How Risk Based Decision Making improves Energy Efficiency in Oil and Gas Industry - Implementing Environmental and Resource Management - page 177

boosted the use of natural gas in particular as a fuel for power plants. The main
drivers of the huge increase in consumption are: 1. LNG introduction in highly
populated and developing countries like China and India; 2. The USA becoming
an importing country and its gas deficit increasing sharply; and 3. Gas fired power
plants becoming more popular in countries where nuclear plant programs have
been stopped or cancelled (Cosmao and Mello 2005).
Both LNG and LPG are transported over long distances from the source to the
distributor as a liquid. While petroleum gas is predominantly composed of pro-
pane with lesser amounts of butane and is transported under high pressure, natural
gas is composed of methane which can be condensed at near to atmospheric pres-
sure, albeit at extremely low temperatures. When in liquid form both are non-
flammable, the biggest hazard related to them however comes with atmospheric
release as both gasses are extremely flammable. The comparative physics of va-
pour cloud formation is however different as the components of petroleum gas are
heavier than air and therefore tend to form a denser cloud than the lighter, more
easily dispersed natural gas. This means that the risk of an explosion and/or fire-
ball is higher for petroleum gas. In addition the auto-ignition temperature of natu-
ral gas is higher than that of petroleum gas, although the flammability range (the
concentration range within which a gas/oxygen mixture will burn) of petroleum
gas is narrower than that of natural gas. In terms of overall safety however it can
be said that LNG is preferable to LPG. In terms of efficiency, while the heavier
petroleum gas is more energy dense, combustion of natural gas is more efficient,
with less production of CO 2 .
The example given here is that of a Natural Gas Distribution (NGD) project in
a city with a population of 1 million. Adhering to the Company codes of practice,
a comprehensive Health, Safety and Environmental Impact Assessment (HSEIA)
was carried out during the project's feasibility study phase. The Company had the
objective of undertaking the design and construction of a natural gas distribution
system within its supply areas in the city, which included both gas distribution
systems and gas utilisation systems. The gas distribution system is comprised of a
number of facilities, including primary and secondary pressure regulating stations
(PRS), distribution pipelines and distribution mains.
The risk of the Company's natural gas distribution facilities to surrounding
population, environment and occupational health was analysed and assessed (due
to confidentiality agreements the name of the Company and actual results are not
discussed in this paper). A comparison was made for different aspects of existing
LPG network and proposed NGD. The HSEIA concluded with the result that
changing over to natural gas was a practical and cost-effective solution to provide
cleaner and efficient source of fuel for domestic, commercial and industrial uses.
However, since the pipeline ran through a populated area of the city, certain rec-
ommendations were proposed to reduce the risk to ALARP level. Thus an RBDM
approach was employed to aid decision making on safety, environmental pollution
and change over to more efficient energy with prioritisation of actions to be im-
plemented.