Different locations and field conditions require various drilling methods to produce oil and gas. Three major operational methods are identified to be slim holes, conventional and casing drilling. Despite many affecting parameters, torque and drag are two highlighted factors for the determination of the best drilling method. Torque and drag play a significant role in the feasibility of drilling and its final costs. In this study, the influence of the torque and drag are investigated for the determination of optimum drilling type in consideration of the same S-shape well trajectory for all cases. Consequently, slim hole drilling showed minimum torque and drag value which meant that this method can be a good choice. Furthermore, casing drilling displayed maximum torque and drag in this study resulting in high sensitivity to the high degree of deviation. On the other hand, due to the constant weight of casing while drilling, this method showed a smooth increasing trend in terms of drag force while slim hole and conventional drilling showed significant changes in different parts of well trajectory. The number of build and drop sections significantly affect the amount of torque loss, while up to 50% to 70% of torque loss was observed in the drop or build section
