NUMERICAL MODEL OF THE GEOTHERMAL WELL LOCATED AT THE UNIVERSITY OF ORADEA CAMPUS

The well from the University of Oradea campus is a typical low enthalpy geothermal well, about 3,000 m deep, 80÷85°C wellhead temperature, and multiple feed zones. A 3-D numerical model has been defined and used to simulate the heat transfer and the hydrothermodynamic processes in the well and in the surrounding rock along the entire well. The paper presents the model’s grid, the thermal and hydrodynamic properties of each block, the natural state simulation, the static and dynamic calibrations, and some preliminary results for artesian discharge. THE ORADEA GEOTHERMAL RESERVOIR Romania is located in Central Europe, North to the Balkan Peninsula, on the lower course of the Danube river, and on the Black See coast. The geological research carried out between 1960 and 1980 proved the existence of significant geothermal resources in some regions, mainly in the western part of the country. Over 200 drilled wells show the presence of geothermal resources. The proved reserves (with the already drilled wells exploited by downhole pumps) are about 200,000 TJ for 20 years. The total installed capacity of the existing wells for energy uses is 320 MW t (for a 30°C reference temperature). The main uses of geothermal energy are: space heating and domestic hot water, greenhouse heating, health and recreational bathing, industrial process heat, and fish farming. The City of Oradea is located in the Western part of Romania, close to the Hungarian border, has a population of about 250.000 people, and is the capital city of the Bihor County. The Oradea geothermal reservoir comprises two specific aquifers, hydrodynamically connected via fractures, the Triassic aquifer Oradea and the Cretaceous aquifer Felix Spa respectively. Although a significant natural recharge exists, the exploitation with a total flowrate of 300 l/s generates pressure drawdown in the system, that is prevented by reinjection. The total installed capacity is over 30 MWt. The Felix Spa reservoir is currently exploited by 6 wells, 50÷ 450 m deep. The total flowrate available from these wells is 210 l/s. The geothermal water has wellhead temperatures of 36 ÷48°C and is only used for recreational and health bathing. The Oradea aquifer is located in Triassic limestone and dolomites, at depths of 2,200 ÷3,400 m, on an area of about 113 km, and is exploited by 12 wells, with a total artesian flowrate of 140 l/s and wellhead temperatures of 70÷105°C. The water is of calcium-sulfatebicarbonate type, with no scaling or corrosion potential. There are no dissolved gases, and the mineralisation is lower than 0.9÷1.2 g/l. The reservoir is bounded by faults. There are also internal faults in the reservoir, dividing it into four blocks which do not cause discontinuities in the circulation of the water in the reservoir. The main circulation is from the northeastern part of the reservoir, along preferential pathways represented by the fault system at the boundary (Figure 1). The terrestrial heat flow is about 90 mW/m , and the geothermal gradient 2.6÷4.1 °C/100m. Properties such as ionic composition, high radioactivity and the content of rare gases, indicate an active circulation along paths partially in contact with the crystalline basement. The water is about 20,000 years old, the recharge area being in the Western Carpathian Mountains 20÷30 km East of