Synergy of CO2 removal and light hydrocarbon recovery from oil-field associated gas by dual-membrane process

CO2 enhanced oil recovery technology is widely used in depleted oil-fields; however, the CO2 content in the associated gases is increased accordingly, which is unfavorable for both light hydrocarbon recovery and natural gas purification. This work proposes a dual-membrane associated gas recovery process, which couples hydrocarbon separation and CO2 removal in the dual-membrane modules and improves the process efficiency. The dual-membrane module contains both hydrocarbon-selective and CO2-selective membranes, enabling the hydrocarbons and CO2 to be recovered from bulk flow separately and simultaneously. The hydrocarbons are enriched in the permeate side of the hydrocarbon-selective membrane, and the permeate stream is re-pressurized for recovering valuable hydrocarbons. Meanwhile, CO2 is concentrated in the permeate side of CO2-selective membrane for enhanced oil recovery usage. The synergetic separation in the dual-membrane module significantly reduces the hydrocarbon loss while removing CO2, and results in higher hydrocarbon recovery than the single-membrane process or series-linked membrane process. The production cost savings of the dual-membrane module process are greater than 9%, because of the mutual promotion of hydrocarbon enrichment and CO2 removal by the dual-membrane module. (C) 2015 Published by Elsevier B.V.