| Abstract |
The Pannonian basin is a high temperature basin, which contains medium as well as low enthalpy geothermal regions. This document reviews the three main geothermal power plant opportunities in the Pannonian Basin. The first opportunity is the smallest in its scale including the establishment of micro power plants. Their capacity is below 1 MWe. The reservoir is in deeper zones of sediments with Lower Pannonian sandstone rocks. Their depth is maximum 2500 metres. In the Hungarian regulations the reservoirs with depths of less than 2500 metres are covered in the Water Management Act, and the Water Authority is the decision maker concerning the geothermal projects. The temperature range of these reservoirs is 80 – 110oC. The Lower Pannonian sediments are able to provide maximum 30 kg/s yield, therefore the total mass rate of a system is between 30 – 60 kg/s depending on the number of production wells. The capacity of the power plant can hardly achieve 1 MWe even if two production wells supply the surface system. These kinds of systems can be installed in a profitable way, only if new wells are not to be drilled, but they are already existing as abandoned hydrocarbon or operating thermal wells. If an operating direct heat utilization system has over 100oC well-head temperature, it is recommended to evaluate the opportunity to install a micro electricity generation block. Depending on the yield, a 105 – 75oC temperature step can be appropriate to supply a micro geothermal power plant. The presentation analyses this technological situation. The second opportunity is the establishment of small scale power plants with a capacity of 1 – 3 MWe. 2500 – 3500 metres deep fractured carbonate reservoirs can supply the power plant with heat energy. The temperature range at the well-head is 120 – 150oC and the temperature step in the block is 50 – 60oC. The flow rate is 50 – 100 kg/s, but unfortunately, at least two production wells are needed. A binary type power plant block is appropriate at this temperature rate. The third opportunity is the Enhanced Geothermal System. Two versions can be planned. The smaller version focuses on the enhancement of a fractured carbonate reservoir with reservoir stimulation. In this case the original 1 – 3 MWe can be increased to 2 – 5 MWe. In the “classical” case the reservoir is created in the crystalline basement under the Pannonian sediments by hydraulic fracturing. The depth of the fractured zone is at 3.5 – 5 km and the temperature at the production well head is 180 – 220oC. The achievable power plant capacity is 5 – 12 MWe depending on the number of production wells. Over 200oC the establishment of a flash type power plant block can be evaluated. The ambitious objective of the Hungarian National Renewable Energy Action Plan can be achieved if all the three main opportunity types are implemented. The presentation determines the most prospective regions of the Pannonian Basin, where the different types of geothermal power plants can be established. |