Scale inhibitor selection criteria for downhole (SQUEEZE) application in a chalk reservoir

Gordon Michael Graham, Eric James Mackay, I Wattie, Lorraine Scott Boak

    Research output: Contribution to conferencePaper

    Abstract

    This paper describes a scale inhibitor (SI) screening study for
    potential application offshore in high volume (30,000 STB per day) horizontal wells in a fractured chalk reservoir. In addition to scale inhibitor effectiveness, potential “pseudo scale” issues are highlighted by an examination of static scale inhibitor/rock interactions and surface analysis using SEM and EDAX techniques. This led to the selection of two generically different products for core flooding studies: a phosphonate based scale inhibitor (Phos) and a sulphonated – polyacrylate co-polymer (VS-Co). The first product (Phos), was a significantly more effective carbonate scale inhibitor; however static inhibitor/rock interaction studies indicated the potential for pseudo scale formation. Thus, in order to minimise the risk to production caused by the increased skin factor (associated with possible near wellbore plugging due to uncontrolled pseudo scale (Phos/Ca2+) precipitation), a less effective product (in terms of carbonate scale performance (VS-Co) was also selected for detailed evaluation in core flooding studies.

    Results from the scale inhibitor core flooding studies and subsequent field application modeling using the Heriot-Watt University SQUEEZE V scale application software indicate, as expected, the potential for significantly longer field squeeze lifetimes when using the Phos based SI than would be expected
    when examining the VS-Co species. However, significantly reduced permeabilities were recorded for the phosphonate based species as a result of Phos / Ca2+ in situ precipitation, which was clearly evident in post treatment SEM analysis.

    In summary this paper describes a typical screening study for SI selection prior to field application. It demonstrates how appropriate chemical selection and field application modeling can highlight potential problems. This may then lead to the
    selection of a poorer performing product (in terms of inhibition and potential squeeze lifetime) which may be the safest option due to potential formation damage arising from the application of an otherwise more effective product.
    Original languageEnglish
    Pages1-13
    Number of pages13
    Publication statusPublished - Feb 2001
    EventInternational Symposium on Oilfield Chemistry - Houston, United States
    Duration: 13 Feb 200116 Feb 2001

    Conference

    ConferenceInternational Symposium on Oilfield Chemistry
    CountryUnited States
    CityHouston
    Period13/02/0116/02/01

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