Geology Reference
In-Depth Information
t
Mud volcanism (Kerch-Taman area).
t
Heightened neotectonic activity in the Upper Eocene com-
plex area.
t
Blocking by the regional water barrier (Beloglin Formation)
of the Upper Eocene lens-shaped clayey low-permeability
reservoirs from zones of hydrodynamic discharge.
Still, the simultaneous generation in the sediments of syngenetic AHFP
is a possibility. Syngenetic AHFP emerges due to the consolidation of
incompetent members uncompensated by fluid outflow due to the release
from them of the “regenerated” water and elastic neotectonic deformations
of reservoirs. This generation is facilitated by nonuniformity, lithological
variability of productive intervals commonly alternating with clayey vari-
eties of the section.
he
Oligocene-Lower Miocene
complex (Maikopian Formation) com-
prises mostly clays with rare rather thin lens-shaped reservoirs. It is a
regional seal. Maximum thickness of the series is 3,000 m in the West Kuban
Trough and 5,000 m in the Kerch-Taman area (Durmishyan, Muradian
and Rachinsky, 1976). AHFP in the Maikopian Formation's reservoir
intervals is nonuniformly developed over the area and basically reflect the
changes in thickness of the entire complex. The highest excess formation
pressure and abnormality factor values are recorded on the structures in
the Kerch-Taman area and in the centroclinal portion of the West Kuban
Depression. There, the series' thickness is significant (over 1,500-2,000 m).
These parameters are: on the Kerch Peninsula (Fontanov, South-Sivash,
Gornostayev, Slyusarev and Korenkov prospects), 20.3-32.3 MPa and
1.67-1.87; in the West Kuban Trough (West Afip prospect), 44.3 MPa and
1.89; on the East Afip prospect, 40.3 MPa and 1.90; on the Seversk, 32.0-
35.6 MPa and 1.64-1.72; in the Novo-Dmitriyev Field, 41.2 MPa and 1.84.
In the zone of decreased Maikopian thickness on the Southern flank of the
depression (the Klyuchevaya, Dysh and Saratov prospects area) abnormal-
ity factors are usually minimal, 1.01-1.20.
As stated, formation pressure abnormality correlates with total thick-
ness of the mostly clayey Maikopian formation. Lens-shaped and sporadic
development of reservoirs in the formation determines mixed origin of
their AHFP. The syngenetic component is due to phenomena like:
t
The invasion of high-pressure fluids released from the
Maikopian clay members.
t
Water from dehydration of montmorillonite minerals group.
