Evolution of Balçova Geothermal District Heating System Turkey

Transcription

1 GRC Transactions, Vol. 39, 2015 Evolution of Balçova Geothermal District Heating System Turkey Mahmut Parlaktuna Middle East Technical University, Department of Petroleum and Natural Gas Engineering, Ankara, Turkey Keywords Balçova geothermal, district heating, Agamemnon Fault Abstract Balçova geothermal field is located in a densely populated area which makes direct heat applications very efficient and economical. Heat produced from Balçova geothermal field is utilized for three main purposes: greenhouse heating, balneology and residential heating. Among these three applications, the latter one is the main application throughout the Balçova Geothermal District Heating System (BGDHS). The field produces hot water from two different horizons: one shallow and one deeper zone. This paper presents the encountered problems and their solution strategies while expanding the system to the current state of 35,000 residence equivalent capacity (1residence equivalent = 100 m 2 heated area). 1. Introduction Balçova geothermal field is situated 11 km southwest of city of İzmir in western Anatolia (38.2º latitude, 27.0º longitude) (Figure 1). It is located along the E W trending Izmir Fault Zone. The most important tectonic feature in the region is the E W oriented Agamemnon-I Fault, which extends over 30 km. (Yılmazer, 1989; Öngür, 2001). Other than this main fault, series of E W and S N oriented faults and fractures can be observed in the region but the NE SW oriented Agamemnon-II Fault is the most pronounced one (Figure 2). The hot waters recharging in the Balçova region circulate through the major, about 2 km long, fracture zone associated with the Agamemnon-I Fault. Faults and fractures within the Izmir Flysch formation provide a hydrothermal system to Balçova region. The meteoric precipitations in recharge area infiltrate through faults, fractures into deeper parts of the region (deeper than 2000 m), are heated by an undefined heat source, and rise along the Agamemnon Fault (Figure 3). From this zone, the thermal water flows mainly into two permeable horizons: one in the alluvium located in the upper 100 m of the system, and the other more permeable layers of the Izmir Flysch formation between 300 and 1100 m depth (Satman et al., 2001). Figure 1. Location map of Balçova Geothermal Field. 145

2 There are more than 40 wells drilled in Balçova geothermal field. Some of those wells are gradient wells aiming to get information on geology as well as geothermal gradient of the region and indicated by G. The wells indicated by B or BG are shallow wells while the wells with BD are deep wells (Figure 4). The depths of shallow wells are in the range of m while the deep wells have an average depth of 700 m. As of today, twelve wellbores are utilized as producers and three wellbores (BD-3, BD-8 and BT-1) are continuously used for re-injection purposes (Table 1).Two wellbores listed in Table 1 (BD-10 and BD-15) are mainly used for re-injection but they were also used as producers, especially during summer time to supply the demand from swimming pools and balneology. On the other hand, other re-injection wells given as red characters in Table 1 are seldom used as re-injectors during peak times. As indicated in Table 1, the maximum capacity of the production wells is over 2300 m 3 /h, which was not tested yet. The producing temperatures of the wells are in the range of 97 to 140 C. 2. Utilization of the Field Balçova geothermal field is located in a densely populated area (Figure 4) which makes direct heat applications very efficient and economical. Produced heat from Balçova geothermal field is utilized for three main purposes: greenhouse heating, balneology and residential heating. Among these three applications, the latter one is the main application Talus Aluvium Flysch Basement Heat source F lt Agamemnon-III Fault Agamemnon-II Fault Agamemnon-I Fault Figure 2. Location map of Agamemnon I and Agamemnon II faults (after Yılmazer, 1989). Figure 3. Hydrogeological model of Balçova geothermal field (modified after Aksoy, 2001). Table 1. List of active wells. 1. Meteoric precipitations infiltrate through faults, joints and fractures. 2. Water is heated by an undefined heat source. 3. Hot water ascends due to buoyancy difference between hot and cold water and due to the pressure gradient. 4. Hot water changes flow laterally through two main zones. 146

