Mixed Fleet Drilling Approach to Geothermal Resource Exploration along the African Rift

Geothermal well drilling is the single most expensive component and can account for up to 50% of geothermal resource development cost. Proper application of available technology and expertise within the region can help lower the cost of drilling and thus accelerate the pace of geothermal resource exploration across the African rift system. Whereas shallow temperature gradient wells and slim holes have been used by developers as the main peak into the potential productivity of a field their usefulness after drilling is limited to data gathering, community water supply and in very rare cases geothermal resource harnessing. Slim wells are not necessarily cheaper than regular geothermal wells when drilled with high capacity rigs. The sheer number of water wells drilled between (0 – 500m) in the Riftvalley as compared to geothermal wells makes water drilling technology and expertise best placed to drill this portion of the reservoir with support from geothermal drilling engineers to be able to anticipate and control kicks and blow outs. Recent advancements in the water drilling sector has seen the entry of bigger rigs and lower drilling costs. Drilling materials requirements for a water rig are modest compared to a standard deep drilling rig. Leveraging on the vast readily available water drilling technology and expertise will definitely push the cost of drilling a geothermal well down. A top-holed well provides reservoir data, water resource and in some cases geothermal resource with a possibility for drilling deeper to tap a bigger geothermal resource. A phased geothermal well drilling approach allows for reduced cost in the tophole with the option of drilling deeper in future if the data for this section is promising. A mix fleet of water and deep drilling rigs if well applied can push the cost of drilling a geothermal well down. GDC owns one(1) water rig that can drill 354m and seven (7) deep drilling rigs with capacity of drilling upto 7kms. The water rig can be used to drill the 26” hole and 17 ½” hole reducing well cost.