Oil and Gas
Development on the Sakhalin Island Shelf: An Assessment of Changes in
the Okhotsk Sea Ecosystem
Alexander Leonov
The vast amount of
oil and gas deposits on the Sakhalin Island Shelf has been surveyed
intensively over the last twenty years. Many large companies (Marathon,
Shell, Exxon, Sodeco and others) have already completed preliminary
plans on oil and gas production on the eastern and north-eastern sites
of the Sakhalin Island Shelf within the framework of the Sakhalin-1 and
Sakhalin-2 projects. The stocks of just one of the five surveyed
deposits (Odoptinskii) amount to more than 200 million tons of oil and
1011 cubic meters of gas [1]. The
total amount of oil and gas on the north-eastern shelf of Sakhalin
Island is 1.2 billions ton and 800 billion cubic meters respectively
[2].
Under the proposed Sakhalin-1 project, Sakhalin
Island will become a large oil and gas extracting center and supplier
to the Far East and abroad. 65 prospecting wells have been drilled on
the Sakhalin Island Shelf [3]. The project calls for the construction
of six drilling platforms (one self-elevating), the drilling of more
than 600 wells (up to 3000 meters deep) producing more than 60,000 tons
of oil and 80 million cubic meters of gas per day, the laying of a
system of underwater pipelines (with a diameter of up to 720 mm), the
building of large shore facilities, and the removal of up to 70,000
cubic meters of the seabed [4].
This paper will
analyze the impact of the modern marine oil and gas industry on a
marine environment and fisheries in marine shelf and oceanic zones. The
extraction of oil and gas in a marine environment has been a sector of
the global economy for the last 20 years. This paper will examine the
negative impact of this industry on marine ecosystems and biological
resources. It will determine the degree of damage caused by water
pollution and changes in fishery conditions in regions where oil and
gas extraction has occurred. It will formulate the steps necessary for
preserving the environment in regions of oil and gas extraction.
The Environmental Effects of Marine Shelf
Oil and Gas Extraction
There are many examples of humanity's negative
impact on water ecosystems, such as the discharge of industrial wastes,
the washout from fertilizers, toxic chemical dumping, the damming of
rivers, and unsustainable water consumption. The large-scale
development of marine shelf oil and gas deposits has also had a
negative impact. The technology for oil and gas recovery used in Russia
for land-based continental deposits is combined with ecological risk
owing to significant losses of extracted raw materials.
The most
widespread and dangerous consequence of marine oil and gas (as well as
any other) industry is pollution of the environment [5]. Pollution is
associated with all kinds of activities at all stages of a deposit's
development. Globally, the oil and gas industry disposes of more than 3
billion tons of solid wastes, about 500 km3
of sewage and about 1 billion tons of aerosols per year [6, 7]. These
releases are composed of more than 800 substances, many of them related
to oil and its by-products. Globally, the total annual loss of oil
during its production and transport exceeds 45 million tons; 22 million
tons are lost on land; about 7 million tons are lost in the sea; and 16
million tons enter into the atmosphere as a result of the incomplete
combustion of liquid fuel [7]. The essential part (up to 10 to 20%) of
the total volume of marine gas production is burned up in flare systems
and gas generators on platforms and is a source of atmospheric
pollution.
Practically all stages in the development and
production of hydrocarbons are accompanied by discharges of liquid,
solid and gaseous waste (Table 1). The
typical discharge volumes of the most widespread and hazardous
substances are shown in Table 2.
There are four
main stages in the development of oil and gas deposits [1]:
geological
and geophysical surveys and evaluation of raw material stocks (seismic
and drill exploring);
the preparation of a deposit for exploitation (installing
stationary platforms, laying pipelines, constructing shore terminals,
drilling works, testing wells, etc.);
the deposit's exploitation (extraction, separation and
primary processing of hydrocarbons; the sinking and reparation of
wells; the transportation of liquid and gaseous products, etc.);
completion and termination (dismantling work; the removal of
platforms and pipelines; the preservation of wells, etc.).
Each of these
stages is characterized by certain activities and has an influence on
the environment (Tables 3 and 4). This influence has a complex character
and is seen in the form of the physical, chemical and biological
effects in an aquatic environment, the seabed bottom and, partially, in
the atmosphere.
The mean time of a deposit's exploitation is 20
to 40 years. However, after only 5 to 10 years, an area may have new
petroleum platforms, abandoned drill constructions, different devices
for laying underwater pipelines, oil tankers, vessels for seismic
investigation, etc. Thus, the local effects are integrated and become
regional. Their character and intensity can be distinguished depending
on the combination and number of natural and technical factors. For
example, in the North Sea, there are around 4000 drill wells (160 are
working from stationary platforms), and about 250 underwater terminated
wells and more than 5000 km of underwater pipelines [13].
