Controlled Directional Drilling in Kenya and Iceland (Time Analysis)

Abstract

Directional drilling is the most widely used method for drilling geothermal wells due to its various advantages. Drilling more 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 the total drilling time per well and, hence, reduce drilling costs. This study highlights 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 and it takes about 41 days to drill them 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. This shows that the drilling rates are similar in these countries although the difference of 4 days is quite significant, considering the large costs involved in drilling a well per day (Daily rates). For power projects the cost of drilling geothermal wells for production or reinjection is about 40% of the project’s total investment. Half of the drilling cost then again comes from the rental of rigs and services (day rates) and the other half is from materials and infrastructure. The wells are typically drilled in anywhere from 30 to 60 days and thus the effectiveness, or speed of drilling, impacts the greatly the cost. This can be analysed by comparing the results for wells within the same field and to some extent between different areas or parts of the world.