Seismic stratigraphy and tectono-structural framework of the Bjarni area, Hopedale Basin, Labrador Sea

Martin, Michelle Rae (2007) Seismic stratigraphy and tectono-structural framework of the Bjarni area, Hopedale Basin, Labrador Sea. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (16MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The Labrador shelf and slope Mesozoic sedimentary area is divided by the Okak Arch into two large basins, the Saglek Basin and the Hopedale Basin. The Hopedale Basin is the more southerly basin and extends from the Cartwright Transfer Fault Zone (CTFZ) in the south to the Okak Arch in the North: a distance of approximately 500 kilometres from 55° to 59° latitude North. It is part of a large, oval, tectonic depression having an area of about 175 000 square kilometres. The basin has an uneven basement floor consisting of stretched continental crust, exhumed continental mantle (transitional crust) and oceanic crust. The thickest sediment accumulation is located on the outer shelf and inner slope. -- A recent seismic grid collected by Geophysical Service Incorporated (GSI) during 2003, 2004 and 2005 has produced a regional 2D seismic coverage adequately covering this vast area that contains the giant Bjarni/North Bjarni gas field. These non-exclusive seismic lines were graciously donated to Memorial University of Newfoundland to be used for regional tectonic, structural and seismic stratigraphic investigations and mapping. -- Using these donated data, several seismic sequences were defined, correlated to well information and mapped throughout the area surrounding the Bjarni/North Bjarni field. The study indicates that the Lower Cretaceous Bjarni Formation is widespread, was deposited in a large rifted area and contains the basin's main reservoir and source rock. Seismic correlations indicate that the Bjarni reservoir extends beyond the shelf and into the outer slope region. This new interpretation increases the probability that there are still many undrilled Bjarni plays on the shelf and on the slope. -- On the basis of seismic character observed on lines that extend into deepwater, it is apparent that there was a significant amount of postrift mantle exhumation on the Labrador margin expressed as serpentinized ridges as well as predrift lava flows mapped on continental and transitional crust domains. Thick syndrift and postdrift sediments overlie this oceanic crust. -- Kinematic modelling of a representative dip line illustrates that most of the extension took place in a continental setting during the Early Cretaceous. Multiple periods of subsidence followed; the most significant being the prominent thermal subsidence during the Late Tertiary. This subsidence along with margin tilting created the Labrador Shelf as seen today. -- As proven by past drilling, the Hopedale Basin contains all elements of a rich petroleum system. With new interpretation of the main reservoir-Bjarni sandstone-combined with previously documented geochemical data, it is evident that there is significant remaining hydrocarbon potential along the Labrador Shelf. Preserved Paleozoic carbonates on top of basement highs as well as draping and onlapping of the Bjarni sandstones on rotated basement blocks are the most significant hydrocarbon plays. Several leads have been indicated during regional mapping. -- Currently there is only minor exploration interest in the Hopedale Basin due to its remote location and its vulnerability to natural hazards including high frequency of icebergs, long-lasting pack ice and variable weather. These natural hazards have resulted in no exploration drilling or landsales in the basin for over 25 years even though it has already been proven to hold over 4.2 Tcf of gas. Hopefully, increasing demand for gas, high commodity prices, new drilling and production technologies and new seismic surveys supplemented by hydrocarbon detection methods (AVO, LMR, etc.) will encourage companies to develop the existing discoveries and explore for new ones.

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