Geology Reference
In-Depth Information
flank frameworks over tectonic, stratigraphic and lithological unconformi-
ties actually played a limited role. This view limits the potential for the dis-
covery in its most subsided traps of large oil and gas accumulations. It also
limits the reality of their accumulation within the up-dip structures under
the concept of hydrocarbon synchroneity with the enclosing deposits and
of dominating off-reservoir
mechanism of hydrocarbon movement under
the differential entrapment concept.
The latter statement is supported by a consistent increase from the flank
framework toward the central deep-water area of stress in the Productive
Sequence (Red-Bed Sequence) hydrodynamic system. It boils down to the
limitation of migration processes revealed by the development there of cul-
minating super-hydrostatic formation pressure (AHFP) and close to geo-
static pore pressure (AHPP). The hydrocarbon saturation of the Productive
Sequence (Red-Bed Sequence) is regionally controlled by deep-seated
faults in the sediment cover. Its areal distribution spatially corresponds
with their development, which provides for the migration communicabil-
ity between Mesozoic- Paleogene-Miocene oil and gas source rocks and
the accumulating Pliocene intervals. These make domination in the basin
of a large-scale vertical interformational fluid-mass transfer in the forma-
tion of regional, zonal and local oil and gas occurrences and demand cor-
rections to be made in the exploration process.
Because of the association of large oil and gas resources in the Productive
Sequence (Red-Bed Sequence) over the deep-water central South Caspian
with the depth interval 7-9 km, some Azerbaijani geologists advocate the
need to explore there. We will not detail our serious doubts (from geo-
logic viewpoint) in legitimacy of possible hydrocarbon accumulation in
substantial amounts at such depths, in hydrodynamically closed quasi-
stagnant, poorly drained natural reservoirs. Still, the proposal to explore
them now or in the near future suggests critical attitude in terms of the
economic efficiency of such projects and appears premature. Besides, when
reviewing these proposals, negative exploration and appraisal results in the
region during the recent years at somewhat shallower depths on the struc-
tures fringing the recommended deep-water area (see above) should be
analyzed and taken into account.
We feel obligated to assess the views of scientists who consider as
mandatory the association of hydrocarbon saturation in the Productive
Sequence (Red-Bed Sequence) with the channel and deltaic facies of
paleo-river systems. Exploration and appraisal operations in the areas of
their local development found no large-scale oil- and gas-saturation in the
areas of Paleo-Kura and Paleo-Pirsagat, south and central anticlinal zones
of the Baku Archipelago, Paleo-Volga-North Apsheron zone of highs and
