Experimental Investigation of Salt Precipitation during Gas Injection into a Depleted Gas Reservoir

Abstract

Abstract Water vaporization and its induced damage around the wellbore are important issues with a wide application. This phenomenon could be observed wherever dry gas is injected into gas and oil reservoirs in presence of connate water. Gas injection for EOR, pressure maintenance or storage purposes and carbon dioxide sequestrations in aquifers are examples where it could happen. There are two counteracting factors existing in vaporization phenomenon, water saturation decrease and induced permeability impairment by salt precipitation in the porous medium. Water saturation decrease tends to raise injectivity or productivity by providing higher share of passage to gas. Salt precipitation tends to reduce them by the damages induced. The interaction of these two factors determines how productivity or injectivity will alter. It is a quite new subject finding its interest in application however limited researches are done on this up to now and many aspects are left unknown. We conducted an experiment to investigate the impact of water vaporization on injectivity for core samples of an Iranian gas reservoir candidate for gas storage. According the results, the medium with higher permeability experiences an improved injectivity during gas injection while the medium with lower permeability experiencing an impaired injectivity. Now distribution of each medium around the wellbore dictates if a field application would face injectivity increase or decrease. Finally, the interaction of two effective factors mentioned above differs for each porous medium and water system. Therefore, an experimental investigation for each system should be performed in lack of a general formulation for injectivity or productivity alteration because of water vaporization around the wellbore.