A Method Of And A Device And An Electronic Controller For Mitigating Stick-slip Oscillations In Borehole Equipment

Abstract

A method for mitigating stick-slip oscillations in borehole equipment while drilling a borehole in an earth formation is described. The borehole equipment is modelled by a computational model for computer simulation. The model has elements representing a particular mechanical and physical behavior of the borehole equipment. In a simulated stick mode of the borehole equipment, physical quantities are loaded to the elements, which quantities represent an initial state of the borehole equipment 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 and bottom hole assembly of the borehole equipment is recorded and a lower limit of the rotational speed of the drive system is determined for which the rotational driven speed of the bottom hole assembly is zero.

Description

technical field [0001] The present invention generally relates to drilling equipment for drilling boreholes in formations of the earth. More specifically, the present invention relates to a method, device and electronic controller for mitigating stick-slip oscillations in such a drilling rig while drilling and a drilling device equipped with and according to such a method, device and electronic controller. Background technique [0002] The term borehole generally refers to the result of a drilling operation into the earth vertically, horizontally and / or deflected using a drill string comprising a drill bit at its lower end. ). At the upper or top end of the drilling line, the drilling line is driven at the surface by a drive system, called a top drive or rotary table. The top drive or wheel is driven by an electric motor or any other type of drive motor to provide rotary motion to the drill bit in the borehole. [0003] Typically, a borehole string is an elongated structu...

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Problems solved by technology

[0014] The problem with this known method is that the frequency approximation does not correctly describe the physical behavior of the drilling equipment in the viscous mode where the bottom hole assembly comes to a complete standstill, since the velocity of the bottom hole assembly is clearly equal to zero

Additionally, the fact that the bottom-hole assembly rotates at a relatively low speed makes it more difficult to obtain a sufficiently accurate approximation of the sinusoidal waveform, and because practical drilling systems exhibit non-linear behavior

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