NUMERICAL STUDIES OF FLUID AND HEAT FLOW AND SOLUTE TRANSPORT IN THE ALBERTA BASIN FROM 100MA TO 60 MA

The Alberta Basin in Canada is an extensively studied sedimentary basin, widely known for its energy and mineral resources. The formation of ore deposits and the migration and accumulation of hydrocarbons in the basin are greatly affected by the flow of formation waters. There is, however, a strong disparity between hydrogeologic and geochemical estimates of the residence time of brines in this basin. The main purpose of this project is to take into consideration both the hydrogeologic results as well as the geochemical observations to simulate solute transport in the basin. The 2D finite element FORTRAN code, COMPACT, has been modified and is being used for this study. As part of this basin-scale fluid, heat and solute transport study, compaction and density driven flow from 100Ma to 60Ma are currently being modeled along a 700 Km wide cross-section from west to east in the Alberta Basin. Preliminary results suggest overpressure development due to low permeability aquitards in the deeper parts of the basin in the west. It is found that simulations of compaction-driven flow can be subject to numerical difficulties when the pressure differential estimated in successive iterations in a given time step is large. A regional fluid drain appears to exist from west to east along permeable layers below thick, over-pressured shales of the Colorado Group of rocks. Overpressure development and numerical stability of simulations are found to be sensitive to the permeability structure of the basin. Density-driven flow is found to exist below evaporate layers in the basin.