Geological Factors 

The story of Leduc emerged in large part due to the Alberta marine environment some 400 million years ago. Alberta was once covered by ancient shallow seas which were ideal for the growth of reefs during the late Devonian period. These warm tropical waters supported a myriad of organisms that are now preserved as fossils. As these shallow seas covered large parts of the continent that are now dry lands, they became a breeding ground for coral reefs to grow. Specifically, Leduc would become the location of a great coral reef containing oil. 

Petroleum is often found in the sediments laid down in ancient seas, in sedimentary rocks. Within and around the Devonian Reefs, oil began in the remains of various plants and animals that lived in the sea or washed down into it with mud from streams and rivers. This organic residue settled to the bottom of the ancient seas and accumulated, layer upon layer. As these layers accumulated over millions of years, the organic materials were forced into adjacent porous coral reefs. As a result, porous rock growth decreased and the organic materials transformed into oil and natural gas due to pressure, heat and other geological factors. These layers managed to seal the corals (due to the porous rock's tiny holes) into large pockets of pressurized oil and natural gas waiting to be tapped.

These Devonian reefs would lead to Imperial Oil's discovery in 1947 of petroleum in a buried reef at Leduc, triggering an intense search for Devonian Reefs in the subsurface of Western Canada.