| Abstract |
Berlin geothermal field is a liquid-dominated system with temperatures in the range 270-305?C according to the chemistry and measured temperatures from 5 deep wells (depth of 1900- 2300 m). Well enthalpy varies between 1200 and 1400 kJ/kg (18-30% steam quality), showing a power potential from 5 to 12 MWe. The geothermal fluids are of typical sodium-chloride composition with 3000 to 6000 mg/kg of reservoir chloride and silica content ranging from 600 to 900 mg/kg, and 0.25-0.50% by weight of non-condensable gases in the steam separated at 8 bara. Commercial production began in February 1992 with start-up of well TR-2 using a 5 MWe backpressure turbine. Well TR-9 began production with a second backpressure turbine in January 1995. These two wells generate a total of close to 8 MWe. The total water extracted, around 100 kg/s, is being reinjected. Chemistry of the fluid from wells TR-2 and TR-9 indicates some changes with time, specially for well TR-9, with a cooling in the silica geothermometer from 284?C to 200?C after 2 years of injection, and recovery, after 3 years of production, from 200?C to 285?C. Well TR-2 probably shows some effects of reinjection, with an increase in the reservoir chloride from 4000 to 5000 mg/kg in the first year, and a decrease in the noncondensable gases from 0.36 to 0.10 % in weight. From tracer tests (I131 as tracer) we have deduced that some connection exists between wells TR-2 and TR-9. Evaluations of mineral saturation indicate that calcite and quartz are close to equilibrium. A minimum separation pressure of 8ñ10 bara is required due to the higher content of silica in the separated water. According to geochemical and physical data the main process affecting the reservoir is boiling, due mainly to the drawdown pressure of about 6 barg. There is no influence of reinjection in the production area, according to the isotope and production characteristics. |