Page 213 - Origin and Prediction of Abnormal Formation Pressures

188 E AMINZADEH, G.V. CHILINGAR AND J.O. ROBERTSON JR.

(1) 1.0-
0
0
d~
..,.,_
>
r 0.75-
r Q 9 ~ 9
0
0 0
0
0 0.5-
o.--
O
=1===
ry
- I I l I
0.25 0.5 0.75 1.0
Ratio of resistivities, pip~
Fig. 7-1 I. Relationship between ratio of sonic velocities Va/Vn and the ratio of resistivities Pa/Pn in shales.
Va and Vn are sonic velocities in abnormally-pressured and normally-compacted shales, and Pa and Pn are
resistivities of abnormally-pressured and normally-compacted shales. (After Kerimov et al., 1996.)

The coefficient of correlation between the parameters V (Va/V.) and/5 ((Pa/Pn)) is
0.87 and the mean-squared estimation error for Va is 190 m/s. The average relative error
of velocity estimation is 6%, ranging from zero to a maximum of 14%. Thus, Va can be
estimated from the Pa/P. ratio and the Vn obtained from the normal compaction trend in
the area studied.
The relationship between the ratios Va/V, and pa/p. is presented in Fig. 7-11.

BIBLIOGRAPHY
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