Stress superposition controls the evolution of radial faults around salt diapirs (Espírito Santo Basin, SE Brazil)

Radial faults are common types of geological faults in salt-bearing basins and have an impact on hydrocarbon production, carbon sequestration, and energy storage. High-quality 3-D seismic and well data are used in this work to investigate the evolution of radial faults in the Espírito Santo Basin, SE Brazil. The mapping of 706 radial faults, with lengths ranging from 300 m to 8400 m, resulted in the recognition of eight zones with alternating grabens and horsts around a diapir (Diapir A). Grabens are formed in saddles separating Diapir A from other salt structures and are crossed by conjugate radial faults. Horst zones found between these grabens have only a few randomly distributed radial faults. Importantly, stress superposition played an important role in controlling the formation of radial faults; the distribution of radial faults in graben and horst zones is justified by the effect of hoop stresses related to diapir growth that are superposed on (1) hoop stresses resulting from other salt diapirs, (2) lateral compressional stresses resulting from salt flow, and (3) local extensional stresses generated close to diapir walls. We show that grabens are likely to experience fluid flow, while horsts tend to be favorable traps for unconventional hydrocarbons, carbon sequestration, and energy storage. All in all, stress superposition in salt-bearing basins is one of the primary controls on the distribution and evolution of radial faults.