Research on the Limit of Downward Velocity of Completion String in Deep, Ultra Deep, Long Horizontal Section Horizontal Wells

The friction between the completion string and the wellbore wall of a deep and ultra deep horizontal well is high, making it prone to jamming accidents. This article is based on the third-order difference method and Hamilton's principle, considering whether the pipe string can meet the strength requirements during the down process. A numerical calculation model of the down dynamics of the completion pipe string with a packer under the influence of the down velocity is established, and the influence of the down velocity on the down behavior of the completion pipe string is studied. The results indicate that when the downward velocity of the pipe column exceeds a certain critical value, it is prone to buckling deformation and self-locking of the pipe column. This critical value is defined as the limit of the downward velocity of the pipe column; The gap between the packer and the wellbore decreases, the frictional resistance of the completion string increases, and the limit of the downward velocity decreases; When the pipe is lowered at its maximum speed, the axial force transmission efficiency of the pipe near the inclined point is the lowest, the axial force oscillates violently, and the pipe is prone to fracture. The research work in this article provides a theoretical basis for the decision-making of well completion string insertion.