Rig selection and comparison of top drive and rotary table drive systems for cost effective drilling projects in Kenya

Abstract

Drilling rigs have been undergoing technological advancement over time. With this advancement has come a lot of improvements right up to the latest, modern AC top drive rigs that come with a high degree of automation. The depth capacity of the rig is determined by the rating of draw works, mast and mud pumps. Since drilling constitutes a high percentage of the geothermal development cost, the need to select rigs with a high efficiency and low drilling cost is paramount. There is also a need to identify drilling tools and equipment to be utilised to improve drilling performance. The top drive system is proving to be more advantageous than the convectional Kelly drive system. The automation of drill pipe handling and use of a iron roughneck improves safety and efficiency. The ability to circulate and rotate while running in the hole or pulling out of the hole reduces the chances of the bottom-hole assembly getting stuck. It also enables cooling of the bit, especially when running in the hole, thus increasing bit life. The advanced technology involved in top drive rigs comes with a higher cost and requires a highly skilled operating workforce. The use of downhole motors and good quality bits has also resulted in a faster drilling rate.