Page 132 - Basic Well Log Analysis for Geologist

LOG INTERPRETATION

Figure 44, Chart of porosity (@) versus irreducible water saturation (Sy ;,,) for estimating permeability and determining bulk
volume water (C = Sy x @).
Courtesy, Schlumberger Well Services.
Copyright 1969, Schlumberger.
Given: Porosity (@) = 25% and irreducible water saturation (Sy ;,,) = 40% for an oil-bearing sandstone.
Procedure:
1. Find porosity (@ = 25%) on the bottom horizontal scale. and find irreducible water saturation (Sy j, = 40%)
on the left-hand vertical scale.
yl The vertically oriented curved line on which this point falls represents permeability. In this case, permeability
Follow the two values into the chart to the point where they intersect.

(K) equals 100 md for oil (lower scale) and 10 md for gas (top scale).
4, The diagonally oriented, curved, hyperbolic lines (C = S,, x @) represent lines of equal value for bulk volume
water. In this example, the bulk volume water equals 0.10 (BVW = 0.10).

Note: [tis important to remember that this churt iy only valid for estimating permeability (K) in zones at irreducible
water saturanion (Sy iq).
Zones at irreducible water saturation (S,, ;,,) have bulk volume water values (BVW = X S,,) which are fairly
constant. On the chart, data points from different intervals in a zone at irreducible saturation
(Sw in) will plot in a coherent pattern, on or parallel! to one of the curved hyperbolic lines.
Data points from zones not at S, ;, will scatter from this pattern.

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