Page 122 - Basic Well Log Analysis for Geologist

LOG INTERPRETATION

IPF=292 BO+I3 BWPD
96% OIL

ww
“—
.O6 ———_
ee
04

-_
+

.05 40 AS
POROSITY, @

Figure 39. Crossplot of porosity versus water
IPF = 212 BO+100 BWPD
saturation used to determine bulk volume
68% OIL
water. Because production of water in a well
can affect a prospect's economics, it is
important to know the bulk volume water and
whether the formation is at irreducible water
saturation (Sy ;,,).
This crossplot cxample is taken from the
Ordovician Red River B-zone, Beaver Creck
Field. Golden Valley County, North Dakota
(after Jaafar, 1980).
When values of bulk volume water plot along

hyperbolic lines or, in other words, are

T 005 T constant or close to constant, the formation ts
homogeneous and close to irreducible water
AS .20
saturation (Sy, ;,-). Remember, a reservoir at
POROSITY, @
Sw in Will not produce water. Note that in

Figure 39A (top diagram) the bulk volume
IP=WATER O&A
water values are close to constant (parallel to
O% OIL
the 0.04 hyperbolic line) and the formation
produces 96% oil.
formation has more water than it can hold by
As the amount of formation water increases.
the bulk volume water values become
scattered from the hyperbolic lines and the
capillary pressure. Thus more water is
produced relative to oil. Figure 39B (middle
diagram) shows a well producing 68% oil, and

Figure 39C (lower diagram) shows a well
producing 0% oil (all water). Note the scatter
—~—_BYW Sw
8
of crossplot values froin the hyperbolic lines
in Figures 39B and 39C.
T
T
TOT
TT

15
40
10
.20
30
35
25
@
POROSITY,

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