Geology Reference
In-Depth Information
same time, the tectonic effect is not unique in each specific case. It includes
a double aspect: a positive one when the integrity disruptions play creative
role in the formation of accumulations, and a negative one when they are
paths for the dissipation of earlier formed aggregations.
In this connection, it is necessary to find the boundary conditions,
beyond which certain aspect of fault functioning becomes dominant. The
issue may be solved by revealing and analysis of the connections (if they
are present) between the fluid amount accumulated in the traps and the
faulting intensity of each traps.
The following parameters give quantitative description of the tectonic
conditions of local structures: per-unit volume faulting (
d
i
) and folding
intensity (
К
ин
) (Chapter 5); the lower water volume accumulated in the traps
(parameters
h
a
and
Н
з
.
п
in the South Caspian Depression) (Chapters 3, 4);
and parameter М (%) (total net oil thickness to gross ratio in the produc-
tive section of individual fields, amount of the hydrocarbon reserves per
unit area of the structures
Q
i
, MMT/km
2
).
Table 8.2 lists the values of all stated parameters for the main fields in
oil and gas areas of the South Caspian depression considered to be a type
model. The data is evidence of the presence in each area of clear similar-
ity in the correlation parameters, which allows treating them as genetic
(functional).
Figure 8.4 shows correlations between intensity (
К
ин
), per-unit vol-
ume faulting (
d
i
) of local structures in the region, measure of the pres-
ence of lower alkaline waters in their sections (
h
a
,
Н
з
п
), parameter
М
and hydrocarbon reserves density (
Q
i
). As may be seen for all oil and gas
areas the correlation
Q
i
=
f
(
d
i
),
Q
i
=
f
(
К
ин
),
Q
i
=
f
(
h
a
),
Q
i
=
f
(
Н
з
.
п
),
М
=
f
(
d
i
) and
М
=
f
(
h
a
) have a single-mode nature with a clear maximum.
Qualitatively different are only the correlations
h
a
=
f
(
d
i
), and Н
з
п
=
f
(
h
a
).
(Figure 8.4
f
,
g
).
The data in Figure 8.4 enable us to state:
t
With the increase in the intensity and per-unit volume fault-
ing of structures to a certain for each oil and gas area values,
the section's saturation and hydrocarbon reserves density
increases; farther growth in the intensity and faulting results
in declining of both parameters.
t
In actual conditions of the South Caspian Depression's
Middle Pliocene, the highest hydrocarbon reserves den-
sity is associated with local structures of about average for
an oil and gas area values of the per-unit volume faulting.
Optimum value of this parameter is 0.20-0.40.
