Orientação e magnitude de tensões na bacia potiguar: implicações para evolução de bacias em margens passivas
This study presents new stress orientations and magnitudes from the Potiguar basin in the continental margin of Brazil. We analyzed breakout and drilled induced fractures derived from resistivity image logs run in ten oil wells. We also used direct Shmin measurements determined from hydraulic fractu...
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| Formato: | Dissertação |
| Idioma: | por |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/18828 |
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| Resumo: | This study presents new stress orientations and magnitudes from the Potiguar
basin in the continental margin of Brazil. We analyzed breakout and drilled induced
fractures derived from resistivity image logs run in ten oil wells. We also used direct
Shmin measurements determined from hydraulic fractures and rock strength laboratory
analysis. In addition, we compared these results with 19 earthquake focal mechanisms
located in the crystalline basement.
We observed that stress directions and magnitudes change across the basin and
its basement. In the basin, the SHmax gradient of 20.0 MPa/km and the SHmax/Shmin ratio
of 1.154 indicate a normal stress regime from 0.5 to 2.0 km, whereas the SHmax gradient
of 24.5MPa/km and the SHmax/Shmin ratio of 1.396 indicate a strike slip stress regime
from 2.5 to 4.0 km. The deeper strike-slip stress regime in the basin is similar to the
regime in the basement at 1-12 km deep.
This stress regime transition is consistent with an incipient tectonic inversion
process in the basin. We also noted that the SHmax direction rotates from NW SE in the
western part of the Potiguar basin to E W in its central and eastern part, following
roughly the shoreline geometry. It indicates that local factors, as density contrast
between continental and oceanic crust and sediment loading at the continental shelf
influence the stress field. The concentration of fluid pressure in faults of the lowpermeability
crystalline basement and its implications to establish a critically stressed
fault regime in the basement is also discussed |
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