Dissolution behaviors of alkyl block polyethers in CO2: Experimental measurements and molecular dynamics simulations

In this work, dissolution behaviors and microscopic dissolution mechanisms of alkyl block polyethers in CO2 are investigated. The effects of CO2-philic group type (polyoxypropylene groups (PO groups) and polyoxyethylene groups (EO groups)), the number of PO groups, and the alkyl chain length are analyzed. The experimental results show that the cloud-point pressures of alkyl block polyethers in CO2 increase with the decrease of the percentage of PO groups in the total polymerization degree (PO + EO), the increase in the alkyl chain lengths and the PO group numbers, which are in good agreement with molecular dynamics simulation results. Further simulation studies indicate that dispersion force interactions, Lewis acid–Lewis base interactions, and intermolecular hydrogen bonds result in different solubilities of alkyl block polyethers in CO2. During the application of surfactant– CO2 systems in unconventional reservoirs, it is preferable to maintain carbon numbers of the alkyl chain within 12 and the number of PO groups within 6 in alkyl block polyoxypropylene ethers.