In autumn 2005 the Drilling Department of the RAG put a new Triplex-Mud pump into operation and replaced the 20-years old Duplex-Mud pumps. The application of this pump enables higher pressures and pump rates and therefore a better bore hole cleaning and an increased net and gross rate of Penetration (ROP), because of less wiper trips, can be expected. In the context of this diploma thesis the sensitivity of the parameters of the hydraulic calculation of a well was analysed. With help of the hydraulic program Wellplan from Landmark the influence of the parameters on the total system pressure loss was calculated and visualized. The calculated values were matched with the field data of a current well and the differences were analysed. In this thesis, the method of measurement of drilling fluids with a so-called Fann Viscometer was challenged and alternative methods of measurement were analysed. Some tests were performed on a HPHT Rheometer to earn information about the pressure and temperature behaviour of drilling fluids. Further, the values of measurement of the Rheometer and the Fann Viscometer were compared and a correction factor was developed. To avoid the necessity of using a second mud pump an optimum liner configuration was developed for each hole section, with the result that a 7 liner for the pump was bought.