Canada's East Coast Offshore Exploration And Development

Abstract

Abstract Canada's east coast offshore continental shelf is extensive and has excellent oil and gas potential. Numerous Mesozoic sub-basins have been explored, and the principal targets are Late Jurassic to Early Cretaceous clastic reservoirs found in a variety of plays and trapping modes. Exploration activity has only taken place over the past 20 years, with approximately 250 wells drilled. Some 41 discoveries have been made containing an estimated total recoverable resource of about 1.3 billion barrels of oil and 10.0 TCF of gas. The Hibernia oil discovery, offshore Newfoundland, and the Venture area gas Discoveries, offshore Nova Scotia, are the accumulations most likely to be developed in the near future. Introduction This paper gives a generalized overview of the geological setting, the exploration history and the hydrocarbon development potential of Canada's east coast offshore. There have been several excellent papers written over the past 15 years describing Canada's east coast offshore geology. This paper attempts to summarize the major findings of these earlier works in a generalized overview. Although references are not quoted, readers are referred to a recent publication by Grant, McAlpine and Wade (AAPG Mem. 40, 1986, pp. 177–205) for an excellent geological synthesis of the Atlantic offshore margin of eastern Canada. The subject area (Fig. 1) encompasses the offshore continental margin of Atlantic Canada from northern Labrador to southern Nova Scotia, a distance of over 3500 km. The continental shelf out to the 1000-m isobath covers a vast area readily drillable with modern technology. This accessible shelf can be subdivided into four regions, each with its unique physiographic setting, underlying geology and exploration history. These are the Labrador Shelf, the northern Grand Banks/northeastern Newfoundland Shelf, the southern Grand Banks and the Scotian Shelf. Common to each of these areas is a wedge of Mesozoic/Cenozoic sediments that expands seaward from a zero edge to thousands of metres in thickness in specific Mesozoic sub-basins or depocentres. These Mesozoic sub-basins or "thicks " tend to be elongated, fault controlled and separated by basement-cored shelf areas or arches. The Mesozoic sub-basins have been the focus of exploration activity, and are the areas where practically all the significant discoveries have been made. Surrounding the sub-basins, structurally monotonous shelf areas and arches are covered by a much thinner veneer of Mesozoic sediments and are only marginally prospective. Offshore areas such as the Gulf of St. Lawrence, Bay of Fundy and Baffin Bay have been less intensely explored and are only briefly mentioned. The petroleum industry has been seriously exploring the east coast offshore for only the past 20 years. During that time there have been approximately 250 wells drilled and over 800 000 km of seismic shot. This has resulted in a tremendous increase in the geological understanding of the area. The discovery of significant accumulations of oil and gas has confirmed its hydrocarbon potential. Canada's east coast offshore is, however, an extremely hazardous and costly frontier in which to explore. The rewards have not always justified the finding costs and interest and activity levels have fluctuated over the past two decades.