| Abstract |
Slim hole drilling has been utilized for decades, to identify and delineate geothermal resources, and to provide wells that can serve as resource management tools in producing geothermal fields. In this paper, we investigate and identify the current cost issues and advantages associated with slim hole drilling, specifically focusing on the use of small hydraulic diamond core drills, and will compare the relative costs and operational considerations of utilizing slim hole drilling versus conventional rotary drilling for exploring, delineating, and monitoring geothermal reservoirs. Additionally, a discussion of the specific benefits of slim hole drilling is included. Slim hole hydraulic coring rigs are highly portable, small rig platforms that were originally designed for minerals and mining exploration. These rigs can either be scow or truck/track mounted, are fully hydraulic-powered, and all support equipment can normally be contained on 4 to 6 trucks; they can be easily moved and rigged up in one day. Experience has indicated that slim hole coring costs are about 1/3 of the cost of drilling a full-scale rotary well, leading to the conclusion that three slim hole exploration/ delineation wells can be completed for about the same financial commitment as one large rotary well, obtaining substantially more geological information about the geothermal system. The recent international focus on ‘small resource’ geothermal opportunities will often not support high up-front exploration costs, especially in rural, ‘off-grid’, or remote undeveloped or developing countries. The slim hole drilling process can provide viability to these marketplaces, at a fraction of the cost of drilling conventional rotary exploration wells. Indeed, in some cases slim holes can actually serve as producers and injectors for small-scale electrical power generation. |