FIGURE Q1: Relative Permeabilities plot of a Water-Wet Rock With the help from F
ID: 114323 • Letter: F
Question
FIGURE Q1: Relative Permeabilities plot of a Water-Wet Rock
With the help from FIGURE Q1, explain about
a. The microscopic point of view of relative fluid flow at:
i. Sw = Swc
ii. Swc < Sw < Sor
iii. Sw = Sorw [ 9 MARKS]
b. Possible values of x and krw at Sorw with strong justification. [6MARKS]
c. The effects on the curves if the rock formation is oil wet. [ 5MARKS]
Explanation / Answer
Figure 1 is showing relative permeability of Water wet rock.
a) i)When Sw= Swc, the irreducible water saturation is important. This indicates the minimum water saturation that can be obtained in the reservoir under normal condition. This region exhibits continuous saturation (funicular) in oil phase and discontinuous saturation (pendular) in water phase.
ii) Swc< Sw< Sor - when this condition comes, indicates both the water and oil phase is in continuous saturation stage. Sor is the residual oil saturation when the oil can no longer flow in a normal immiscible water/oil system.
iii) When <Sor, the oil phase becomes discontinuous droplets and here the water saturation is continuous.
b) Possible value of x is 50% water saturation and at Sor the value of Krw is 5-30%, average 15%.
c) If the formation is oil-wet, it shows the mirror image of water-wet system. Here water is out from the center of the flow channels, so it is easier to flow.
To get wettability we have to go to the 50% saturation point on the horizontal axis and from there vertically up the lowest curve. This curve is for the fluid which flows with the greater difficulty and represents the prmeability of the wetting phase.
In oil-wet system, the irreducible water saturation is lower than for the water-wet system. End-point ranges and averages are just opposite from the water-wet system.
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