Microscopic mechanisms of oil recovery by near-miscible gas injection

Mehran Sohrabi Sedeh, Ali Danesh, Agha Dabir Tehrani, Mahmoud Jamiolahmady

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    126 Citations (Scopus)

    Abstract

    As gas flooding becomes a more viable means of enhanced oil recovery, it is important to identify and understand the pore-scale flow mechanisms, both for the development of improved gas flooding applications and for the predicting phase mobilisation under secondary and tertiary gas flooding. The purpose of this study was to visually investigate the pore-level mechanisms of oil recovery by near-miscible secondary and tertiary gas floods. High-pressure glass micromodels and model fluids representing a near-miscible fluid system were used for the flow experiments. A new pore-scale recovery mechanism was identified which significantly contributed to oil recovery through enhanced flow and cross-flow between the bypassed pores and the injected gas. This mechanism is strongly related to a very low gas/oil interfacial tension (IFT), perfect wetting conditions and simultaneous flow of gas and oil in the same pore, all of which occur as the gas/oil critical point is approached. The results of this study helps us to better understand the pore-scale mechanisms of oil recovery in very low-IFT (near-miscible) systems. In particular we show that in near-miscible gas floods, behind the main gas front, the recovery of the oil continues by cross-flow from the bypassed pores into the main flow stream and as a result almost all of the oil, which has been contacted by the gas, could be recovered. Our observations in high-pressure micromodel experiments have demonstrated that this mechanism can only occur in near-miscible processes (as opposed to immiscible and completely miscible processes), which makes oil displacement by near-miscible gas floods a very effective process. © Springer Science+Business Media B.V. 2007.

    Original languageEnglish
    Pages (from-to)351-367
    Number of pages17
    JournalTransport in Porous Media
    Volume72
    Issue number3
    DOIs
    Publication statusPublished - Apr 2008

    Keywords

    • Gas injection
    • Micromodel
    • Near-miscible
    • Pore-scale mechanisms
    • Three-phase flow

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