System and methods for optimizing coiled tubing string configurations for drilling a wellbore are provided. A length of a rotatable segment of a coiled tubing string having rotatable and non-rotatable segments is estimated based on the physical properties of the rotatable segment. A friction factor for the rotatable segment is calculated based on the estimated length. An effective axial force for one or more points of interest along the non-rotatable and rotatable string segments is calculated, based in part on the friction factor. Upon determining that the effective axial force for at least one point of interest exceeds a predetermined maximum force threshold, an effective distributive friction factor is estimated for at least a portion of the non-rotatable segment of the string. The rotatable and non-rotatable string segments are redefined for one or more sections of the wellbore along a planned trajectory, based on the effective distributive friction factor.
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