Estimation of Mass Transfer Coefficient of Contaminant Migration across CO2 - Brine Interface in CO2 Geological Sequestration

Abstract

Injection of CO2 into subsurface formations is one of key technologies for reducing greenhouse gas emissions. However, the injected CO2 could cause migration of subsurface substances, volatile organic contaminants, for example, which may threat ground water system seriously. Mass transfer of volatile organic contaminants moving into CO2 phase through interfaces is one of fundamental problems of safety assessment and risk analysis in CO2 sequestration. In this paper, we proposed a method to calculate mass transfer coefficients of the volatile contaminant moving into CO2 phase by defining a length of interfacial mass transfer region, LIMTR, on the basis of the interphase mass transfer characteristics of oil volatilization in CO2-brine-oil three phases in porous media. The calculation results were compared with the results obtained by numerical simulations. The calculation results show that the lumped mass transfer coefficient kg ranges from 10-7 to 10-2 1/s, and the mass transfer coefficient Kna ranges from 10-6 to 10-1 1/s. By using the proposed method, the interphase mass transfer coefficients for the CO2-brine-oil three-phase system can be readily obtained without the specific interfacial areas between multiple phases known.