Finite element analysis on drilling string axial vibration in a crooked hole

Various kinds of drilling string vibration behaviors exist while deviated well (crooked hole) is drilling; the serious drilling string axial vibration will cause bit jumping, which is one of the most factors influencing deviated well drilling. Serious bit jumping phenomenon indicates that drilling string axial vibration shouldn't be neglected. This research studies on the whole drilling string in the crooked hole as subjects, and analyzes the laws that the whole drilling string axial dynamic behavior followed under the condition periodic exciting force exists. Through the whole and the part drilling string finite element analysis, mass matrix, stiffness matrix and dynamic matrix equation are acquired. Using computer program, distribution laws of drilling string axial vibration frequency are acquired, which indicates bit jumping occurs when forced vibration frequency and natural frequency are closed to each other. This paper provides a theoretical basis of researching drilling string dynamic behavior in the crooked hole, and the obtained observation would be a further guidance for analyzing drilling string vibration on extended reach well drilling. © 2013 American Society of Civil Engineers.