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TEXT №7.

1. Read the text.
2. Find the key sentence in each paragraph and translate it into
Ukrainian.

The quantity of petroleum, in terms of the volume of oil
or gas in place in the reservoir also varies from reservoir to
reservoir. Reservoirs are rarely full, in the sense that the
petroleum column rarely extends down to the point at which it
would spill out of the trap (the spill points). They are never full
in the sense of occupying all the available pore space, because
petroleum does not displace all the water in the pore spaces.
Irreducible water saturation of 20 to 40% of the pore space is
quite common. However, if the reservoir exists by virtue of
cracks, joints and fissures, the total volume of these may be very
nearly filled with petroleum due to their large volume in relation
to the enclosing surface area and the consequent relative
reduction in the water absorbed to solid surfaces and trapped in
the interstices.
The volume of petroleum in a field, and its distribution in
different reservoirs, is clearly important. The volume of oil or
gas in place in a reservoir is estimated by estimating the total
volume of rock that contains oil or gas, multiplying the product
by the best estimate of the mean porosity of the reservoir, and
then multiplying the product by the best estimate of the
proportion of oil in the pore spaces (the oil saturation). The
volume of recoverable oil-oil that is recoverable by present
technology at present prices-is obtained by multiplying the
volume of oil in place by a recovery factor (usually 25-30%).
The volumes of gas are given at standard temperature and
o
pressure, such as 15 C and 760 mm of mercury (the standard
always being stated). During production, these estimates are
revised by reservoir engineers on the basis of performance, new
data, trends and theory.