Current sinusoidal and helical buckling models are valid only for initially straight coiled tubing (CT). This paper stresses the effect of the pipe initial configuration (residual bending) on the sinusoidal and helical buckling behaviors in deviated wells. Using the conservation of energy and the principle of virtual work, new general equations are derived for predicting the sinusoidal and helical configurations of CT. These new equations reduce to those previously published when the CT is initially straight in deviated wells. Numerical examples are provided to show the effect of the initial amplitude, the inclination angle, and the size of a borehole on the sinusoidal and helical buckling behaviors of CT with the residual bending.

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