Controle estratigráfico sobre a silicificação hidrotermal na falha Afonso Bezerra, Bacia Potiguar, Brasil

Abstract

Hydrothermal silicification has a significant impact on petrophysical properties of reservoir rocks. The main constraints on silica-rich fluids are the faults, their damage zones, and variations in the host lithology. However, although the influence of host lithology on silicification is partially understood, further studies are required to clarify its role and spatial impact. In this study, the Cretaceous sequences of the Potiguar Basin, comprising the sandstones of the Açu Formation and the limestones of the Jandaíra Formation, as well as the crystalline rocks of the Neoproterozoic basement, are crosscut by the Afonso Bezerra Fault System, where significant occurrences of hydrothermal silicification are observed from the basement to the surface. This study employed seismic data, along with well data, and applied seismic attributes to enhance the visualization and mapping of stratigraphic units and the geometry of the hydrothermal silicification. A statistical spatial analysis of the silicified body was conducted to assess the relationship between silicification and stratigraphy. The results revealed that silicified body concentrate along the strike of the Afonso Bezerra Fault, which appears to be the main conduit controlling the uprise of hydrothermal fluids. Width variations and shape changes of the silicified zone connected to the variations of lithology. Carbonate rocks exhibit extensive silicification associated with wider volumes of affected rocks, whereas siliciclastic rocks show narrower and less pervasive silicification. In the crystalline basement, silicification is confined to fault zones. This spatial distribution evidences the primary control of tectonics and host lithology on hydrothermal fluid flow, thereby enhancing our understanding of hydrothermal silicification compartmentalization.