The development of
any oil field results in the release of polluting substances into the
atmosphere. As for the development of marine deposits, this fact has
not attracted special attention so far. However, oil and gas recovery
experience on land shows that releases into the atmosphere occur at all
stages of development. The most widespread sources of such releases are
[1]:
-
the
continuous or periodic combustion of gas and excessive quantities of
hydrocarbons during the testing and operation of wells and the
continuous combustion of flares and low pressure ignition devices for
gas removal from tanks and pressure regulation systems;
-
the
combustion of gaseous and liquid fuel in power equipment (gas turbines,
internal combustion engines) on platforms, vessels, and shore
structures;
-
the releases from degasified
drill solutions, technological reagents and extracted hydrocarbons used
in various operations for production, processing, transportation and
storage.
The volumes of annually combusted petroleum gas
in Russia amount to 10 to 17 billion cubic meters [14]. Preliminary
calculations for Great Britain's marine oil and gas industry have shown
that about 10% of produced gas (approximately 46 billion cubic meters)
is combusted in flare systems and used for its own oil field power
requirements [15]. The total amount of releases resulting from the
production of oil and gas in Great Britain's sector of the North Sea
are estimated at 20,000 tons annually; the emission of methane is about
75,000 tons annually (or accordingly, less than 0.02 and 0.08% of all
atmospheric releases of volatile organic compounds in Great Britain).
Similar assessments for marine oil and gas fields on the Norwegian
Shelf showed the dominance of carbon dioxide gas (88%) in atmospheric
releases as well as nitrogen oxides and volatile organic substances
[16].
Deposit waters
entering from underground oil and gas bearing structures during the
industrial extraction of hydrocarbons account for a large amount of
pollution. In some cases, the additional disposal of large volumes of
marine water (tens or even hundreds of thousands of tons) is primarily
pumped through forced channels to maintain well pressure. These waters
are usually polluted by oil, low-molecular hydrocarbons, inorganic
salts, technological reagents and suspended substances and should be
treated before disposal into the sea. Such treatment in marine
conditions, however, is technologically hindered [17].
Data from the 1980s for British oil and gas
fields in the North Sea show that 60 to 78% of all usable chemical
materials were disposed as wastes into the sea (or annually 117,000 to
138,000 tons) [15].
The volume of
drill wastes is usually within 1000 to 5000 cubic meters per each
passed well, and their amount is usually measured by tens (for one
commercial platform) and many hundreds of thousands of cubic meters
(for larger deposits). In the North Sea, 22,000 tons of oil, 100,000
tons of chemical admixtures (inorganic and low toxic), and 4900 tons of
potentially dangerous compounds (biocides, corrosion inhibitors,
detergents, demulsifiers, oxygen absorbents, etc.) entered the water
with drill slime disposals in 1988 [18].
At present, two main types of drill solutions
are used - mixtures based on oil and other organic substances (diesel
fuel, paraffins and others) or water (fresh or salt with the addition
of clay and other components). During the last 10 years, the preference
has been given to the least toxic water-based drill solutions. However,
in some cases (for example, in the drilling of inclined wells in solid
rock) oil-based solutions are used [5].
Accidents remain
inevitable events for any oil field. As well, they are a pollution
source at all stages of the industrial exploitation of oil and gas
deposits (during prospecting drilling, industrial production, and
transportation by pipeline and oil tankers). The most prevalent reasons
for accidents are: equipment failures, staff errors and extreme natural
phenomena (seismic activity, glacial fields, storms, etc.). The
ecological consequences of accidents are especially dangerous near the
coast, in shallow water or in the areas with slow water exchange [1].
One of the main factors behind ecological risk
in marine oil fields is the failure of underwater pipelines. The
reasons for their damage can be quite varied (from material defects and
pipe corrosion, up to ground erosion, tectonic shifts in the seabed,
and effects of ship anchors and bottom trawls). The evaluated mean
probability of accidents with underwater pipelines in North America and
Western Europe is 0.00093 and 0.00064 respectively, and the main cause
for these failures is welding defects [4].
