Available online xxxx Editor: P. Shearer Keywords: geyser CO 2 -driven eruptions faults carbon sequestration wellbore leakageThe CO 2 bubble volume fraction, eruption velocity, flash depth and mass emission of CO 2 were determined from multiple wellbore CO 2 -driven cold-water geysers (Crystal and Tenmile geysers, in Utah and Chimayó geyser in New Mexico). At shallow depths the bubble volume fraction ranges from 0 to 0.8, eruption velocities range from 2 to 20 m/s and flash depths are predominately shallow ranging from 5 to 40 m below the surface. Annual emission of CO 2 is estimated to be (4.77 ± 1.92) × 10 3 , (6.17 ± 1.73) × 10 1 , (6.54 ± 0.57) × 10 1 t/yr for Crystal, Tenmile and Chimayó geysers, respectively.These estimates are coherent with Burnside et al. (2013) showing that the rate of CO 2 leakage from wellbores is greater than fault-parallel or diffuse CO 2 leakage. The geyser plumbing geometry consists of a vertical wellbore which allows for the upward migration of CO 2 -rich fluids due to artesian conditions. The positive feedback system of a CO 2 -driven eruption occurs within the well. Active inflow of CO 2 into the regional aquifers through faulted bedrock allows geysering to persist for decades. Crystal geyser erupts for over 24 h at a time, highlighting the potential for a wellbore in a natural environment to reach relatively steady-state high velocity discharge. Mitigating high velocity CO 2 -driven discharge from wellbores will, however, be easier than mitigating diffuse leakage from faults or into groundwater systems.