Geology Reference
In-Depth Information
4.2
Geothermal Regime in the South Caspian
Depression
A detailed review of the association between oil and gas occurrences
and geothermal component of the total geo-fluid-dynamic regime in the
regions is best conducted using an example of the thoroughly studied South
Caspian Depression. There, all correlations between hydrocarbon satura-
tion and geothermal parameters have most contrasting manifestation.
Following are features of the geothermal components of the total geo-
fluid-dynamic field in the South Caspian Basin:
t
he
Mesozoic
sediments in the most subsided part of the
basin. We estimate temperature (
t
mz
) at the base of the com-
plex (basement surface) at subcrops (-26) and (-28) km
respectively at 458-484 and 489-514°С (see Section 4.2.1)
with the geothermal gradients (
G
t
=
dt
/
dH
) of 1.53-1.58 and
1.50-1.57°С/100 m. Temperature normalized for the same
depths (
t
mz
norm
) is 17.6-18.6 and 17.5-18.4°С/km. For basin's
Azerbaijan portion the correlation
“temperature vs. depth
”
for the Mesozoic complex in the depth interval 0.5-28 km
is: -
t
mz
= 13.9 + 0.0635
H
0.871
with the geothermal gradi-
ents
G
t
mz
-2.48-1.48°C/100 m; in the Turkmenistan portion,
interval 0.5-23 km,
t
mz
= 16.8 + 0.073
H
0.851
and
G
t
mz
= 2.46-
1.39°C/100 m.
t
he
Paleogene-Miocene
sediments in the most subsided part
of the basin at the base of the complex (top of the Mesozoic):
model
t
pg-mi
values in the depth interval 8.7-10.5 km
are 171-
231°С, the
G
pg-mi
values are respectively 2.17-2.27°С/100 m,
t
pg-mi
np
19.7-22.0°С/km. In basin's Azerbaijan portion in the
depth interval 0.5-12 km
t
pg-mi
= 13.9 + 0.0544
H
0.898
and
G
pg-mi
- 2.59-1.87°C/100 m; in the Turkmenistan portion these
parameters within the depth interval 0.5-9 km are:
t
pg-mi
=
16.8 + 0.5375
H
0.602
and
G
pg-mi
- 2.72-0.86°C/100 m.
t
he
Pliocene
sediments at the subcrop (-1,000)
m:
t
PS(RS)
−
ranges between 27-59.5°С;
G
t
PS(RS)
in the interval
1-5 km is
1.19-2.30°С/100 m. In the deepest areas of the complex at
its base (top of the underlying Miocene-Paleogene)
t
PS(RS)
within the 6.25-8.3 km depth interval it is 127-178°С. The
temperature normalized at the base of PT-KT (Productive
Sequence/Red-Bed sequence) (
1000
np
t
PS(RS)
),
is 18.1-23.5°С/km.
