaw flow in a single equivalent fracture and one-dimensional heat conduction in the surrounding rock. This allows us to estimate the system?s thermal power. |