Contribuição do atrito nos esforços axiais de colunas de produção e injeção em poços de petróleo submetidos a carregamentos operacionais

Abstract

This work proposes the numerical modeling of tubing strings in oil wells subjected to operational loadings to determine the contribution of friction to axial forces. Tubing strings undergo different combinations of forces throughout their lifespan related to thermal variations, pressures, self weight, buckling, and friction. The accurate prediction of these forces and the sizing of the column are essential to ensure well safety without the need for workover and to maintain the integrity of one of the first elements of the well barrier system. Friction forces, impacting axial forces, are generated when buckling of the tubing occurs due to the formation of contact regions between the string and the casing. In directional wells, the weight and trajectory of the tubing naturally generate friction forces along the casing. Due to the variety of operational loadings, a general solution to the buckling-induced friction problem requires numerical solutions. In the literature, there are models that assess only the friction from buckling or from weight and trajectory, while others even propose a combined analysis of these friction sources, but only for specific cases and without evaluating the loading history. In this direction, a model with all these criteria allows for a more realistic friction analysis. The adopted methodology is divided into five macro steps to achieve the proposed objective: i) studies on tubing strings and operational loadings; ii) studies on friction models and aspects of buckling in tubular structures; iii) computational modeling of buckling-induced friction in the tubing of vertical wells; iv) incorporation of new effects into buckling-induced friction modeling; v) case studies. Based on the conducted case studies, the inclusion of friction through the capstan effect results in a noticeable increase in friction forces, even in wells with minimal inclination. Combining this effect with helical buckling in production scenarios represents the most critical form of friction, potentially substantially impacting axial forces compared to analyses without friction. In the case of the investigated horizontal injection well, the influence of friction due to weight becomes particularly relevant, and during the evaluation of shut-in operation, an increase in compression to be supported by the column is observed. The main contribution of this work is the improvement of numerical modeling for the calculation of axial forces, considering, in addition to temperature, self-weight, and the balloon effect, friction, and different buckling modes in the tubing of directional wells.