Modeling of CO2-driven Cold-water Geyser in the Northeast Qinghai-Tibet Plateau

Abstract CO2-driven geysers are important natural analogs of CO2 leakage in geologic carbon sequestration. This study investigated a CO2-driven cold-water geyser evolved within an abandoned wellbore in the northeast Qinghai-Tibet plateau, maintaining a steady eruption period of 330 s and a maximum instantaneous aqueous phase discharge rate of ∼67.53 kg/s. Based on the geological conditions and wellbore configuration, a 3D wellbore-reservoir coupled numerical model was developed. The simulation results are in good agreement with the experimental data, and the CO2 emission of the geyser was estimated as 315.36 t/yr. The mechanism of the periodic eruptions was analyzed by the spatiotemporal variation in various primary variables including pressure, temperature, gas saturation, fluid flow rates, and phase velocities within the wellbore, and is coherent with the reports by Lu et al., 2005 , Watson et al., 2014 , i.e., the eruption is controlled by the evolution of flow patterns, and the periodicity is regulated by the coupling of the self-enhancing and self-limiting process. The parameter sensitivity analysis indicated that the wellbore diameter, reservoir permeability, thickness, pressure gradient, and CO2 mass fraction in groundwater have a profound effect on the behavior of the periodic eruptions, and these causalities could serve as a reference to identify the direct inducement for the evolution of analogous periodic eruptions.