And the evolution of the stages involved in the oil and gas

 
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The exploration industry in Canada has gone through ups and downs that have little to do with 
the amount of oil or gas left to be found and more to do with the balance between supply and 
demand. For example, the Norman Wells oil field in the Northwest Territories was first 
discovered in 1920, but it was then considered too remote to be of interest to southern Canada. 
A modest amount of oil was refined there to meet regional demands. It was not until the 
mid-1970s that decreasing supplies and increasing oil values made large-scale development at 
Norman Wells worthwhile. 
Technology also can have an impact on exploration activity, extensive exploitation of the large 
volumes of heavy oil in the Lloyd Minster area was dependent on the development of 
enhanced recovery techniques. 
2.1 Exploration methods 
Visible surface features such as oil seeps, natural gas seeps, pockmarks (underwater craters 
caused by escaping gas) provide basic evidence of hydrocarbon generation (be it shallow or 
deep in the Earth). However, most exploration depends on highly sophisticated technology to 
detect and determine the extent of these deposits using exploration geophysics. Areas thought 
to contain hydrocarbons are initially subjected to a gravity survey, magnetic survey, passive 
seismic or regional seismic reflection surveys to detect large-scale features of the sub-surface 
geology. Features of interest (known as leads) are subjected to more detailed seismic surveys 
which work on the principle of the time it takes for reflected sound waves to travel through 
matter (rock) of varying densities and using the process of depth conversion to create a profile 
of the substructure. When a prospect has been identified and evaluated and passes the oil 
company's selection criteria, an exploration well is drilled in an attempt to conclusively 
determine the presence or absence of oil or gas.