Development and Application of a BHA Vibrations Analysis Model

Abstract

BHA lateral vibration has been identified as one limiter that may hinder the rate of penetration (ROP). Based on Newton’s equations of motion and Euler-Bernoulli beam bending equation, a steady-state forced-frequency response dynamic model was developed to analyze vibration performance for a single point mass in the BHA surrogate. Wherein, the connection between points relied on massless springs or dampers. The frequency-domain model more accurately represented actual mechanical states for a particular BHA configuration. On this basis, the state vector for a mass point was calculated by the semi-analytical transfer function matrix method at any given position in the BHA surrogate, which greatly reduced the number of discrete elements and the associated computing time. It caused rapid screening of a large number of design alternatives on a PC. The state vector included the lateral and angular deflections, as well as the beam bending moment and shear load, which were integrated as a dynamic vibration performance index called Lateral Vibration Strength Estimate (LSE) utilized to quantitatively evaluate the lateral vibration state. The field application demonstrates that the methods for modeling bottom hole assembly (BHA) vibration performance during drilling to enable improved design in pre-drill and operation for enhanced drilling rate of penetration, to reduce downhole equipment failure in drilling. Field validation for the surveillance tool was performed by comparing high-frequency downhole memory sensor data (100samples/second data rate).