How Is Crude Oil Extracted

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8 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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Ecological Management factors associated with Offshore Oil and
Gas Extraction



How Is Crude Oil Extracted


Offshore
oil production accounts for about
30
%

of
the total world oil
production




Offshore
gas production for about
half

of the world production of natural gas.



8,300
fixed or floating offshore platforms worldwide in 1999
.


(U.S. National Research Council ;
NRC
)


M
ore than 6,500 offshore oil and gas installations worldwide

(The UNEP
Offshore Oil and Gas Environment
Forum;
OEF
),



about
4,000 of which
are in
the U.S. Gulf of Mexico
,



950 in Asia,


700
in the Middle
East,
and


400
in Europe.


E

Oil and Gas Rigs


These structures are, in many cases, movable.
What is more, they can float while being
moved, and often while drilling. Further,
offshore rigs have drilled in waters over 7,500
feet (over 2,200 meters) deep and as far as
200 miles (over 300
kilometers
) from shore".
It should also be noted that the lifetime of a
rig is generally about 20 years. At the end of
that time, unless it is re
-
used or redeveloped,
it must be decommissioned.

The major potential
environmental
effects

from offshore drilling



Discharge of wastes, including drilling fluids
(also referred to as drilling
muds
), drill cuttings
and produced formation water.



The
decommissioning of platforms/rigs

is also
a potential environmental problem.

SHIP'S DESIGN



Single hull
is a ship construction term. In tankers with
single hulls, oil in the cargo tanks is separated from the
seawater only by a bottom and a side plate. Should this
plate be damaged as a result of a collision or stranding,
the contents of the cargo tanks risks spilling into the
sea.


In
double hull

tankers the cargo tanks are surrounded
with a second internal plate which is at a sufficient
distance from the external plate (generally 1.5
-
2
metres) to safeguard cargo tanks from damage and
thus reduce the risk of oil pollution. The double hull
construction incorporates both double bottoms and
double sides.





In 1992, the MARPOL Convention was amended to make it mandatory
for tankers of 5,000 dwt and more (ships ordered after 6 July 1993) to
be fitted with double hulls.




The requirement for double hulls that applies to new tankers has also
been applied to existing ships under a programme that began in 1995




All tankers have to be converted (or taken out of service) when they
reach a certain age (up to 30 years old).



An additional possible measure is to limit the size of individual tanks
within ships so that spills that occur at least are smaller.



The U.S. has banned single hull
-
vessels in their waters and has stronger
liability legislation in their Oil
Polllution

Act.



MAINTENANCE & SHIP OWNER RESPONSIBILITY





COMPETENT CREW


NAVIGATIONAL AIDS AND ON BOARD EQUIPMENT



Better navigational equipment


for example, electronic charting


is needed. All ships must have
radar systems to improve navigation (large ships must have two systems that operate independently).
In busy shipping corridors, traffic separation schemes and vessel traffic control are required to reduce
the risk of a collision. In some areas, mandatory
pilotage

should be introduced.


High
-
standard fire
-
fighting equipment must be available and strict fire safety regulations apply on
board.


Monitoring and control equipment should be installed on ships so that discharged oil
-
water mixtures
can be traced back to the ship that was carrying the oil.

SURVEILLANCE



The purposes of surveillance is to function as a deterrent from discharging ship
-
generated wastes
altogether, as a means of detection of discharges already made, and as a tool to combat, as effectively
as possible the spills that have been detected. Airborne surveillance which increases the ship's risk of
being caught in the process of making illegal discharges can be an effective measure to prevent
discharges and thus reduce marine pollution from shipping. In the future, airborne surveillance on a
regional scale should be introduced in more areas, particularly in the MARPOL Special Areas (as is
already the case in the Northeast Atlantic and the Baltic Sea).

INSPECTIONS



Frequent inspection of ships, particularly older ones, are imperative. Since 1995 all tankers and bulk
carriers aged five years and over have been subject to a specially enhanced inspection programme
which is intended to ensure that any deficiencies


such as corrosion or wear and tear resulting from
age or neglect


are detected.

RECEPTION FACILITIES



Better facilities are needed in ports for ships to leave their oily liquid waste and solid oily waste. In
MARPOL Special Areas, such port reception facilities are required.


