Comparison of drilling in geothermal fields in Krafla, Icaland and Tendhao, Ethiopia

Abstract

This report compares the drilling of geothermal wells in Iceland and Ethiopia, describing the technology applied and practical activities. For this study, well KJ-32 in the Krafla geothermal field in Iceland (drilled 1998) and well TD-5 in the Tendaho geothermal field in Ethiopia (drilled 1997) were selected. In Krafla 35 wells have been drilled to date and of these 9 wells are directional, as is the case for well KJ-32. The well was drilled from the kick of point (KOP) to final depth with a steerable down hole motor and measurement while drilling (MWD). The target was to produce from the lower reservoir with a temperature of up to 320_C and to reach inaccessible parts of the reservoir below 1100 m. In Tendaho, six wells have been drilled, three deep wells and three shallow wells. Well TD-5 was drilled vertical to a depth of 516 m to intersect a shallow reservoir with a temperature of 240_C. The basic rig parts such as the mast, pumps, and cementing units are quite similar in the two countries and the casing program also. The drill strings make-up and use of logging tools, cementing material and manpower is, however, different. The opportunity was given to me to witness cementing operations at Nesjavellir and at Krafla. This included a three week period on site at Krafla during completion of well KJ-33 and the beginning of drilling well KJ-34.