Influência de zonas de dano com interação e linkagem de falhas no fluxo de fluido em meios porosos siliciclásticos, Bacia Rio do Peixe, NE Brasil.

Abstract

Several factors influence the development of fault damage zones. However, the influence of the interaction and linkage of fault segments in fault zones and its implications for the spatial distribution of subseismic structures and characterization of permeability and, consequently, the flow of fluid in porous media, still need further explanation. This study analyzes the relationship between the structural context and the petrophysical properties through the characterization and modeling of structural elements and permeability in an outcrop located in the lower block of an boundary fault (Portalegre Fault) of the Rio do Peixe Basin, Northeastern Brazil. Based on data acquired from two scanlines, we analyzed the cumulative frequency of deformation bands crossing the damage zone and the protolith, and identified three

fault zones marked by three inner damage zones. The first fault zone is related to a seismic- scale segment of the Portalegre Fault, while the second and third fault zones are associated with

two secondary subseismic faults. The spatial distribution of subseismic structures is marked by decreases and increases in the frequency of deformation bands according to the distance from each fault. We performed the petrophysical characterization of these fault zones and recognized a pattern of successive increases and decreases in permeability as we move away from the fault and approach another. These interpretations were used in the construction of permeability models that show that permeability across the fault zone varies without a well-defined pattern and that the impact of deformation bands on permeability is much more evident perpendicular to the preferential dip direction of these structures. The structural complexity of the studied fault zone and the variations in the dip direction of the analyzed segment of the Portalegre Fault led us to the interpretation of a linking damage zone. The patterns observed here are opposed to the distribution pattern of subseismic structure and permeability of a wall damage zone, which comprises a gradual decrease in frequency of structure, a gradual increase in permeability as we move away from the main fault, and an influence of the deformation on the equivalent permeability even if parallel to the structures. Thus, this study highlights the effect of the interaction and linkage of fault terminations on the distribution of deformation bands and its impact on permeability, clarifying some aspects associated with the structural heterogeneities of siliciclastic reservoirs affected by fault zones