The Russian
experience in the development of oil fields in Siberia shows that the
oil outflow from pipelines is a common phenomenon: 1 to 2% of the oil
extracted in Russia is lost as a result of accidental spills and
releases. The amount of these losses (for example, in the Tumen' area
in Komi Republic) is estimated in the hundreds and thousands of events,
and the volume of oil spilled is estimated in the millions of tons [19,
20]. If this rate of loss is repeated in oil and gas deposit
development on the Sakhalin Island Shelf, serious consequences will
occur. The construction of a main pipeline is planned along a greater
part of the eastern coast of Sakhalin Island and through main rivers
where the spawning and the reproduction of unique salmon populations
occurs. On the whole, the construction of oil pipelines threatens to
pollute rivers and lakes, as well as soils and underground water
resources [21].
Despite the increased attention to ecological
safety and accident prevention in marine oil fields, emergencies are
inevitable. Statistics show that on the American shelf of the Gulf of
Mexico, the number of emergency oil spills (in volumes of more than
1000 barrel (one barrel = 134 kg) per billion barrels of oil extracted
or displaced averages 0.79 (during drill work on platforms); 1.82
(during oil transportation by pipelines) and 3.87 (during
transportation by tankers) [22]. The volume of oil spilled during
failures at drill works on the Great Britain Shelf in the period from
1980 to 1988 were between 0.00011 and 0.0029% of the amount of annually
extracted oil on similar drill platforms [23].
The probability of
accidents occurring on drilling wells is 0.1 to 0.5%, and, during their
repair, 1 to 2.5% [24]. In cases of larger oil spills (more than 10,000
tons), emergencies do not exceed 3% [4]. Available studies show that
2.3% of the total number of marine drill platforms experience large
failures annually [25]. Oil spills on a surface may be easily noticed
and handled. However, about 33% of reported releases from marine wells
were in the form of natural gas in the shallow-water areas of a shelf,
and about half of these cases were connected with the serious failure
and damage of drill installations [26].
The ecological consequences of oil tanker
transportation and failure statistics are considered in detail in many
publications [9, 27-29]. The probability of tanker accident (more than
10,000 tons of tonnage) is evaluated as 2.3% for each 10 million tons
of deadweight. In other data, the specific accident rate of oil tankers
with tonnage more than 6000 tons was around 2% at the end of the 1980s
[30].
Running aground
on coastal reefs, collisions with other ships, and fires and explosions
of cargo are often mentioned as the main reasons for tanker accidents
and other large oil spills. In 1989, the amount of oil spilled in
tanker accidents was 114,000 tons; in 1990, 45,000 tons. The total
annual volume of pollution from marine oil transportation is more than
500,000 tons [27].
Many examples are available in literature and
statistics on large tanker accidents (about 2% per year) which clearly
illustrate the high risk of emergencies during hydrocarbon
transportation in the Barents Sea. They also testify about the possible
catastrophic consequences of accidents because the damage can exceed
all recorded cases. Calculations confirm the validity of this fear: for
oil tankers with a tonnage between 5000 to 50,000 tons the area of oil
and gas condensate spills could be between 3000 to 50,000 square
kilometers; for super-tankers, spills could reach up to 84,000 square
kilometers [31]. This would have a devastating effect on fisheries.
An examination of
large tanker accidents, covered in detail in literature, begins with
the Torrey Canyon tanker accident near the English Channel in
1967, when a spill of 95,000 tons of oil polluted the Atlantic coast of
France and England with many consequences to the environment and
fisheries. Many other accidents, such as the Amoco Cadiz
(1978, 220,000 tons of oil), the Exxon Valdez (1989, 40,000
tons of oil), the Braer (1993, 85,000 tons of oil) have
followed. Each of these accidents had its own causes, but in all cases
the level of petroleum pollution reached lethal or threshold
concentrations for marine fauna (especially for birds and mammals),
with consequences far beyond ecological damage to the sea and the coast
[1].
Regarding the scale and burden of the
consequences that followed after the Exxon Valdez, the costs
of the clean-up were 2 billion dollars; compensation for the
environmental damage and to the local population was above 3.5 billion
dollars. About 15 billion dollars should be added to these costs for
judicial procedures [32].
Other dangerous
situations can arise with gas-carrier ships, which are used alongside
with oil tankers for the transportation of liquefied natural gas. Such
accidents are less probable in comparison with oil tanker spills, but
they threaten the destruction of all forms of life in an area up to 400
square kilometers [29]. Of seven gas carrier ship accidents (recorded
until 1980) transporting liquefied natural gas, three cases were caused
by explosions.
An accident with a ship transporting methanol
(a toxic substance completely dissolvable in water) may lead to an
ecological tragedy. Calculations have shown that an accident involving
a similar ship with a tonnage of 35,000 tons, for example, in a coastal
zone in the western part of the Murmansk area would destroy thousands
of square kilometers of fisheries [31].
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