Análise multiescalar de afloramento digital análogo de reservatório carbonático na formação salitre

Abstract

The present study investigates the influence of sub-seismic fractures on the interconnectivity and flow of fluids associated with folded carbonate rocks and their role in the stages of evolution of the karst process in the Brejões System, Irecê Basin, Northeastern Brazil. We also seek to promote the geophysical characterization (Electrical Resistivity Tomography – ERT) of the Brejões I and the associated karst system. We carried out 3D remote sensing surveys on the surface with an Unmanned Aerial Vehicle (UAV) and subsurface with Terrestrial Laser Scanning (TLS). Based on the digital outcrops, we analyzed fracture attributes and bedding measurement, fracture length distributions, persistence estimations, topological, morphometric, and geophysical investigation. Multiscale analysis shows that fracture corridors, caves, and canyons occurred along a hinge of an N-S-oriented anticline or parallel to it. The fracture dataset from the surface and subsurface are related and two compression events related to the Brasiliano Orogeny (740-560 Ma). Power-law exponents greater than 2.5 suggest the influence of all fracture lengths on the connectivity of the Brejões System, emphasizing fractures smaller than 50 m. The topological analysis demonstrated a highly connected fracture network, above the percolation limit, with extensive clusters and several levels of interactions. These results are supported by the wide distribution of persistence values in the fracture intensity (P21) and density (P20) maps. The morphological attributes applied in geophysical prospection allowed the optimization of its stages and direct correlation with the signature of the cave. The ERT method showed a wide range of electrical resistivity (100 - 10,000 Ohm.m), thus reflecting different levels of weathering and karstification in the Brejões System. Based on the geomorphological and structural scenario described, type I and II reservoirs were associated with the Brejões System. Their marked anisotropy may imply preferential fluid migration routes, which may impact all phases of exploration. Our results reveal that mapping fold-related damage zones can be an alternative approach for identifying sub-seismic scale fracture corridors. The application of LiDAR as an auxiliary methodology in the stages of geophysical prospecting with ERT gives a new perspective to the analysis of the 3D effects in karst environments.