Page 79 - Origin and Prediction of Abnormal Formation Pressures

ORIGIN OF ABNORMAL FORMATION PRESSURES 61

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if) I x..x -~ x x -'~.._ X x x
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0.5 1.0 1.5 2.0 2.5 3.0
DISTANCE FROM FAULT, KM
I00

j 80 B
(..9 e 13
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~ .60
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4O
17'
W
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~ 20 0 22
012 O 9
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0.9 0.9'5 1.0 i.05 I.i 1.15 1.2
_FORmAl" tON PRESSURE
HYDROSTATIC PRE SSURE
Fig. 2-23. Correlations between the thickness of gas-filled rocks and distance from the fault (A), and between
the pressure abnormality and water salinity (B) for pre-Jurassic formations of the North Rakushechnoye
field, Mangyshlyak Peninsula, west coast of the Caspian Sea, Kazakhstan. (Modified after Larichev and
Timurziev, 1987; in Gurevich and Chilingarian, 1997, fig. 8, p. 328.)

(Fig. 2-24). Thus, fluids were collected at the roots of the fault and transferred (in-
jected) upward through the fault into formations within the fractured zone. The pressure
distribution, therefore, is controlled by these injection scenarios. To predict a pressure
abnormality of this type, approaches that are different from the current ones should
be used. A combination of various geophysical methods with geologic studies can be
recommended for a case like this.