Environmental Statement 2008.FH10

3.3 The Environmental Aspects of our Operations
Environmental aspects are elements of our activities, products
or services that can interact with the environment. Figure
3 illustrates the main environmental aspects we have identified
for our offshore locations. We have grouped our significant
environmental aspects into four areas:
• Atmospheric emissions
• Energy use
• Discharges to water including spills
• Waste
3.3.1 Atmospheric Emissions
We burn natural gas and sometimes diesel as fuel on our
facilities to generate the power that is required to run our
operations. In addition, our facilities are designed to ‘flare’
(burn) and ‘vent’ (release unignited) a certain amount of
hydrocarbon gas for safety reasons. Most locations have a
continuous stream of gas to flare or vent designed to stop
the ingress of air into the facilities that could cause explosive
mixtures in the process. Additional amounts are also released
through this route during installation shutdown, when all
hydrocarbon gas systems are depressurised and when certain
equipment items are out of service (either planned or
unplanned).
The majority of our emissions to air are the products of
these combustion processes. The emissions include carbondioxide,
nitrogen oxides, sulphur dioxide, carbon monoxide,
unburnt hydrocarbons and particulates. These atmospheric
pollutants have global (climate change), regional (acidification)
and local (air quality) effects.
3.3.2 Energy Use
In addition to atmospheric emissions, consumption of diesel
and gas to provide energy is an important issue from the
point of view of depletion of natural resources. We are
currently developing GHG and Energy Management Plans
for each of our major installations.
3.3.3 Discharges to water
Most of our discharges to water consist of surplus water
from our oil and gas wells. This "produced water" is a mixture
of naturally occurring water in the reservoir, and seawater
that has been injected into the reservoir to support the
pressure and sweep oil towards the production wells. We
separate the produced water from the oil and gas, and discharge
most of it into the sea. The separated water contains a small
amount of residual oil as well as chemicals both naturally
occurring such as salts, and others such as corrosion inhibitors
and de-oilers.
As well as produced water, many of our wells produce sand
and scale which accumulates in pipework and vessels and
needs to be cleaned out from time to time. When pipework
and vessels are cleaned, the sand and scale is also cleaned to
remove as much oil as possible before it is discharged.
Produced sand contains similar materials to produced water
and may also contain small amounts of Naturally Occurring
Radioactive Material (NORM) which may occur naturally in
an oil or gas reservoir. All discharges are monitored and
recorded.
We also use seawater for cleaning purposes. After use any
‘wash water’ is cleaned before being discharged back into the
sea via specially designed drains. Legally permitted levels of
cleaning chemicals and some oil may remain in the water
when it is discharged. Other drains on our installations
discharge surface water, such as accumulated rainwater or
seawater, which do not normally contain any oil or chemicals,
as well as emergency fire-fighting water and foam, directly
into the sea.
Finally the smallest contribution to our discharges to the sea
comes from leaks and spills from our wells and equipment.
Such spills may consist of oil, gas, chemicals, or a mixture of
the three. Continuous monitoring, adherence to procedures
and rehearsal of emergency response keeps these unintended
discharges to a minimum.
3.3.4 Waste
A variety of solid and liquid wastes are produced from both
our on and offshore operations including drilling waste such
as cuttings and spent muds; wastes such as oily rags, fluorescent
tubes and batteries, and also office and packaging wastes such
as paper, card and wood.
Some wastes can be treated and re-injected into reservoirs
e.g. drill cuttings under the appropriate legal licences. However
the majority of wastes are shipped to shore for onshore
disposal. All waste, irrespective of where it is produced, is
transferred to licensed facilities for either treatment and
disposal; or sorting and bulking prior to transportation for
final disposal.
All waste is transported and disposed of in accordance with
our European waste management policy, in particular through
application of the waste hierarchy to prevent and reduce
waste as far as possible and minimise the volume of waste
to landfill.