| 摘要 |
For mitigating stick-slip oscillations in borehole equipment (10) while drilling a borehole in an earth formation, the borehole equipment (10) is modelled (31) by a computational model for computer simulation. The model comprises elements representing a particular mechanical and physical behaviour of the borehole equipment (10). In a simulated stick mode of the borehole equipment (10) physical quantities are loaded to the elements, which quantities represent an initial state of the borehole equipment (10) prior to a transition from stick mode to slip mode. From a simulation of such transition, a time response of rotational speeds of a drive system (15) and bottom hole assembly (11) of the borehole equipment (10) is recorded and a lower limit of the rotational speed of the drive system (15) is determined for which the rotational driven speed of the bottom hole assembly (11) is zero. |
