Imaging of oil layers, curvature and contact angle in a mixed‐wet and a water‐wet carbonate rock

Kamaljit Singh, Branko Bijeljic, Martin J. Blunt

Research output: Contribution to journalArticle

78 Citations (Scopus)
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Abstract

We have investigated the effect of wettability of carbonate rocks on the morphologies of remaining oil after sequential oil and brine injection in a capillary‐dominated flow regime at elevated pressure. The wettability of Ketton limestone was altered in situ using an oil phase doped with fatty acid which produced mixed‐wet conditions (the contact angle where oil contacted the solid surface, measured directly from the images, θ=180°, while brine‐filled regions remained water‐wet), whereas the untreated rock (without doped oil) was weakly water‐wet (θ=47 ± 9°). Using X‐ray micro‐tomography, we show that the brine displaces oil in larger pores during brine injection in the mixed‐wet system, leaving oil layers in the pore corners or sandwiched between two brine interfaces. These oil layers, with an average thickness of 47 ± 17 µm, may provide a conductive flow path for slow oil drainage. In contrast, the oil fragments into isolated oil clusters/ganglia during brine injection under water‐wet conditions. Although the remaining oil saturation in a water‐wet system is about a factor of two larger than that obtained in the mixed‐wet rock, the measured brine‐oil interfacial area of the disconnected ganglia is a factor of three smaller than that of oil layers.
Original languageEnglish
Pages (from-to)1716-1728
Number of pages13
JournalWater Resources Research
Volume52
Issue number3
Early online date12 Feb 2016
DOIs
Publication statusPublished - Mar 2016

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