OFFSHORE ENVIORNMENTAL IMPACT

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NOME DO EVENTO OCORRIDO EM __/__/__
OFFSHORE ENVIONMENTAL IMPACTS
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Course Out lines:
1-Oil Pollution of the Sea
2-Oil spills in the sea
3-Waste discharges during the
offshore oil and gas activity
4- Gas impact on fish and other marine
organisms
5-Accidents during the offshore oil and
gas development.

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Oil Pollution of the Sea
• Tables 1 and 2 show the
variety of oil pollution
sources and give expert
estimates of the scales of
distribution and impact of
each of these sources on
the marine environment

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Table 1. Sources and scale of oil pollution input into the marine environment
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Types and Source of Input
Environment Scale of Distribution and Impact
Hydrosphere Atmosphere Local Regional Global
Natural:
Natural seeps and erosion of bottom sediments
+ - + ? -
Biosynthesis by marine organisms + - + + +
Anthropogenic:
Marine oil transportation (accidents, operational discharges from
tankers, etc.)
+ - + + ?
Marine non-tanker shipping (operational, accidental, and illegal
discharges)
+ - + ? -
Offshore oil production (drilling discharges, accidents, etc.) + + + ? -
Onland sources: sewage waters + - + + ?
Onland sources: oil terminals + - + - -
Onland sources: rivers, land runoff + - + + ?
Incomplete fuel combustion - + + + ?

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3. DADOS DO ACIDENTE E DO ACIDENTADO/
VICTIM AND ACCIDENT INFORMATION
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Table 2. Estimates of global inputs of oil pollution into the marine environment
(thousands tons/year of oil hydrocarbons)
Source 1973* 1979** 1981* 1985*** 1990***
Land-based sources:
Urban runoff and discharges
2,500 2,100
1,080
(500-1,250)
34% 1,175 (50%)
Coastal refineries 200 60
100
(60-600)
- -
Other coastal effluents - 150
50
(50-200)
- -
Oil transportation and
shipping:
Operational discharges from
tankers
1,080 600
700
(400-1,500)
45% 564 (24%)
Tanker accidents 300 300
400
(300-400)
- -
Losses from non-tanker
shipping
750 200
320
(200-600)
- -
Offshore production
discharges
80 60
50
(40-60)
2% 47 (2%)
Atmospheric fallout 600 600
300
(50-500)
10% 306 (13%)
Natural seeps 600 600
200
(20-2,000)
8% 259 (11%)
Total discharges 6,110 4,670 3,200 100% 2,351

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4. DESCRIÇÃO DO ACIDENTE / ACCIDENT
DESCRIPTION
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Oil spills in the sea
Oil spills in the marine environment
•Fate and behavior of oil in the marine environment:
Complex processes of oil transformation in the marine environment
start developing from the first seconds of oil's contact with
seawater. The progression, duration, and result of these
transformations depend on the properties and composition of the oil
itself.
•Physical transport:
the distribution of oil spilled on the sea surface occurs under the
influence of gravitation forces. It is controlled by oil viscosity and the
surface tension of water. Only ten minutes after a spill of 1 ton of
oil, the oil can disperse over a radius of 50 m, forming a slick 10-
mm thick. The slick gets thinner (less than 1 mm) as oil continues to
spread, covering an area of up to 12 km2
.
Dissolution:
Most oil components are water-soluble to a certain degree,
especially low-molecular-weight aliphatic and aromatic
hydrocarbons. Polar compounds formed as a result of oxidation of
some oil fractions in the marine environment also dissolve in
seawater

