Multivariate and geochemical analyses of brines in Devonian strata of the Western Canada Sedimentary Basin for geothermal energy development

Abstract

Geothermal favorability maps in the Western Canada Sedimentary Basin (WCSB) are focused on depth and temperature. The transfer of mass and heat by a geothermal system, however, depends on the brine's transport and thermodynamic properties, which are predominantly controlled by its solute geochemistry. As an ongoing attempt to identify, map, and model potential geothermal reservoirs in sedimentary formations in the WCSB, we collect brine samples from various databases and perform rigorous quality control to identify representative formation waters from the carbonate platforms and reefs of the Leduc and Swan Hills formations, and the sandstone of the Granite Wash and Gilwood formations. We carry out multivariate analysis on 1963 representative samples using major chemical components, i.e., sodium, potassium, calcium, magnesium, chloride, bicarbonate, sulfate, and brine's pH. Principal component and cluster analyses identify distinguishable hydrogeochemical groups and the corresponding influential constituents. We then examine the direct influence of fluid chemistry on the engineering aspects of geothermal energy development in terms of parasitic loads and geochemical risks. The high salinities and associated high densities in one of the groups generate significant parasitic loads, e.g., greater than 55% at 110 °C. The geochemical modeling in each group demonstrates the potential scaling risks of dolomite, calcite, and brucite. The geochemical approaches presented here can be applied to geothermal energy development in sedimentary basins around the world.