Wormhole Generations in Indiana Limestone with CO2 Intrusion: Numerical Simulations Based on Core Flooding Experiments

摘要

In this paper, we examined possible impact factors for calcite dissolution and wormhole generation in limestone formations with CO2 saturated brine intrusion by continuum-scale reactive transport simulations. Previous core-flood experiments that mimic near-wellbore region conditions of Geological CO2 Storage (GCS) fields were used as verification cases. Simulation results reasonably reproduce the experimental results. The results suggest that the initial permeability distribution of the core and pre-existing large permeability zones along the core were key factors for wormhole generation. Porosity distribution also affects wormhole generation, but not significantly. According to our simulation results, CO2 saturated brine injection rate, injection pattern, calcite dissolution rate, and permeability anisotropy do not significantly impact calcite dissolution and wormhole generation. The Damkohler (Da) numbers were 0.45-0.9 for the experiments at the core scale in this study, which are in accordance with the value for wormhole growth in previous studies. The numerical models would be applicable in further studies at core scale or a larger scale, and the findings that existing levels of high-permeability pathways help drive wormhole generation and the time scale over which the phenomenon occurs are directly applicable in a field injection scenario.