Many factors such as rift history, crustal structure and distribution of high thermal
conductivity salt bodies throughout the sediment pile affect the present day thermal
structure of the deepwater Scotian Slope. Understanding the basin's thermal evolution is
crucial in determining the hydrocarbon maturation potential of this deepwater frontier
basin. The Late Jurassic Verrill Canyon Formation of the deepwater slope has been
inferred as the primary source rock interval for the Scotian Basin. However, to date, only
twelve boreholes have sampled the Scotian Slope, and of these, none penetrate beneath
the uppermost Jurassic sediments. Therefore, the distribution and maturation of deeper
source rock intervals through standard vitrinite reflectance analysis remains unknown. In
this study we attempt to better constrain the thermal history and maturation potential of
the central Scotian Slope using a combination of recently acquired seafloor heat flow
data, 2D seismic reflection data, available well data, simple lithospheric rift models and
3D thermal and petroleum systems modelling. We have derived a method of combining
seafloor heat flow data with simple lithospheric rift models to provide first order
constraints on the hydrocarbon maturation potential of frontier basins in dynamic 3D
thermal models for regions lacking vitrinite reflectance and temperature data from
boreholes.
In July 2008, 47 seafloor heat flow measurements were acquired across the
central Scotian Slope in an attempt to better constrain the region's thermal structure.
Locations seaward of the salt diapiric province, thus unaffected by the high thermal
conductivity of salt, recorded seafloor heat flow values of ~41-46 mWm-2. Significant
increases in seafloor heat flow were noted for stations overlying salt diapiric structures,
reaching values upwards of 72 mWm-2. The seafloor heat flow data have been corrected
to remove the conductive effects of salt and the cooling effects of seafloor sedimentation
on measured heat flow. The corrected data are compared with basal heat flux predictions
from simple lithospheric rift models as constrained using crustal ( ) and lithospheric ( )
stretching factors after Wu (2007) to constrain heat flux history through time. Seafloor
heat flow and simple modelling results suggest present day basal heat flux does not vary
significantly across the slope. Present day basal heat flux across the central Scotian Slope
is ~44-46 mWm-2.
Basal heat flux curves from simple lithospheric rift models are used to constrain
the heat flux history in 3D thermal and petroleum systems models of the central Scotian
Slope. Numerous basal heat flux histories were tested to determine which heat flux
history yielded the best match between modelled and measured seafloor heat flow data
and to determine how varying basal heat flux affects the modelled hydrocarbon
maturation of Verrill Canyon source rocks. The basal heat flux history which yielded the
best match to measured seafloor heat flow data suggests that the Late Jurassic source rock
interval rests primarily within the late oil window. Variations in radiogenic heat
production across the margin associated with thickening continental crust were tested and
suggest that significant variations in both maturation and seafloor heat flow may occur if
radiogenic heat producing elements occur in high enough concentrations in the crust.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:NSHD.ca#10222/13134 |
| Date | 24 November 2010 |
| Creators | Negulic, Eric |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
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