Page 169 - Geology and Geochemistry of Oil and Gas

138 ORIGIN OF OIL AND NATURAL GAS

According to Brod, various components of oil could have formed at different
stages of organic matter transformation and at different lithogenetic stages. Thus, a
complex chemical system called crude oil formed within reservoirs in the process of
the formation of accumulation. That is why Brod could not accept the term microoil:
in his view, hydrocarbons and non-hydrocarbon organic compounds dispersed in
rocks are not macro- or microoil.
It appears that Vassoyevich (1976) was correct in concluding that integrated ge-
ological and geochemical studies of the modern and ancient sediments provide ev-
ergrowing body of data, which indicates that each stage of lithogenesis is
accompanied by its own characteristic hydrocarbon generation. It should also
be remembered that the parent organic matter is also changing simultaneously
(Maksimov et al., 1977).
The Vassoyevich’s concept of a relation between the hydrocarbon generation and
catagenetic stages was broadened into the doctrine of oil and gas generation cycles
(Eremenko et al., 1949, 1978; Maksimov et al., 1972, 1976). As discussed later, the
‘‘stagewise’’ and ‘‘cyclic’’ nature do not have the same meaning. In discussing the
organic matter transformation into crude oil, it is necessary to consider the trans-
formation factors.
The major error implicit in most hydrocarbons-to-crude oil transformation con-
cepts is the attribution of an exclusive role to a single factor. This will result in the
detachment from the natural environment where all these factors are operative and
intertwined. The transposition of laboratory experiments onto the natural environ-
ment, without a full account for its multifaceted character, always results in errors.
Besides, an active energy influence on the source organic matter is attributed to each
factor. At the same time, no serious consideration was given until recently to the
energy facet of the issue, although it is only natural that organic matter in itself has
the sufficiently high reserves of energy for the subsequent transformations.
It was suggested that the living matter accumulate the sun energy, which is sub-
sequently transferred to the organic matter. It appears that this is not accurate. The
heat of the Earth itself should not be forgotten. All geologically ‘‘live’’ planets,
including the Earth, release much more heat than they receive from the Sun. The
processes of life cannot ignore that energy source. One confirmation of the above is
the presence of life at great depth in the oceans, where the sunlight does not reach.
No doubt, the energy stored in the living organisms or in organic matter is much
greater than that in the oil or coal. The processes of transformation of matter with
loss of energy are very common in the Earth’s crust.

8.2. STAGEWISE NATURE AND CYCLIC TRANSFORMATION OF ORGANIC MATTER
The issue of stagewise transformation of organic matter was analyzed by many.
As the energy is concerned, there is no significant disagreement in the identification
of the organic matter transformation stages. There is some disagreement regarding
the stage boundaries (especially in the case of temperature), but this, in our opinion,
is of minor importance.