Doctoral Thesis
DOI
10.11606/T.18.2015.tde-28072015-131559
Document
Author
Full name
Cristiano Eduardo Agostini
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2015
Supervisor
Committee
Nicoletti, Rodrigo (President)
Pederiva, Robson
Plácido, João Carlos Ribeiro
Watanabe, Flávio Yukio
Title in Portuguese
Modelagem da dinâmica e análise de vibrações de colunas de perfuração de poços de petróleo em operações de backreaming
Keywords in Portuguese
Dinâmica de rotores
Poços de petróleo
Vibrações
Abstract in Portuguese
Title in English
Dynamic modeling and vibration analysis of oilwell drillstring during backreaming operations
Keywords in English
Petroleum wellbore
Rotor dynamics
Vibration
Abstract in English
Oil well drill string vibrations have been studied extensively throughout the world, mainly due to the highly damaging effects caused by these vibrations in the drill string elements. The high costs involved in the operations have led scientists and companies to seek the best results, whether in wellbore project or during real time construction. This thesis presents a non-linear mathematical model for drill string vibrations analysis during backreaming operations, that is, pulling out drill string with pumping and rotation simultaneously. The model proposed aims to study the effects of lateral vibrations on the lower portion of the drill string, commonly known as Bottom Hole Assembly (BHA). The modeling approach is based on analytical, nonlinear and lumped parameters, which considers the effects of drilling fluid damping, stabilizer and drill collar contact with the borehole wall and drill pipe torsional stiffness, with MATLAB® numerical routine implementation to solve the system of differential equations. To setup of the proposed mathematical model, an experimental test rig was built in scale with a real drill string, simulating the dynamic condition of the drill string. The results show good correlation between the mathematical model, experimental test rig and real field data. Parametric analysis were performed to study the influence of backward whirl, lateral acceleration and accumulated damage in the drill string. A probabilistic model was proposed for the study of drill string vibrations with mathematical model experimentally calibrated. The work discusses the statistical results for the drill string vibration using Monte Carlo approach, considering the uncertainties in borehole diameter and friction coefficient. The results show that the lateral acceleration is smaller in borehole diameter closer to the drill bit diameter with low friction coefficient, besides not being significant influence due to the backreaming speed. For wellbore with greater uncertainty in the borehole diameter and for drill string with high speed rotation, a higher lateral acceleration value was observed.