Geology Reference
In-Depth Information
(Novo-Dmitriyevskoye, East Severskoye, Zybza-Gluboky Yar, Akhtyrsko-
Bugundyrskoye and Abino-Ukrainskoye fields) is equal to the hydrostatic.
The reasons may be significant area, regional consistency and invariability
of water-bearing intervals, good reservoir properties (porosity 16-18%),
isolation from underlying high-pressure complexes by the Albian and
Upper Cretaceous barriers and from the overlying ones by Middle Eocene
clays (the Khadyzhen, Kaluga and Kutais formations). In combination,
these may provide hydraulic communication between the intervals and,
therefore, equalizing formation pressure according to the laws of hydro-
statics. A number of local depositional gaps in this zone also suggest a pos-
sibility of the paleo-discharge system, which could have provided initial
formation pressure normalization to hydrostatic level. Normal formation
pressure in reservoirs and abnormal pore pressure in the separating clay
intervals indicates limited hydraulic communication between permeable
and impermeable intervals and low degree of migration even at very pres-
sure gradients between them.
In the
Upper Eocene
complex (in the east of the trough - the Kuma
Formation) AHFP is omnipresent in reservoirs of mostly lower (flyshoid)
part of the section overlain with marly-clayey series. Recorded excess for-
mation pressure and abnormality factor values reach their maximum in the
region on the Kerch Peninsula structures and in the Kaluga, Azov and Levkin
anticlinal zones of the West Kuban Trough. Their values there are: at the
Moshkarev prospect, 8.2-20.3 MPa and 1.59-1.92; in the Novo-Dmitriyev
Field, 4.7-9.6 MPa and 1.17-1.37; in the Kaluga Field, 6.8-8.3 MPa and
1.24-1.38; in the East-Northern Field, 10.2 MPa and 1.35; at the Karsk
prospect, 5.7-6.0 MPa and 1.24-1.49; at the Severskaya prospect, 26.8 MPa
and 1.5; in the Abino-Ukrainskoye Field, 14.9-23.6 MPa and 1.52-1.96; in
the Akhtyrsko-Bugundyrskoye Field, 16.3-16.8 MPa and 1.65-1.79; at the
Levkin prospect, 32.9-33.6 MPa and 1.71-1.87. In the eastern Azov zone,
along the line of Zybza-Gluboky Yar - Chernomorskoye fields excess pres-
sure and abnormality factor values decline to 6.2-8.7 MPa and 1.24-1.30.
AHFP in permeable beds of the region are mostly epigenetic and mostly
caused by the injection of high-pressure fluids from the underlying sec-
tion. That is determined by numerous factors such as:
t
Presence of maximum excess formation pressure and abnor-
mality factor values on local highs.
t
Commonality on the local highs of large faults providing
for large-scale hydraulic communication between different
stratigraphic units in the section.
