EQUIVALENT MODELS OF VERTICAL WELLS CLOSURE IN SALINE ROCKS

Resumo

This work proposes the development of a strategy to use equivalent models to estimate the
closure of a salt mass drilled by a vertical well. Drilling in areas with salt formations is a great challenge,
since these rocks develop high creep strain rates – continuous deformation even under constant tension.
Due to this phenomenon, the well diameter tends to reduce over time, what can delay the drilling process
for days or even lead to the well abandonment. To avoid these problems, computational models using
the Finite Element Method are used to predict the behavior of these rocks during drilling. To design
the drilling process, several simulations are needed and they may take many hours or days. Thus, it is
interesting to develop approaches that reduce the simulation time, allowing to evaluate the same scenario
considering different values for the project variables. The methodology adopted in this work is divided
into seven stages: a) definition of the base study scenario; b) simulation of the reference scenario; c)
elaboration of rules for the division of the massif into one and two-dimensional models; d) modeling and
simulation of pre-defined portions; e) verification of the errors; f) possible adjustments in the rules of the
massif division; g) application of the strategy in other scenarios for its validation. With the validation
of this strategy, it is possible to reduce the computational cost and the time of elaboration of the well
project. To validate the strategy, the result of the simulation of a synthetic scenario is presented, where
approximate answers were obtained with reduction in the computational cost, wich leads to a reduction
in the well design time.