A permeability-change relationship in the dryout zone for CO2 injection into saline aquifers

Abstract

Injectivity is critical for injection of CO2 into saline aquifers. Previous model studies indicate that injectivity can be impaired by salt precipitation near the injection well. These results are largely determined by the relationships between permeability and salt precipitation. In this study, we develop a new relationship for permeability change owing to salt precipitation near a CO2 injection well. This relationship 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. Using this relationship, we can link permeability change to the effects of saturation in a CO2–brine system and the pore-size distribution of porous media. Its usefulness is demonstrated by the good agreement between predicted results and observations from a laboratory experiment. The developed methodology, in principle, can also be applied to other two-phase flow systems involving chemical-reaction-induced permeability changes.