Modeling nonisothermal modified salinity water flooding of chalk reservoirs

    Activity: Talks and presentationsConference presentations


    Modified salinity water (MSW) flooding is shown to be more effective at higher temperatures in the coreflooding tests from the chalk reservoirs. The improvement of oil production that is widely linked to wettability alteration is determined by the physicochemical interaction between potential determining ions (PDIs) in the MSW and formation water, rock surface chemistry, and crude oil components, mostly organic polar groups. These interactions can be described by the chemical reactions between the ionic species in the aqueous phase and at the water-rock and water-oil interfaces. The chemical equilibrium between these species is shown, e.g., zeta potential measurements of the chalk particles, to be heavily affected by temperature change. A large number of chemical reactions, however, makes it increasingly difficult to predict the effect of temperature on the outcome of MSW flooding since each chemical equilibrium responds differently to the change of temperature depending on the enthalpy of reaction. In chalk cores, oil recovery is improved at higher temperatures in the presence of PDIs. This has led to the view that seawater or MSW is more efficient at higher temperatures (notably higher than 70°C).

    This study aims to develop a mechanistic model that can systematically and quantitatively reproduce the observed laboratory link between increasing temperature and improved oil recovery. The reactions enthalpies of the chalk surface are inferred from the work of Bonto et al. Then, we include the temperature dependence of viscosity, the dissolution of chalk, and precipitation of minerals, e.g., anhydrite. We couple the PHREEQC geochemistry package with an inhouse finite volume solver for our geochemical and nonisothermal multicomponent multiphase transport calculations. The link between the geochemistry and multiphase transport properties is established through the available adsorption sites.

    We first validate the model using inhouse and literature core flooding data, with the transport parameters obtained from the work of Ciriaco et al. at different temperatures. Then we apply the model to a 2D domain that resembles a North Sea chalk field in which cold seawater is being injected. We show that the results match qualitatively with the field data demonstrating the capabilities of our improved model.
    Period19 Apr 202122 Apr 2021
    Event title21st European Symposium on Improved Oil Recovery
    Event typeConference
    Conference number21