| Abstract |
Natural conditions in Hungary are very favorable for geothermal energy production and utilization. The anomalously high terrestrial heat flow (~0.09 W/m2), the high geothermal gradient (~0.05 oC/m), and the vast expanses of deep aquifers form an important geothermal resource. The Pannonian Basin is encircled by the Carpathian Mountains. The Earth’s crust here is relatively thin (~25 km) due to sub-crustal erosion. There are two types of geothermal reservoir in Hungary. One type of geothermal reservoir can be found in the carbonate rocks from the Triassic age, characterized by secondary porosity. These can be fractured or karstified rock masses with continuous recharge and significant convection. About 20% of the Hungarian geothermal wells produce from such carbonate rock formations, mainly in the western part of the country. (Toth, A., 2010). The other type of geothermal reservoir is the Pannonian sedimentary reservoir, which is multilayered, composed of sand and shale. Lower Pannonian sediments are mostly impermeable; the upper Pannonian and Quaternary formations contain vast, porous, permeable sand and sandstone beds. The latter forms the upper Pannonian aquifer, which is the most important thermal water resource in Hungary. About 80% of Hungarian geothermal wells produce from sedimentary reservoirs. In 2004 a geothermal well was drilled in the Orosháza-Gyopárosfürdõ region in the southeast part of Hungary. The depth of the production wells was 1560 m. The flow rate was 15-30 m3/h and produced 90 oC water. In 2010 and 2011 two injection wells were drilled into the same reservoir. The injected water temperature was about 45-50 oC. Our study aims to examine this geothermal system. Based on what happened in this operating geothermal system, we analyzed the interaction of the region’s natural geothermal environment with other wells which have modified flow systems. The flow between and around the three wells was investigated using a hydrodynamic model. Scenario models are based on Visual Modflow programs, and show how the system would be affected if operated without reinjection, thus demonstrating injection's importance. |