INTEGRATED RESERVOIR MODELING FOR ENHANCED GEOTHERMAL ENERGY SYSTEMS IN CENTRAL ALBERTA, CANADA

摘要

The province of Alberta has a high demand of thermal energy for both industrial and residential applications. Currently, the vast majority of the heat used in these applications is obtained by burning natural gas. Geothermal energy production from deep aquifer systems in the sedimentary basin could provide an alternative source of heat that would be both sustainable and help Alberta reduce greenhouse gas emissions. To date there has been no geothermal field development in Alberta because the average geothermal gradient of 30 °C/km was considered to be too low for economic geothermal energy generation. However, with technologies for Enhanced Geothermal Systems (EGS), it may be possible to develop geothermal resources from the sedimentary rocks in the Alberta Basin. A feasibility study based on existing and newly gained data is necessary to identify scenarios for geothermal energy production in the region. In this paper, we investigate the potential of these geothermal energy systems by geological modeling and reservoir simulation in terms of EGS. Geological modeling enables us to map and quantify the subsurface conditions and delineate thermal resources. Reservoir simulation is then used to identify the potential productivity of thermal energy. A regional scale geological model of the Central Alberta Basin has been developed for an area around Edmonton with a horizontal extent of 200 km x 160 km (Weides et al., in press). This model is based on stratigraphic data from about 7000 wells and includes all major formations from the surface to the Precambrian basement. In Central Alberta, four Devonian carbonate formations and the Cambrian Basal Sandstone Unit are identified as the highest geothermal potential zones. Four formations were selected for more detailed investigations; thermal, hydraulic, and mechanical properties of these formations are obtained from geological databases, literature, and from new laboratory measurements. Finally, thermal-hydraulic reservoir simulations for a 5 km × 5 km site in the city of Edmonton were performed to evaluate reservoir development concepts. Hydraulic fracturing treatments are simulated for the various geological formations. Different utilization concepts are presented for possible applications of geothermal energy generation in residential, industrial and agricultural areas.