Title: Modelling of Effective Tension in Torque and Drag Analysis for Highly Deviated Wells
Authors: Preye Nelson Toun-Aregha
Eniye Oguta
Isaac Eze Ihua-Maduenyi
Volume: 10
Issue: 4
Pages: 164-180
Publication Date: 2026/04/28
Abstract:
In this study, a stiff string model analysis of the effective tension in an ER well in the Niger Delta Basin, which had a measured depth of 35,017 ft, was carried out using the WELLPLAN software. The results showed that the highest effective tension occurred during tripping out, which had a range of 669.8 to 795.3 kips at the surface, while the entire string was in tension and buckling was eliminated. However, this resulted in a higher load at the surface. On the contrary, tripping in and sliding had a much lower effective tension, ranging from 95.1 to 187.4 kips, as the entire string was in compression due to the effects of the increased OHFF values, which resulted in compressive drag force opposing the motion of the string. Notably, compressive zones occurred during tripping in and sliding from the bottomhole to 2,742 ft, while rotating on the bottom resulted in compression up to 9,950 ft. However, the compressive zones resulted in sinusoidal buckling tendencies at all OHFF values ranging from 0.2 to 0.3, while helical buckling was not predicted, indicating the mechanical feasibility of the design. Sensitivity analysis revealed that if the weight of the mud is increased from 9.6 to 10.8 ppg, the tension will be reduced by 41.7 kips during tripping in and 70.5 kips during tripping out, which proves the load-mitigating potential of buoyancy. With the increase in tripping speeds, the tension is reduced during the descent (surge effects) and increased during the ascent (swab effects). The effects of the rotary speeds are opposite during tripping in and tripping out, as they increase the tension during tripping in due to friction-breaking mechanisms and reduce the tension during tripping out due to the same mechanisms. From the results, it is evident that the effective tension modeling is a crucial component in the identification of buckling-prone sections and the proper management of friction in ERD operations.