Geobaric Field in Alpine Mobile Belt Basins - Fluid Dynamics of Oil and Gas Reservoirs - page 211

highs, 1.48-1.76 (56-71%); in the Elburs trough, 1.55-1.80 (65-95%).
There are no direct data for the South Caspian deep depression. Seismic,
gravimetric, electric and magnetic surveys as well as acoustic sounding
data show drastic decline in interval wave velocities, chaotic position of
individual events, rock density inversion in the section and stable negative
electric and magnetic anomalies. These are indications that PT-KT there
is being composed mostly of unconsolidated (high porosity) clays (over
90%). This suggests that the К AHFP values there are at least 1.70-1.80 at
К AHPP of about 2.10-2.30.
For individual areas, the formation pressure values excess over the
hydrostatic are as follows: the North-Apsheron zone of highs, Apsheron
Peninsula, South-Apsheron Trough 0-7; Kobystan (Djeyrankechmes
Depression and Alyat Ridge) 2-14.5; Baku Archipelago, Lower Kura
Depression, Balkhan zone of highs, Gograndagh-Chikishlyar zone, Fore-
Elbrus trough 2.6-40 MPa. On the whole, the Middle Pliocene waterhead
complex displays rather significant excess formation pressure reaching
sometimes 50% and greater. A particular feature in their vertical distribu-
tion is relative closeness to the hydrostatic head within the depth intervals
down to 2,000-2,500 m ( К AHFP to 1.30) and significant diversion from it
deeper than 3,000 m ( К AHFP 1.50-1.92).
The correlation between К AHFP , clay content of the section, thickness and
depth of the PT-KT surface is a direct one. Maximum factor values corre-
spond with maximum clay content, thickness and interval top subsidence
depth. The correlation between К AHFP and depths of AHFP zones surface is
an inverse one. Maximum factor values correspond with their minimum
depths.
In the latter case, the AHFP zones tops are sometimes positioned within
the sediments overlying the Lower Pliocene sequence in the Akchagyl and
Apsheron (Upper Pliocene) Stages. That happens in the Baku Archipelago
(Bulla-More-2, Umid (Andreyev Bank), Aran-Deniz (formerly Persiyanina
Stone), Inam (Borisov Bank), etc.; in the Lower Kura Depression (Padar,
Kyurovdagh, M. Kharami, Kyzylagach, etc.); in the Gograndagh-
Chikishlyar zone of highs (Erdekli, Gograndagh, Chikishlyar, etc.); in the
Fore-Elbrus trough (Enzeli-More, Gozel Tepeh).
The abnormal distribution over the basin of high pore pressure (AHPP)
and its association with the aforementioned section parameters are quali-
tatively identical. The range of the К AHPP values in the region is on the whole
1.13-2.30. Minimum values are recorded at the prospects with minimum
К AHFP (the western subzone of the Apsheron-Balkhan Sill, North-Apsheron
zone of highs and Apsheron Peninsula). Maximum values are found in the
Lower Kura Depression, Baku Archipelago and Gograndagh-Chikishlyar