Analysis of well testing, temperature and pressure in high-temperature wells of Aluto-Langano, Ethiopia

Abstract

Drilling in Aluto-Langano geothermal field started in 1981 with the aim of harnessing steam for electricity power production. Eight wells were drilled between 1981 and 1986, thereof four productive, one reinjection and three non-productive wells. Recently, between 2013 and 2015, two directional wells were drilled and they are still undergoinging different measurements and tests. Measurements from the wells, LA-9D and LA-10D, as well as from an older one, LA-3, were analysed and are presented in this report. Results from analyses of injection tests for wells LA-3 and LA-10D are characterized by having fairly good transmissivity and storativity values and the injectivity indices are rather low. The evaluated fluid enthalpy for wells LA-9D and LA-10D is in the range of 1600-2200 kJ/kg, with steam flow ranging from 5 to 9 kg/s with separation pressure of 1 bar-a as well as with separation pressure of 5 bar-a of Aluto-Langano pilot power plant. Formation temperatures of wells LA-9D and LA-10D were estimated by extrapolation of temperature logs from their warm up periods. The results suggest that the reservoir temperature is in the range of 300-315°C and reservoir pressure in the range of 85-100 bar for both wells