The Geothermal Potential of Remote Regions; a Case Study of Anticosti Island, Québec (Canada)Thursday, November 22, 2018 - 11:00 to 11:19 Theatre 2
Anticosti Island is located in the Gulf of St. Lawrence and, like most remote regions of Canada, relies entirely on fossil fuels for both electricity and heat production. As an effort to diversify energy sources and reduce greenhouse gas emissions, a geothermal resource assessment of this sedimentary basin was achieved, developing a 3D geological model that was used as a basis to simulate conductive heat transfer and evaluate temperature distribution at depth.
The Anticosti sedimentary basin consists of a lower Ordovician to lower Silurian carbonate platform, which unconformably overlies the Precambrian basement. The 3D geological model of the basin, which integrates data from 24 oil and gas exploration wells and public seismic lines, encloses eight distinct geological units mainly composed of limestone and shale, with dolostone at the base of the sequence, and more sandstone in the eastern part. The thermal conductivity and the internal heat generation rate of each geological unit were evaluated from stratigraphic records and geophysical well logs. The undisturbed ground temperature near surface, used as a first type boundary condition for the 3D numerical model, was calculated from meteorological data. A constant heat flow of 15 mW·m 2 was imposed at the base of the model at 40.5 km (Moho depth) as a second type boundary condition, while vertical side boundaries were considered adiabatic. Available bottom-hole temperature data were corrected for drilling disturbance and for paleoclimate effects. Terrestrial heat flow and a heat generation of the Precambrian basement were calculated analytically at the location of the 24 wells, according to 1D temperature profiles. Basement heat generation values were interpolated in 2D and included in the corresponding layers of 3D model.
The 3D heat conduction model was solved in steady state with the finite element method using FEFLOW. Results show that a temperature of 120 °C, which is considered the lower limit for efficient electricity production with a binary geothermal power plant, can be reached between 4 and 5.4 km depth in the Precambrian basement. The most promising temperature anomaly is located in the southeast of the island, reaching 120 °C at 4 km depth. However, the potential for the development of a geothermal plant in the near future is almost inexistent since the area is barely populated. The most populated area of the island is the locality of Port-Menier, in the northwest, with a population of 218 inhabitants. A temperature of 120 °C is reached at a depth of about 5 km below this locality. Direct geothermal energy use to heat building appears more feasible, with temperature of 57 °C reached at a depth of 2.1 km. Dolostones of the Romaine Formation having a relatively high permeability, reaching more than 10 mD, are present at this depth at the base of the sedimentary sequence. Future work perspectives include laboratory analysis to measure thermal properties of rock samples from all geological units to improve the numerical model defining geothermal resources and reducing uncertainty in temperature evaluation at depth.