Summary

Most of the problems caused during drilling wells, such as pipe sticking, poor wellbore cleaning, sidetracks and even wellbore lost, are generated by some phenomena manifested in wellbore wall, such as Break-out, Wash-out y Kea-seat, which give origin to some slides of the wellbore wall known as cavings, the above problems and their effects contributes to increase the non productive time.

Currently, the caving volumes are used as a warning signal of wellbore instabilities during real time monitoring, since according to its morphological classification and produced volume represent kind of wellbore damage and its critical nature respectively. Considering the above aspects, the main aim of this research is to propose a new approach to estimate cavings volumes, in order to identify the kind of wellbore failure and the corrective actions in real time. Besides it can simulate the most critical aspect of the problem predicting the cavings volumes and the depth which they come from in order to prevent and mitigate them, thus reducing the non productive time during wellbore drilling.

In this new approach, a simulation of drilled wellbore is carried out using the Finite Elements Method taking into account the failure criterion and the material constitutive model to each cell of the simulation mesh, these considering the rock mechanical properties, mud weight and in situ stress state, in order to quantify the cells volume that failed in the simulation and reproduce the cavings volume of wellbore wall that would be produced during drilling.

An analytical approach is proposed in order to validate the results of the simulation. It consists approximating the cavings volume to the volume of a triangular prism, and calculating it by using geomechanics parameters such as in situ stresses, break-out angle and its width, mud weight and pore pressure. All these geomechanics parameters were obtained from wellbore logs.

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