Geology Reference
In-Depth Information
Other regions show similar situations. In the Los Angeles Depression -
in the Long beach, Santa Fe Springs and Englewood fields, maximum
reserves density comes with the elevated ground water hardness and salin-
ity, compared with the background in other, less saturated fields. In the
Internal zone of the Carpathian trough - the highest oil-gas-saturation
fields Bitkov, Dolina, North Dolina, Tynyava and Strutyn, rich commer-
cial hydrocarbon aggregations are spatially connected with positive hydro-
chemical anomalies caused by the penetration into productive Oligocene
intervals of the lower metamorphosed chlorine-calcium Mesozoic brines
mixing with the background desalinated alkaline varieties of ancient infil-
tration genesis (Babinets and Malskaya, 1975; Kolody, 1983; Lozinsky
and Bankovsky, 1972). In the Indolo-Kuban Trough - in the Anastasyev-
Troitsk field, the largest in the region gas-oil accumulation of the IV hori-
zon (Meotian Stage) is in contact, against the general chlorine-calcium
saline background waters (of up to 200 mg-equiv or 57 g/l), with a zone
of locally distributed low-salinity (up to 100 mg-equiv or 30 g/l) hydro-
carbonate-sodium waters fringing the diapir core of the structure and a
buried mud volcano (Shaulov, 1968; Shaulov and Fedotova, 1975). In the
Moshkarev, Kuybyshev, Vladislavov and other prospects in the Kerch-
Taman area, semi-commercial hydrocarbon flows from Neogene inter-
vals are only associated with intervals of sporadic presence of alkaline
lower waters in the hard formation water medium. In the Tersk-Caspian
Trough -in the Starogroznen, Octyabrsk and Andreyev fields as well as in
the Zagros trough, which are the Agha-Djari, Marun and Binak fields, in
contact with oil accumulations of the largest density reserves values are
the highest salinity chlorine-calcium mixes of hard syngenetic and foreign
brines enriched in chlorine, calcium and magnesium waters clearly dis-
tinct both from the background and from the formation waters at other,
less productive structures (Volobuyev, 1986).
The association between oil and gas occurrences and hydrochemical
anomalies is recorded not only for individual fields as a whole but also for
their individual areas and fault-blocks. The best example is provided by the
fields in the Tersk-Caspian Trough where the Upper Cretaceous complex
includes the largest reserves density. And several areas there correspond
with positive hydrochemical anomalies where total ground water salinity is
30-140 mg-equiv over the background value. These areas are: the western
plunge of the Karabulak-Achaluki field, the merger zone over the faults of
Eldarovo and Orlinaya with the western part of the Khayan-Kort struc-
ture and with the eastern extremity of the Malgobek-Voznesensk fold and
the western plunge of the same structure (Volobuyev, 1986; Kissin, 1964;
