The Analysis Of Vibration Spectrum On Drill String Of Extended Reach Well

Drill failure is an important issue which always influences drill security and cost. And the strong vibration of drill string is a crucial factor for drilling failure. There are three basic vibration modes for drill: axial vibration, lateral vibration and torsion vibration. Three vibration analyses are applied on established mechanical model of drill string. Spectrum law of drill string is acquired on the analyses of linear infinitesimal method and finite method. The common regulation of drill string is arrived at by stick-slip phenomena of ERD well.Finite method of ERD well straight hole is produced by both actual shaft body data and BHA which are got from ANSYS software. With marginal conditions, frequency distribution law of shaft drill string has been had by straight hole drill string model analysis and software simulation. It emphasizes on certain vibration mode. It also simulates coupling vibration and sums its law.For example, Bohai QHD32-6-A26H field, with the ANSYS software, it has established ERD well finite model from bottom to top. After analyses, parameters of ERD well drill string's axial vibration, lateral vibration, torsion vibration and spectrum for coupling vibration are derived. So does its law.Harmonic response analysis has been dealt on the basis of ERD well drill string in bottom. Sine wave cycle action has been pressured on drill bit with 1kN, 5kN, 10kN and 50kN. Response curve on drill bit is reached by harmonic response analyses. Spectrum line coincides with vibration spectrum. Obviously, it is induced by resonance under cycle action. And the amplitude is determined by drill pressure.