The production of heat and electricity from geothermal energy is an old concept and has been around since the early 1900’s. However, many geothermal projects are plagued by high up-front exploration costs and have financing difficulty because of the geological risk, namely low permeability, and many fail in the exploration phase. True closed loop systems extract heat through the process of conduction which has challenges such as limited conductive heat transfer through rock and high drilling costs of multilateral wells. We report on a system designed to address these issues through the drilling of long, closed loop, multilateral wells in sedimentary basins. This paper demonstrates standard geological and geophysical workflows for oil and gas prospecting can be applied in closed loop geothermal development for the determination of geothermal gradient, rock characterization, thermal conductivity prediction and well planning in sedimentary basins. Subsurface characterization involves a multidisciplinary approach of stratigraphic correlation, structural mapping, seismic and geomechanical interpretation and determination of heat gradient and rock petrophysics. Many sedimentary basins are highly explored for oil and gas, CO2 sequestration, geothermal and mining applications providing easier access to data. Results from the technology demonstration project include formation temperature of 75 degrees C, rock conductivity of 4.5 W/mK, porosity of 6%, annualized thermal output of 800 KWth. Observations include pre spud predictions of thermal conductivity using mineralogy can reduce thermal output risk. Multi-lateral closed loop systems reduce permeability risk because subsurface characterization can be performed using data available in many sedimentary basins and does not rely on the presence of high flow capacity reservoirs, unlocking vast untapped geothermal potential around the globe.
Geothermal Energy in Canada: Moving Forward