Patent ID: 9657523
Date: 2017-05-23
CPC Classifications: E21B,G01H,G05B,G06F

Claim:
1. A method for estimating a location for disposing a tool in a drill tubular having a drill bit, the method comprising: performing a modal analysis of the drill tubular to determine natural eigenfrequencies and corresponding eigenmodes of torsional oscillations of the model; selecting a predominant natural eigenfrequency and corresponding eigenmode from the determined natural eigenfrequencies and corresponding eigenmodes, the predominant eigenfrequency having a frequency that is higher than the lowest determined eigenfrequency and providing a mode shape corresponding to the predominant eigenfrequency having an absolute single maximum amplitude of torsional deflection at the drill bit; performing a forced modal analysis of the drill tubular at the predominant eigenfrequency with a force or moment acting on the drill bit to provide a correlation between forced torsional deflection amplitude and position; and estimating the position to be within a range of positions wherein a vibration qualification of the tool is greater or equal to the torsional deflection amplitude throughout the range.