SOUZA, D. H. S.; http://lattes.cnpq.br/4829751123520146; SOUZA, Daniel Henrique Silva de.
Resumo:
Deformation bands are structures formed by localized deformation and exhibit the
capacity of the porosity and permeability changes in sedimentary rocks. Therefore, it has
the capacity to change the flow properties on reservoir rocks. Deformation bands may
occur in the individual form (singles) and as bands nucleation (clusters). The genesis of
deformation bands can be associated to formation, growth and coalescence of structures
named “microcracks”. These strutures are formed and grow approximately to the
maximum compression axis (σ1). The main objective of this work is create an evolutive
model for the brittle structures of “Outcrop 1”, which is related to the Antenor Navarro
Fomration, based in the development and coalescence of microcracks and predict the
nucleation location of occurrence. The methodology consists in the analysis, mapping and
data collect of planes and lines of the aimed outcrop, and compution of paleotensors that
acted in its genesis. This compution was made by the utilization of the software
TectonicsFP which uses the data of planes and lines to provide the paleotensors related
to formation of these structures. The structural analysis in outcrop resulted in the
identification of two brittle structures system, one E-W and another NE-SW. These
systems own linkage patterns with each other, allowing to infer that only a set of
paleotensors acted in the genesis of both of them. The geometric set of the outcrop, along
with de linkage patterns between the deformation bands systems, is similar to the process
of microcrack linkage. Preview researchs, about formation of structures by the interaction
of microcracks, were based in laboratory and microscopy analysis. However, studies
about their development in larger scales remains absents. The microcracks genesis would
happen parallelly to the maximum compressive axis (σ1), and would be related to the
action of “stress intensity factor” (SIF) mode I (tensile), while the linkage of microcracks
would be caused by the stress intensity factor mode II (shearing). The SIF mode II would
create a structure denominated “linkage microcrack”, which would bond the coalescente
structures, which a larger nucleation of deformation bands would occur in the analogous
surroundings of linkage microcrack in the outcrop scale. Ultimately, the current
geometric configuration of the outcrop would be a fractal resultant of development of
genesis, growth and coalescence of microcracks.