Measurement of Z-factors for carbon dioxide sequestration

Experimental measurements of compressibility factors (Z-factors) for CO₂-hydrocarbon mixtures at three specified temperatures and pressures from 50 to 5000 psia were presented. The results of experimental Z-factors were used to quantify economic benefits, such as EOR and enhanced condensate vaporization, of geologic storage of CO₂ in gas reservoir. The major components of gas reservoir were identified as N₂, CO₂, methane, ethane, propane, n-butane, n-pentane, hexane, and heptane-plus. The laboratory measured Z-factor was much lower than hydrocarbon gas mixtures at the specified temperatures and pressures. That offered the opportunity to store larger surface volumes of CO₂ than hydrocarbon gases. Five times the storage was possible depending on pressure, temperature, and hydrocarbon gas composition. Storage of CO₂ increased of the CO₂/HC gas mixture compressibility (Z-factor) was low. If a liquid condensate occupied the reservoir pore space and the addition of CO₂ vaporized the liquid, additional pore space was acquired for CO₂ storage. This is an abstract of a paper presented at the AIChE 2004 Annual Meeting (Austin, TX 11/7-12/2004).