The scope of this work is to minimize the costs of a newly drilled well. The two possibilities that were taken into consideration to reduce the drilling costs are to drill holes with smaller diameters than conventional drilling and drilling with casing. This work analyzes the potential of the technologies to reduce the drilling costs. The work starts with an introduction of the two technologies. In addition the advantages of drilling smaller holes compared to conventional and drilling with casing are identified. It provides an overview of the various applications of these technologies, such as for exploration, low-cost development wells and monitoring wells. Also a peek on the effect of reduced hole sizes on production is discussed, and some artificial lift technology applicable in such low diameter holes is presented. It further describes the main components of a drilling rig and focuses on those parts of the whole drilling system, that have the greatest influence when talking about slimhole or casing drilling. A concept for an “optimum” rig for these technologies is developed, stating components already available on the market. Also the calculations which were performed to identify the system configuration of the aforementioned section are introduced and the system designed is checked for technical feasibility (e.g. loads, pressures, etc.). Finally the cost saving potential of the two technologies discussed in this work is estimated.