Estratigrafia mecânica e análise estrutural aplicadas ao estudo de bandas de deformação na bacia Rio do Peixe, NE, Brasil.

Abstract

The deformation bands change physics properties and mechanical of the rocks, influencing the flow on the porous rocks. These structures are principally in porous sandstones and usually are associated with a distensive setting. Moreover, deformation bands are research targets related to quantification and transformation of petrophysics properties and rheologic of the rocks from a reservoir. In this context, this study seeks to analyze the deformation bands and their influence in porous sandstones at the Rio do Peixe basin. This study addresses the following issues: (i) what is the deformation bands behavior in different layers of sandstones; (II) what is the mechanical resistance of the sedimentary units shows in the propagation of brittle deformation. To that, the structural data, mechanical stratigraphic and geomechanics were taken in the field with the aim to realize a digital geologic model. During the mechanic structural characterization in a scanline, uniaxial mechanical analyzes were realized using Schmidt hammer at the areas with and without deformation. The results indicate that stratigraphic units with higher granulometry allow smaller deformation bands inflection as higher thickness of these. Similarly, the stratigraphic units with smaller granulometry allow higher frequency of the deformation bands. Besides that, deformed areas showed higher values of uniaxial compressive strength when compared to units with smaller granulometry that have smaller uniaxial compressive strength. The mechanic stratigraphic control has the thickness of the layer as a differential parameter when affected by deformation, where layers with higher thickness have higher resistance from the deformation concerning to frequency and inflexion. The 3D geologic model provides the cave shape visualization, stratigraphic units and their limits, besides penetrability, spacing and geometry of the structures. The adaptation of the mechanical stratigraphic technique for deformation bands used the petrophysical parameters, UCS and frequency of these structures to define the mechanical unit. Although of being the same lithostratigraphic unit, the granulometric differences and of structure provided different mechanic resistances to the layers, precluding the propagation of deformation bands for these distinctions.