Brine Salinity: A Deciding Factor for Carbondioxide Dissolution and Trapping during Geological Sequestration

Abstract

Adequate geological storage of carbondioxide in saline aquifers is a function of several factors that requires understanding and examination. Previous works have argue that solubility of carbondioxide in brine decreases as the salinity of the brine increases, but it is unclear in the literature the impact of salinity on carbondioxide (CO2) trapping during sequestration. This work adopt a simulation based approach to determine CO2 dissolution and trapping at different salinities. A dataset was written and validated with CMG’s greenhouse gases simulator and the thermodynamics properties calculation carried out with Peng-Robinson equation of state. Four sensitivity analyses was conducted with brines of no salinity (pure water), salinity of 100000ppm, 200000ppm and 300000ppm and model outputs compared for CO2 sequestration. The result shows that CO2 solubilised in water with zero level salinity, and a lower gas cap size was formed at the top of the structure. Later, gas cap size increases as the salinity level increases at the top of the structure. Also, the moles soluble in water decreases as the salinity level increases with the least moles for zero water salinity. Alternatively to the moles solubilised, the number of moles of CO2 trapped increases with the salinity level. CO2 storage in deep saline aquifers is the best storage techniques but its injection into aquifer of high salinity reduced its solubility.