Patent ID: 8453764

Claim:
A method of monitoring the operation of a drill string drilling into an earthen formation so as to form a bore hole using a drill bit, comprising the steps of: (a) drilling a bore hole having a first diameter in said earthen formation by rotating said drill bit at a first rotary speed and applying a first weight on said bit; (b) making a determination of the value of said first rotary speed at which said drill bit rotates; (c) making a determination of the value of said first weight on said bit; (d) making a determination of the value of said first diameter of said bore hole; (d) measuring vibration in said drill string at at least one predetermined location along said drill string while rotating said drill bit at said first speed and applying said first weight on said bit; (e) using a finite element model of said drill string to predict the vibration in said drill string at said at least one predetermined location based on said determined values of said first rotary speed of said drill bit, said first weight on bit and said first bore hole diameter; (f) comparing said measured vibration to said predicted vibration and determining the difference therebetween; (g) revising said finite element model so as to reduce said difference between said measured vibration and said vibration predicted by said model; (h) drilling a bore hole having a second diameter in said earthen formation by rotating said drill bit at a second rotary speed and applying a second weight on said bit; (i) making a determination of the value of said second rotary speed at which said drill bit rotates; (j) making a determination of the value of said second weight on said bit; (k) making a determination of the value of said second diameter of said bore hole; (l) using said revised finite element model of said drill string to predict the vibration in said drill string based on said determined values of said second rotary speed of said drill bit, said second weight on bit and said second bore hole diameter.