3 Parlaktuna Figure 4. Well locations of Balçova geothermal field. throughout the Balçova Geothermal District Heating System (BGDHS). There are three main flow loops within BGDHS system (Figure 5): Geothermal water loop in which produced geothermal fluid at an average temperature of 120 C is sent to Heating Centers to exchange the heat energy of it to the closed loop of city water with the help of heat exchangers. Geothermal fluid after heating centers is re-injected into ground at an average temperature of 60 C. City water loop: In this loop, the city water is circulated in a distribution network between the heating centers and residences. The city water is heated to a temperature of 90 C at the Heating Centers and headed to residences in which each residence has its own heat exchanger to heat its radiator water. Residences loop: This is the loop within a single residence through which the heat energy of city water is transferred to the radiator system. There are eight heating centers within the system to cover the residential area of Balçova - Narlıdere districts. Each heating center serves the residences to their close vicinity. Heating Centers do not serve with their full installed capacities since some of the residences do not subscribe for the BGDHS. As seen in Figure 6, both heated area and peak flow rate increase with time and an area of 3.5 million m2 is being heated by In addition to heating centers, BGDHS has two pumping stations and more than 350 km pipeline network. Individual houses, governmental institutes and private firms such as Dokuz Eylül University Hospital, University Dormitories, Izmir Economy University Campus, one shopping center and hotel are the subscribers of BGDHS. As other applications Balçova geothermal field supplies geothermal water to two health centers-hotel for balneological purposes, namely Balçova Thermal Figure 5. Schematic plan of Balçova Geothermal District Heating System. Hotel and Kaya Hotel. 147

4 3. Development of the Utilization The General Directorate of Mineral Research and Exploration of Turkey (MTA) did the first geothermal drilling studies in the region in Resistivity, thermal probing, and selfpotential surveys were conducted. Three wells were drilled including the first geothermal exploratory well in Turkey. First well (S-1) resulted with a mixture of hot water and steam at 124 ºC at a depth of 40 m. S-2 and S-3/A were drilled to 100 m and 140 m, with downhole temperatures of 102 C, and 101 C, respectively. S-3/A did not flow. From 1981 to 1983, 16 wells (7 gradient and 9 production wells) ( m), were drilled. They encountered temperatures of 50 ºC to 126 ºC with flow rates of 4 20 kg/s. In 1982, system of geothermally heated hotels, curing center, swimming pools, and hot water began operation. Nine wells produced 4,500,000 kcal/h (~18,828 MJ/h) for surrounding hotels, buildings, and greenhouses. A district heating system with a total capacity of 2.2 MW t began operation in 1983 for heating offices, hospital, and dormitories of Dokuz Eylül University (~30,000 m²). Heating for Turkey s largest indoor swimming pool, which has a capacity of 1,600,000 kcal/h (~6,694 MJ/h), began operation in February In 1989, two new wells (B-10 and B-11) were drilled to 125 m that encountered fluids with temperatures of 109 and 114 C and flow rates of 5 and 3 kg/s, respectively. Geothermal heating of an 11,000 m² curing center became operational with a capacity of 1,200,000 kcal/h (~5,020 MJ/h) on September in Heating system for an additional 110,000 m² (1100 Residence equivalent (RE), 1 RE = 100 m 2 heated area) plus hot water for the Hospital of Faculty of Medicine at Dokuz Eylül University was installed on February in An additional system with capacity of 6,900,000 kcal/h (~28,869 MJ/h) (8.0 MW t ) began running on November in The most important stage was realized by starting the operation of the BGDHS in There are some milestones on the management of BGDHS. It was managed by a private geothermal company in the period of until the establishment of Balçova Geothermal Inc. In 2005, the status of company as well as its name was changed. Its name became Izmir Geothermal Inc. and Izmir Governorship and Municipality of Izmir became the founders of the company with 50% share. Since then the company is run by professional employees but reports to the Directors of Board formed by the representatives from the shareholders. Balçova geothermal reservoir is a water dominated hydrothermal reservoir, which is prone to relatively high pressure drop to fluid production. The main precaution for the decline in pressure within geothermal reservoirs is the re-injection of produced fluid. At the early years of operation (October 2000 February 2002) re-injection into a shallow well (B-9) was tried but resulted with rapid decline in fluid temperatures (10 15 C) nearby shallow wells (Figure 7) (Aksoy et al., 2008). In order to find a permanent solution to the re-injection Figure 6. Increasing trend of heated area and peak flow rate by time. Re-injection from shallow wellbore B-9 and temperature decline in neighboring shallow wellbores Figure 7. Re-injection trials from B-9 (Aksoy et al., 2008). 148

