There are a significant number of extended reach wells that cannot be effectively intervened to total depth due to tubing string lock-up. If the horizontal section of the wellbore is sufficiently long, the axial compressive load needed to convey the tubing into the wellbore will cause the tubing to buckle. Buckling initiates in a sinusoidal mode and progresses to a helical mode. Once the tubing buckles helically, the string quickly locks-up due to increased normal forces and frictional interaction with the wellbore. We have developed an innovative technique to model extension of tubing conveyance in deep wells.

Several commercial vibration devices attempt to extend intervention depths in extended reach wells. One of the primary modes of vibration employed in these devices is axial. We developed a simulation tool to enhance understanding of how axial vibration devices extend reach. In the first section, we introduce a 1D finite rigid body dynamic model. This computational tool models the propagation of axial excitation in the presence of borehole frictional contact. A Coulombic dry friction law describes the interaction between tubing and borehole wall. 3D static computations precompute static axial loads and contact forces that serve as inputs to the 1D model. This allows the user to predict the behavior in complex 3D wellbore trajectories and to simulate several dynamic scenarios in a matter of minutes. In the second section, the behavior of axial excitation in the presence of frictional contacts is explored with the model. Simulations predict the distance of axial vibration propagation along a tubing string in a wellbore. A simple relationship is postulated that captures the axial wave propagation length as a function of axial excitation and tubing/borehole parameters. Modeling results demonstrate a mechanism by which axial vibration can extend reach. Synthetic case studies show the possible reach extension for prescribed axial load excitations. Results from a scaled experimental setup demonstrate the mechanism seen in the simulations.

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