Ichnology, sedimentology, and stratigraphy of the Hibernia Formation, Jeanne D'arc Basin, offshore, Newfoundland

Schatz, Elizabeth Rose (2018) Ichnology, sedimentology, and stratigraphy of the Hibernia Formation, Jeanne D'arc Basin, offshore, Newfoundland. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The Jeanne d’Arc Basin is located approximately 350 km east of St. John’s, Newfoundland, Canada. The basin contains many prolific hydrocarbon reservoirs and is still actively explored and studied. The Hibernia Field, on the western edge of the basin along the Murre Fault, contains four sandstone reservoirs: the Jeanne d’Arc Formation (Late Jurassic), the Hibernia Formation (Early Cretaceous), the Catalina Formation (Early Cretaceous), and the Ben Nevis-Avalon Formation sandstones (Early Cretaceous). The Hibernia Formation, Hibernia Field, is a sandstone reservoir of fluvial deltaic origin and is estimated to contain 1644 million barrels of oil. The Hibernia Formation in the southern Jeanne d’Arc Basin displays good reservoir potential but few studies have been undertaken. Seventeen lithofacies are identified from core analysis of seven core samples from the southern Hibernia expression: three from the Upper Hibernia Zone and four from the Lower Hibernia Zone. Six facies associations were inferred and a wave-influenced delta classification was determined. Ichnological analysis resulted in the identification of 10 distinct ichnofabrics. Core plug data was analyzed by lithofacies and ichnofabric to assess trends in permeability and porosity in the Upper Hibernia Zone. Cross bedded medium- to coarse-grained sandstones (Facies 10, interpreted as deltaic mouthbar sandstones) display the highest permeabilities up to 962 mD and porosities averaging 13%, and commonly contain Ophiomorpha burrows. Minipermeametry of a slabbed core section from Facies 10 showed that clay material was removed from the host sediment immediately surrounding the burrow effectively enhancing the porosity and permeability. Cryptobioturbated and unbioturbated, parallel laminated storm beds display the same range of permeabilities and porosity; however, the cryptobioturbated storm beds display higher vertical connectivity between sandstone laminations as shown from minipermeametry analysis. Deeply eroded and amalgamated storm bed tops can result in vertical connectivity between potential reservoir-quality sandstone units. Muddy siltstone facies containing Phycosiphon-dominated ichnofabric are observed to have increased porosity which has the potential to serve as a conduit for hydrocarbon migration since the Phycosiphon burrow halo is lacking in clay material and shows increased porosity when compared to the host rock. Analysis of facies distribution using both core logs and wireline log data allowed for the placement of a paleoshoreline (Valanginian). Stratigraphic analysis of the southern expression of the Hibernia Formation suggests that autocyclic lobe switching, longshore drift from west to east, and tectonically-driven sea level changes were the main controlling factors on facies distribution. Sandstones in the Hebron Field area displayed higher permeability and porosity characteristics than equivalent facies in the West Bonne Bay area. Further exploration is recommended for the Hebron Field, specifically in shoreface settings where storm beds are amalgamated and interbedded with deltaic mouthbars.

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