Drilling dynamics

摘要

A method of determining movement dynamics of a drillstring is provided that includes the steps of calculating or measuring a friction coefficient for the sliding contact between the drillstring and the sidewall of a borehole, the friction coefficient being a varying function of non-zero sliding velocities; and predicting movement dynamics of the drillstring using the measured friction coefficient.

主权项

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.