Successful High Enthalpy Aquifer Technology Field Trials - Hydraulic Stimulation of Shallow Underground Thermal Storage Wells at an Industrial Facility in Norway

Abstract

Abstract Industrial waste heat has enormous energy potential, with up to 50% of industrial energy output being lost as waste heat globally, according to the US Department of Energy (www.energy.gov). This loss is a needless drain on finances for industrial plants and creates enormous greenhouse gas emissions. The concept of a High Enthalpy Aquifer Technology (HEAT) system was developed to store and recover seasonal waste heat from industrial processes and turn bedrock into large-scale natural thermal batteries. The Kvitebjørn Varme (KVAS) district heating waste incineration facility in Tromsø, Norway, was the chosen site for a trial project to commercialize the HEAT concept. This technology has the potential to create huge savings on energy and greenhouse gas emissions for industrial plants. A hydraulic stimulation method was developed to facilitate the injection and heat storage process, to reactivate the existing natural fractures, and to establish a hydraulic connection between the injector and the ten surrounding producer wells. Multiple closely spaced fractures were needed to increase the fracture volume for storage and improve the thermal exchange capacity of the rock. The formation is naturally fractured and contains brittle hairline clay-filled fractures which can be flushed during the hydraulic stimulation, and then propped with natural sand to facilitate the injection storage process. The planned stimulations involved a rig-less workover unit, specialized high pressure pumping equipment, and a high-pressure jetting tool which enabled selective perforation of the cemented casing and placement of 35 hydraulic stimulation stages. During each of the stimulation stages, continuous monitoring on the active flowing producers confirmed positive connections to the producer wells. A monitoring system was installed to detect seismic anomaly events and a nearby monitoring well was used to detect ground water level changes during the stimulation. No chemicals were used in the process, only silica sand and water being used. A combined volume of 1,288m3 water and 88 tonnes of silica sand was utilized. The stimulations increased the total flow rate on the producer well with one order of magnitude. The HEAT system installed at Tromsø is now expected to store and to retrieve up to 8.0 GWh from the industrial facility annually. This HEAT system solution offers a low footprint at surface, utilizing less than 10 wells which is far less than traditional borehole thermal energy storage (BTES) plants. The HEAT system can be installed at any number of industrial plants with a constant high level of waste heat. The heat storage does not incur emissions and has minimal energy loss. This solution does not require rare earth elements (REE) or any other elements to be used for the energy storage process. This trial concept was successfully proven, and operationally has further scope to be streamlined, further reducing the cost of each stored GWh.