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a) petroleum reservoirs
b) in sedimentary rocks
c) in the laboratory
d) on the surface

Варіант 5.

The occurrences of petroleum in the world strongly suggest
that that petroleum rarely, if ever, originates in the reservoir in
which it is found, but rather in other rocks, known as source rocks,
from which the petroleum migrates to the trap.
The study of petroleum generation is hampered by the fact
that we cannot scale the possible processes in the laboratory with
confidence, so all hypotheses are based on interpretations of
geochemical observations. It is also hampered by the fact that we
do not know with confidence what the source rocks are for most
known petroleum accumulations. If source rocks cannot be
identified with certainty, they cannot be studied with
understanding.
There is general agreement that the main source of
petroleum is organic matter buried with a fine-grained sediment,
usually a mudstone; and that diagenesis of this organic matter
leads to a “proto-petroleum” which, before or during migration,
becomes modified by the physical and chemical environment-
particularly by increasing temperature during burial-until it sooner
or later becomes the petroleum we find in the accumulation.

І. Choosing the Correct Definition for a Context:

According to Passage 3 the main source of petroleum is:

a) nonorganic matter
b) mineral matter
c) organic matter
d) synthetic matter