Modelagem geológica 3D em uma zona de dano da Falha Portalegre, Bacia Rio do Peixe, Nordeste do Brasil.

Abstract

Fault Zones are composed of three architectural elements: core, damage zones and protolith. Damage zones can be formed by small faults, joints and deformation bands. Deformation bands can affect the petrophysical properties of reservoirs by up to six orders of magnitude. Although the petrophysical characterization of deformation bands and host rocks are well characterized, understanding their spatial distribution and how to represent them in seismic scale models is still a matter of debate. The objective of this work is to study in a multiscale way the heterogeneity of fault zones and their properties, highlighting their existing similarities and limitations. For this, three areas of different scales containing the target outcrop of study were selected, structural data were acquired from seismic analysis, scanlines and UAV mapping. Petrophysical property data were obtained using the mini-air permeameter, and the clay mineral content using gamma-ray profiles. From the analysis of damage zones in outcrop and the construction of 3D geological models, it was noted that the occurrence of secondary faults and clusters in the outcrop cause an increase in deformation intensity due to the increase in the frequency of structures, causing zones of damage with relevant impact at meso and macro scale, under facies and permeability distribution. It was identified that the finer particle size units have greater deformation intensity, higher clay mineral content and lower permeability values. The Kx and Ky directional permeability values always present significant reductions in the regions close to the faults, due to the compaction effect of these structures, whose value disparity between them can reach up to 3 orders of magnitude from the first to the second; the occurrence of nearby secondary faults compacts their surroundings and generates a local negative impact on permeability. Finally, it was possible to observe that there is a pattern that is repeated in the different observation scales with regard to the layout of the damage zones and the negative impact of permeability due to the occurrence of secondary failures, so it is extremely important , the identification of these elements to understand their influence in the studies of fluid flows in reservoirs.