March 21, 2022 – 8:30am Central Time
Implementing Soft String and Stiff String Models for Torque and Drag Calculations
Monday, March 21, 2022
8:30 am – 9:30 am Central Standard Time
Speaker: Darlington Etaje, University of Calgary
Soft string and stiff string models are two different mathematical models which are used for torque and drag analysis. (S. Menand, SPE, H. Sellami, SPE, M. Tijani, and O. Stab, École des Mines de Paris; D. Dupuis, SPE, 2006). They were developed to describe the mechanical behavior of the drill string inside the borehole, and they have their own theoretical background and assumptions. The soft string model is widely used in the industry, and it assumes that the drill string has a continuous surface contact area with the wellbore as it deforms to the shape of the wellbore. The model ignores the bending stiffness in the drill string and borehole clearance. For a smooth well geometry, the model has a good approximation of forces and contact loads (R. F. M. and R. Samuel, 2007). This presentation walks through step-by-step modeling of stiff string and soft string torque and drag calculations. It also shows extra considerations when implementing a closed loop coding system for these calculations on MATLAB.