Porosity-permeability relationships in modeling salt precipitation during CO2 sequestration: Review of conceptual models and implementation in numerical simulations

Previous model studies indicate that injectivity can be impaired by salt precipitation near the injection well during CO2 injection (Pruess and Müller, 2009). These results are largely determined by the relationship between permeability and salt precipitation which is developed by Verma and Pruess (1988). Liu et al. (2013) presents a new relationship for permeability change owing to salt precipitation near a CO2 injection well, which differs from previous relationships in that it considers the fact that the salt precipitation occurs only in pore space occupied by brine during the precipitation process, and in that it is based on well-established relative-permeability relationships for two-phase flow in porous media. This work reviews the conceptual models based on which these porosity-permeability relationships are developed. The Liu et al. (2013) model is implemented in the multi-phase reservoir simulator TOUGH2, and simulation is conducted and compared with results in Pruess and Müller (2009). Results show that the two constitutive relations give opposite conclusions in whether CO2 dry-out will clog the reservoir. In contrast to the conclusion from Pruess and Müller (2009) that permeability will decrease to essentially zero near the injection well, the new simulation predicts much less reduction in permeability. Discussions are given at the end on the evaluation of each relation and relevant experimental evidences.