Page 29 - Geology and Geochemistry of Oil and Gas

8 SYSTEMS APPROACH IN SCIENCE

cognition in many petroleum geology problems or in development of hierarchical
systems.
It is advisable to begin the analysis with construction of a simple system that
includes the simplest constituents. Subsequently, depending on the major task of
investigation, many other systems or subsystems may be identified. At the first stage,
however, it is recommended to identify a geologic system comprising the following
elements: rocks, water, organic matter (or its transformation products), and gases. A
general basis for their separation as a common system is their simultaneous and
regular presence within a limited geologic space. The primary element of the system
is the rock (mineral) portion. However, the other constituents are not neutral in the
system’s evolution. They interact with one another and with the surrounding matrix
(rock), and are unequal in terms of their mass. The rocks usually constitute tens of
percents of the mass and volume of the system (coal and peat are excluded). Water
and water vapor fill the pores in rocks and compose a few tens of percent to infinitely
small amounts in the system. Organic matter or its transformation products are
usually within a few percentage points, rising sometimes up to 10% (coal, peat) or
dropping to infinitely small amounts. Natural gases are mostly dissolved in the
liquids of the system. Individual elements of this system and the system as a whole
are exceptionally sensitive to changes in the temperature, pressure, and geochemical
environment.

1.3. SYSTEMS APPROACH IN PETROLEUM GEOLOGY

The objects of study in geologic sciences are geologic bodies (systems). A concept
of the geologic system covers the entire domain of specific geologic terms related to
particular geologic bodies. There are various definitions of a ‘‘geologic system’’. For
instance, ‘‘geologic system is such a system that is formed by interaction of the
planet’s near-surface layers; this interaction includes the effect of both the Earth and
the Universe that became exterior to the planet. The geologic system includes the
Earth’s crust in its structure’’ (Kurazhkovskaya, 1970).
Within the framework of applied geology, a geologic system is a well-organized
natural assembly of interconnected and interacting elements of lithosphere having
common development history and comprising a single natural unit with properties
that are not inherent in their individual elements (Buryakovsky and Dzhafarov,
1983).
Thus, it is possible to define specific systems depending on their natural properties
(for natural bodies) or on the objective of their creation (for engineering and natural
systems). As an example, let us consider compaction of deposits occurring in a
complex laminated system of rocks saturated with various fluids and subjected
to numerous diagenetic processes. Buryakovsky and Dzhevanshir (1987) proposed
a concept of lithofluidal system, which is useful for understanding compaction
processes. They stated that the lithofluidal system is a well-organized natural as-
sembly of interacting solid, liquid and gaseous elements of lithosphere having