Patent ID: 8990021
Filing Date: 2015-03-24
Classification: E21B

Abstract:
1. A method of determining movement dynamics of a drillstring in a borehole, comprising the steps of: (a) calculating or measuring a friction coefficient for a sliding contact between the drillstring and a sidewall of the borehole, wherein the sliding contact comprises a rotational contact between the drillstring and the sidewall, wherein the borehole is a deviated borehole, and wherein frictional force between the drillstring and the deviated borehole includes a component proportional to a side force between the drillstring and the deviated borehole and the friction coefficient comprises a varying function of non-zero sliding velocities; and (b) using a processor to predict movement dynamics and rotational velocity of the drillstring using a model of drillstring behaviour that includes the calculated or measured friction coefficient as a parameter.