ABSTRACT

A plot of 415 points from all reservoirs on a scatter diagram of oil gravities versus depth in the Western Canada sedimentary basin indicates that oil gravity is a function of reservoir depth. Diagrams for the individual reservoirs show the same relationship. A contour map of oil gravities has a generally northwest-southeast strike with values increasing from 6° API in the northeast to 55° API in the southwest.

The relationship between gravity and depth is considered to be the result of temperature and pressure as well as other less clearly defined factors. Cardium, Viking, Nisku and Leduc oils are considered to show typical depth-gravity relationships for the basin. Mississippian oils appear to represent a separate group of values; this is probably due to their position in traps at a major unconformity. Blairmore and Beaverhill Lake oils show less variation with depth than other oils and also appear anomalous in other respects.