Controlled directional drilling in Kenya and Iceland

Abstract

Directional drilling is the most widely used method for drilling geothermal wells due its various advantages. Drilling multiple wells from the same pad allows for fewer rig moves, less surface area disturbance as well as making it easier and cheaper to exploit the resource being drilled for. Current technology allows the driller to steer the well to the target with high precision and this allows exploitation of resources that would otherwise be difficult or impossible to reach. The study in this report shows that almost 50% of the total time in directional drilling is spent on activities that are not related to actual cutting of the formation by the drill bit. Minimising time spent on these activities will reduce total drilling time per well and, hence, reduce drilling costs. This study highlights the calculations of well trajectory and an analysis of the actual time taken for all activities in drilling of 12 directional wells in Kenya and 14 directional wells in Iceland. The results show that the average depth drilled per day for Iceland is about 56 m, and for Kenya it is about 48 m. The average depth of the Icelandic wells is 2379 m, taking about 41 days to drill, and the average depth for Kenyan wells is 2830 m, taking about 58 days. Comparison of drilling times in Iceland and Kenya indicates that for a well of 2830 m, it will take about 54 days to drill in Iceland while it will take about 58 days to drill in Kenya. These drilling rates are similar, although the difference of 4 days is significant considering the large costs involved in drilling per day.

The government of Kenya has started an ambitious programme to increase its power production from geothermal energy. The capacity of geothermal power in Kenya is estimated to be about 7000 MWe, valued at about USD30 billion. Efficient drilling practices will be required in order to optimise exploitation of its more than 14 prospects. The Geothermal Development Company’s ten year business plan indicates that it intends to drill about 500 wells in Olkaria, Menengai, Silali and four other fields and realise at least 2000 MWe by 2019. Within this period it intends to procure 12 deep drilling rigs with a depth capacity of 5000- 6000 m. The rigs should have a capacity to drill deep directional geothermal wells. The study carried out in this report indicates what has been achieved in the past and will act as a benchmark for planning for future drilling, as it addresses good practices that can assist in improving cementing, logging and bit selection. Also, the computer programs generated in this report will be used in monitoring actual drilling to ensure the target is reached within acceptable limits.