Over the past 20 years in the Middle East Region, the performance of Underbalance Coiled Tubing Drilling (UBCTD) has significantly improved, with regular use in several areas. Improvements in application selection, drilling technologies & procedures have also helped to expand the scope of available reservoir targets. Widening the available choice of down hole tools is one main factor that has led to an improvement in drilling performance and one such technology is the 2 7/8" downhole turbine drive motor (turbine). Historically, the choice of turbines for UBCTD had been restricted to harder formations but for over a decade now, turbines have been used in these UBCTD applications in KSA – consistently producing steady drilling performance and meeting well objectives. In a recent bid to optimize drilling performance, a newly designed high-power 2-7/8" downhole turbine was introduced for KSA in 2018. This new turbine utilized in varying downhole environments, from hard and abrasive sandstone to the typically targeted carbonate reservoirs. Trials were performed in varying downhole temperatures to evaluate the performance improvement. Today this turbine has shown a visible improvement in both performance and reliability compared to the alternative turbine options. The new turbine design integrated with existing MWD technology in order to execute the drilling operation in UBCTD with higher drilling efficiency and better economic returns. In order to establish performance improvements, a set of success indicators was established: Power delivery efficiency. Performance in varying reservoirs Turbine and MWD tool Reliability Directional drilling performance Downhole tool vibration monitoring. These success indicators were closely monitored during 2018 and the results revealed a significant increase in overall footage drilled. BHA reliability also improved. From these two major factors, the utilization of 2 7/8" downhole turbines have significantly increased.