Geology Reference
In-Depth Information
A number of factors indicate the domination of the Maracaibo depres-
sion by the cross-flow-injection water-exchange (migration). It is deter-
mined by the large-scale mostly vertical fluid-mass transfer whose volume
is controlled by the fault conductivity. Among these factors are:
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Spatial hydrochemical zoning described in Chapter 2. It
shows the actual effect of vertical (from the bottom upward)
ground water cross-flow through the fault system.
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Development in the Eocene-Pliocene range of formation
water mixes corresponding with the mixing mechanism of
former Mesozoic chlorine-calcium and syngenetic hydro-
carbonate-sodium waters.
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The commonality of genetically interrelated positive com-
ponent, concentration, geothermal (Chapter 4) and negative
piezometric distortions of regional backgrounds associated
with fault zones, structures and parts thereof and consistent
association with them of the commercial oil and gas occur-
rences (Chapter 6).
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Intense development of surface high-temperature oil-, gas-
and water-shows in most faulted areas, etc.
The stratigraphic range of such migration covers the Cretaceous-
Pliocene interval (the physical range of 8-0.3 km).
This conclusion finds additional support in the results of special petro-
leum geochemical studies. They established the identity of the Cretaceous-
Paleogene oils and a number of their specific features:
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Their correspondence with the type of the natural filtrates.
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Their autochthonous in the Cretaceous and allochthonous
in the Cenozoic presence in the enclosing reservoirs.
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Their Cretaceous and Eocene age in Miocene-Pliocene res-
ervoirs (Hunt, 1982).
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Oil-saturation specifics in individual fields (their stacked
nature, concentration of major reserves in the most faulted
blocks and areas (Anikeyev, 1964; Martinez, 1973; Miller,
Edwards and Walcott, 1961; Rachinsky, 1987, 1989)).
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Wide stratigraphic range of hydrocarbon accumulations
from basement (La Paz, Mapa and Tatumo fields) through
the Pliocene (Bakirov, Varentsov and Bakirov, 1970; Beka
and Vysotsky, 1976; Geologic structure…, 1959).
