Bravo Dome is a commercial natural CO2 field that supplies the gas to depleted oil fields for enhanced oil recovery. In order to understand the distribution of CO2 across the greater Bravo Dome region, including southeastern Colorado and northwestern New Mexico, and to assess the impacts of high CO2 concentrations on microbes in the subsurface, 7 samples were collected from sites associated with high natural CO2 concentrations. Four water samples were collected, two from wells producing within Bravo Dome, one from an oil and gas field north of Bravo Dome associated with high CO2 concentrations, the Oakdale field, and one sample from a shallow groundwater well on the Rafter K ranch that effervesces CO2. Three samples were collected from the associated gas streams from two Oakdale field wellheads and from the Rafter K well. The samples were filtered for biomass, extracted, amplified, and 16S rRNA gene sequencing was performed on the Illumina MiSeq platform.