The UND-CLR Binary Geothermal Power Plant in the Williston Basin, ND
The question of whether power production can be achieved economically using oil field fluids was answered positively in March 2016 when the UND-CLR Geothermal Power Plant in North Dakota produced power using a125 kW prototype high- efficiency ORC manufactured by Calnetix. NREL’s’ CREST model gives the LCOE for this US DOE demonstration project as $0.06 per kWh. Installation costs were $3000 per kW for the optimum ORC system and power grid costs in the region are $0.08 per kWh. As such, UND-CLR and other similar geothermal power plants have the potential to serve as economical distributed electric power generators, or as energy storage systems, in power grids. However, application of this demonstration to other oil-producing basins requires analysis of multiple factors. Economics of electrical power generation in oil and gas settings balances on several key parameters including resource temperature, fluid production capacity, efficiency of heat-to-power conversion, ability to adopt existing infrastructure, competitive costs, and time scale for ROI. Finding the economic nexus for success requires conjunction of geology, engineering, technology, and economics. Geological factors that characterize the Williston Basin geothermal resource are temperature and fluid production capacity in permeable formations. Heat flow in the basin ranges from 50 mW m-2 to 70 mW m-2, and 100-130 ºC temperatures in the fluid-producing carbonates at 3 to 4 km depths are due to high geothermal gradients in 2 km of low thermal conductivity (1.0 to 1.2 W m-1 K-1) overlying fine-grained clastic rocks. The water supply at the UND-CLR site comes from two ~2.8 km deep X ~1.6 km long open-hole lateral wells. The temperature is 103 ºC at the well and 98 ºC at the ORC inlet located 400 m from the wellhead. The wells were drilled by CLR for a water-flood secondary recover project and although the pipelines are buried, they are not insulated. Water flow is routed through the ORCs before it enters the injection plant. Cooling of the water in the ORC benefits CLR by reducing heat stress on components of the injection pumps. The hydrostatic head for the producing formation, Lodgepole (Cret.) is at the ground surface and submersible electric pumps positioned at ~ 750 m depths in vertical section of the long lateral wells resulted in no drawdown of the fluid resource. The key points are that use of existing infrastructure avoids drilling costs for geothermal development and, horizontal drilling in the aquifers increases borehole exposure to the resource and significantly increases the capacity for fluid production. Engineering and technological challenges in accessing the resource require information on the characteristics of the producing formation and in selection of the optimum ORC technology. CLR acquired formation permeability, water quality, and rock properties and UND was only involved as a beneficiary of CLR’s research. Selection of the optimum ORC system involved solicitation of bids from ORC manufacturers given, fluid production volumes, water quality, temperatures, and the need for air-cooled condensers. Significantly, recent advances in ORC technology promise to increase power production by 2 to 4 times over the currently installed system.
AAPG Datapages/Search and Discovery Article #90346 ©2019 AAPG European Region, 3rd Hydrocarbon Geothermal Cross Over Technology Workshop, Geneva, Switzerland, April 9-10, 2019