Geochemical Interpretation of Seabed Cores and Their Relation to Petroleum Systems of the Northwestern Atlantic Margin, Offshore Newfoundland and Labrador, CA

Graham Dillabough

The need to de-risk the petroleum systems in the offshore Labrador region has led to a unique study involving the geochemical analysis of regional seabed cores along the Canadian Atlantic margin, with the aim of identifying hydrocarbon microseepage in the offshore. Exploration along the Labrador margin has been largely dormant over the past 3 decades, with the last exploration well in the area spud in 1983. Recent regional long offset 2D seismic acquisition by TGS-PGS over the slope and deep water regions of the Labrador Sea, along with activity in Western Greenland, have sparked renewed interest in the region. Critical to understanding the exploration potential of the region is the need to delineate the active petroleum systems and their potential source rock equivalents. Possible petroleum sources for the slope and deep water remain largely undefined, although to the south is the prolific Kimmeridgian source rock of the Grand Banks, to the north the Cretaceous oil prone source rocks of western Greenland, and to the west by the dominantly gas prone source rocks of the Hopedale Basin. Using an extensive archive of ocean seabed core samples stored at the Geological Survey of CA-Atlantic, covering all areas offshore from the east coast of CA, a subset of approximately 170 cores along the entire Labrador margin (Flemish Pass to the Saglek Basin, south to north respectively) were sampled for analysis. Cores collected over the last 11 years for regional surficial geology and geohazard studies were selectively used in the initial phase of this study. These cores were stored in sealed plastic sleeves under refrigerated conditions (4°C). The aim of this study was to test a geochemical sampling technique to detect positive indications of petroleum hydrocarbons within archived cores. Using the Amplified Geochemical Imaging technology from W. L. Gore & Associates, hydrocarbon signatures in the nanogram range have been identified. To date, this technology has been tested and successfully used on fresh core material, but it had not been extensively attempted on archived material. When plotted spatially, some of the geochemical signatures correlate with seeps, identified from satellite observations, and hydrocarbon chimneys, seen on 2D seismic. A subset of cores taken within a short distance of the Mizzen SDL discovery well, Mizzen O-16, had strong positive results for hydrocarbons. These particular samples were taken from the base of 10-m long cores and frozen immediately after core collection in 2001. Using this as a type response, signatures away from existing well control along the Labrador margin can be assessed for microseepage probability. When compiled by basin, the data highlight potential petroleum signatures by region. Continuing work is planned to validate these early results, aid in defining the petroleum source families, and ultimately to assist in linking microseepage to subsurface petroleum systems.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013