Modeling the effect of water vaporization and salt precipitation on reservoir properties due to carbon dioxide sequestration in a depleted gas reservoir

Abstract

Abstract Vaporization of water during both gas reservoir development and CO 2 geological sequestration in saline formations can cause salt precipitation with rapid loss of formation porosity and permeability. Water vaporization and precipitation of halite around a single well from stage production to CO 2 injection are studied to investigate the effect on reservoir properties in a gas reservoir. This paper identifies and quantifies post-flood dry zones and permeability changes in depleted gas reservoir after CO 2 exposure with the comparison in gas production period by performing the numerical simulation with the compositional simulator. Simulation results indicate that water vaporization and salt precipitation occur during gas production, and can be intensified by CO 2 injection. Dry supercritical CO 2 injection vaporizes the brine promoting brine concentration and halite precipitation. The simulation indicates a drying area with a radius of 78 m around wellbore after CO 2 injection. Porosity reduces with the most scope of 58%, and permeability can be decreased by up to 93.9% due to salt precipitation. And the injectivity is damaged by 99.77% at the end of injection period based on maximum permeability reduction. Moreover, six factors are investigated to conduct the influence analysis, showing that higher salinity brine, higher injection rate, higher irreducible water saturation, lower initial permeability, higher temperature and with capillary flow are conditions enhancing the salt precipitation due to dry CO 2 injection.