Oil and Gas Exploration
Prince Edward Island, located on the east coast of Canada in the Gulf of St. Lawrence, lies on a large sedimentary basin that may have significant reservoirs of natural gas. In fact, exploration activities have identified the existence of these potential reservoirs, including a significant discovery made offshore in East Point, PEI. However, Prince Edward Island's hydrocarbon potential has yet to be fully assessed as, to date, only twenty exploratory wells and one re-entry well have been drilled on and around the province.
Petroleum and natural gas are found in, or associated with, sedimentary source rocks which, as newly deposited sediments, contained an abundance of animal or plant remains. The source potential of carboniferous rocks in the Gulf of St.Lawrence area is of particular interest to Prince Edward Island because of wide-spread distribution of these rocks at drillable depths, both onshore and offshore.
Specifically, PEI is underlain entirely by rocks correlative with those of the Pictou Group of Nova Scotia and New Brunswick. On the Island, these deposits of sandstones, shales and conglomerates are informally termed the "Prince Edward Island Redbeds." Understanding of the surface and subsurface geology of the Prince Edward Island Redbeds may be enhanced by reading Geology of Prince Edward Island by H.W. van de Poll.
The direct evidence of the hydrocarbon potential of carboniferous rocks on and around Prince Edward Island is the H.B.-Fina East Point E-49 well drilled off the province's eastern shore in 1970. This well had gas shows in sandstones that are closely associated with coal beds which are age equivalents of the Pictou Coalfield occurrences in Nova Scotia. Additionally, the Horton Group of carboniferous sandstone which underlies the Pictou formation has yielded both oil and gas in the neighbouring Maritime provinces. The continental origin of the sediments underlying Prince Edward Islands suggests that the region should be considered mainly for its natural gas potential as the possibilities for petroleum discovery are comparatively low.
To be recoverable, hydrocarbons must migrate and move into porous reservoir rocks where they concentrate and may be withdrawn through drilled holes. Both the porosity and permeability of the PEI Redbeds make them generally good reservoir rocks. Cementation is variable, however, and porosity decreases with depth.
The migration of hydrocarbons under pressure continues within the reservoir rock until some substance barrier or "trap" is encountered. There are a variety of types and shapes of traps but they all possess a common element in that further migration of the hydrocarbons is prevented by an overlying impermeable structure. Prince Edward Island is characterized by structural traps within the Pictou Group which result from folding, faulting or a combination of both of these processes. These traps are commonly associated with salt domes which are the result of the upward movement of salt masses under differential pressure. Other traps involve anticlinal structures which occur from an upward arching of rock strata.
For further information regarding oil and natural gas exploration on Prince Edward Island, please contact Ron Estabrooks.