EXPLORING GEOTHERMAL POTENTIAL FOR GEO-EXCHANGE AND HYDROTHERMAL SEDIMENTARY AQUIFER PROJECTS (HSA) IN THE PICEANCE BASIN

The growing demand for energy, coupled with an increasing interest in renewable energy alternatives, notably geothermal energy, has garnered attention (Kiran and Salehi, 2020). Despite this, the oil and gas industry continues to grapple with the challenges of cost and sustainability when it comes to adopting eco-friendly practices and reducing emissions. Oil and gas fields present promising opportunities for geothermal electricity generation. Repurposing existing oil and gas wells is particularly promising due to several key factors. Hydrocarbon formation occurs at elevated temperatures, which often correlates with a higher geothermal gradient in these fields compared to the surrounding regions. This natural thermal advantage makes them ideal candidates for harnessing geothermal energy. These wells provide valuable well logs and other data that can significantly aid in identifying hot sedimentary aquifers (HSAs) (Lacazette et., al 2024). Sedimentary basins with extensive well logs often contain porous and permeable strata, capable of yielding the large volumes of brine required for geothermal power generation. This geothermal brine can be efficiently extracted from beneath active or previously developed oil and gas production sites.

The primary aim of this research is to identify areas within the Piceance Basin that show a prospective geothermal gradient potential to repurpose existing oil and gas (O&G) wells for the extraction of geothermal energy. This approach can be potentially utilized to regulate the heating and cooling systems of public buildings located in Mesa and Garfield counties, Colorado. The chosen wells must be depleted or no longer economically viable for production. The process involves injecting cold water and environmentally friendly fluids into a selected well, allowing it to naturally heat within the earth, and then extracting the heated fluids from a nearby well. The extracted hot water will be circulated to surface heat exchangers/heat pumps installed within the designated schools. Depending on the season, this geothermal energy will be used for either heating or cooling purposes.

In Colorado, a considerable amount of subsurface data is available online through the USGS web page, where data such as well logs and core samples with some petrophysical data (i.e., porosity, permeability, thin sections, ultraviolet light, descriptions, etc.) are available to the public.

We explored a workflow to integrate data sources and analyze hot sedimentary aquifers to evaluate their potential as reservoirs for geothermal applications. We analyzed subsurface data to evaluate the common reservoirs within the Piceance Basin, such as the Cretaceous Williams Fork, Iles, Dakota, and Burro Canyon Formations. These formations represent a significant portion of the area's stratigraphic section that contains energy resources. We generated geothermal gradient and heat-in-place maps for each reservoir and explored the potential of using current abandoned wells as candidates for potential repurposing in geothermal projects.

Preliminary results show that there is a mixed behavior of geothermal gradients due to the highly organic-rich lithologies found within the stratigraphic section. Organic-rich areas, such as the Cameo coal within the Williams Formation, act as strong insulators that modify the geothermal gradient within the basin. Using calculations from wellhole temperatures, we established an empirical estimation of the thermal conductivity along the areas with well logs and populated the estimated values within a regional basin model. The highest geothermal gradients are shown towards the south and southwest margin of the basin. Additionally, geothermal gradient maps illustrate the shift in gradient with increasing depth of stratigraphic intervals, revealing an overall rise in gradient towards the southern region of the basin in Garfield and Mesa counties. The findings of this research provide an essential first step for evaluating geothermal energy potential within the Piceance Basin and the possibility of using existing oil and gas infrastructure for small geo-exchange projects.