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Oxidation and destruction:
Chemical transformations of oil on the water surface and in the water column start to reveal themselves no earlier than a day
after the oil enters the marine environment. They mainly have an oxidative nature and often involve photochemical reactions.
Microbial degradation:
The fate of most petroleum substances in the marine environment is ultimately defined by their transformation and degradation
due to microbial activity. About a hundred known species of bacteria and fungi are able to use oil components to sustain their
growth and metabolism.
Self-purification:
As a result of the processes previously discussed, oil in the marine environment rapidly loses its original properties and
disintegrates into hydrocarbon fractions. These fractions have different chemical composition and structure and exist in
different emigrational forms
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Waste discharges during the offshore oil and gas activity
Sources, types, and volumes of waste discharges
Practically all stages and operations of offshore hydrocarbon production are accompanied by
undesirable discharges of liquid, solid, and gaseous wastes.
The proportions and amounts of discharged wastes can change considerably during production.
For example, the amount of solid drilling cuttings usually decreases as the well gets deeper and
the hole diameter becomes correspondingly smaller.
Produced waters, including injection waters and solutions of chemicals used to intensify
hydrocarbon extraction and the separation of the oil-water mixtures, are one of the main sources
of oil pollution in the areas of offshore oil and gas production.
Recently, a technology was developed to remove the drilling wastes, especially cuttings, by
reinjection their slurry into a geological formation. This gives some hope to achieving zero
discharge of oil-containing wastes during offshore oil and gas production

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Chemical composition of discharged wastes
As noted earlier, the spectrum of
chemicals entering the marine
environment at different stages of oil
and gas production is very wide.
They include many hundreds of
individual compounds and their
combinations

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Drilling fluids and cuttings:
Drilling wastes deserve special attention. The volume of drilling wastes usually ranges
from 1,000 to 5,000 m3
for each well. Such wells can number into dozens for one
production platform and many hundreds for a large field.
 Produced waters:
Produced waters usually include dissolved salts and organic compounds, oil
hydrocarbons, trace metals, suspensions, and many other substances that are
components of formation water from the reservoir or are used during drilling and other
production operations. Besides, produced waters can mix with the extracted oil, gas, and
injection waters from the wells. All of the above make the composition of the discharged
produced waters very complex and changeable. It is practically impossible to speak about
some average parameters of this composition, especially because reliable and complete
analytical studies of these wastes are very rare

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Other wastes:
Large quantities of produced waters, drilling
mud's and drilling cuttings, discussed above, as
well as discharges of storage displacement and
ballast waters are the source of regular and
long-term impacts of the offshore industry on
the marine environment

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Gas impact on fish and other marine
organisms
•The first important feature of interaction between gaseous traces and marine organisms is the quick
fish response to a toxic gas as compared with fish response to other dissolved or suspended
toxicants.
Medical toxicology distinguishes between three main types of intoxication by methane:
Light: results in reversible, quickly disappearing effects on the functions of central nervous and
cardiovascular systems
Medium: manifests itself in deeper functional changes in the central nervous and cardiovascular
systems and increase in the number of leukocytes in the peripheral blood
Heavy: results in irreversible disturbances of the cerebrum, heart tissues, and alimentary canal

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Another critical environmental factor that
directly influences the gas impact on water
organisms is the concentration of dissolved
oxygen. Numerous studies show that the
oxygen deficit directly controls the rate of fish
metabolism and decreases their resistance to
many organic and inorganic poisons.
•This decrease sometimes depends more on
the species characteristics and the rate of
their gas metabolism rather than on the nature
of the poison

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Accidents during the offshore oil and gas development.
Accidents inevitably accompany offshore development. They are the sources of environmental
pollution at all stages of oil and gas production. The causes, scale, and severity of the accidents'
consequences are extremely variable. They depend on a concrete combination of many natural,
technical, and technological factors.
Examples of Offshore Accidents:
1-Drilling accidents:
Drilling accidents are usually associated with unexpected blowouts of liquid and gaseous hydrocarbons
from the well as a result of encountering zones with abnormally high pressure.
2- Transportation and storage accidents:
2.1- Tanker transportation: The main causes of tanker accidents that lead to large oil spills include
running aground and into shore reefs, collisions with other vessels, and fires and explosions of the cargo
2.2- Storage: Underwater storage tanks with capacities of up to 50,000 m3
are built near the platform
foundations or are anchored in the semi submerged position in the area of developments and near the
onshore terminals. Of course, a risk exists of damaging the underwater storage tanks and releasing their
content, especially during tanker loading operations and under severe weather conditions.
2.3- Pipelines: Complex and extensive systems of underwater pipelines have a total length of thousands of
kilometers. They carry oil, gas, condensate, and their mixtures. These pipelines are among the main factors
of environmental risk during offshore oil developments

OFFSHORE ENVIORNMENTAL IMPACT

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