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Concept of relative permeability. If two fluids flow simultaneously in a porous medium, the permeability of each fluid is reduced by the presence of the.

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Presentation on theme: "Concept of relative permeability. If two fluids flow simultaneously in a porous medium, the permeability of each fluid is reduced by the presence of the."— Presentation transcript:

1 Concept of relative permeability

2 If two fluids flow simultaneously in a porous medium, the permeability of each fluid is reduced by the presence of the other one! Fluid 1 Fluid 2 Fluid 1 P1 P2 k 1 and k 2 are effective permeabilities and modified by saturations of the fluids

3 rel perm vs. saturation k r is called relative permeability and depends on saturation (also rock type and geometry and fluid properties) End- points Curvatures

4 Different demonstrations

5 Log scale

6 General comments on rel perms Relative permeabilities only provide the general description of the process not the mechanism! It is a very simple tool to describe multi-phase flow in porous media Often used as fitting parameters in history-matching exercises Absolute permeability does not depend on wettability while rel perms do Like capillary pressure there are two drainage rel perms and imbibition rel perms

7 Gas-oil relative permeability Gas flows above a critical gas saturation (Sgc) When pressure drops below bubble point pressure, gas bubbles appear in oil, however they must coalesce and form a gas phase before gas can really move S gc = 0 – 8%

8 Capillary end effect

9 Capillary pressure end effect gives rise to increasing wetting phase saturation towards outlet of the core

10 Determination of relative permeability Steady-state method: Fluids are injected with fixed flowrate into core until equilibrium is reached. Unsteady-state method:

11 Empirical correlations Corey: Brooks-Corey:

12 Normalizing oil relative permeability data kro Log scale S on, log scale Slope is no

13 Normalizing water relative permeability data krw Log scale S wn, log scale Slope is nw End point, krw0

14 Model Fit

15 Estimation of S or kro Log scale S on, log scale We choose Sor that gives straight line

16 Different wettabilities wettabilitynonwk rw 0 Water-wet Intermediate Oil wet


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