one six-hundredth of its original volume and the nonmethane components
are largely eliminated. At the receiving terminals, the LNG is reconverted
to a gaseous state by passage through a regasifying plant, whence it can
be fed as required into the normal gas distribution grid of the importing
country. Alternatively, it can be stored for future use in insulated tanks or
subsurface storages. Apart from its obvious applications as a storable and
transportable form of natural gas, LNG has many applications in its own
right, particularly as a nonpolluting fuel for aircraft and ground vehicles.
Current production from conventional sources is not sufficient to satisfy
all demands for natural gas.
1.4 Natural Gas Reserves
Two terms are frequently used to express natural gas reserves: proved
reserves and potential resources. Proved reserves are those quantities of
gas that have been found by the drill. They can be proved by known reservoir
characteristics such as production data, pressure relationships, and
other data, so that volumes of gas can be determined with reasonable
accuracy. Potential resources constitute those quantities of natural gas
that are believed to exist in various rocks of the Earth’s crust but have not
yet been found by the drill. They are future supplies beyond the proved
reserves.
Different methodologies have been used in arriving at estimates of the
future potential of natural gas. Some estimates were based on growth
curves, extrapolations of past production, exploratory footage drilled, and
discovery rates. Empirical models of gas discoveries and production have
also been developed and converted to mathematical models. Future gas
supplies as a ratio of the amount of oil to be discovered is a method that
has been used also. Another approach is a volumetric appraisal of the
potential undrilled areas. Different limiting assumptions have been made,
such as drilling depths