Page 203 - Petrophysics 2E
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176 PETROPHYSICS: RESERVOIR ROCK PROPERTIES
30 120
25
8
k 20
0
C
15
CT
2
LL 10
5
0
- 10 12 14 16 18 20 22 24 26 28 30+
Porosity, YO
Figure 3.50. Porosity histogram and distribution for all samples.
TABLE 3.1 1
CLAsSlFlCAllON OF POROSITY DATA INTO RANGES OF 2 PERCENT POROSITY
FOR ALL SAMPLES
Porosity Mid-value Cumulative
Range, of range, No. of Frequency Frequency
% % samples F, % Fc, %
Less than 10 9 1 3.45 3.45
10-12 11 0 0.00 3.45
12-14 13 1 3.45 6.90
14-16 15 3 10.34 17.24
16-18 17 4 13.79 3 1.03
18-20 19 8 27.59 58.62
20-22 21 1 3.45 62.07
22-24 23 1 3.45 65.52
24-26 25 3 10.34 75.86
26-28 27 3 10.34 86.21
28-30 29 2 6.90 93.10
30 + 31 2 6.90 100.00
Totals 29 100
of symmetry is further confirmed in Figure 3.5 1, which is plot of porosity
data versus the cumulative frequency on a arithmetic probability graph.
Theoretically, if the porosity data approximate a straight line, then a
normal curve, which is completely defined by the arithmetic mean, is a
reasonable fit of the data.