Geology Reference
In-Depth Information
5. Methanation of oils from the basin's flanks toward its
center together with a decrease in non-hydrocarbon
components in the gases.
6. A continuous decrease in geochemical age of oils and
condensates in the same direction against the back-
ground of:
a. low original content of C
org
in PS/RBS (0.3-0.8 kg/ton),
b. rapid depositional rate (750-900 m/MMY),
c. short duration of deposition (8 MMY),
d. low heating of the section (temperature gradient of
14.8-22.1
C/km), and
e. high abnormality coefficient of formation pressures
(up to 1.53).
C. The process of hydrocarbon generation and accumulation
have been modeled by the authors (based on the meth-
odology proposed by N.B.Vassoyevich, N.V.Lopatin and
D.Waples). A thermodynamic model of these processes has
been developed and adjusted for the patterns of hydrocar-
bon distribution by the reserves, phase composition, geo-
chemical type, and thermobaric environment of reservoirs.
The results indicate the spatial and temporal evolution of the
oil- and gas-generation foci: ever younger portions of the
Mesozoic-Pliocene section are sequentially involved in the
generation processes toward the basin's center. The major
gas-generation focus occurs in the apocatagenesis and meta-
genesis zones of the Mesozoic section. The major liquids-
generation zone occurs in the Paleogene-Miocene section
with a clearly subordinate role played by the lower portion
of PS/RBS (
MC
1
-MC
2
and, partially,
MC
3
grades).
D. The present-day position of the oil-generation zone in the
Caspian Sea Basin section occurs at a depth of 8-10 km,
whereas that of wet gas and condensate-generation zone, at a
depth of 12-14 km. Thus, the processes occur in rocks under-
lying PS/RBS rocks, which clearly establishes allochtonous
origin of its hydrocarbons.
E. At present, the hydrocarbon gas phase and high-temperature
methane and carbon and nitrogen dioxides are generated
predominantly. They have high desorbing capacity, which
provides for a high DOM (dispersed organic matter) yield
by way of its being dissolved in the compressed gas and
dominant gas saturation of the basin's deep section.
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