Page 228 - Origin and Prediction of Abnormal Formation Pressures

202 G.V. CHILINGAR, W. FERTL, H. RIEKE AND J.O. ROBERTSON JR.
~,%

1.0 I.I 1.2 1.3 1.4 Pres/Pah
I0
,ooo 20 40 30 60 Rm, ohm'm 9 - el I I ,'
<! ti
w
9
i
l
I
I
13
20
I I
!1 ,I
1500 I~" / i .'1 ,Jr J
"I'. I ,115
I
I
II ~ .'~JJ j
2000 tl /2";;I "~''1 ;ik T 6 I I
'"0 ' ~-I I I
"'
I+I
:
2,oo rl i / ...,, :
" 112
01~-+- /22% I
o
~
~

I
s 3~176176 .-! .......... ~-~~_
.,. ,
-v , I 'T4,
*1 J...~0.3% I
-~--~ .-.~,
WlI" ,-- 1. I
It.I
9
9
ZI,~I/#
4000 ~ * ! s 8b~ ,1~ 2
O0 I ~ 0 0 IlL I
4500 * '~ *~'~- ** ,, '~9 1,3
o~**, o.~.~.~.
+
i ~ - . ~ ,I:,~ 's 15 '
+ooo - i';'+~ o o ,"J', , I
Fig. 8-9. Variation with depth of (/) electric resistivity of the Buregskiy shales, (II) porosity, and (III)
Pres/Pahyd ratio for the subsalt carbonates of the northern structural-tectonic zone in the Pripyatskiy Deep.
Prospects with overpressure: 1 = Dneprovskaya; 2 = Vetkhinskaya; 3 -- Krasnosel'skaya; 4 = Bar-
sukovskaya; 5 -- South Rechitskaya; 6 - Malodushinskaya; 7 = Demikhovskaya; 8 -- East Pervomayskaya;
9 -- Pervomayskaya; 10 -- South Ostashkovichskaya; //= Rudninskaya; 12 = Vishanskaya; 13 = Sudovit-
skaya; 14 = Malynskaya; 15 -- Glusskaya; and 16 = East Drozdovskaya. (Modified after Zavgorodniy and
Pakhol'chuk, 1985, fig. 3.)
Deep are illustrated in Fig. 8-9. Additional detailed information on overpressures is
listed in Table 8-1.
The standard average deviation of measured formation pressures (Pr~) from Curve
III in Fig. 8-9 equals +0.03. According to Zavgorodniy and Pakhol'chuk (1985), two
"stabilized Pres/Pahyd regimes" have been encountered in the region" the first one occurs
at 3000 m with a Pres/Pahyd ratio close to 1.14, whereas the second one starts at 3500
m with the pressure ratio asymptotically approaching the value of 1.18 (Fig. 8-9, Curve
III). (Pahyd = assumed hydrostatic pressure.)