| Autor: |
Emily Barnabas Kiswaka, Maarten Felix |
| Rok vydání: |
2020 |
| Předmět: |
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| Zdroj: |
Marine and Petroleum Geology. 119:104463 |
| ISSN: |
0264-8172 |
| DOI: |
10.1016/j.marpetgeo.2020.104463 |
| Popis: |
Seismic surveys of the Permo-Triassic successions in Norwegian Sea sub-basins have been studied to determine the distribution of organic-carbon-rich intervals in the deeper basinal areas. Upper Permian to Lower Triassic organic-carbon-rich deposits had been described in cores from the margins of the basin, but their distribution in the deeper parts of the basin was unknown. The distribution of the organic-carbon-rich deposits in the deeper basin areas has been determined using a combination of amplitude versus angle/offset (AVA/AVO) analysis and an assessment of strata-bound deformation structures. AVA/AVO anomaly class IV, which has a negative normal incident reflection coefficient that decreases with angle/offset, has been used to predict the presence of organic-carbon-rich rocks in this work. The intercept (I) and gradient (G) plots (IG-crossplots) together with the Near-Far angle amplitude comparison of the seismic surveys have been used to complement the interpretation. The IG cross-plotting was done by selecting small windows (data probes) along the intervals speculated to be organic-carbon-rich. Any data probe which displayed AVO class IV elements on the IG crossplots and exhibited amplitude dimming with angle has been considered to indicate an organic-carbon-rich layer. The results of this work show the presence of both Upper Permian and Middle Triassic organic carbon rich sediments in the deeper parts of sub-basins within the Froan and Helgeland basins in the Norwegian Sea area. Two and one organic-rich intervals are indicated in the Froan and Helgeland basins respectively. The distribution of these organic-rich rocks was partly tectonically controlled, resulting in spatially limited deposits in the compartmentalized Froan Basin but more extensive deposits in the Helgeland Basin. None of the Lower Triassic sections examined in this study showed AVA/AVO characteristics indicative of organic-carbon-rich sediments on IG crossplots. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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