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A New Oil Play: Sable Sub-Basin Offshore Nova Scotia

Wilson, Hamish *1; Luheshi, Matt 1; MacMullin, Roderick A.2
(1) RPS Energy, Henley on Thames, United Kingdom.
(2) Department of Energy, Halifax, NS, Canada.

The Sable sub-basin contains the only current production offshore Nova Scotia. Main producing fields are gas, around 2.0TCF recoverable with 40 mmbbls liquids. Depressed gas price and recent well failure discouraged exploration. 2 small light oil fields(Panuke & Cohasset) and oil shows to the North provide intriguing evidence of an oil play in the shallow water shelf region. We present an updated geoscience model to predict reservoir/seal distribution and a new petroleum systems model suggesting an oil charge around the rim of the Sable sub basin. We also demonstrate extensive exploration resource in the Sable & Huron sub basins(shelf/present day slope). Reservoir/Seal/Trap:Lower Cretaceous Mississauge and Logan Canyon deltaic sequences are main reservoir for producing fields and principle exploration target. Reservoirs found in delta top facies sealed by intra-formational shales. Seal failure has been key well failure mode in Sable Island exploration wells. Recent work focused on mapping regional MFS sequence boundaries that form sealing horizons combined with maps of channel systems provides a predictive approach to highgrade undrilled dip closed features. The reservoir is proven in the Sable Sub basin; this work demonstrates reservoirs extend NE to an underexplored region. Fields are trapped in rollover structures with growth faults that sole out into salt canopies. Structures are likely NE of Sable Island but not mappable on existing 1970’s 2D seismic data. Evidence for an Oil Play: A full basin scale 3D petroleum systems model has been constructed using BEICIP’s Temis 3D modeling package. Well evidence and fluid isotope data point to Upper Jurassic Tithonian as main source rock for producing gas fields. Source rock mainly gas prone with associated liquids. Maturation & migration modeling suggests liquid charge from source rock from basin margins and over intra basinal highs. Oil charge migrates laterally to trap in shallower reservoirs along basin margin as in Cohasset/Panuke. The later gas charge then sources main sable gas fields. We predict oil in shallow reservoirs associated with basement highs/around the basin margin. Resource Potential: Expulsion modeling suggests presence of substantial YTF resources in shelf region. Within the sub basin are several undrilled dip closed features, close to infrastructure. CRS mapping indicates play sweet spots to NE Sable Island where there have been no effective play tests supported by modern 3D data.


AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California