Abstract

Depleted hydrocarbon reservoirs, deep saline reservoirs, and un-mineable coal seams are considered the best geological sequestration candidates for carbon dioxide (CO₂) geologic storage formations. CO₂ sequestration in carbonate reservoirs provides a good way to reduce CO₂ release to the atmosphere. This work investigates the effect of the temperature, pressure, and brine salinity on the petrophysical changes in the carbonate cores due to CO₂ storing. Two groups of experiments were undertaken; (1) investigating the CO₂ solubility under different salinities, pressures and temperatures, and (2) studying the effect of CO₂ storage duration on porosity and permeability of carbonate rocks. Actual cores saturated with 25 000 ppm NaCl brine were used. The potential of the CO₂ storage capacity and variations in porosity and permeability are evaluated and quantified. The results showed that solubility of CO₂ decreases with increase in brine salinity and/or temperature. The increase of pressure causes an increase in CO₂ solubility. The results also indicated that storing CO₂ more than 150 days increases the porosity and permeability of carbonate rocks. The application of the achieved results is expected to have good impact on design storage process of CO₂ in deep saline water incarbonate reservoirs, and on validation of developed mathematical models.

Key words: Carbon dioxide (CO₂) storage, sequestration, carbonate formation, petrophysical properties, deep saline reservoirs.