Geology Reference
In-Depth Information
t
With increasing in per-unit volume faulting of structures,
the saturation degree of their sections with lower waters (
h
a
)
progressively grows.
The consistent increase in
h
a
and
Н
з. п
values with growing
d
i
. (Figure 8.4,
f
,
g
) is accompanied, beginning at certain value,
with parallel decline in the
section saturation and
reserves density (Figure 8.4,
d
,
e
,
h
) in an evidence
of dual function for the lower alkaline waters in the region. Under some
structural-tectonic conditions, they facilitate the formation of commercial
aggregations; under other conditions, they destroy them.
he
Q
i
=
f
(
h
a
) and
М
=
f
(
h
a
) correlations (Figure 8.4,
d
,
e
) show that the
increase in
h
a
values to 30-50% positively affects the productivity. The
h
a
above this value causes drastic decrease in oil and gas occurrences. That
shifts the balance between migrating hydrocarbons and waters in favor of
the latter, hence, defining the excessive activity of geo-fluid-dynamic con-
ditions facilitating the destruction of accumulations. In our belief, the opti-
mal
h
a
value is 30-50%, which corresponds with maximum reserve density
values.
All graphic data in Figure 8.4 give reason to conclude that the fault-
ing of local structures (causing the presence of alkaline waters genetically
associated with hydrocarbons) and its increase determining growth in
the extent of traps' hydrocarbon saturation positively affect the accumu-
lation only to a certain extent. Further increase in faulting, therefore in
ground water mobility, results in the elimination of hydrocarbon concen-
tration conditions in the reservoirs or in the destruction of earlier formed
accumulations.
The nature of the established correlations together with the aforemen-
tioned concepts give us reason to believe that the formation or dissipation
of hydrocarbon aggregations in the Middle Pliocene of the South Caspian
Depression closely relates with the conditions of the fluid invasion from
the overlying complexes. An important role belongs to the alkaline ground
water dynamics functionally associated with the tectonic conditions of
local structures and, first and foremost, with hydroconductivity of tectonic
unconformities.
The association of most fields in the region with the ascending branches
of the derived correlations suggests that the tectonics of local structures
in the Middle Pliocene as a whole facilitate the processes of accumulation
formation. This is despite their unfavorable appearance caused by intense
fragmentation. Especially favorable in this respect are structures in the
Apsheron area with their maximum hydrocarbon reserves per unit area.
The identified correlations give reason to believe with sufficient reliability