CARGO OWNER AND OIL CONSUMER RESPONSIBILITY



At Sea : Contingency plans and response techniques


CONTINGENCY PLANS


As summarized by
Environment Canada
, a contingency
plan “is
a plan for action

prepared in anticipation of an oil spill. “ Contingency plans are essential because they

establish practical plans of action for all types of oil spills so that, when spills do occur,

a quick response can minimize the damage. The first step in developing a plan is to

learn as much about the area as possible. Regardless of the geography or the size of

an area, contingency plans normally include:



identification of authority and a chain of command;



a list of persons and organizations that must be immediately informed of a spill;



an inventory of available trained spill personnel and spill response equipment;



a list of jobs that must be done (in order of priority);



a communication network to coordinate response;



probable oil movement patterns under different weather conditions; and



sensitivity maps and other technical data.

Planners need to know about:




important or sensitive physical and biological resources
within or near the area, such as marshes, unusual flora
(plant life) and wildlife resources such as fish, shellfish,
marine mammals and birds;



important habitat areas required by particular species for
spawning, feeding or migration;



tides, currents and local climatic conditions, such as wind
and severe weather patterns;



shoreline characteristics; and



proximity to roads, airports, trained response personnel, oil
spill clean
-
up equipment, etc."


RESPONSE TECHNIQUES




As summarized by International Tanker Owners Pollution Federation
Ltd (
ITOPF
), "there are two approaches for responding to marine oil
spills at sea:


the
enhancement of natural dispersion

of the oil by using
dispersant
chemicals
, and


containment and recovery

of oil using
booms

and
skimmers
.


Sorbent materials

may be useful in the final stages of clean up as a
polishing tool. (Once oil strands on shore, a

shoreline clean
-
up will be
necessary.)

Despite continuing research, there has been little change in the

fundamental technology for dealing with oil spills.

Alternative techniques are constantly being sought and old techniques

re
-
assessed.


Two techniques currently receiving fresh attention are
in
-
situ burning

and the enhancement of the natural biodegradation of oil through the

application of micro
-
organisms and/or nutrients

Aerial reconnaissance

Also, according to ITOPF:


is an essential element of effective response to
marine oil spills. It is used for assessing the
location and extent of oil contamination and
verifying predictions of the movement and fate of
oil slicks at sea.


Aerial surveillance

provides information
facilitating deployment and control of operations
at sea, the timely protection of sites along
threatened coastlines and the preparation of
resources for shoreline clean
-
up. Observation can
be undertaken visually or by use of remote
sensing systems.

On Land : Contingency plans and response techniques


Regardless of the geography or the size of an area, contingency plans on land are similar to those for “At Sea”
and in addition:

RESPONSE TECHNIQUES



"Given the difficulties of cleaning up oil at sea, many oil spills result
in contamination of shorelines. The oil which reaches the coast
generally has the greatest environmental and economic impact. It
also determines to a large extent the political and public perception
of the scale of the incident, as well as the costs.


It is important to start removing oil promptly from contaminated
shorelines because as time passes and the oil weathers, it will stick
more and more firmly to rocks and sea walls, and may become
mixed with or buried in sediments.


Shoreline clean
-
up is usually straightforward, however, and does
not normally require specialised equipment. Reliance is frequently
placed on locally
-
available equipment and manpower, rather than
specialised equipment.


Good organisation and management are the key to effective clean
-
up. Poorly thought out and uncoordinated clean
-
up efforts usually
result in inefficient use of resources and excessive quantities of
waste for disposal." (
ITOPF
)


Initial clean
-
up responses to a spill at sea are often based upon the use of
dispersant chemicals or the containment and recovery of oil using booms
and skimmers

Whilst these techniques can be of use in the right circumstances, there are many

difficulties associated with employing them effectively.


The type of oil and concerns over potential impacts of dispersed oil can preclude
dispersant use. For example, they are not effective against many commonly
transported oils which have a high viscosity, and soon become ineffective against
lighter oils because natural weathering processes or the formation of water
-
in
-
oil
emulsions greatly increases oil viscosity, often very quickly (a few hours to one to
two days).


The application of dispersant to treat large quantities of spilled oil also requires
specialised equipment and extensive logistical support. Containment and recovery
is limited by sea conditions and the relatively small oil encounter rate which the
available systems can achieve.

Together, these factors usually mean that
only a small fraction of a major spill can be
dealt with at sea, and it is almost inevitable that oil will threaten coastal
resources
.

••• Protective strategies are seldom employed to the extent possible and it will
usually be necessary to mount a shoreline response operation. Priorities for
protection and clean
-
up will need to be agreed and care must be taken to ensure
that the techniques selected do not do more damage than the oil alone.


