DEEP BASIN CHARACTERIZATION WITH VOLUMETRIC THERMAL MODELING: A STRATIGRAPHIC HYDROTHERMAL EXAMPLE FROM THE GREAT SALT LAKE BASIN, UTAH

Augmented datasets from geological, geophysical, hydrological, and heat flow research of the Great Salt Lake (GSL) basin in Utah are utilized to create new 3-dimensional (3D) conductive heat transfer models using a finite-element modeling program. These data are integrated to characterize the potential of unconventional deep sedimentary geothermal, also known as stratigraphic hydrothermal, reservoirs identified in the GSL basin. To provide constraints for the thermal model, the basin geometry and model parameters are derived from stratigraphic framework, seismic structural cross sections, petrophysical data from legacy oil and gas wells, outcrop analog studies, and geophysical data. Structural mapping from regional gravity and seismic reflection data defines major extensional faults and three major sub-basins where sedimentary geothermal reservoirs are buried by 2–3 km of Miocene-recent, low-conductivity sediment. Oil and gas wells in the GSL basin exhibit heat-flow values ranging from 106 to 119 mW/m², indicating an elevated background heat flow of 100 mW/m². These moderate to high heat-flow values combined with insulating effects of thick (2 to 3 km), low-thermal conductivity sediments typical in the Basin and Range Province result in higher temperatures at depth compared to adjacent bedrock geotherms. The most prospective reservoirs are fractured Paleozoic carbonates, which reach temperatures greater than 150°C at 3 km depth in the Gunnison Bay basin. Petrophysical logs indicate porous and permeable reservoirs in carbonate units below the 150°C isotherm have estimated porosity values ranging from 5% to 15%. These porosity values are higher than many analogous fractured commercial petroleum reservoirs and comparable to other sedimentary geothermal developments. We present new heat transfer models constrained by existing data from known geothermal gradients and material properties to explore the extent and character of geothermal potential in deep sedimentary reservoirs using the GSL basin as an example. These new thermal models are part of an emerging workflow to help locate and characterize the dynamics of unconventional deep sedimentary geothermal systems prevalent in the Great Basin of the western USA.