ANALYSIS OF DRILL STRINGS IN VERTICAL AND DEVIATED HOLES USING THE GALERKIN TECHNIQUE

This paper presents an analytical investigation into the use of Galerkin's technique for the analysis of oil field drill strings in vertical and deviated holes. The technique is used to present results for drill string dynamic stability in vertical holes and drill string static deflection in curved and straight inclined holes. In the first case, the critical loads and natural frequencies for lateral vibration are calculated assuming that the drill string is hinged at both ends. In the latter case, emphasis is placed on the particular conditions of low weight on bit and large drill string pendulum length for which other solution techniques run into difficulties. Results from Galerkin's technique compare well with those from other semi-analytical solutions of the problems and it is shown that the technique offers a simple and easily programmable alternative for the analysis of deviated drill strings.