The disposal of oil and debris may become a major problem

both during and after
a clean
-
up operation. Several disposal options are however available.


The U.S.
EPA

summarizes as follows:

"
Mechanical
containment or recovery

equipment includes a variety of:




booms, barriers
, and
skimmers
, as well as
natural

and
synthetic sorbent materials
. (A sweep system is a
combination skimmer and boom attached to a ship or a small
boat.)



Mechanical containment is used to capture and store the
spilled oil until it can be disposed of properly. ”




Chemical and biological methods


can be used in conjunction with mechanical means for containing and cleaning up oil spills
.



Dispersants

and
gelling agents

are most useful in helping to keep oil from
reaching shorelines and other sensitive habitats.



Biological agents

have the potential to assist recovery in sensitive areas
such as shorelines, marshes, and wetlands. Research into these
technologies continues to improve oil spill cleanup.


Physical methods are used to clean up shorelines.


Natural processes such as evaporation, oxidation, and biodegradation can
start the cleanup process, but are generally too slow to provide adequate
environmental recovery.



Physical methods, such as wiping with sorbent materials, pressure
washing, and raking and bulldozing can be used to assist these natural
processes.


Scare tactics

are used to protect birds and animals by keeping them away
from oil spill areas. Devices such as
propane scare
-
cans, floating
dummies
, and
helium
-
filled balloons

are often used, particularly to keep


away birds."

Shoreline clean
-
up methods

(see, e.g., U.S.
EPA
,
NOAA

+
NOAA

and
USCG
,
ITOPF
, and
Environment Canada
):



No action (when a shoreline is very remote or inaccessible, when natural removal rates are
fast, or clean
-
up activities will do more harm than if the oil is left to be removed by natural
processes)


Natural recovery (evaporation, oxidation, and biodegradation can start the clean
-
up
process, but are generally too slow to provide adequate environmental recovery)


Application of
barriers or
berms



Physical
herding



Manual oil removal
/cleaning


Mechanical oil removal



Use of
sorbents

(passive collection)


Use of
vacuum



Removal of
oily debris


Sediment reworking/tilling (raking, bulldozing)



Vegetation cutting/removal



Shoreline flooding

(deluge)


Ambient
low
-
pressure

or
high
-
pressure water washing

(pressure washing, flushing)


Warm
-
water or
hot
-
water high
-
pressure washing

(see also
here
)


Slurry sand blasting

Possible shoreline clean
-
up methods also include
:

(however, in many countries these methods may only be used
after special permission from the authorities):



the use of solidifiers (gelling agents),


shoreline cleaning agents,


fertilizers to enhance biological remediation,
and


in situ burning.

The environmentally acceptable disposal of oil
and oily waste (debris) is important


As pointed out by EPA: "Cleanup from an oil spill is not
considered complete until all waste materials are
disposed of properly. The cleanup of an oiled shoreline
can create different types of waste materials, including
liquid oil, oil mixed with sand, and tar balls. Oil can
sometimes be recovered and reused, disposed of by
incineration, or placed in landfills".


All these methods must be employed with high
consideration for the environment in order to avoid
new problems of air pollution or leakage of toxic
substances into groundwater and rivers.


Sensitivity of coastal environments to oil
:

Location (where the oil is stranded) and shoreline geology, as well as type of
oil that needs to be taken care of, and of course the type and sensitivity of
the biological communities (species and habitats) that are likely to be
affected by the clean
-
up operation, are important factors in the choice of
clean
-
up method(s)


see
NOAA

and
EPA
.


The U.S.
Coastguard

have listed shoreline types, from the least (low figures; at
top here) to the most sensitive ones to oil pollution:


Exposed rocky cliffs and seawalls


Wave cut rocky platforms


Fine to medium
-
grained sand beaches


Coarse
-
grained sand beaches


Mixed sand and gravel beaches


Gravel beaches/Riprap


Exposed tidal flats


Sheltered rocky shores/man
-
made structures


Sheltered tidal flats


Marshes


Other shore types and shallow underwater
habitats are also very sensitive to oil pollution,

including:


Mangroves

(And according to ITOPF: "Leaving residual oil
to weather and degrade naturally is usually recommended for
sensitive shoreline types such as salt marshes and mangroves,
because they have been shown to be more easily damaged by
the physical disturbance caused by clean
-
up teams and
vehicles than by the oil itself. If any cleaning is attempted, it
should be carried out with specialist guidance and advice.")


Coral reefs