Geothermal Energy Storage: A Conceptual Assessment of Geologic Thermal Storage Systems in North Dakota

Abstract

ABSTRACT Geothermal energy and Aquifer thermal energy storage can provide beneficial ways of storing energy in excess and providing energy when needed. North Dakota's renewable energy system is impacted by its harsh winters. Geologic aquifer thermal aquifer storage system is a large scale geothermal system that can act as energy storage media. Aquifer thermal storage systems are dependent on heat conductivity of rocks, storage capacity of aquifer, fluid flow, geochemistry and geo-mechanics. The goals of the project are to 1) evaluate the amount of energy that can be stored in deep aquifers; 2) access the amount of energy that is thermally recoverable; 3) monitor changes in geo-mechanical parameters. CMG STARS, a three-phase multi-component thermal and steam additive simulator, was used for the thermal numerical simulation which takes into account the geo-mechanics (thermal dilation and re-compaction). A conventional reservoir with representative porosity and permeability is modelled in CMG and Semi Analytical Model (SAM) was used to calculate the wellbore dynamics involved with geothermal operations. This is used to calculate heat transfer to the surrounding formation and determine our heat loss. Our preliminary results show us the reservoir pore volume dilation re-compaction model changes from cold water injection. The grid block void porosity dilation re-compaction model changes are greatly influenced by grid block pressure. INTRODUCTION Geothermal Energy and Aquifer Thermal Energy Storage (ATES) Geothermal energy refers to the earth's thermal energy that can be converted into electrical energy. Emissions from the geothermal energy industry are substantially low, which is an excellent asset to reaching a low-carbon economy. Hot dry rocks and hydrothermal resources are the primary geothermal energy sources. Water from surface seeps through faults and cracks of earth and is warmed by hot rocks or water is trapped by impermeable layers to create geothermal reservoirs. Sedimentary basins have great geologic and reservoir properties for low-cost energy generation for geothermal energy. Hot water moves from deep sources to shallow reservoirs for hot water geothermal reservoirs. Hydrothermal systems use steam or water for electricity generation. Enhanced geothermal systems extract thermal energy from geothermal resources with lower permeability and fluid saturation. (Grant & Bixley, 2011)(Barbier, 2002)