An Advanced Simulation Model for Drawworks and Fastline Dynamics Uncovers Risks of Spooling Errors and Other Hazards

Abstract

Summary The fastline is the part of the drilling line running between the drawworks drum and first sheave of the crown block assembly. Lateral vibrations of the fastline can be severe, have a negative effect on wear rates, and can cause damage to equipment with subsequential downtime. In the worst cases, severe vibrations can cause injury or even be fatal to personal. The goal of this paper is to show how a simulation model can help to identify risk factors and remedies to minimize the likelihood of spooling errors and other hazards. This paper presents the results from an advanced simulation model describing both the generation and decay of fastline vibrations. The model includes a dynamic drawworks model having many features, such as a multilayer Lebus drum spooling, line elasticity, sheave and line inertia, and realistic speed control response of the drawworks motors. The simulation results strongly indicate that a dominating high-risk factor for error spooling is a low fastline tension force resulting from a combination of a low hook load and dynamic effects, like a high fastline speed and a rapid speed ramp-down (high deceleration rate). Other risk factors include poor damping of the generated fastline vibrations and high fastline inclination (deviation from vertical). Even though inherent bending resistance of the wire rope is a significant damping mechanism for high-frequency vibrations, it is very weak for low-frequency vibrations generated by tension variations or by axial deflection speed reversal at layer shifts. The improved model also shows that a conventional stabilizer dampens fastline vibrations poorly. In contrast, a new type of the stabilizer, which is placed closer to the fast sheave and uses passive but tuned dampeners, shows promise. Even though it is placed at a further distance from the drum, simulations strongly indicate that it can effectively dampen low frequency fastline vibrations and thereby decrease the risk of hazards.