Water-oil relative permeability,related to all two-phase flow properties,characterizes two-phase flow and displacement processes in porous media.Therefore,relative permeability is inherently complicated,and its functional form is difficult to determine in a particular reservoir study.For example,adding various chemical agents into the displacing aqueous phase during alkaline-surfactant-polymer combination chemical flooding significantly changes interfacial tension(σ) on water-oil interfaces,and also increases the degree of difficulty in measuring such changes in the laboratory.To overcome the limitations of the existing laboratory measurements of relative permeability, which are applicable only for high ranges of interfacial tension(e.g.,σ>10~(-2) mN/m),we present a comprehensive experimental study of two-phase relative-permeability functions in much lower,realistic interfacial tension water-oil systems.In particular,we have(1) developed an improved steady-state method of measuring water-oil relative permeability curves;(2) proved that the two critical values,N_(C1)(0.0005) and N_(C2)(0.1) or σ_(C1) (3mN/m) and σ_(C2)(10~(-2)mN/m) exists,observed in capillary number or interfacial tension with the selected water-wetting cores under laboratory temperature conditions;(3) shown that a logarithmic relation exists between water-oil two-phase relative permeability and interfacial tensions.The experimental results and proposed conceptual models will be useful for feasibility studies,optimal designs,and numerical simulations of different chemical flooding operations in oil reservoirs.
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