MODELING RESERVOIR AND COST ESTIMATES FOR GEOLOGIC CARBON SEQUESTRATION IN WASHINGTON STATE USING SCO2TPRO

Estimates of reservoir storage capacity are essential to plan capital-intensive carbon capture, utilization, and sequestration (CCUS) projects for mitigating climate change. We estimate storage properties and costs across Washington State using SCO₂T^PRO, a CCUS screening tool that couples machine learning-based dynamic CO₂ injection and plume evolution modeling with economics. We also use SCO₂T^PRO to calculate per-well injection rate, the total number of wells required to utilize the modeled storage capacity, and the associated injection costs in $/tonne of CO₂. To match the scale of a nation-wide reservoir assessment, we report our data by 50 x 50 km grid cells that may contain multiple overlapping reservoir injection zones.

We identify the greatest storage capacity in the Montesano Formation, a Miocene shallow marine sandstone of the coastal range and plain of southwest Washington with 4,688 million tonnes of CO₂ (MtCO₂) capacity per individual injection zone per 50 x 50 km grid cell. These values are followed by significant capacity in the Columbia River Basalt Group, a Miocene flood basalt in the Columbia Basin of eastern Washington (3,567 MtCO₂ per zone per grid cell); the Chuckanut Formation, an Eocene fluvial sandstone in the Bellingham Basin of northwest Washington (2,151 MtCO₂); and the McIntosh and Skookumchuck Formations, fluvial to marine sandstones of the southern Puget Lowland (1,092 MtCO₂). Although SCO₂T^PRO does not currently incorporate reactive transport modeling, this study fills an important gap left by previous carbon storage assessments that neglected to consider flood basalt as a reservoir. Identifying storage sites by geology and injection cost allows planners to evaluate siting criteria for carbon management hubs connecting point source emissions and direct air capture facilities to viable storage reservoirs.