This paper presents a new modeling technique to predict collapse pressure of oval coiled tubing. Through finite element analysis, a failure mechanism for tubing collapse is identified and a collapse model proposed. This model relates the tubing collapse pressure with its yield strength, ovality and its D/t ratio. Collapse pressures predicted by this model correlates well with FEM prediction. Collapse experiments were also performed to generate test data for collapse pressure under various ovality. To better simulate the actual material behavior in a typical tubing operation, the ovality in the collapse experiments was generated through a fatigue machine. Predictions from this model are compared against the experimental data as well as other published test data and good agreement is achieved. This new model predicts very well the effect of the ovality and axial force on the collapse pressure. The paper concludes with an introduction to an enhanced software that incorporates this new modeling technique for collapse prediction.
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