SIMULATION OF GENERATION AND PROPAGATION OF TENSILE FRACTURES IN LAMINATED CARBONATES OF THE CRATO FORMATION CONSIDERING STRATIGRAPHIC HETEROGENEITY

Resumo

The Crato-PE Fm is part of the Araripe Basin, being one of the largest areas in relation to
the interior basins of north e astern Brazil. This led to the reactivation of old paddles for inversions,
and converting an old graven into a horst. This work seeks to simulate numerically a generation and
propagation of natural fractures for the effect of vertical lithological variation on fractures. In the
present work, it is proposed the use of the technique of fragmentation of high aspect ratio mesh
elements to model, together with the constitutive model of Damage to traction, a generation and
propagation of fractures. This type of model is able to divert the effect of the materials when submitted
to progressive processes of mechanical degradation by reducing the rigidity of the material. The
problem analysed is the simulation of the generation and propagation of extension fractures in a
profile considering interleaving of laminate layers with other types of lithology’s, representing a
faciological variation with impact on the mechanical competence of the layers on the genesis and
propagation of the extension fractures. In order to perform the study of fracture generation and
propagation, we used the fragmentation technique with special interface finite elements. This
technique was chosen because it numerically represents the behaviour of intensively fractured media,
in which the special interface elements are located between the regular finite elements. Was
considered submitted to a vertical tension representing a vertical burial state, and a horizontal tension
variation the extension direction. The base and one of the lateral borders of the domain are restricted
as to the displacement in the normal direction. The analysis is in flat deformation considering a
Lagrangean approach for the deformations. It has been found that as the prescribed tensile stress on
the left side of the section increases, horizontal tensile stresses develop in the layers, but with a higher
concentration in the laminate layer of greater stiffness and tensile strength.