New and unconventional reserves are now being developed in more isolated and remote locations by drilling extended-reach horizontal wells (ERWs). The complexity of designing tubulars for ERHWs depends on the well objectives, target’s location and wellbore trajectory. Tubular design must be compatible with the intended wellbore trajectory to minimize the downhole dynamic events such as torque and drag, buckling and vibrations. The existing dynamic models for calculating anticipated axial load and torque distribution for tubulars in ERHWs consider only the effect of the normal contact loads and frictional forces. However, lateral and torsional vibrations are critical to the tubular design for ERHWs because vibrations contribute to the total normal contact load. This study uses the unbalanced force and fluid added mass theories to quantify the magnitude of the normal contact load generated during lateral vibrations of a near-straight tubular section in an ERHW. The generalized model is developed using the knowledge of engineering mechanics to integrate axial load, torque, buckling and vibrations models. The integrated dynamic equations neglect the hydraulic effects in drilling tubulars and weight-on-bit term in completion tubulars. It was observed that the downhole dynamic events contribute a relatively higher percentage to torque transfer than they do to axial load transfer. Also, when all the downhole dynamic events occur together and the critical buckling loads have not been reached, torque and drag events contributes the major portion of the axial load transfer followed by lateral vibrations. The model equations developed in this paper are validated using the well data from one of the world’s longest ERHWs. The calculation of axial load and torque distribution accounts for the underestimated values of loads and torque obtained from previous dynamic models. This study will lead to better drilling optimization through the minimization of failures, non-productive times, and ultimately reduced total drilling costs.

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