Searching for Petroleum Resources in Offshore Atlantic Canada
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Diagram of an Atlantic-style continental margin including the continental shelf, slope, and rise.
Canada and many other nations need a stable and secure supply of oil and natural gas; this has led to increased exploration, including around Atlantic Canada. Exploring for petroleum in the offshore is very costly, therefore a good understanding of the regional geology and petroleum systems is necessary to improve the chance of successfully finding oil and gas. Researchers at Natural Resources Canada (NRCan) are studying the subsurface beneath the continental shelves and slopes of Atlantic Canada to better understand how these regions were formed and to identify areas with oil and gas potential.
Development of the margin and sedimentary basins
The Atlantic Canada continental margin (located beneath the continental shelf and slope – see diagram) developed along the edge of the ocean basin after the continent of Pangea broke up and the pieces began to drift apart. The initial North Atlantic Ocean was small and shallow; salt and other evaporates which formed when seawater evaporates, precipitated to form thick layers at the bottom of the basin. As the ocean basin widened, sediment that was carried by river systems to the edge of the continent was deposited into the basin. Additional material was added from marine organisms and other sources. Large sedimentary basins developed as sedimentation continued and the compacted layers built up thicker and farther from the shore. Presently, some of the basins along the Atlantic Canadian margin contain sedimentary rocks up to 15 km thick.
Plant and animal matter were swept into the basin and buried beneath other sediment. This provided the organic material that was necessary to form present day petroleum. The formation of petroleum deposits was influenced by the later development of complex structures and faults within these sedimentary rocks, in response to compressive stresses and the deformation of the evaporite layer.
A three dimensional image of the top of a sedimentary rock layer beneath the ocean, created from geophysical surveying in the Atlantic offshore.
Methods and Techniques
NRCan scientists are studying factors that influenced the development of the Canadian continental margins and petroleum resources. Research activities include:
- Geophysical surveying to image the sedimentary rock layers and underlying crust;
- Laboratory studies to analyze traces of petroleum;
- Modeling studies to recreate depositional and deformational history; and
- The dating of microfossils deposited with the sediments.
Specialized laboratory and computing facilities at NRCan’s Geological Survey of Canada (GSC) in Atlantic Canada and elsewhere provide the expertise and equipment needed for these precise measurements and computations. Data and key findings resulting from this work can be readily accessed through various online digital databases.
The drilling rig Bill Shoemaker was used to drill several exploration wells on the Canadian Atlantic margin.
Key Findings
- There is considerable variation in how the continental crust thinned and deformed during rifting; continental crust ranges from 5 to more than 40 km in thickness.
- The Scotian margin is home to a spectacular variety of salt structures resulted from the later movement and deformation of salt layers deposited during early basin formation.
- A more precise framework for the history and paleoenvironment of the offshore has been developed, due in large part to recent advances in techniques for identifying and correlating key events during basin formation.
An example of a dinocyst, a microfossil that is often found in marine sedimentary rocks. It is used to identify the age and depositional environment of rocks along the continental margin.
NRCan Making a Difference
The following NRCan research will support petroleum companies and regulatory boards in their decision making concerning exploration investment and resource development by providing sound geologic knowledge on areas that potentially have substantial quantities of oil and gas.
Key NRCan research goals are to:
- Determine the potential for oil and gas resources and predict optimum conditions for petroleum generation;
- Determine the present day distribution of major sedimentary rock units within individual basins;
- Determine the present day thickness of continental crust beneath the basins, and predict the behaviour of the crust during the initial stages of ocean formation and continental margin development; and
- Determine the development and distribution of salt structures along the continental margin and study the interactions between salt and overlying sediments during the depositional life-cycle of the basins.
For additional information, visit:
BASIN database of offshore petroleum geology
or contact:
Dr. Sonya Dehler
Natural Resources Canada
Geological Survey of Canada (Atlantic)
sdehler@nrcan.gc.ca
Tel: (902) 426-4289