5 practice of the field, a deep well, BD-8, was drilled at the eastern part of the field in 2002, which turned out to be a very powerful wellbore for re-injection (>700 m 3 /h). Although the re-injection capacity of the field increased after the drilling of BD-8, addition of the produced geothermal fluid into city loop due to the leaks from the network decreased the amount of hot water available from the re-injection, and the ratio of re-injection to production continued to decrease within the period of (Figure 8). This observation was interpreted as continuous pressure decline within reservoir (Figure 9). Decline in the water level at the observation well ND-1 resulted in an interpretation that the total water level decline was more than 80 m for the heating season in It is fortunate that remediation of pipeline network after 2005 (Figure 10) decreased the production rate for the same heating capacity since there was no need to add geothermal water into city loop, which was actually a permanent loss (Figure 11). This was caused by an increase in re-injection / production ratio (Figure 12) and an obvious recovery of reservoir pressure (Figure 13). The decreasing trend of water level of ND-1 during changed its direction to a recovery after 2006 because of the increase in re-injection/production ratio. Every subscriber of the BG- DHS needs to pay for the service that they obtain. The very first practice for this payment in BGDHS is known as Area Based Payment. The subscriber pays a fixed price per month depending on the area to be heated. This practice do not take into account any energy efficiency or energy saving. Since the payment is not dependent on the amount of energy used, in general the users heat their houses to relatively higher temperatures, which results with an inefficient use of energy. This observation forced the Izmir Geothermal to take an action and by 2006, all new subscriptions are made as Energy Based Payment by using calorimeters. Those subscribers had to pay the price of the energy they Figure 8. Production re-injection rates during Figure 9. Forecast for reservoir pressure decline. Figure 10. Renewal of pipeline network. 149

6 were supplied who started to pay attention on energy efficiency measures such as insulation applications, thermostatic radiator valves, turning off radiators in unused space or lowering the comfort temperature in the leaving area. All these measures resulted with decrease in energy use for the same area. Average energy consumption was 14,150,000 kcal/re/year (~59,204 MJ/RE/ year) and 7,560,000 kcal/re/year (~31,631 MJ/RE/year) for area-based and energybased subscribers, respectively in As indicated area-based subscribers consume about twice energy compared to the energybased subscribers. Another consequence of the change in pricing is the decrease in annual payment by users. Energy efficiency law of Turkey became compulsory since May 2012; therefore all area-based users of BGDHS were converted to energy-based. Figure 11. Hourly water loss from pipeline network. Conclusion Balçova geothermal field is a successful example of a direct heating application of geothermal energy with integrated use of its energy for space heating (residential and greenhouse) and balneological use. It is obvious from the development practice of BGHS that the system should be closely monitored and necessary precautions need to be made to maximize the utilization of the energy. References Aksoy, N.: Monitoring Balcova-Narlidere geothermal system with tracers. PhD thesis, Dokuz Eylul University Graduate School, Izmir, Turkey, (2001) (in Turkish). Aksoy, N., Serpen, U. & Filiz, S.: Management of the Balcova Narlidere Geothermal Reservoir, Turkey. Geothermics 37 (2008), Öngür, T.: Geology of Izmir Agamemnon hot springs - Balcova geothermal area and new conceptual geological model. Report for Balcova Geothermal Ltd., Izmir, Turkey, (2001) (in Turkish). Satman, A., Serpen, U. & Onur, M.: Reservoir and production performance of Izmir Balcova- Narlıdere geothermal field. Project report, Balcova Jeotermal Ltd., Izmir, Turkey, (2001) (in Turkish). Yilmazer, S.: Geochemical features of Balcova hot springs and geothermal energy possibilities for the area. PhD thesis, Akdeniz University Graduate School, Isparta, Turkey, (1989). Reinjection/production ratio Figure 12. Production-re-injection rates and ratio during Figure 13. Water level measurements (m) at ND-1 during