Finite element modeling of the stability of single wellbores and multilateral junctions
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This dissertation describes investigation of the stability of single holes and multilateral junctions in order to optimize their design. The investigation is based on finite element three-dimensional modeling using the commercial software ABAQUS. The stability of single holes and multilateral junctions was analyzed at different orientations in a three-dimensional in-situ stress field. Traditional stressdisplacement analysis in steady-state was coupled with transient phenomena to compute strain and stress behaviors and changes in pore pressure due to disturbances created by drilling. This coupled analysis allowed for the inclusion of time dependent processes and the non-linear processes that influence the behavior of the system compounded by rock, fluids contained in the rock, and insitu stresses. The three-dimensional wellbore stability modeling presented here overcomes the limitations of common assumptions in wellbore stability analysis, such as linear poroelasticity, homogeneous and isotropic formations, and isotropic in-situ stress field, because this modeling accounts for the sources of non-linearity affecting the strain and stress responses of rock. This study showed that precise knowledge of the in-situ stress field is an important geomechanical parameter needed to optimize the orientation of a single wellbore and the orientation of the lateral at the junction in a multilateral scenario regarding stability. In addition, performing stress-displacement analysis of multilateral junctions identified critical areas regarding failure in the junction area. Geometry, placement, and orientation of the junction were analyzed, and the results provided a real insight to propose strategies to optimize drilling and completion design of multilateral wells. Comparisons of the predictions of this numerical approach with experimental data recently published showed that this numerical approach is reliable for simulating the steady-state phenomena and some transient phenomena encountered in wellbore stability analysis of both single holes and multilateral junctions.