Page 304 - Hydrocarbon Exploration and Production Second Edition

Surface Facilities 291

gas feedstock, CAPEX, and operating expenditure (OPEX), are in the range
US$20–25 per barrel.

11.1.4.5. Liquefied petroleum gas
Liquefied petroleum gas (LPG) is a mixture of propane and butane used as fuel
for heating appliances, vehicles and also as a replacement for environmentally
damaging gases previously used as refrigerants and aerosol propellants (e.g.
chlorofluorocarbons (CFCs)). The ratio of propane and butane depends
on the intended use of the LPG, and also indirectly on the season (summer vs.
winter).
LPG is generated as a by-product during crude oil refining, and is also
recovered from oil and gas production during the standard processing at the
surface. As LPG has a significantly higher calorific value than typical natural
gas, it cannot be substituted directly for methane, but has to be diluted with
air to produce a synthetic natural gas (SNG) that can be used in emergency
back-up systems for civilian and military installations, and more widely in emerging
markets before a natural gas distribution system has been fully developed. Where
LPG is used as fuel in motor vehicles it is referred to as autogas, and is stored in
a separate tank within the vehicle and blended in with the flow of petrol to the
engine.

11.2. Facilities

The hardware items with which the processes described in Section 11.1 are
achieved are called facilities, and are designed by the facilities engineer. The
previous section described the equipment items used for the main processes such
as separation, drying, fractionation and compression. This section will describe
some of the facilities required for the systems which support production from
the reservoir, such as gas injection, gas lift and water injection, and also the
transportation facilities used for both offshore and land operations.

11.2.1. Production support systems
Although the type of production support systems required depend upon reservoir
type the most common include
water injection
gas injection
artificial lift.

11.2.1.1. Water injection
Water may be injected into the reservoir to supplement oil recovery or to dispose
of produced water. In some cases, these options may be complementary. Water will