Geology Reference
In-Depth Information
The domination of the vertical fluid-mass transfer in the region is addi-
tionally supported by petroleum geology data. They include:
t
Epigenetic bitumen (up to 0.16-0.18%) in clay members
over the crests of the Starogroznenskoye and Khayan-Kort
fields (64).
t
Direct traces of fluid migration from the underlying sedi-
ments into the Upper Cretaceous reservoirs (“contami-
nation” by epigenetic bitumens in the fractured zones
underneath OWC in the carbonate massifs at a distance of
up to 200 m from the separation surface) in the Karabulak-
Achaluki and Zamankul fields (Neruchev, 1969).
t
Reznikov (1970) established genetic unity of the oils in
all stratigraphic intervals of the penetrated sediment sec-
tion; estimates of hydrocarbons' geochemical age gave their
mostly Middle Jurassic origin in the Upper Cretaceous
accumulations.
The data on the distribution of potentially oil-producing intervals in the
section do not agree with the concept of elision water-exchange and sup-
port the domination of vertical migration. This function could hardly have
been performed by the Lower Cretaceous and Upper Jurassic sediments.
The reason is that clayey members in the former are thin and were mostly
deposited under an oxidized environment (Neruchev, 1969) and the lat-
ter, except for the Callovian, are carbonates. Besides, evaporites are widely
developed in the Titonian Stage over substantial area of the region. The
evaporites are a barrier for the hydrocarbon and accompanying ground
water migration. A logic assumption is that the fluids were fed from the
Lower-Middle Jurassic, possibly even deeper horizons, through large faults.
The vertical fluid-mass transfer in the Tersk-Caspian Trough covers the
depth range of 10-7 km and the stratigraphic interval from Permotriassic
(?) through Jurassic-Miocene.
5.2.2.4
he Zagros Trough
The hydrodynamical situation in the region's sedimentary section is deci-
sively against the possibility of functioning there of an infiltration-type
waterhead system. This conclusion is based on:
t
Omnipresence in the section of highly-metamorphosed
chlorine-calcium brines (total salinity, 80-300 g/l).
