Carlos Wong

B.Sc., Honours Earth Sciences, Dalhousie University (2014)

M.Sc. Thesis

PETROLEUM SYSTEM MODELLING OF POTENTIAL LOWER JURASSIC SOURCE ROCKS ALONG THE SCOTIAN MARGIN

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A mature source rock is the key element in a petroleum system and it is the critical risk when exploring in undrilled areas where there are very few direct indications of hydrocarbons (either from surface seeps or seismic data). On the Scotian Margin, there are proven offshore commercial hydrocarbon fields in Jurassic and Cretaceous reservoirs that have geochemical characteristics consistent with proven Upper Jurassic source rocks - but the unequivocal linkage between source and reservoir has not been demonstrated. (Silva, Wong and Wach, 2015; Fowler, Webb, Obermajer et al., 2016). Below this proven interval, in rocks of Lower and Middle Jurassic age, source rocks are abundant globally, related to restricted marine and lacustrine depositional environments associated with the break-up of Pangea, although it is uncertain whether source rocks of this age are present on the Scotian Margin. If they are, and they have a suitable thermal history, then there is the potential for commercial petroleum systems that are currently undiscovered. The objective of this study is to address this technical problem through 2D thermal modelling. This study integrates source rock geochemistry and depositional history from proven source rocks in Morocco (the conjugate margin) with basin modelling of the Scotian Margin in a more detailed approach than previous studies, such as the 2011 Play Fairway Analysis (PFA). These models test the Lower Jurassic source rocks by testing the kerogen type and demonstrating the thermal maturity range of each kerogen type in the Scotian Basin.

This thesis presents the results from the construction and testing of 2D Petroleum System models on four shelf-to-slope regional seismic lines (NovaSPAN 1100, 1400, 1800 and 2000) using PetroMod software, together with new data from the 2011, 2015 and 2016 Nova Scotia Department of Energy sponsored Play Fairway Analysis, and outcrop data from Aït Moussa in the Middle Atlas, Morocco. Several organic-rich intervals have been identified along the Mesozoic conjugate margins of the Central and North Atlantic. The similarity of the depositional environments and paleogeography of the Scotian margin with the conjugate Western European and Northwest African domains, which contain proven Lower Jurassic source rock successions, suggests the presence of a similar interval in the offshore Scotian margin. If present, there is uncertainty in the source rock characteristics (quantity, quality, and maturity). With ongoing and future petroleum exploration offshore Nova Scotia, resolving these uncertainties is necessary to reduce the risks associated with exploration. In this study, the software PetroMod version 2018.1 (Schlumberger) was used to construct 2D models of source rock maturation of potential Lower Jurassic rocks on the Scotian Margin using dip lines of the ION NovaSPAN geophysical dataset (NVR1-1100, NVR1-1400, NVR1-1600, NVR1-2000). In each model, different source rock variables (hydrogen index and total organic carbon) were used based on data from the High and Middle Atlas Basins (Morocco). Results suggest potential Lower Jurassic source rocks in the Scotian Basin are within the oil maturity window in the south, and transition to the gas maturity window to the north, due to burial depth and salt mobilization. The Lower Jurassic interval has a range of maturity and potential for generation of hydrocarbons. The transformation ratio (organic matter to hydrocarbons) varies throughout the Scotian Basin when modelled with different types of kerogen. Data limitations are recognized as only five 2D seismic lines are used to map the maturity of the Scotian Basin.

Keywords: Scotian Basin, Petroleum Systems, Lower Jurassic Source Rocks, Modelling, Source Rocks, Petroleum  Systems Modelling, Source Rock Maturity, PetroMod
Pages: 207
Supervisor: Grant Wach