Sensitivity Analysis of Geothermal Drilling Parameters-A Case Study of Well Mw-17 in Menengai Kenya

Abstract

Rate of penetration (ROP) is one of the most important factors that determines the success or failure of a drilling project. Very low rates of penetration implies that the overall time it will take to complete drilling a well will be very long and vice versa. Time has a direct bearing on the cost of drilling. Long time taken to drill a well may lead to cost overruns and hence failure to successfully complete the drilling project. It is therefore very important to control the ROP in such a way that drilling will be done within the planned timelines and hence cost. There are several factors that affect the rate of penetration when drilling geothermal wells. These factors were looked at in great detail in my previous paper entitled Modelling of Geothermal Drilling parameters- a case study of well MW-17 in Menengai Kenya. The parameters that affect ROP are: Formation strength, Formation depth, Formation compaction, Pressure differential across the hole bottom, Bit diameter and weight on bit, Rotary speed, Bit wear, Bit hydraulics. Of these parameters, the driller can very easily control the Rotary speed (Rotations per minute-RPM) and the Weight on bit (WOB). These parameters have a direct relationship with ROP. Increasing them will lead to increase in ROP. This is the reason why these parameters were considered in this paper; to see the extent to which they affect the ROP when they are increased or decreased by a certain percentage. The analysis also identifies the ddorminant parameter that can be utilized more to achieve greater ROP.