Page 174 - Geology and Geochemistry of Oil and Gas

ROLE OF ENERGY IN THE OIL GENERATION PROCESS 143
As mentioned before, the rate of heating of organic matter must affect substan-
tially the yield and composition of the generated product. According to Urov (1992,
p. 126), at a low rate of heating the mobile hydrogen atoms from the cyclic areas of
kerogen have enough time to migrate to the periphery of micromolecules. The sep-
aration and transfer of hydrogen occurs; aliphatic side chains detach mostly as
saturated compounds, and the solid residue gradually loses hydrogen and is car-
bonized. Price et al. (1986) also mentioned that a hydrogen-rich organic matter
(sapropelic) requires higher temperatures for transformation.
The potential energy of oil and gas is the transformed solar energy buried with
organic matter. The accumulation and sometimes the release of potential energy is a
thermodynamically viable process for the entire Earth’s crust and, in particular, for
the sedimentary rocks. An example is the formation of argillaceous sequences (ac-
cumulation of the surface potential energy) and their subsequent transformation
with a loss of energy.
The energy of organic matter (buried solar energy) is insufficient for its trans-
formation into oil and gas. Thus, an input of additional energy is required to initiate
(and accelerate) chemical reactions. The input of additional energy could be the heat
of the Earth.
If the internal energy of organic matter is insufficient for the generation of oil and
gas, and the additional energy is required, then the 100-year-old controversy of the
organic vs. inorganic origins of petroleum becomes meaningless. The discussions on
this subject are fruitless (Zhabrev, 1993). Even the most common orthodox version
of the organic hypothesis by Vassoyevich (1975, 1976, 1979) with the ‘‘main phase’’
(heat of the Earth) appears to be dualistic. The fraction of inorganic hydrocarbons in
the Earth’s crust at this time, optimistically, is no more than a few percent, and most
likely just a few tens of 1% (Zhabrev, 1993, p. 12). Thus, the following two questions
arise:
1. What processes provide for the accumulation of potential chemical energy and
what traces of these processes can be identified in the oil?
2. What energy sources may have been utilized, and which ones are most likely?
Undoubtedly, the endogenic heat has been among the major energy sources.
However, many exothermal processes occur in the lithosphere, and their energy may
have been utilized to transform (and to move) organic matter and its derivatives.
Mostly, the heat field, which is one of many energy fields of the Earth, has been
studied with respect to its association with the oil and gas generation cycles. The
electromagnetic field is poorly studied in this respect. There are reasons to believe
that the electromagnetic forces directly affect chemical reactions and lower the ac-
tivation thresholds. They certainly affect the migration of petroleum. These forces
should be additionally studied based on the concepts of (1) the Earth as a capacitor
with the minus in the crust and the plus in the ionosphere; (2) the Earth as an electric
power generator (rotation of a conductor in the magnetic field).
Here, the writers would like to mention the term ‘‘electrodiagenesis’’ introduced
by Serruya et al. (1967). Movement of fluid (due to compaction of sediments, for
example) generates potential gradients, which in turn may affect the diagenetic