(457h) A Case Study from Wyoming Dry Fork Carbonsafe Project: The Effects of Wettability Variation on CO2 Storage Capacity Assessment

Meeting global net-zero carbon emission targets will require geologic carbon disposal. The Wyoming Dry Fork Station (DFS) CarbonSAFE project in the Powder River Basin includes subsurface characterization to determine how 50 MT of CO₂ could be permanently stored in less than 30 years. This presentation describes how storage capacity changes with wettability variations in the targeted storage reservoirs.
Contact angle (CA) measurements of CO₂ droplets on three potential storage reservoirs’ (the Lower Cretaceous Lakota Sandstone, Jurassic Hulett Sandstone, and Pennsylvanian Minnelusa Formation at the DFS site) rock samples in synthetic formation water (SFW) and interfacial tension (IFT) tests between SFW and CO₂ were conducted. The representative rock samples of each formation were carefully selected. In addition to nine samples of reservoir rock, two sealing formation Fuson and Opeche shale samples were also tested. A high pressure and temperature (HPHT) IFT and CA measurement system was deployed for IFT tests and CA tests at samples’ respective reservoir pressures and two additional increased pressures to mimic the pressure change after the CO₂ injection. These tests demonstrated that the average IFT increased with increasing pressure for each sample. These rock samples at the studied reservoir conditions all showed water-wet behavior and became more water-wet as pressure increased further above reservoir pressure, indicating that as CO₂ injection continues, the rock could become more water-wet, making residual trapping more effective. In addition, the Opeche formation cap rock showed the maximum height of the CO₂ column above the free water level at which CO₂ can be trapped by the cap rock is 4002.5 ft, which is double what the Fuson is capable of and suggests the underlying Minnelusa formations could be favored as the main CO₂ storage reservoir.
In addition to the micro-wettability tests, macro-wettability and CO₂ storage potential were assessed via core-flooding tests for the samples from Lakota, Hulett, and Minnelusa Formations. If injectivity could be guaranteed regardless of low permeability, then the lower permeabilities and less water-wet formations promote higher CO₂ storage potential. Nevertheless, permeability appears to be less of a factor in the CO₂ storage potential compared to the wettability in the same reservoir, which dominates the CO₂ storage potential performance and sets the baseline for long-term CO₂ residual trapping.