Spatial characteristics of Middle Devonian oils and non-associated gases in the Rainbow area, northwest Alberta

Previous studies indicate that the Middle Devonian of the Rainbow sub-basin represents a closed petroleum system with the Muskeg evaporite acting as the regional seal. To investigate the spatial and compositional characteristics of hydrocarbons in this area, multivariate statistical methods were used to study the geochemical signatures of a suite of Middle Devonian oils and analyze the geographic distribution characteristics of the non-associated gas accumulations in the sub-basin. The results suggest that there are two genetic groups of oils derived from slightly different source rocks. Geographic correlation of an oil group with a particular depositional facies indicates that communication between source and reservoir is the primary control on the variation of spatial characteristics of the oils. Geographic distribution characteristics of the non-associated gas accumulations, oil pool size and reservoir character suggest that cross-formational migration of hydrocarbon may have occurred in major fracture systems. The findings of this study may provide useful clues for future oil and gas exploration in this and adjacent, relatively unexplored, regions.