Wettability alteration during low-salinity water-flooding in carbonate reservoir cores

Waleed Alameri, Tadesse Weldu Teklu, Ramona M. Graves, Hossein Kazemi, Ali M. AlSumaiti

    Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

    90 Scopus citations

    Abstract

    Production enhancement by low-salinity waterflood in carbonate formations is a subject of intense speculation. Several mechanisms are attributed to enhanced oil recovery by low-salinity waterflooding in carbonate formations. Review of experimental data in the literature indicates that the main mechanism involves interaction of Na+, Cl-, Ca2+, Mg2+, SO42- and crude oil carboxylate ions (R-COO-) with the rock in the electrical double layer (EDL) near the surface of carbonate pores, leading to wettability alteration. In this study, we performed four seawater floods in heterogeneous low-permeability carbonate cores followed by low-salinity floods. The core permeability is between 0.5 to 1.5 md, and porosity in the range of 18 to 25%. Cores were aged for eight weeks at reservoir pressure and temperature. We also conducted pendant drop oil-brine IFT measurement, and captive oil-droplet contact angle at different brine salinity, with and without the presence of surfactant. The carbonate core flood results show that removing NaCl from seawater or diluting the seawater twice and four times yielded about 8% incremental oil. In one experiment, the change in the effluent ionic concentrations was measured, and it was observed a decrease in Ca2+, Mg2+, Cl-, and SO42-. Using pendant drop IFT measurements, oil-brine IFT increased with decreasing salinity both in presence and in absence of 1,000-ppm surfactant. From captive oil-droplet contact-angle measurements, it was observed that cleaned un-aged carbonate core slabs were water-wet, and became more water-wet as salinity decreased (both in presence and in absence of 1000-ppm surfactant). The wettability of crude-aged carbonate core slabs altered from oil-wet to intermediate-wet as salinity decreased. And, the wettability changed from intermediate-wet to water-wet with decreasing salinity in presence of 1,000-ppm surfactant. Moreover, addition of small amount of surfactant alters the wettability of crude-aged or cleaned un-aged carbonate core slabs towards water-wet. The degree of water-wetness achieved by surfactant solution depends on salinity level.

    Original languageBritish English
    Title of host publicationSociety of Petroleum Engineers - SPE Asia Pacific Oil and Gas Conference and Exhibition, APOGCE 2014 - Changing the Game
    Subtitle of host publicationOpportunities, Challenges and Solutions
    Pages1199-1216
    Number of pages18
    ISBN (Electronic)9781634395267
    DOIs
    StatePublished - 2014
    EventSPE Asia Pacific Oil and Gas Conference and Exhibition - Changing the Game: Opportunities, Challenges and Solutions, APOGCE 2014 - Adelaide, Australia
    Duration: 14 Oct 201416 Oct 2014

    Publication series

    NameSociety of Petroleum Engineers - SPE Asia Pacific Oil and Gas Conference and Exhibition, APOGCE 2014 - Changing the Game: Opportunities, Challenges and Solutions
    Volume2

    Conference

    ConferenceSPE Asia Pacific Oil and Gas Conference and Exhibition - Changing the Game: Opportunities, Challenges and Solutions, APOGCE 2014
    Country/TerritoryAustralia
    CityAdelaide
    Period14/10/1416/10/14

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